Document y0M2ZQNa3gewJ5XNEVrL1kEE

American Water Works Association ANSI/AWWA C403-89 (Revision of ANSI/AWWA C403-84) AWWA STANDARD FOR THE SELECTION OF ASBESTOS-CEMENT TRANSMISSION AND FEEDER MAIN PIPE, SIZES 18 IN. THROUGH 42 IN. (450 mm THROUGH 1050 mm) eMOWNCTOtaO SKNOMDaV Effective date: Nov. 1, 1989. First edition approved by AWWA Board ofDirectors Jan. 28, 1978. This edition approved Jan. 29, 1989. Approved by American National Standards Institute, Inc., Aug. 24, 1989. AMERICAN WATER WORKS ASSOCIATION 6666 West Quincy Avenue, Denver, Colorado 80235 AWWA Standard This document is an American Water Works Association (AWWA) standard. It is not a specification. AWWA standards describe minimum requirements and do not contain all of the engineering and administrative information normally contained in specifications. The AWWA standards usually con tain options that must be evaluated by the user of the standard. Until each optional feature is specified by the user, the product or service is not fully defined. AWWA publication of a standard does not constitute endorsement of any product or product type, nor does AWWA test, certify, or approve any product. The use of AWWA standards is entirely voluntary. AWWA standards are intended to represent a consensus of the water supply industry that the product described will provide satisfactory service. When AWWA revises or withdraws this standard, an official notice of action will be placed on the first page of the classified advertising section of Journal AWWA. The action becomes effective on the first day of the month following the month of Journal AWWA publi cation of the official notice. American National Standard An American National Standard implies a consensus of those substantially concerned with its scope and provisions. An American National Standard is intended as a guide to aid the manufacturer, the consumer, and the general public. The existence of an American National Standard does not in any respect preclude anyone, whether he has approved the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not conforming to the standard. American National Standards are subject to periodic review, and users are cautioned to obtain the latest editions. Producers of goods made in conformity with an American National Standard are encouraged to state on their own responsibility in advertising and promotional materials or on tags or labels that the goods are produced in conformity with particular American National Standards. Caution Notice: The American National Standards Institute (ANSI) approval date on the front cover of this standard indicates completion of the ANSI approval process. This American National Standard may be revised or withdrawn at any time. ANSI procedures require that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of publication. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute, Inc., 1430 Broadway, New York, NY 10018 (212) 354-3300. Copyright 1989 by American Water Works Association Printed in USA li Committee Personnel The AWWA Standards Committee on Asbestos-Cement Pressure Pipe, which reviewed and approved this standard, had the following personnel at the time of approval: Robert S. Bryant, Chairman Leo A. Kinney Jr., Vice-Chairman Consumer Members R.S. Bryant, Department of Water and Power, Los Angeles, Calif. Roger Graff, City of San Diego, San Diego, Calif. R. W. Greaves, American Water Works Service Company, National City, Calif. D. H. Nelson, Thousand Oaks Utilities Department, Thousand Oaks, Calif. (AWWA) (AWWA) (AWWA) (AWWA) General Interest Members . KM. Bell, Underwriters Laboratories, Inc., Northbrook, 111. T.J. Brown Jr., Factory Mutual Research Corporation, Norwood, Mass. L.J. Dosedlo,* Underwriters Laboratories, Northbrook, 111. B.R. Elms,t Standards Engineer Liaison, AWWA, Denver, Colo. L. A. Kinney Jr., US Bureau of Reclamation, Denver, Colo. H.L. Olson, Denver, Colo. KF. Olson,t Council Liaison, Tacoma Public Utilities, Tacoma, Wash. J.S. Rego Jr., Water Registrar, Fall River, Mass. E. F. Straw, ISO Commercial Risk Services, Inc., Atlanta, Ga. Producer Members (UL) (FMR) (UL) (AWWA) (UBRC) (AWWA) (AWWA) (NEWWA) (ISO) M. L. Dellar, Consultant, Montreal, Que. Gustavo Herrera, Asbestos Monterrey, S.A., Monterrey, N.L., Mexico S. G. Leyshock, CAPCO Pipe Company, Inc., Litchfield, 111. Robert Novick, Certain Teed Corporation, Englewood, Colo. W.R. Perrell,* Cement Asbestos Products Company, Birmingham, Ala. B.J. Pigg, Asbestos-Cement Pipe Producers Association, Arlington, Va. (AWWA) (AWWA) (AWWA) (AWWA) (AWWA) (AACPP) Alternate tLiaison, nonvoting in L Contents SEC. PAGE Foreword I History of Standard.................... ... II Major Revisions.......................... III Metrication.................................. IV Information Regarding Use of This Standard.......................... vii Standard 1 General 1.1 Scope............................................ ...... 1 1.2 References................................... ...... 2 1.3 Symbols and Abbreviations...... ...... 2 1.4 Permeation.................................. ...... 4 2 General Design 2.1 Strength and Design Factors.... ...... 4 2.2 Combined Loading Theory........ ...... 7 2.3 Three-Edge, Vee-Shaped Bearing Load............................ ...... 8 3 External Loads 3.1 Introduction................................. ...... 8 3.2 Earth Loads................................ ...... 8 3.3 Superimposed Loads................. .... 21 4 Hydrostatic Pressure 4.1 Introduction................................. .... 24 4.2 Operating Pressure.................... .... 24 4.3 Surge Pressure............................ .... 25 5 Design Criteria and Use of Pipe Selection Charts 5.1 Combined Loading Curves........ .... 25 5.2 Safety Factors............................. .... 26 5.3 Use of Selection Charts for Economical Design.................. .... 26 5.4 Discussion................................... .... 27 5.5 Illustrative Problem on Pipe Selection......................................... 27 SEC. PAGE Appendices A Friction Loss of Head Chart-- Coefficient of Flow, C = 140.................................... . 48 B Surge Pressure Analysis B.l B.1.1 B.1.2 B.1.3 B.1.4 B.1.5 Water Hammer or Surge Forces Involved.............................. .. 49 Rate of Velocity Fluctuation........ .. 49 Wave Motion.................................. .. 49 Causes............................................ .. 49 Effects............................................. .. 50 B.2 B.2.1 B.2.2 B.2.3 Water Hammer Analysis Wave Velocity................................ .. 50 Maximum Pressure...................... .. 50 Critical Time.................................. .. 51 B.3 B.3.1 B.3.2 B.3.3 Valve Closure Effective Time............................... .. 51 Relation to Surge Control............ .. 51 Determining Effective Time........ .. 52 B.4 B.4.1 B.4.2 B.4.3 B.4.4 Pumped Systems Complexity..................................... .. 53 Alternative Layouts...................... .. 53 Water Column Separation........... .. 54 Entrapped Air............................... .. 54 B.5 B.5.1 B.5.2 B.5.3 Methods of Control Negative Surges............................. .. 54 Surge Control Devices.................. .. 54 Economic Considerations............. .. 55 B.6 Surge Calculation Example B.7 Air in Pipelines B.7.1 Entrance of Air............................. .. 56 IV A SEC. PAGE B.7.2 C Recommendations to Combat Air Entrapment........... .. 57 Frictional Power Requirements.......................... .. 58 Figures 1 Classes of Bedding for Conduits in Trench.................................... .... 6 2 Load Pressure Curve.................... .... 7 3 Assembly for Three-Edge, Vee- Shaped Crushing Strength Test.............................................. .... 8 4 Classification of Construction Techniques.................................. .... 9 5 Values of Cd for Trench Conditions......... .......................... .. 11 6 Embankment Conditions............. .. 17 7 Values of Cc for Positive Projecting Pipe........................... .. 17 8 Values of Bd/Bc at Which the Trench and Positive Projecting Pipe Equations Give Equal Loads............................................ .. 18 9 Values of Cn for Negative Projecting Pipe and Imperfect Ditch Conditions........................ ... 19 10A Positive Projecting Pipe Projection Ratio - x/Bc........... .. 19 10B Negative Projecting Pipe Projection Ratio = x/Bd........... .. 19 11 Projection Ratio p' for the Imperfect Trench Embankment Condition............ ... 21 12 Values of Ct for Tunnel Conditions................................... .. 22 13 Superimposed Loads.................... .. 24 14A Combined Loading Curves for 18-In. Transmission Pipe.......... .. 28 14B Combined Loading Curves for 20-In. Transmission Pipe.......... .. 29 14C Combined Loading Curves for 21-In. Transmission Pipe.......... .. 30 14D Combined Loading Curves for 24-In. Transmission Pipe.......... .. 31 14E Combined Loading Curves for 27-In. Transmission Pipe.......... .. 32 SEC. PAGE 14F Combined Loading Curves for 30-In. Transmission Pipe............ 33 14G Combined Loading Curves for 33-In. Transmission Pipe............ 34 14H Combined Loading Curves for 36-In. Transmission Pipe............ 35 141 Combined Loading Curves for 39-In. Transmission Pipe............ 36 14J Combined Loading Curves for 42-In. Transmission Pipe............ 37 14A(m) Combined Loading Curves for 450-mm Transmission Pipe......... 38 14B(m) Combined Loading Curves for 500-mm Transmission Pipe......... 39 14C(m) Combined Loading Curves for 525-mm Transmission Pipe......... 40 14D(m) Combined Loading Curves for 600-mm Transmission Pipe......... 41 14E(m) Combined Loading Curves for 675-mm Transmission Pipe......... 42 14F(m) Combined Loading Curves for 750-mm Transmission Pipe......... 43 14G(m) Combined Loading Curves for 825-mm Transmission Pipe......... / 44 14H(m) Combined Loading Curves for 900-mm Transmission Pipe......... , 45 14l(m) Combined Loading Curves for 975-mm Transmission Pipe......... . 46 14J(m) Combined Loading Curves for 1050-mm Transmission Pipe......., 47 B.l Time (Te) = Effective for Full Cut Off Uniformly at Maximum Rate............................. 52 C.l Yearly Power Cost to Compensate for Friction Loss of Head............. 59 Tables F.l Conversion Factors.......................... ix 1 Earth Loads (lb/lin ft)................... 12 2 Recommended Safe Design Values of c for Tunnel Conditions........... 20 3 Impact Factors F............................. 23 4 Values of Load Coefficients Cs for Concentrated Superimposed Loads Centered Vertically Over Conduit.......................................... 23 SEC. PAGE 5 Concentrated Superimposed Wheel LoadL (Measured in lb!ft [kN/m]) on Asbestos-Cement Transmission Pipe Single Wheel = 16,000 lb (7250 kg)..... 23 6 Design Internal Pressure and Design External Load Intercepts for Use With Selection Curves for Transmission Pipe.................. 26 SEC. PAGE 7 Minimum Safety Factors for Use With Asbestos-Cement Transmission Pipe Selection....... 26 C.l Present Worth of an Income of $1.00 per Year for the Next N Years......................................... 60 VI Foreword This foreword, is for information only and is not a part ofAWWA C403. I. History of Standard. A new pipe material consisting of an intimate mix ture of Portland cement and asbestos fibers was introduced to the North American market in 1931 following years of use in other countries, particularly Italy. In the ensuing years, this type of pipe gained popularity. In 1949, AWWA established a committee, chaired by S.M. Clark of Greeley and Hanson, Chicago, 111., on standard specifications for asbestos-cement pipe. The committee developed a standard for asbestos-cement water pipe, AWWA C400-53T, which was approved by the AWWA Board of Directors as tentative on May 15, 1953. In 1958, the committee was reactivated as Committee 8340D on Asbestos-Cement Pipe under the chairmanship of Roy H. Ritter of Whitman, Requardt, and Associates, Baltimore, Md., to review several suggested changes and to recommend revisions to the standard. The committee produced a revised tentative standard adopted as AWWA C400-64T on Jan. 27, 1964. It was advanced to stan dard without revision on July 2,1965, and designated as AWWA C400-65. The committee concluded that an installation guide was desirable to bring cer tain important requirements on the inspection, handling* installation, and field test ing of asbestos-cement pressure pipe to the attention of users. The committee sub mitted its final draft in 1963, and it received approval as tentative, AWWA C60364T, on Jan. 27, 1964. It was advanced to standard without revision on Aug. 9, 1965, and designated as AWWA C603-65. In early 1968, the committee was reactivated as the Standards Committee on Asbestos-Cement Pipe to review and revise all AWWA standards on asbestoscement pipe. The committee produced a revised standard approved by the AWWA Board of Directors on Jan. 31, 1972, and designated as AWWA C400-72, Standard for Asbestos-Cement Pressure Pipe for Water and Other Liquids. AWWA C401-64, Standard Practice for the Selection of Asbestos-Cement Water Pipe (originally designated AWWA Handbook H2), was first approved by the AWWA Board of Directors on Jan. 27, 1964. Although it covered pipe sizes up to and including 36 in. (900 mm), it was primarily intended for use with asbestos-cement pipe in smaller distribution sizes (4 in. through 16 in. [100 mm through 400 mm]). In the winter of 1972-73, the committee was reorganized and enlarged to include representatives of national organizations having an interest in the scope of the committee and wanting to participate in the work. The reorganized committee reaffirmed AWWA C400-72 without revision so that it could be presented to the American National Standards Institute for designation as an American National Standard. In 1975, the committee produced a revised standard that was approved by the AWWA Board of Directors on Jan. 26, 1975, and designated AWWA C400-75, Stan dard for Asbestos-Cement Pressure Pipe, 4 In. Through 24 In., for Water and Other Liquids. The asbestos-cement pipe manufacturers developed a new series of large pipe classifications, designed to give greater freedom of selection to design engineers. This was of particular significance for large-diameter pipeline projects where the savings in material cost can exceed the increased cost resulting from more detailed * vn design, better control of methods of installation, and provision of surge controls, when justified. To provide the user with a ready reference and specification for this type of pipe, known as transmission pipe, the committee approved AWWA C402-75, Stan dard for Asbestos-Cement Transmission Pipe, 18 In. Through 42 In., for Water and Other Liquids. The possibility of confusion between the two 1975 standards, AWWA C400 and AWWA C402, was carefully reviewed by the committee. The results were AWWA C402-77, which covers sizes 18 in. through 42 in. (450 mm through 1050 mm), and AWWA C400-77, which covers sizes 4 in. through 16 in. (100 mm through 400 mm). There is now no overlap of sizes. Consequently, it was desirable to revise AWWA C401-64 so that it would be compatible with AWWA C400-77 and to develop a new pipe selection standard to be compatible with AWWA C402-77. AWWA C401-77, Standard Practice for the Selec tion of Asbestos-Cement Distribution Pipe, 4 In. Through 16 In., for Water and Other Liquids, and AWWA C403-78, Standard Practice for the Selection of Asbestos-Cement Transmission and Feeder Main Pipe, Sizes 18 In. Through 42 In., were approved in May 1977 and January 1978, respectively. The 1978 edition of this standard was revised to include the three-edge, vee-shaped bearing method for crush testing, revision of bedding condition descriptions and load factors used in calculating earth loads to correspond with those contained in ASCE Manual of Prac tice 37, Design and Construction of Sanitary and Storm Sewers,* and revision of the crush values for pipe. That revision was approved by AWWA Board of Directors on Jan. 30, 1984, and designated AWWA C403-84. II. Major Revisions. Major changes made to this revision of the standard include: 1. A statement concerning potential permeation of pipe materials by low molecular weight petroleum products or organic solvents was added as Sec. 1.4. 2. A footnote concerning derivation of equivalent metric pressures was added to Table 6. 3. Sec. B.1.4 was revised to discuss three major causes of water hammer: (1) valve closure or opening, (2) pump start-up or shutdown, and (3) entrapped air. III. Metrication. Metric conversions of all dimensions and physical require ments have been included in this standard (Table F.l). Metric dimensions are direct conversions of US customary inch-pound units and are not those specified in Inter national Organization for Standardization (ISO) standards. IV. Information Regarding Use of This Standard. This standard provides for pipe sizes ranging from 18 in. (450 mm) through 42 in. (1050 mm). However, current production in the United States is limited to a maximum size of 24 in. (600 mm). Effective July 21, 1986, the Occupational Safety and Health Administration (OSHA) revised its standards for workplace exposure to airborne asbestos particles. The current standard makes the employer responsible for ensuring that employee exposures to airborne asbestos fiber concentrations do not exceed stringent exposure limits. The OSHA construction standard on asbestos, 29 CFR 1926, prescribes initial air monitoring and other compliance measures. The OSHA requirements apply to *Available from American Society of Chemical Engineers, 345 East 47th St., New York, NY 10017. vm Table F. 1 Conversion Factors US Customary Unit Conversion Factor Metric Equivalent inch (in.) foot (ft) pounds per square inch (psi) pound (lb) pounds per square foot (lb/ft2) pounds per cubic foot (lb/ft3) x 25.4 x 0.3048 x 6.894757 x 0.4536 x 0.0478803 x 16.0185 = millimetre (mm) = metre (m) = kilopascals (kPa) = kilogram (kg) = kilonewtons per square metre (kN/m2) = kilograms per cubic metre (kg/m3) 'Metric pipe inside diameter sizes are nominal and may not directly convert from the equivalent inches. the manufacture, shipping, handling, installation, and repair of asbestos-cement pipe and appurtenances. It is recommended that users and prospective users of asbestos-cement pipe familiarize themselves with the current OSHA asbestos work practice standards. IX This page intentionally blank. American Water Works Association A ANSI/AWWA C403-89 (Revision of ANSI/AWWA C403-84) AWWA STANDARD FOR THE SELECTION OF ASBESTOS-CEMENT TRANSMISSION AND FEEDER MAIN PIPE, SIZES 18 IN. THROUGH 42 IN. (450 mm THROUGH 1050 mm) SECTION 1: GENERAL Sec. 1.1 Scope This standard has been prepared so that design engineers may determine the correct pressure classification of asbestos-cement transmission pipe to use under various combinations of internal pressure (static, operating, and surge) and external load (earth and superimposed live loads). Combined loading curves depicting the relationship between hydrostatic loading and external loading capabilities are included to expedite the selection of the correct pipe strength classification. NOTE: Information to assist the engineer in selecting the most economical size of pipe is in the Appendices. Appendix A contains a friction loss of head chart based on the Hazen and Williams formula. Appendix B is a detailed analysis of surge pressure factors. Appendix C includes tables to assist the engineer in determining the yearly power costs to overcome loss of head due to friction. The Appendices are for information only and are not a part of AWWA C403-89. 1.1.1 Pressure classes. The pipe strength classifications of 30, 35, 40, 45, 50, 60, 70, 80, and 90 refer to the similarly numbered classes specified in AWWA C402, 1 2 AWWA C403-89 Standard for Asbestos-Cement Transmission Pipe, 18 In. Through 42 In. (450 mm Through 1050 mm), for Water and Other Liquids. 1.1.2 Installation. Detailed coverage of the installation of asbestos-cement pipe can be found in AWWA C603, Standard for Installation of Asbestos-Cement Pressure Pipe. Sec. 1.2 References This standard references the following documents. They form a part of this standard to the extent specified herein. In any case of conflict, the requirements of this standard shall prevail. ASTM* C500--Standard Test Method for Asbestos-Cement Pipe (Rev. A). AWWA C403-84--Standard Practice for the Selection of Asbestos-Cement Dis tribution Pipe, 4 In. Through 16 In. (100 mm Through 400 mm), for Water and Other Liquids. Design and Construction of Sanitary and Storm Sewers. Manual of Engrg. Prac. No. 37. Amer. Soc. Civ. Engrg., New York (1976). KERR, S.L. Practical Aspects of Water Hammer. Jour. AWWA, 40:6:699 (June 1948). MARSTON, ANSON. The Theory of External Loads on Closed Conduits in the Light of Latest Experiments. Bull. 96. Iowa State Col. Engrg. Exp. Sta., Ames, Iowa (1930). SCHLICK, W.J. Supporting Strengths for Cast-Iron Pipe for Water and Gas Ser vice. Bull. 146. Iowa State Col. Engrg. Exp. Sta., Ames, Iowa (June 1940). Sec. 1.3 Symbols and Abbreviations Bc = outside diameter of a pipe, in feet (metres). Bd = width of trench measured at the top of pipe, in feet (metres). B.F. = bedding factor, which is a load factor correlating three-edge, vee- shaped bearing test loads to field loads associated with specific bedding conditions. Bt = maximum width of a tunnel excavation, in feet (metres). c = coefficient of soil cohesion, in pounds per square foot (kilonewtons per square metre). Cc = load coefficient for the positive projecting embankment condition. It is a function of the ratio H/Bc, the projection ratio p, and the settle ment ratio rsd. Cd = load coefficient for the trench condition. It is a function of the ratio H/Bd and the backfill material. Cn = load coefficient for the negative projecting embankment condition, as well as the imperfect trench condition. It is a function of the ratio H/Bd, the projection ratio p', and the settlement ratio rsd. Cs = load coefficient for concentrated or distributed superimposed loads. It is a function of the ratio Bc/2H and the ratio L/2H for concentrated loads, or the ratio D/2H and the ratio M/2H for distributed loads. Ct = load coefficient for tunnel conditions. It is a function of the ratio H/Bt and the type of soil surrounding the tunnel. *American Society for Testing and Materials, 1916 Race St., Philadelphia, PA 19103. ASBESTOS-CEMENT TRANSMISSION PIPE 3 D width of the area over which the distributed superimposed load acts, in feet (metres), F impact factor. H depth of cover, in feet (metres), for all conditions except the tunnel condition. For the tunnel condition, H is the distance from the ground surface to the top of the tunnel excavation, in feet (metres). k Rankine's ratio of lateral earth pressure to vertical pressure, L effective length of the pipe, in feet (metres). For pipe less than 3 ft (1 m), the actual length of the section should be used. For all other lengths, an effective length of 3 ft (1 m) should be used, M length of the area over which the distributed superimposed load acts, in feet (metres). P internal pressure, in pounds per square inch (kilopascals), that the pipe will withstand when no external load exists, Pc concentrated load, in pounds (kilonewtons*). Pd distributed load, in pounds per square foot (kilonewtons pounds per square metre*). Po static, working, or operating pressure, in pounds per square inch (kilopascals). Ps surge pressure or water hammer, in pounds per square inch (kilopascals). Pt total internal pressure, in pounds per square inch (kilopascals), above which, in combination with some external load Wt applied in threeedge, vee-shaped bearing, the pipe will withstand, p projection ratio for the positive projecting embankment condition. It is defined as the ratio of the distance that the top of the pipe projects above the original ground surface, in feet (metres), to the outside diameter of the pipe, in feet (metres) (see Figure 10A, page 19). projection ratio for the negative projecting and imperfect trench condition. It is defined as the ratio of the vertical distance from the original ground surface down to the top of the pipe, in feet (metres), divided by the width of the trench, in feet (metres), for negative projection, and as the ratio of the vertical distance from the top of the excavated trench down to the top of the pipe, in feet (metres), divided by the diameter of the pipe, in feet (metres), for the imper fect trench condition (see Figures 10B and 11, pages 19 and 21). rsd settlement ratio for positive projection, negative projection, and imperfect trench conditions, S.F. safety factor. coefficient of internal friction of backfill material, coefficient of friction between backfill material and the trench wall, W external load, in pounds per linear foot (kilonewtons per metre) of pipe, in the three-edge, vee-shaped bearing test that the pipe will withstand when no hydrostatic pressure exists. *Note: Pc and Pd are loads measured as a mass. However, to use them in equations using SI units, the mass unit must be converted to force by multiplying by 9.8062 (g, the acceleration of gravity). 4 AWWA C403-89 We = total earth load, in pounds per linear foot (kilonewtons per metre), to which the pipe is subjected. Ws = total superimposed load, in pounds per linear foot (kilonewtons per metre) of pipe, transmitted through the burial environment to the pipe by factors other than the earth loads. Wsc = concentrated superimposed load, in pounds per linear foot (kilo newtons per metre) of pipe, transmitted through the burial environ ment to the pipe by factors other than the earth loads. Wsd = distributed superimposed load, in pounds per linear foot (kilonewtons per metre) of pipe, transmitted through the burial environment to the pipe by factors other than the earth loads. Wt = total external load, in pounds per linear foot (kilonewtons per metre) of pipe, applied in three-edge, vee-shaped bearing above which, in combination with some internal pressure Pt, the pipe will withstand. we = weight of earth, in pounds per cubic foot (kilonewtons per cubic metre*). Sec. 1.4 Permeation The selection of materials is critical for water service and distribution piping in locations where there is likelihood the pipe will be exposed to significant concentra tions of pollutants comprised of low molecular weight petroleum products or organic solvents or their vapors. Research has documented that pipe materials such as polyethylene, polybutylene, polyvinyl chloride, and asbestos cement; and elastomers, such as used in jointing gaskets and packing glands, may be subject to permeation by lower molecular weight organic solvents or petroleum products. If a water pipe must pass through such a contaminated area or an area subject to contamination, consult with the manufacturer regarding permeation of pipe walls, jointing materials, and so forth, before selecting materials for use in that area. SECTION 2: GENERAL DESIGN Sec. 2.1 Strength and Design Factors The strength of asbestos-cement transmission pipe must be sufficient to withstand the combined forces of all types of internal pressures (static, operating, and surge) and external loadings (earth, live, and impact). Sound engineering prac tice also requires that adequate safety factors be applied to strength requirements to ensure performance under other than ideal or calculated loading conditions. The magnitude of these safety factors is inversely proportional to the confidence that the designer has in engineering estimates of actual operating conditions. Safety factors are included in Sec. 5. *Density, as used in the equations in this standard, refers to force exerted per unit volume under the acceleration of gravity, rather than mass per unit volume. Where true density is known in pounds per cubic foot, that value should be used in equations using US customary units; where true density is known in kilograms per cubic metre, it must be converted to newtons per cubic metre by multiplying by 9.8062 (g, the acceleration of gravity) before the value is used in equations using SI units. ASBESTOS-CEMENT TRANSMISSION PIPE 5 2.1.1 Bedding conditions. The bedding conditions described below and shown in Figure 1 have been selected as representative of typical installation conditions encountered in the field. 2.1.1.1 Class A--concrete cradle or concrete arch bedding. This class of bed ding may take either of two forms: 2.1.1.1.1 Concrete cradle. The pipe shall be bedded in a monolithic cradle of plain or reinforced concrete having a minimum thickness of one fourth the outside pipe diameter (minimum of 4 in. [100 mm]) under the barrel and extending up the sides for a height equal to one fourth the outside diameter. The cradle shall have a width at least equal to the outside diameter of the pipe barrel plus 8 in. (200 mm). Backfill shall be compacted above the cradle and extending to 12 in. (300 mm) above the crown of the pipe. The load factor for class A concrete cradle bedding is 2.2 for plain concrete with lightly compacted (85 percent to 95 percent proctor or 40 percent to 70 percent relative density) backfill; 2.8 for plain concrete with carefully com pacted (95 percent proctor or 70 percent relative density) backfill; and 3.4 for reinforced concrete with p = 0.4 percent, in which p is the ratio of the contact area of steel to the area at the invert. 2.1.1.1.2 Concrete arch. The pipe shall be embedded in carefully compacted granular material having a minimum thickness of one fourth the outside diameter between barrel and bottom of trench excavation and extending halfway up the sides of the pipe. The top half of the pipe shall be covered with a monolithic plain or reinforced concrete arch having a minimum thickness of one fourth the outside diameter (minimum of 4 in. [100 mm]) at the crown and having a minimum width equal to the outside pipe diameter plus 8 in. (200 mm). The load factor for class A concrete arch-type bedding is 2.8 for plain concrete; 3.4 for reinforced concrete with p = 0.4 percent; and 4.8 for reinforced concrete with p = 1.0 percent, in which p is the ratio of the area of steel to the contact area of concrete at the crown. 2.1.1.2 Class B--first class bedding. Class B bedding may be achieved by either of two construction methods: 2.1.1.2.1 Shaped bottom with carefully compacted backfill. The bottom of the trench excavation shall be shaped to conform to a cylindrical surface with a radius at least 2 in. (50 mm) greater than the radius to the outside of the pipe and with a width sufficient to allow six tenths of the width of the pipe barrel to be bedded in fine granular fill placed in the shaped excavation. Carefully compacted backfill shall be placed at the sides of the pipe to a thickness of at least 12 in. (300 mm) above the top of the pipe. Shaped trench bottoms are difficult to achieve under current con struction techniques. 2.1.1.2.2 Compacted granular bedding with carefully compacted backfill. The pipe shall be bedded in compacted granular material placed on a flat trench bottom. The granular bedding shall have a minimum thickness of one fourth the outside pipe diameter (minimum of 4 in. [100 mm]) and shall extend halfway up the pipe barrel at the side. The remainder of the side fills and a minimum depth of 12 in. (300 mm) over the top of the pipe shall be filled with carefully compacted material. 2.1.1.2.3 The load factor for either construction method is 1.9. 2.1.1.3 Class C--ordinary bedding. Class C ordinary bedding may be achieved by either of two construction methods: 2.1.1.3.1 Shaped bottom. The pipe shall be bedded with "ordinary" care in an earth foundation formed in the trench bottom by a shaped excavation that will fit the pipe barrel with reasonable closeness for a width of at least 50 percent of the outside pipe diameter. The side fills and area over the pipe to a minimum depth of 6 AWWA C403-89 Concrete cradle, load factor 2.2.3.4 CLASS A Bc + 8ff min (200 mmi .It bc W-----kI g| f0.4"(m100inmm i Y Concrete arch, load factor 2.2.3.4 Carefully* compacted granular material Carefully* ^ compacted ` granular material Shaped bottom with tamped backfill, load factor 1.9 CLASS B Compacted granular bedding, load factor 1.9 Shaped bottom, load factor 1.5, not recommended CLASS C Compacted granular bedding, load factor 1.5 Flat bottom, load factor 1.1, impermissible bedding, not recommended Loose backfill Note: In rock trench, excavate at least 6 in. (150 mm) below the coupling of the pipe except where concrete cradle is used. * Carefully compacted backfill or granular material: 95% proctor or 70% relative density, t Lightly compacted backfill: 85-90% proctor or 40-70% relative density. Revised and reprinted with permission from ASCE, Manual 37, Design and Construction of Sanitary and Storm Sewers (1976). Figure 1 Classes of bedding for conduits in trench. ASBESTOS-CEMENT TRANSMISSION PIPE 7 6 in. (150 mm) above the top of the pipe shall be filled with lightly compacted fill. The shaped bottom bedding is not recommended for pipeline construction because it is impractical and costly. 2.1.1.3.2 Compacted granular bedding with a lightly compacted backfill. The pipe shall be bedded in compacted granular material placed on a flat trench bottom. The granular bedding shall have a minimum thickness of 4 in. (100 mm) under the barrel and shall extend one tenth to one sixth of the outside diameter up the pipe barrel at the sides. The remainder of the side fills and a minimum depth of 6 in. (150 mm) over the top of the pipe shall be filled with lightly compacted backfill. 2.1.1.3.3 The load factor for either construction method is 1.5. 2.1.1.4 Class D--flat bottom trench, impermissible bedding. In this class of bedding, the bottom of the trench is left flat, and no care is taken to secure compac tion of backfill at the sides and immediately over the pipe. The load factor for class D bedding is 1.1. Class D bedding is not recommended for pipeline construction. Under present construction conditions, class B or class C bedding with a compacted granular bedding is generally a more practical and economical method of installation. Sec. 2.2 Combined Loading Theory Tests of asbestos-cement pipe under various combinations of internal pressure and external crush load applied in three-edge, vee-shaped bearing (see Sec. 2.3) indi cate that there is a relationship between the combined loads at the point of pipe fracture. This relationship can be represented by a parabolic curve as shown in Figure 2. The equation for the load pressure parabolic curve, which is known as the Schlick formula, may be expressed as (Eql) o Figure 2 Load pressure curve. External Load 8 AWWA C403-89 Sec. 2.3 Three-Edge, Vee-Shaped Bearing Load The combined loading curve shown in Figure 2 is calculated on the basis of crush strengths determined by laboratory tests employing the three-edge, veeshaped bearing test method (see ASTM C500 and Figure 3). Because the field-supporting strength of a pipe is influenced by the bedding conditions and by the lateral pressure acting against the sides of the pipe, it is necessary to apply a bedding load factor to the laboratory three-edge, vee-shaped bearing loads to corre late them to the actual field loads. Since the external load equals the bedding factor times the vee-shaped bearing load, the bedding factor equals the external load divided by the three-edge, vee-shaped bearing load. Figure 1 shows the load factors to be applied for each bedding class. SECTION 3: EXTERNAL LOADS Sec. 3.1 Introduction For the design of asbestos-cement distribution pipe, external loads Wt are defined by the following equation: WT = ------W- f7P+ Ws*----- X (S.F.) (Eq 2) Sec. 3.2 Earth Loads Earth loads We, to which pipe is subjected, are a function of the soil density, pipe diameter, depth of cover, and construction techniques employed in laying the pipeline. They depend on the interplay between the weight of the prism of earth directly over the pipe, called the interior prism, and the frictional shearing forces, plus or minus, transferred to that interior prism by the adjacent outside prisms of Figure 3 Assembly for three-edge, vee-shaped crushing strength test. ASBESTOS-CEMENT TRANSMISSION PIPE 9 earth. The magnitude of earth loads varies with the construction technique employed. There are two major construction techniques normally encountered-- trench and embankment. Another technique, the tunnel condition, is not normally found, but nevertheless has unique design methods that make its inclusion in this discussion necessary. Figure 4 shows these three construction techniques. 3.2.1 Marston's equation. For asbestos-cement transmission pipe design, earth loads are calculated by the general form of Marston's equation We = CweBd2 (Eq 3) NOTE: Density as used in this equation and the following equations actually refers to force exerted per unit volume (pounds per cubic foot or kilonewtons per metre) under the acceleration of gravity, rather than mass per unit volume. Where true density is known in pounds per cubic foot, that value should be used in equa tions using US customary units; where true density is known in kilograms per cubic metre, it must be converted to newtons per cubic metre by multiplying times 9.8062 (g, the acceleration of gravity) before the value is used in equations using SI units. Figure 4 Classification of construction techniques. 10 AWWA C403-89 Soil densities we range in value from 100 to 135 lb/ft3 (16 to 21 kN/m3). In the qq absence of actual site information, a value of 120 lb/ft (19 kN/m ) is recommended for asbestos-cement transmission pipe design. 3.2.1.1 C is a coefficient that is dependent on the following: 1. Ratio of the height of fill to the width of trench or pipe diameter. 2. Shearing forces between the interior and adjacent earth prisms. 3. Direction and amount of relative settlement between interior and adjacent earth prisms for embankment conditions. The calculations used to find the value of the coefficient will depend on the installation conditions employed in laying the pipe. 3.2.1.2 Values for Bd and C must be determined to calculate earth loads by Eq 3 for the trench, embankment, and tunnel construction techniques. The following subsections describe the different conditions and explain the methods for finding the values needed to use Marston's equation for soil loading. 3.2.2 Trench condition. A trench condition is defined as that in which the pipe is installed in a narrow trench, generally less than two to three diameters in width, cut in undisturbed ground, and backfilled to the original ground surface, as illustrated in Figure 4. For this condition, Eq 3 is rewritten as: We = CdWeBd2 (Eq 4) 3.2.2.1 The values of Cd are obtained from Figure 5, in which curves A, B, C, D, and E take into account the friction coefficient between the backfill and the sides of the trench for the various soil compositions likely to be encountered. Curve A is for granular materials without cohesion. Curve B is for sand and gravel. Curve C is for saturated top soil. Curve D is for clay. Curve E is for saturated clay. Table 1 (pages 12-16) contains a series of earth-load selection tables. 3.2.3 Embankment condition. An embankment condition is defined as either that condition where the pipe is installed in a trench that is wider than two to three pipe diameters and that is cut in undisturbed ground, or that condition where the pipe is covered with fill above the original ground surface. Embankment conditions are further subdivided into positive and negative projecting pipe categories, depend ing on the location of the top of the pipe relative to the original undisturbed ground. A special case where compressible material is used as part of the backfill, called an imperfect trench, is also classified as an embankment condition. The various embankment conditions are illustrated in Figures 4 and 6. 3.2.4 Positive projecting pipe condition. A positive projecting pipe condition is defined as either that condition where the pipe is installed in a trench cut in undis turbed ground that is wider than two to three pipe diameters, or that condition where the top of the pipe is above the adjacent original ground surface and covered with fill above the original ground surface. For this condition, Eq 3 is rewritten as We = CcWeBc2 (Eq 5) 3.2.4.1 The values of Cc are obtained from Figure 7 (page 17). Cc may also be obtained from Eq 6 when the following conditions exist simultaneously: 1. The ratio H/Bc is greater than 1.3. 2. The product p(rsd) = 0.7. Cc = 1.892H/Bc - 0.96 (Eq 6) ASBESTOS-CEMENT TRANSMISSION PIPE 11 1.0 1.5 2.0 3.0 4.0 5.0 2 1.5 1.0 0.9 0.8 0.7 0.6 ft; Icq3 0-5 l > 0.4 0.3 0.2 0.15 0.10 0.15 0.20 0.25 0.30 0.40 0.50 0.6 0.7 0.8 0.91.0 Values of coefficient or C, 0.1 1.5 Reprinted with permission from ASCE Manual 37, Design and Construction of Sanitary and Storm Sewers (1976). Figure 5 Values of Cd for trench conditions. 3.2.5 Transition width. It will be noted from the preceding discussion that under construction conditions where a trench is cut in undisturbed ground, the fol lowing two methods of computing the earth load are available: (1) the trench condition and (2) the positive projecting pipe embankment condition. The method chosen is dependent on the ratio of the trench width to the pipe diameter. As pre viously stated, when the trench width is less than two to three times the pipe diameter, earth loads are computed by the trench condition equation (Eq 4). The width of trench at which both methods of computation give equal loads is called the 12 AWWA C403-89 Table 1 Earth Loads (Ibllinft) Trench Cover ft 2 2.5 3 4 5 6 7 8 9 10 12 14 16 18 20 2.5 490 640 810 1000 1200 1350 1500 1600 1725 1850 2050 2200 2300 2400 2500 Pipe size 18 in. ID Trench Width--ft 2.75 3.0 3.25 3.5 4.0 4.5 5.0 5.5 640 835 1110 1320 1520 1690 1850 2000 2120 2360 2570 2720 2840 3000 1240 1450 1700 1900 2100 2250 2400 2675 2900 3100 3275 3400 1610 1865 2090 2320 2510 2725 3020 3280 3515 3720 3995 1640 2050 2300 2525 2750 2950 3300 3600 3900 4150 4350 2825 3230 3550 4000 4400 4800 5100 5350 3635 4440 5220 5640 6040 6400 6040 6830 7450 7620 Transition Width 2 ft 5 in. 2 ft 8 in. 2 ft 10 in. 3 ft 1 in. 3 ft 5 in. 3 ft 8 in. 3 ft 10 in. 4 ft 0 in. 4 ft 1 in. 4 ft 3 in. 4 ft 5 in. 4 ft 7 in. 4 ft 9 in. 5 ft 0 in. 5 ft 2 in. Trench Cover ft 2 2.5 3 4 5 6 7 8 9 10 12 14 16 18 20 2.75 545 705 870 1110 1320 1520 1690 1850 2000 2120 2380 2570 2720 2840 3000 3.0 890 1250 1450 1700 1900 2100 2250 2400 2675 2900 3100 3275 3400 3.25 1330 1610 1865 2090 2320 2510 2725 3020 3280 3515 3720 3995 Pipe size 20 in. ID Trench Width--ft -------------------------------------------------------------------------- 3.5 3.75 4.0 4.5 5.0 5.5 1750 2050 2300 2525 2750 2950 3300 3600 3900 4150 4350 1770 2210 2515 2765 3040 3240 3660 4050 4350 4620 4860 2220 2655 3000 3300 3650 4000 4400 4800 5100 5350 3095 3545 3980 4660 5200 5640 6040 6400 4310 5760 6450 7060 7450 6640 7500 8410 Transition Width 2 ft 8 in. 2 ft 10 in. 3 ft 0 in. 3 ft 4 in. 3 ft 8 in. 3 ft 11 in. 4 ft 1 in. 4 ft 3 in. 4 ft 5 in. 4 ft 6 in. 4 ft 10 in. 5 ft 1 in. 5 ft 2 in. 5 ft 4 in. 5 ft 7 in. Trench Cover ft 2.75 2 570 2.5 745 3 870 4 1110 5 1320 3.0 730 915 1250 1450 3.25 1330 1610 Pipe size 21 in. ID Trench Width--ft 3.5 3.75 4.0 4.5 1380 1750 1360 5.0 Transition 5.5 6.0 Width 2 ft 9 in. 2 ft 11 in. 3 ft 2 in. 3 ft 6 in. 3 ft 10 in. Table continued, next page ASBESTOS-CEMENT TRANSMISSION PIPE 13 Table 1 (continued) Pipe size 21 in. ID Trench Trench Width--ft Cover ------------------------------------------------------------------------------------------------------------------------------------------- ft 2.75 3.0 3.25 3.5 3.75 4.0 4.5 5.0 5.5 6.0 6 1520 1700 1865 2050 2210 2325 7 1690 1900 2090 2300 2515 2700 2795 8 1850 2100 2320 2525 2765 3000 3250 9 2000 2250 2510 2750 3040 3300 3725 10 2120 2400 2725 2950 3240 3550 4140 4210 12 2360 2675 3020 3300 3660 4000 4660 5160 14 2570 2900 3280 3600 4050 4400 5200 6000 6100 16 2720 3100 3515 3900 4350 4800 5540 6450 7020 18 2340 3275 3720 4150 4620 5100 6040 7050 7950 20 3000 3400 3995 4350 4880 5350 6400 7450 8460 8920 Transition Width 4 ft 1 in. 4 ft 4 in. 4 ft 6 in. 4 ft 7 in. 4 ft 9 in. 5 ft 0 in. 5 ft 3 in. 5 ft 5 in. 5 ft 6 in. 5 ft 8 in. Pipe size 24 in. ID Trench Trench Width--ft Cover -------------------------------------------------------------------------------------------------------------------------------------------- ft 3.0 3.25 3.5 3.75 4.0 4.5 5.0 . 5.5 6.0 6.5 2 2.5 3 4 5 6 7 8 9 10 12 14 16 18 20 630 805 955 1250 1450 1700 1900 2100 2250 2400 2675 2900 3100 3275 3400 810 1010 1330 1610 1865 2090 2320 2510 2725 3020 3280 3515 3720 3995 1010 1400 1750 2050 2300 2525 2750 2950 3300 3600 3900 4150 4350 1490 1940 2210 2515 2765 3040 3240 3660 4050 4350 4620 4860 2030 2400 2700 3000 3300 3550 4000 4400 4800 5100 5350 2550 3080 3480 3790 4140 4660 5200 5640 6040 6400 3620 4130 4660 5400 6000 6450 7050 7450 4660 5740 6750 7410 8000 8460 6800 7850 8910 9600 10,000 Transition Width 3 ft 1 in. 3 ft 3 in. 3 ft 5 in. 3 ft 9 in. 4 ft 1 in. 4 ft 5 in. 4 ft 8 in. 4 ft 10 in. 5 ft 0 in. 5 ft 2 in. 5 ft 5 in. 5 ft 8 in. 5 ft 11 in. 6 ft 1 in. 6 ft 2 in. Pipe size 27 in. ID Trench Cover Trench Width--ft ft 3.25 3.5 3.75 4.0 4.5 5.0 5.5 6.0 Transition 6.5 7.0 Width 2 2.5 3 4 5 6 7 8 9 10 710 895 1040 1330 1610 1865 2090 2320 2510 2725 905 1095 1400 1750 2050 2300 2525 2750 2950 1540 1940 2210 2515 2765 3040 3240 1600 2050 2400 2700 3000 3300 3550 2200 2735 3110 3480 3790 4140 3385 3900 4300 4700 3980 4590 5190 3 ft 5 in. 3 ft 6 in. 3 ft 8 in. 4 ft 1 in. 4 ft 6 in. 4 ft 8 in. 5 ft 1 in. 5 ft 3 in. 5 ft 6 in. 5 ft 7 in. Note: Values are for clay (part D of Figure 5, k\x = k\T = 0.130) with weight of earth taken as 120 lb/fl3 (1922 k/m3). Correction for other earth weights may be made by simple direct proportions. For corrections of other types of soils, refer to formulas in Sec. 3. Boldface figures indicate maximum earth load for depth of trench. To obtain earth loads in kilonewtons per metre, multiply by 0.014594. Table continued next page 14 AWWA C403-89 Table 1 (continued) Pipe size 27 in. ID Trench Trench Width--ft Cover -------------------------------------------------------------------------------------------------------------------------------------- ft 3.25 3.5 3.75 4.0 4.5 5.0 5.5 6.0 6.5 7.0 12 3020 3300 3660 4000 4660 5400 6060 6390 14 3280 3600 4050 4400 5200 6000 6750 7550 7560 16 3515 3900 4350 4800 5840 6450 7410 8300 8800 18 3720 4150 4620 5100 6040 7050 8000 9000 9960 10,000 20 3995 4350 4860 5350 6400 7450 8460 9600 10,890 11,180 Transition Width 6 ft 0 in. 6 ft 3 in. 6 ft 6 in. 6 ft 8 in. 6 ft 10 in. Trench Cover ft 2 2.5 3 4 5 6 7 8 9 10 12 14 16 18 20 Pipe size 30 in. ID Trench Width--ft --------------------------------------------------------------------------------------------------------------------------------- 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 755 965 1150 1400 1750 2050 2300 2525 2750 2950 3300 3600 3900 4150 4350 1185 1675 2050 2400 2700 3000 3300 3550 4000 4400 4800 5100 5350 1680 2335 2800 3110 3480 3790 4140 4660 5200 5640 6040 6400 2340 3005 3500 3900 4300 4700 5400 6000 6450 7050 7450 3665 4320 4840 5260 6060 6750 7410 8000 8460 4980 5660 6800 7550 8300 9000 9600 6990 8320 9210 9960 10,890 8320 9610 10,980 11,890 10,980 12,300 Transition Width 3 ft 7 in. 3 ft 10 in. 3 ft 11 in. 4 ft 5 in. 4 ft 8 in. 5 ft 0 in. 5 ft 5 in. 5 ft 7 in. 5 ft 10 in. 6 ft 1 in. 6 ft 5 in. 6 ft 9 in. 7 ft 0 in. 7 ft 3 in. 7 ft 5 in. Trench ft 3.75 2 2.5 3 4 5 6 7 8 9 10 12 14 16 18 20 810 1050 1220 1540 1940 2210 2515 2705 3040 3240 3660 4050 4350 4620 4860 4.0 1060 1290 1675 2050 2400 3000 3300 3550 4000 4400 4800 5100 5350 5575 4.5 1815 2335 2800 3110 3480 3790 4140 4660 5200 5640 6040 6400 5.0 2445 3050 3500 3900 4300 4700 5400 6000 6450 7050 7450 Pipe size 33 in. ID Trench Width--ft 5.5 6.0 6.5 7.0 Transition 7.5 8.0 Width 3205 3920 4460 4840 5260 6060 6750 7410 8000 8460 3925 4640 5400 5260 6800 7550 8300 9000 9600 5610 6070 7450 8350 9210 9960 10,890 7550 9030 10,110 11,060 11,890 10,470 12,120 13,020 13,390 3 ft 10 in. 4 ft 1 in. 4 ft 3 in. 4 ft 6 in. 5 ft 1 in. 5 ft 5 in. 5 ft 8 in. 6 ft 1 in. 6 ft 3 in. 6 ft 5 in. 6 ft 10 in. 7 ft 2 in. 7 ft 5 in. 7 ft 9 in. 7 ft 11 in. Table continued next page ASBESTOS-CEMENT TRANSMISSION PIPE 15 Table 1 (continued) Trench Cover ft 4.0 2 2.5 3 4 5 6 7 8 9 10 12 14 16 18 20 920 1130 1325 1675 2050 2400 2700 3000 3300 3550 4000 4400 4800 5100 5350 4.5 925 1145 1550 1950 2335 2800 3110 3480 3790 4140 4660 5200 5640 6040 6400 5.0 1950 2555 3050 3500 3900 4300 4700 5400 6000 6450 7050 7450 Pipe size 36 in. ID Trench Width--ft 5.5 6.0 6.5 7.0 7.5 8.0 8.5 2555 3340 3920 4460 4840 5260 6060 6750 7410 8000 8460 3340 4160 4900 5400 5900 6800 7550 8300 9000 9600 4950 5760 6430 7450 8350 9210 9960 10,890 5760 6540 8150 9170 10,110 11,060 11,890 8150 9750 11,000 12,150 13,020 9750 11,330 12,900 14,140 12,900 14,510 Transition Width 4 ft 3 in. 4 ft 4 in. 4 ft 7 in. 4 ft 11 in. 5 ft 3 in. 5 ft 8 in. 6 ft 0 in. 6 ft 2 in. 6 ft 8 in. 6 ft 10 in. 7 ft 4 in. 7 ft 8 in. 7 ft 11 in. 8 ft 2 in. 8 ft 6 in. Trench Cover ft 4.5 2 2.5 3 4 5 6 7 8 9 10 12 14 16 18 20 990 1290 1520 1950 2335 2800 3110 3480 3790 4140 4660 5200 5640 6040 6400 5.0 1580 2220 2555 3050 3500 3900 4300 4700 5400 6000 6450 7050 7450 5.5 2340 2980 3340 3920 4460 4840 5260 6060 6750 7410 8000 8460 Pipe size 39 in. ID Trench Width-ft 6.0 6.5 7.0 7.5 8.0 8.5 9.0 3680 4320 4900 5400 5900 6800 7550 8300 9000 9600 4500 5360 5760 6430 7450 8350 9210 9960 10,890 6430 7170 8150 9170 10,110 11,060 11,890 7440 8980 9750 11,000 12,150 13,021 9310 11,090 11,980 12,900 14,140 12,830 14,330 15,260 16,130 Transition Width 4 ft 5 in. 4 ft 7 in. 4 ft 9 in. 5 ft 2 in. 5 ft 6 in. 5 ft 10 in. 6 ft 3 in. 6 ft 7 in. 6 ft 11 in. 7 ft 3 in. 7 ft 8 in. 8 ft 1 in. 8 ft 5 in. 8 ft 8 in. 8 ft 11 in. Trench Pipe size 42 in. ID Trench Width-ft ft 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 Width 2 1060 2.5 1390 3 1700 4 2220 5 2555 2350 3080 4 ft 8 in. 4 ft 10 in. 5 ft 0 in. 5 ft 4 in. 5 ft 8 in. Note: Values are for clay (part D of Figure 5, k\i = k\i' = 0.130) with weight of earth taken as 120 lb/ft3 (1922 k/m3). Correction for other earth weights may be made by simple direct proportions. For corrections of other types of soils, refer to formulas in Sec. 3. Boldface figures indicate maximum earth load for depth of trench. To obtain earth loads in kilonewtons per metre, multiply by 0.014594. Table continued next page 16 AWWA C403-89 Table 1 (continued) Pipe size 42 in. ID Trench Trench Width--ft Cover -------------------------------------------------------------------------------------------------------------------------------------------- ft 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 Transition Width 6 3050 3340 3930 6 ft 1 in. 7 3500 3920 4320 4690 6 ft 5 in. 8 3900 4460 4900 5600 6 ft 10 in. 9 4300 4840 5400 5760 6630 7 ft 2 in. 10 4700 5260 5900 6430 7170 7730 7 ft 6 in. 12 5400 6060 6800 7450 8150 8980 9830 8 ft 0 in. 14 6000 6750 7550 8350 9170 9750 10,940 11,550 8 ft 5 in. 16 6450 7410 8300 9210 10,110 11,000 11,980 13,580 8 ft 10 in. 18 7050 8000 9000 9960 11,060 12,150 12,900 14,390 15,250 9 ft 1 in. 20 7450 8460 9600 10,880 11,890 13,020 14,140 15,260 16,430 16,830 9 ft 4 in. Note: Values are for clay (part D of Figure 5, k\i. = k\i' = 0.130) with weight of earth taken as 120 lb/ft3 (1922 k/m3). Correction for other earth weights may be made by simple direct proportions. For corrections of other types of soils, refer to formulas in Sec. 3. Boldface figures indicate maximum earth load for depth of trench. To obtain earth loads in kilonewtons per metre, multiply by 0.014594. transition width. The earth load computed at the transition width is theoretically the maximum external earth load that can be transmitted to the pipe for any given depth of cover. For all trench widths greater than the transition width, earth loads are computed by the positive projecting pipe embankment condition equation (Eq 5). In this latter case and for a given depth of cover, the earth loads are equal to the load that results at the transition width and that is computed by the trench condi tion equation (Eq 4) (see Figure 6). 3.2.5.1 The transition width is determined from Figure 8 (page 18) by multi plying the applicable ratio Bd/Bc by the applicable pipe outside diameter Bc. The applicable ratio of trench width to pipe outside diameter Bd/Bc can be obtained from Figure 8 for any given ratio of backfill height to pipe outside diameter H/Bc. 3.2.6 Negative projecting pipe embankment condition. A negative projecting pipe condition is defined as that condition where the pipe is installed in a relatively shallow trench wherein the top of the pipe is at some elevation below the original ground surface. The trench is then backfilled and compacted, and embankment is constructed thereon to finished grade (Figure 4). For this condition, Eq 3 is rewritten as We = CnWeBd2 (Eq 7) 3.2.6.1 The various values of Cn are obtained from Figure 9 (page 19). The projection ratio p is defined as the ratio of the vertical distance from the original ground surface down to the pipe top to the trench width Bd (Figure 10B [page 19]). For asbestos-cement pipe design, the recommended value for the settlement ratio rsd is zero. 3.2.6.2 When calculating earth loads under negative projecting pipe embank ment conditions, consideration must be given to the transition width as defined in Sec. 3.2.5. For values of the ratio Bd/Bc less than those given in Figure 8, the load on a pipe is determined from Eq 7 for negative projecting pipes. However, as the ASBESTOS-CEMENT TRANSMISSION PIPE 17 aa and bb: The trench width is less than the transition width; earth loads are computed by the trench equation (Eq 4). cc: The trench width is the transition width; earth loads are computed by either Eq 4 or Eq 5. dd and ee: The trench width is greater than the transition width; earth loads are computed by the positive projecting pipe embankment equation (Eq 5). For a given depth of cover the earth loads resulting from trench widths cc, dd, and ee are equal. Figure 6 Embankment conditions. Figure 7 Values of Cc for positive projecting pipe. 18 AWWA C403-89 trench width increases and the ratio Bd/Bc becomes greater than that given in Fig ure 8, the earth load should be determined from Eq 5 for positive projecting pipes. Adherence to the preceding rule will result in the most realistic earth loads for design purposes. 3.2.7 Imperfect trench condition. The imperfect trench condition occurs rather infrequently and is included for general information. The imperfect trench embank ment condition refers to that construction technique wherein the pipe is first installed as a positive projecting pipe. A portion of the embankment is then built up to some elevation above the pipe top and thoroughly compacted as it is placed. A trench the same width as the pipe is then excavated directly over the pipe down to or near to its top and subsequently backfilled with loose compressible material. The remainder of the embankment is then built up to final elevation (Figure 11 [page 21]). For this condition, Eq 3 is rewritten as We = CnWeBc2 (Eq 8) 3.2.7.1 The various values of Cn are obtained from Figure 9. The projection ratio p is defined as the ratio of the vertical distance from the top of the excavated trench down to the pipe top to the pipe diameter (Figure 11). For asbestos-cement pipe design the recommended value for the settlement ratio rsd is equal to --0.3. k = k' = 0.130 k = 0.1924 *// = 0.130 Shaded section to enlarged scale 1 2 34 5 Ratio c !a> ibi Reprinted with permission from ASCE, Manual 37, Design and Construction of Sanitary and Storm Sewers (1976). Figure 8 Values of Bd/Bc at which the trench and positive projecting pipe equations give equal loads. ASBESTOS-CEMENT TRANSMISSION PIPE 19 Coefficient Cn Reprinted with permission from ASCE, Manual 37, Design and Construction of Sanitary and Storm Sewers (1976). Figure 9 Values of Cn for negative projecting pipe and imperfect ditch conditions. Figure 10a Positive projecting pipe projection ratio = x/Bc; Figure 10b Negative projecting pipe projection ratio = x/Bd. 20 AWWA C403-89 3.2.8 Tunnel conditions. There are two types of tunnel construction encountered in normal pipe laying operation. 3.2.8.I. The first type is the most frequently encountered and occurs when a sleeve of a larger diameter than the specified pipe is first jacked through an embankment. The pipe is then placed into the sleeve without becoming an integral part of the tunnel construction. In this example, the sleeve supports the entire earth load, and the pipe contained therein is not subjected to crushing loads. When select ing the required pipe classification for this condition, only the internal pressure needs to be considered for design. 3.2.8.2 The second type of tunnel condition is rarely encountered in distribu tion pipe work, but is discussed here for completeness. It occurs when the pipe itself must carry the entire load. The area through which the pipeline must pass is bored and braced with the necessary supports. The pipe is then placed in the tunnel, and the void between the pipe and tunnel braces is backfilled with compacted earth, grout, or concrete. Once this operation is completed, the earth load automatically transfers from the tunnel supports to the pipe itself. For this condition, Eq 3 is rewritten as We = CTBT(.weBT - 2c) (Eq 9) 3.2.8.3 Values of Ct for different types of soil are obtained from Figure 12 (page 22). If the value for the coefficient of cohesion is not available from laboratory tests, then the recommended safe design values in Table 2 are to be used. 3.2.8.4 In tunnel construction, when the excavation becomes excessive, or when the void surrounding the pipe or tunnel lining is not carefully filled, or when the cohesion of the undisturbed material above the tunnel construction is destroyed by soil saturation or vibration, the earth load should be calculated by Eq 4 for trench conditions. Since it can be exceedingly difficult to either predict or assess whether the tunnel excavation is excessive, it is recommended that Eq 4 be used for most installations for safe asbestos-cement pipe design. 3.2.8.5 It should be noted that the preceding discussion is based on the premise that the tunnel would be constructed in homogenous soils that do not create unusual pressures and stresses. The tunnel construction method described in Sec. 3.2.8.2 (unsleeved tunnels) should not be used through materials that tend to squeeze or swell, such as some types of clay or shale, or through blocky and seamy rock. Under these conditions, the construction method described in Sec. 3.2.8.1 is recommended. Table 2 Recommended Safe Design Values of c for Tunnel Conditions Materials Clay, very soft Clay, medium Clay, hard Sand, loose dry Sand, silty Sand, dense Top soil, saturated Values of c Ib/ft2 (kN/m2) 40 250 1000 0 100 300 100 (1.63) (10.19) (40.77) (0) (4.007) (12.23) (4.007) ASBESTOS-CEMENT TRANSMISSION PIPE 21 Projection ratio = -- W] -* AV f X '' Top of embankment / - . . Compressible backfill O / -w_ ^ C /^ VYVXXXXXX Top of stage construction compacted fill / ------------Trench dug in compacted fill rs Natural ground 1 1 Figure 11 Projection ratio p' for the imperfect trench embankment condition. Sec. 3.3 Superimposed Loads Superimposed loads Ws are external loads other than the normal earth loads transmitted to the pipe. There are two types of superimposed loads as illustrated in Figure 13 (page 24): (1) concentrated Ws! and (2) distributed Ws2. Superimposed loads are frequently referred to as live loads. 3.3.1 Concentrated load. A concentrated load is a load caused by a single force, which may be either static or dynamic in nature. In normal pipe design, vehicular wheel loads are the most frequently encountered concentrated loads. The magnitude of the load produced by concentrated superimposed forces is determined by Wsc = CsFcF L (Eq 10) See Tables 3, 4, and 5 (page 23). 3.3.2 Distributed load. A distributed load is a load caused by a uniform force distributed equally over a given area. The load may be either static or dynamic in nature. The magnitude of the load produced by distributed forces is determined by Wsd -- CsPdFBc (Eq 11) 22 AWWA C403-89 0 1 2 345 Values of coefficient CT Reprinted with permission from ASCE, Manual 37, Design and Construction of Sanitary and Storm Sewers (1976). Figure 12 Values of Ct for tunnel conditions. Table 3 Impact Factors F Depth of Cover ft(m) 1.0-2.0 (0.3-0.6) 2.0-3.0 (0.6-1.0) 3.0 or greater (1.0 or greater) ASBESTOS-CEMENT TRANSMISSION PIPE 23 Impact Factor F 1.2 1.1 1.0 Table 4 Values of Load Coefficients Cs for Concentrated Superimposed Loads Centered Vertically Over Conduit* Depth of Cover ft (m) Pipe Size ID in. (mm) 2 (0.6) 2V2 3 4 5 6 8 10 12 16 20 (0.76) (0.91) (1.21) (1.52) (1.83) (2.44) (3.05) (3.66) (4.89) (6.09) 18 (450) 20 (500) 21 (525) 24 (600) 27 (675) 30 (750) 33 (825) 36 (900) 39 (975) 42 (1050) 0.391 0.422 0.436 0.478 0.510 0.543 0.563 0.590 0.615 0.619 0.289 0.316 0.327 0.362 0.392 0.423 0.446 0.470 0.502 0.506 0.221 0.241 0.251 0.280 0.306 0.332 0.353 0.375 0.404 0.422 0.136 0.150 0.157 0.177 0.195 0.213 0.230 0.248 0.272 0.286 0.092 0.102 0.107 0.120 0.133 0.147 0.159 0.171 0.191 0.202 0.066 0.073 0.077 0.087 0.096 0.106 0.115 0.124 0.140 0.147 0.038 0.042 0.044 0.050 0.056 0.062 0.067 0.073 0.083 0.089 0.025 0.027 0.029 0.033 0.037 0.041 0.045 0.049 0.054 0.063 0.017 0.019 0.020 0.022 0.025 0.029 0.032 0.035 0.041 0.043 0.010 0.011 0.012 0.013 0.014 0.016 0.018 0.020 0.026 0.030 0.006 0.007 0.007 0.008 0.008 0.010 0.011 0.012 0.015 0.017 *For convenience, concentrated superimposed loads resulting from a 16,000-lb (7250-kg) wheel force are presented in Table 5. Table 5 Concentrated Superimposed Wheel Load L (Measured in Ib/ft [kN/m]) on AsbestosCement Transmission Pipe--Single Wheel = 16,000 lb (7250 kg) Cover Over Top of Pipe Pipe Diameter m. (mm) ft (m) 18 (450) 20 (500) 21 (525) 24 (600) 27 (675) 30 (750) 33 (875) 36 (900) 39 (975) 42 (1050) 2 (0.61) 2083 (30.4) 2251 (37.2) 2.5 (0.76) 1541 (22.5) 1682 (24.5) 3 (0.91) 1178 (17.2) 1286 (18.7) 4 (1.22) 725 (10.6) 800 (11.7) 5 (1.52) 490 (7.2) 544 (7.9) 6 (1.83) 352 (5.1) 389 (5.7) 8 (2.44) 203 (2.9) 224 (3.3) 10 (3.05) 133 (1.9) 144 (2.1) 12 (3.66) 91 (1.3) 100 (1.5) 16 (4.87) 53 (0.8) 59 (0.8) 20 (6.09) 32 (0.5) 37 (0.5) 2364 (34.5) 2545 (37.1) 1728 (25.2) 1939 (28.3) 1334 (19.5) 1494 (21.9) 837 (12.2) 944 (13.8) 570 (8.3) 640 (9.3) 410 (6.0) 464 (6.8) 234 (3.4) 267 (3.9) 154 (2.2) 176 (2.4) 105 (1.5) 117 (1.7) 64 (0.9) 69 (1.0) 40 (0.6) 43 (0.6) 2720 (39.7) 2091 (30.5) 1632 (23.8) 1040 (15.2) 710 (10.4) 512 (7.5) 299 (4.4) 197 (2.9) 133 (1.9) 75 (1.1) 45 (0.6) 2896 (42.3) 2992 (43.7) 3149 (45.9) 2256 (33.0) 2368 (34.6) 2510 (36.6) 1723 (25.1) 1878 (27.4) 2000 (29.2) 1136 (16.6) 1224 (17.9) 1321 (19.3) 784 (11.4) 845 (12.3) 912 (13.3) 466 (8.3) 611 (8.9) 662 (9.7) 330 (4.8) 357 (5.2) 390 (5.7) 219 (3.2) 240 (3.5) 261 (3.8) 155 (2.3) 170 (2.5) 187 (2.7) 85 (1.2) 96 (1.4) 107 (1.67) 53 (0.8) 60 (0.9) 63 (0.9) 3280 (47.9) 2677 (39.1) 2154 (31.4) 1450 (21.2) 1018 (14.8) 747 (10.9) 443 (6.5) 288 (4.2) 219 (3.2) 139 (2.0) 80 (1.2) 3301 (48.2) 2752 (40.2) 2250 (32.8) 1525 (22.2) 1077 (15.7) 784 (11.4) 475 (6.9) 336 (4.9) 229 (3.3) 160 (2.3) 91 (1.3) 24 AWWA C403-89 Figure 13 Superimposed loads. SECTION 4: HYDROSTATIC PRESSURE Sec. 4.1 Introduction For the design of asbestos-cement transmission pipe, the internal hydrostatic pressure Pt is defined by Pt = (Po + Pa) S.F. (Eq 12) The S.F. is the design safety factor. Safety factors are based on judgment, past experiences, and sound engineering principles. For asbestos-cement transmission pipe, a safety factor of 2 is recommended when surge or water hammer are calcu lated and added to operating pressure. Sec. 4.2 Operating Pressure The operating pressure P0 is the pressure that exists under normal or steady conditions of operation. The pressure may be induced by pumps, gravity (such as the head created by a reservoir or elevated water tank), or a combination of both pumps and gravity. Under a 100 percent gravity situation, the pressure in the line at a given point is somewhat higher when there is no flow and conditions are static. Under static conditions, the pressure at a given point, measured in feet (metres) of head, is equal to the difference between the elevation of that point and the watersurface level at the reservoir. Under flowing conditions, the pressure at a given point is reduced by the amount of friction and other energy losses resulting from the flow of water from the reservoir to that point. The magnitude of this head loss may be found by using the Hazen and Williams chart in appendix A. In piping systems that have long runs with relatively few fittings and accessories, the recommended value of C (coefficient of flow) is 140. ASBESTOS-CEMENT TRANSMISSION PIPE 25 Sec. 4.3 Surge Pressure Surge pressures Ps are of a transient nature and are caused by unsteady or changing conditions in the pipeline. The terms water hammer, surge, or transient pressure are often used interchangeably to refer to these pressures, which are of brief duration but often of considerable magnitude. A variety of conditions may cause surge pressures. These include a valve opening or closing, sudden movement of air in a line, or a pump starting or stopping. Transient pressures in the larger transmission main sizes are less affected by high and uncontrolled surges generated by rapid closing of fire hydrants. For example, a 6-in. (150-mm) hydrant flowing at 6 ft/s (1.8 m/s) could cause a surge in a 6-in. (150-mm) distribution line of more than 270 psi (1860 kPa). At the same flow rate, this change in velocity of 6 ft/s (1.8 m/s) would only change velocity in an 18-in. (450-mm) transmission pipe by 0.7 ft/s (0.2 m/s), with a resultant surge pressure of only 30 psi (207 kPa). The primary cause of surge pressure in transmission mains is the stopping and starting of pumps and opening or closing of line valves. The surge pressures resulting from these opera tions are more readily controlled by design of the system, and the magnitude of the surge is subject to more precise calculation than is possible by the opening and closing of hydrant valves. Appendix B presents a discussion of water hammer and how it may be controlled. SECTION 5: DESIGN CRITERIA AND USE OF PIPE SELECTION CHARTS Sec. 5.1 Combined Loading Curves Extensive testing and application of statistical analyses have shown that the strength characteristics of asbestos-cement pipe conform to the principles of the combined loading theory developed by the late W.J. Schlick. This theory, commonly discussed in terms of the Schlick formula, represented graphically as a parabola, is used as the basis for the design and class selection of asbestos-cement transmission pipe (See Figures 14A-14J [pages 28-37] and Figures 14A(m)-14J(m) [pages 38-47].). 5.1.1 Curve development. The families of selection curves presented in this standard were developed using the Schlick formula, which establishes a functional relationship between external load and internal pressure. The external and internal load intercepts are tabulated in Table 6. These values represent the end points of the combined loading curves; the intermediate points on the curves are computed by use of the Schlick formula. (It should be noted that all values used for P and W represent a conservative interpretation of the test data.) On the curves, each inter mediate point (Wt, Pt) represents a combination of crush loading and internal pressure that the pipe will withstand when the loads are applied simultaneously. Selection curves in Figures 14A--14J and Figures 14A(m)--14J(m) are presented for each size of pipe from 18 in. through 42 in. and 450 mm through 1050 mm. On the graph for each pipe diameter, a combined loading curve is drawn for each strength classification of that pipe size. The vertical axis represents the internal hydrostatic design pressure P and the horizontal axis represents the external vee-shaped bearing crush design load W. Table 6 lists the values of P and W for the strength classifications of each pipe size. The method for pipe selection is outlined in Sec. 5.3. 26 AWWA C403-89 Sec. 5.2 Safety Factors Safety factors are normally applied by the engineer to the computed design values of crush and internal pressure that are to be resisted by the pipe in service. These factors protect against unforeseen loads that may be placed on the line at some time in the future and against other contingencies, such as improper construc tion. It is the engineer's prerogative to select which safety factors should apply to a given system. Considerable field experience as well as extensive laboratory work has yielded a wealth of information on the behavior of asbestos-cement transmission pipe. For this reason, suggestions for minimum safety factors are made in Table 7. Note that, since the combined loading principle is applicable, the safety factors will be applied to both hydro and crush simultaneously. Note also that water hammer and live load, which are both transient load conditions, are considered as acting simultaneously for design purposes. Since the likelihood of both occurring at the same time is minimal, an additional conservative element is introduced into the design. Sec. 5.3 Use of Selection Charts for Economical Design After all loads on the pipe have been computed (operating pressure, water hammer, earth load, and live load), the most economical strength of pipe to meet the service conditions should be selected. The applicable selection procedure using the suggested safety factors is 1. Add operating pressure and water hammer, P0 + Ps (Sec. 4). 2. Add earth load and live load, We + Ws (Sec. 3). Table 6 Design Internal Pressure and Design External Load Intercepts for Use With Selection Curves for Transmission Pipe Class 30 Class 35 Class 40 Class 45 Class 50 Class 60 Class 70 Class 80 Class 90 Pipe Size 300 psi 350 psi 400 psi 450 psi 500 psi (2100 kPa)* (2400 kPa)* (2800 kPa)* (3100 kPa)* (3400 kPa)* 600 psi 700 psi (4100 kPa)* (4800 kPa)* 800 psi (5500 kPa)* 900 psi (6200 kPa)* in. (mm) Iblfl (kNfm) Ibifi (kN/m) Iblfl (kN/m) Ib/fl (kN/m) lb/ft (kN/m) lb/ft (kN/m) lb/ft (kN/m) lb /ft (kN/m) lb/ft (kN/m) 18 (450) 20 (500) 21 (525) 24 (600) 27 (675) 30 (750) 33 (825) 36 (900) 39 (975) 42 (1050 2800 (41) 3100 (45) 3150 (46) 3500 (51) 4400 (64) 4600 (67) 5000 (73) 5300 (77) 5500 (80) 5600 (82) 3300 (48) 3900 (57) 4100 (60) 4500 (66) 5300 (77) 5600 (82) 6000 (87) 6300 (92) 6600 (96) 7200 (105) 4600 (67) 5300 (77) 6000 (87) 6600 (96) 7000 (102) 7800 (114) 8700 (127) 9100 (133) 9500 (139) 10,000 (146) 5700 (83) 6400 (93) 6700 (98) 7500 (109) 8000 (117) 8700 (127) 9600 (140) 10,400 (152) 11,100 (162) 12,600 (184) 7000 (102) 7900 (115) 8000 (117) 9000 (131) 9700 (142) 10,200 (149) 11,200 (163) 12,300 (180) 13,200 (193) 14,300 (209) 9000 (131) 10,000 (146) 10,200 (149) 11,600 (169) 13,200 (193) 14,100 (206) 15,200 (222) 16,800 (245) 18,000 (263) 20,000 (292) 11,500 (168) 12,600 (184) 13,200 (193) 15,700 (229) 17,400 (255) 18,900 (276) 20,500 (299) 22,000 (321) 23,600 (344) 25,200 (368) 14,700 (215) 15,800 (231) 16,800 (245) 20,000 (292) 21,500 (314) 23,600 (344) 25,800 (377) 27,300 (398) 29,400 (429) 31,500 (460) 18,900 (276) 21,000 (306) 22,000 (321) 25,900 (378) 28,300 (413) 32,000 (467) 34,500 (504) 37,800 (552) 40,900 (597) 44,100 (644) *kPa values were! converted from pounds per square inch and rounded to the nearest hundred. Table 7 Minimum Safety Factors for Use With Asbestos-Cement Transmission Pipe Selection Type of Load Operating pressure plus water hammer, combined with earth load plus live load Safety Factor Hydro Crush 2.0 1.5 ASBESTOS-CEMENT TRANSMISSION PIPE 27 3. Enter the combined loading graph for the appropriate pipe diameter. Plot the values from steps 1 and 2 above as one point. When using the left-hand scales, be sure to multiply the operating pressure plus water hammer by the suggested safety factor of 2.0. When using the bottom scale, be sure to multiply the earth load plus live load by the suggested safety factor of 1.5 and then divide it by the bedding factor (Sec. 2.3). 4. The point plotted will lie between the curves for two pipe strengths. Select the higher strength of the two. This represents the most economical selection consis tent with engineering requirements. Sec. 5.4 Discussion AWWA C401-83 is a standard containing information similar to that contained herein, but dealing with smaller diameter pipes. The effect of water hammer generated by the opening and closing of fire hydrants can be of significant mag nitude in small distribution pipe sizes because of the high velocities generated by open-hydrant flow conditions. Furthermore, it is difficult to accurately evaluate the magnitude of these surges; and, if calculated, control through the use of surge tanks or other devices is impractical. Rather than employ a rule-of-thumb allowance for surge based on an assumed velocity change to compensate for undetermined surge pressures, AWWA C401 incorporates a large fixed safety factor for each asbestoscement pressure class. In the larger sizes covered in this standard, the design is based on an evaluation of surge pressure that can be controlled in design. Calcu lated surge pressure is added to operating pressure before a safety factor of 2 is applied. For external loads, AWWA C401 considers only earth loads, and a recom mended safety factor of 2.5 is applied. In this standard, both earth loads and live loads are added before a factor of safety of 1.5 is applied to the combination of these external loads. In summary, design using this standard is based on a more detailed evaluation of the magnitude of surge pressure and live loadings, and safety factors based on this more precise knowledge of actual operating conditions are applied. Sec. 5.5 Illustrative Problem on Pipe Selection Problem. A 24-in. asbestos-cement transmission pipeline is to be installed in a 4-ft wide trench with 5 ft of cover. The operating pressure will be 100 psi. Surge pressures will be limited to a maximum of 50 psi. A 16,000-lb wheel load is to be assumed, with impact factor = 1. Class C bedding will be used. Select the proper strength of pipe to be used with safety factors of 2.0 in hydro (Po + Ps) and 1.5 in crush (We + Ws). Solution. Following the instructions for use of selection charts with safety fac tors as described in Sec. 5.3: 1. Po + Ps = 100 + 50 = 150 psi 2. We + Ws = 2030 + 640 = 2670 lb/ft 3. (Po + Ps) (S.F.) = 150 x 2.0 = 300 psi 4. WE + Ws (S.F.) B.F. (2670) (1.5) 1.5 = 2670 lb/ft 5. Consult the combined loading chart for 24-in. pipe, using the left-hand and bottom scales. Plot the two loads as a single point on the chart. The point falls between T-35 and T-40. Use T-40. 28 AWWA C403-89 <r oH CJ < Ll. >- <</) cr LlI 2 < X o: HLlI < + LlI CxC CO CO LlI tr Cl O I- < CE LaU o CO Q_ Q. :qLlI D CO CO LXJ CL O CO OUJ O h- <HcOaOo: >- 2000 4000 6000 8000 10 000 12 000 14 000 EXTERNAL CRUSH LOAD (VEE-SHAPED BEARING) - W{LB/FT) 16 000 X SAFETY FACTOR < o2r WT = (EARTH LOAD + LIVE LOAD) BEDDING FACTOR LJ2l-I Figure 14a Combined loading curves for 18-in. transmission pipe. ASBESTOS-CEMENT TRANSMISSION PIPE 29 co 2000 4000 6000 8000 10 000 12 000 14 000 16 000 o <o>r- EXTERNAL CRUSH LOAD {VEE-SHAPED BEARING)-W(LB/FT) X SAFETY FACTOR WT = (EARTH LOAD + LIVE LOAD) <zix: BEDDING FACTOR LU Figure 14b Combined loading curves for 20-in. transmission pipe. 30 AWWA C403-89 x o u< li_ < CO cr < x x uj UJ x3 CO CO UJ X CL o z < cr UJ QO_ it CO CL Q_ c3r CO CO U(TJ CL oz CO UQJ CO 0 oXo>- X < Xz UJ 2000 4000 6000 8000 10 000 12 000 14 000 16 000 EXTERNAL CRUSH LOAD (VEE-SHAPED BEARING) - W( LB/FT) WT = (EARTH LOAD + LIVE LOAD) SAFETY FACTOR BEDDING FACTOR Figure 14c Combined loading curves for 21 "in. transmission pipe. ASBESTOS-CEMENT TRANSMISSION PIPE 31 tr oho 2 h>-- UJ U_ <to tr UJ < X cr < + UJ tzr> to to UJ tr Q. O < tr UJ QO. to Q. Q_ UJ tXr CO CO UJ tr o_ o CO UQJ o h<h(O- 0 o to>r- x <z tr z 2000 4000 6000 8000 10 000 12 000 14 000 16 000 EXTERNAL CRUSH LOAD (VEE-SHAPED BEAR ING ) - W(LB/FT) SAFETY FACTOR WT = (EARTH LOAD + LIVE LOAD) BEDDING FACTOR Figure 14d Combined loading curves for 24-in. transmission pipe. 32 AWWA C403-89 cr ojo-- <b_ I>-- Ld Ll. < (Si ce Ld 5 < x CE HLd < Ld ct3oe CO Ld CE CL O 2 f- < CE Ld COL tao CL I Id (C3OE CO LEd CL O CO OId O I- <h- co 2000 4000 6000 8000 10 000 12 000 14 000 16 000 o O>E EXTERNAL CRUSH LOAD (VEE-SHAPED BEARING )-W (LB/FT) X SAFETY FACTOR <2 WT = (EARTH LOAD + LIVE LOAD ' BEDDING FACTOR CE IH2d Figure 14e Combined loading curves for 27-in. transmission pipe. ASBESTOS-CEMENT TRANSMISSION PIPE 33 Figure 14F Combined loading curves for 30-in. transmission pipe. 34 AWWA C403-89 Figure 14g Combined loading curves for 33-in. transmission pipe. ASBESTOS-CEMENT TRANSMISSION PIPE 35 Figure 14h Combined loading curves for 36-in. transmission pipe. 36 AWWA C403-89 cr ooig >H LlI Li. < CO cLlrI 2 < X cr h-LlI < $ + LU cr 3 CO CO LlI cr Q_ O2 H < cr LU QO_ CO 0. LU c3r CO CO LU cr CL C CO 2 in oQX>- 4000 8000 12 000 16.000 20 000 24 000 X EXTERNAL CRUSH LOAD (VEE-SHAPED BEARING)-W(LB/FTJ X SAFETY FACTOR LlI WT DEARTH LOAD + LIVE LOAD) BEDDING FACTOR Figure I4l Combined loading curves for 39-in. transmission pipe. ASBESTOS-CEMENT TRANSMISSION PIPE 37 co>3c-: 4000 8000 12.000 16 000 20 000 24 000 EXTERNAL CRUSH LOAD (VEE - SHAPED BEAR ING)-W(LB / FT) <2 cUH2cJ SAFETY FACTOR WT = (EARTH LOAD + LIVE LOAD) BEDDING FACTOR Figure 14J Combined loading curves for 42-in. transmission pipe. 38 AWWA C403-89 O EXTERNAL CRUSH LOAD (VEE-SHAPED BEAR ING ) - W ( k N / M ET ER ) < SAFETY FACTOR Wt = (EARTH LOAD + LIVE LOAD) 2 GC BEDDING FACTOR UH2J- Figure l4A(m) Combined loading curves for 450-mm transmission pipe. ASBESTOS-CEMENT TRANSMISSION PIPE 39 0 > <C2C UJ 25 50 75 100 125 150 175 200 EXTERNAL CRUSH LOAD (VEE-SHAPED BEAR ING ) - W (kN/METER) SAFETY FACTOR wT = EARTH LOAD + LIVE LOAD) BEDDING FACTOR 225 Figure 14B(m) Combined loading curves for 500-mm transmission pipe. 40 AWWA C403-89 O oor 0 25 50 75 100 125 150 175 200 225 x EXTERNAL CRUSH LOAD (VEE-SHAPED BEARING )-W (k N/METER ) <czr SAFETY FACTOR WT = (EARTH LOAD + LIVE LOAD) BEDDING FACTOR LU Z Figure I4c(m) Combined loading curves for 525-mm transmission pipe. ASBESTOS-CEMENT TRANSMISSION PIPE 41 or 0oi<- u. 1- UJ Ll. < CO 01 UJ < cn UhJ- < + U01J Z) CO CO UJ 01 CL o l- < 01 UJ CL o o CL CL 0O1 CO CO UQCJ CL zo CO UoJ o t<H- C0O o01 0 25 50 75 -100 '25 150 '75 200 225 EXTERNAL CRUSH LOAD (VEE-SHAPED BEARING )-W (k N / METER ) X SAFETY FACTOR < Wn = (EARTH LOAD + LIVE LOAD) er BEDDING FACTOR Figure l4D(m) Combined loading curves for 600-mm transmission pipe. 42 AWWA C403-89 tr oOk <Li_ > < CO cc U2l 2 < X cc UJ k- < + UJ C3C CO CO UccJ CL oz k- < CC UJ COL D Q_ CL I UJ C3C CO CO UJ cc CL O CO UoJ o < CO oco>c 25 5 0 75 100 125 150 175 2 0 0 EXTERNAL CRUSH LOAD (VEE-SHAPED BEAR ING )-W (kN/METER) 225 SAFETY FACTOR WT = (EARTH L0AD-PLIVE LOAD) BEDDING FACTOR Figure l4E(m) Combined loading curves for 675-mm transmission pipe. ASBESTOS-CEMENT TRANSMISSION PIPE 43 cc ohO < >h-- lJ < CO tr 5 < x q: < $ + UJ Ql. CO CO U(TJ CL O <(T UJ QO_ Q CL CL I Uccz>orJ CO UJ tr CL o CO aUJ o oCO 0 25 50 75 100 125 150 175 200 225 oo>-r EXTERNAL CRUSH LOAD (VEE-SHAPED BEARING)- W (k N/METER ) X < 2: WT= (EARTH LOAD-fLIVE LOAD) SAFTY FACTOR, T BEDDING FACTOR cl HUZJ Figure l4F(m) Combined loading curves for 750-mm transmission pipe. 44 AWWA C403-89 Figure l4G(m) Combined loading curves for 825-mm transmission pipe. ASBESTOS-CEMENT TRANSMISSION PIPE 45 Figure l4H(m) Combined loading curves for 900-mm transmission pipe. 46 AWWA C403-89 50 100 150 200 250 300 350 < oz: EXTERNAL CRUSH LOAD(VEE-SHAPED BEARING)W(kN / METER ) Huj Z SAFETY FACTOR Wt = (EARTH LOAD + LIVE LOAD ) BEDDING FACTOR Figure l4l(m) Combined loading curves for 975-mm transmission pipe. ASBESTOS-CEMENT TRANSMISSION PIPE 47 <z <r EXTERNAL CRUSH LOAD(VEE-SHAPED BEARING ) - W (k N/METER) SAFETY FACTOR WT DEARTH LOAD + LIVE LOAD) BEDDING FACTOR Figure I4j(m) Combined loading curves for 1050-mm transmission pipe. APPENDIX A Friction Loss of Head Chart--Coefficient of Flow, C = 140 This appendix is for information only and is not part of C403. Pipe Diam eter, i NOTE: Loss of head values derived from this chart are for coefficient of flow C = 140. They may be converted to loss of head for other coefficients of flow by means of the following multiplying factors: 1.15 forC = 130 1.34 forC = 120 1.57 forC = 110 1.86 forC = 100 2.26 forC = 90 2.83 forC =80 4.82 forC =60 NOTE: Diameters derived from this chart are for coefficient of flow C = 140. These may be converted to diameters for other coefficients of flow by means of the following multiplying factors: 1.033 forC = 130 1.063 forC = 120 1.100 forC = 110 1.142 for C = 100 1.185 forC =90 1.261 forC =80 1.365 forC =60 Derived from the Hazen and Williams formula: V = 1.318 CR0 63S0M Reprinted by permission of the Johns-Manville Corporation. 48 APPENDIX B Surge Pressure Analysis This appendix is for information only and is not a part ofAWWA C403. SECTION B. 1: WATER HAMMER OR SURGE The slowing down or stopping of any moving mass requires a force or forces to counterbalance the kinetic energy that keeps the mass in motion. The faster a mass is decelerated and brought to a halt, the greater the force that is required. Sec. B.1.1 Forces Involved It is somewhat of an oversimplification, but water hammer, or surge, can be defined in these terms: the shutting of a valve or the stopping of a pump causes a moving column of water in the pipeline to slow down and stop. The forces that bring about this deceleration are exerted radially on the moving water column by the pipeline walls. Conversely, the water exerts added pressure on the pipe, and the hoop stresses in the pipe walls thus increase over the normal operating pressure values. The faster the column of water is brought to a halt, the higher these stresses rise. Sec. B.1.2 Rate of Velocity Fluctuation The pipe wall stresses are thus developed by, and increase in direct proportion to, the internal pressure that builds up as the column of water decelerates. The slower the deceleration, the less the pressure builds up and the less the pipe wall stresses increase. Therefore, it is important to the pipe designer to know how to control the rate of velocity fluctuation, since by controlling this rate the magnitude of the pressure variations is controlled during the transitional periods. With such control, the pipe wall stresses during surge can be kept to a predetermined value that will allow an economical installation. Sec. B.1.3 Wave Motion Water, being liquid, will act in a fairly complex manner when undergoing acceleration or deceleration. Pressure waves are set up that move along the pipeline at a rate of 2500-4500 ft/s (760-1370 m/s), the rate depending on the pipe wall material. The waves will continue until they encounter a boundary condition, such as a reservoir, a closed valve, or a change in pipe diameter, at which point they will reflect back in the opposite direction. The wave motion will oscillate back and forth in the pipe until it is dampened out by the friction effects of the pipe walls. Sec. B.1.4 Causes The three major causes of water hammer or surge are as follows: 1. The closing or opening, fully or partially, of a valve in a pipeline system (Sec. B.3). 49 50 AWWA C403-89 2. The starting up or shutting down of a pump (switch or power failure) (Sec. B.4). 3. Entrapped air (Sec. B.7). Sec. B.1.5 Effects Ignoring the effects of surge in the pipeline can lead to difficulties after the line is in operation. Surge can result in damaged equipment and seriously reduced capacity. SECTION B.Z: WATER HAMMER ANALYSIS The elastic wave theory for surge analysis has been empirically established to be correct by many experiments, the first of which were performed as early as 1890. Its application to pipeline problems will yield results that are accurate and that may be relied on for adequate analysis. Sec. B.2.1 Wave Velocity Water hammer pressures are a function of the maximum rate of change of flow. When a valve is closed or a pump stops, a pressure wave is propagated along a pipeline. The velocity of the wave is the same as the velocity of sound in water, modified by physical characteristics of the pipeline; it is given by the following equation: Where: Vs a/I + kd Ee (Eq B.l) a = pressure wave velocity, in feet per second (metres per second) k = modulus of compression of water, 300,000 psi (2070 MPa) d = internal diameter of pipe, in inches (millimetres) E = modulus of elasticity of asbestos-cement pipe, 3,400,000 psi (23,400 MPa) e = wall thickness, in inches (millimetres) Vs = velocity of sound in water, 4660 ft/s (1420 m/s) Sec. B.2.2 Maximum Pressure If the pressure wave is reflected back from a boundary condition, such as a reservoir, and returns to its initial position after the flow in the line is completely stopped, then maximum water hammer pressure for those conditions will result. Stopping of the flow may be effected by closing a valve or by a pump stoppage. The magnitude of that maximum pressure is given by aV h g (Eq B.2) ASBESTOS-CEMENT TRANSMISSION PIPE 51 Where: h V a g = surge pressure, in feet of water (metres of water) = velocity of water in the pipeline during normal conditions, in feet per second (metres per second) = pressure wave velocity, in feet per second (metres per second) = acceleration due to gravity, 32.2 ft/s2 (9.81 m/s2) Sec. B.2.3 Critical Time The longest elapsed time before final flow stoppage that will still permit this maximum pressure to occur is called the critical time; it is simply the total length that the pressure wave travels in one cycle divided by the velocity of the wave. It is given by the following equation: Where: U L a U = ---- (EqB.3) a = the critical time, in seconds = distance within the pipeline that the pressure wave moves before it is reflected back by a boundary condition, in feet (metres) = pressure wave velocity, in feet per second (metres per second) SECTION B.3: VALVE CLOSURE A valve in a water line may be of several different varieties, including gate, cone, and globe valves. When closing a valve, the area of the cross section of the pipeline that is progressively cut off is not generally proportional to the reduction in flow. In Figure B.l, graph 1 presents a plot of stem travel versus flow in the line for three types of valves. Note that the first 30-40 percent of stem travel has little effect on the flow in the pipeline. Sec. B.3.1 Effective Time As stated previously, water hammer pressure is a function of the maximum rate of change of flow. Therefore, if tangents to the curves in Figure B.l are drawn at the fastest rate of change (or steepest slope), the effective time of closure Te is obtained. (See the curves in Figure B.l with tangents plotted and values of Te determined.) This effective time Te is the time that is used in water hammer cal culations. In most cases, it is about one half of the actual valve closing time. This indicates that if the critical time of a certain installed valve is calculated from Eq B.3 and found to be x seconds, then the actual time for complete valve closure that will cause maximum pressure to occur will be approximately 2x seconds. Sec. B.3.2 Relation to Surge Control In the design of a water system, one of the major considerations in the selec tion of a pipe is the design internal pressure that the pipe will be required to carry in service. The design internal pressure is the operating pressure plus the water 52 AWWA C403-89 Time --(Te) = Effective For Full Cut Off Uniformly at Maximum Rate Full Area Gate, W-------- Te = 39,2%Tt--------- ! Reduced Area Globe. H---------------- Te = 51.7% Tt--------------H l-^--Full Area Cone, TE = 48.6% Tt->| Open Percent Time of Valve Stem Travel - Tr Closed 0 10 20 30 40 50 60 70 80 90 100 90 LioL 80 3 70 oc0) 60 0> CL 50 40 30 20 10 0 Reprinted by permission of the Johns-Manville Sales Corporation. Figure B.l Time (Te) = effective for full cut off uniformly at maximum rate. hammer pressure. To keep the water hammer or surge pressures at a controlled level, calculations must be made to determine the valve closure times that will be required to stay within the design pressure level. Sec. B.3.3 Determining Effective Time Figure B.l presents a convenient three-step method for determining effective valve closure times for a given percentage of the maximum pressure (surge pressure when valve is closed in less than the critical time). 1. Determine the pipeline constant K given by: ,, aV K = 2Ogahho---- (EqB.4) Where: K a = pipeline constant = pressure wave velocity, in feet per second (metres per second) ASBESTOS-CEMENT TRANSMISSION PIPE 53 V = velocity of water in the flow line under normal conditions, in feet per second (metres per second) g = acceleration due to gravity, 32.2 ft/s2 (9.81 m/s2) ho = operating pressure in the line under normal conditions, in feet of water (metres of water) 2. Determine the maximum head that might be developed from the surge by employing the formula hmax = aV/g. 3. Determine the percentage of hmax and find the corresponding effective clos ing time shown on the horizontal axis. This is given in units of 2L/a, which represents the critical time for the pipeline. Note that the time determined is the effective closing time; the actual time of valve stem travel is about twice as long. The reason for this is that the first half of the closing of the valve has little effect on the stoppage of the flow. It is the closing of the final half of the valve stem travel that closes off the flow. The second half is the effective closing time. Therefore, two times the effective closing time is the actual time of the valve stem travel. SECTION B.4: PUMPED SYSTEMS In relation to water hammer and surge, the most important elements in a system are pumps, valves, and air entrapment. In a gravity system, only valves and air entrapment have to be considered. Pumps, valves, and air entrapment must be considered in a pumped system. Sec. B.4.1 Complexity The surge analysis of a pumped system is more complex than in a 100 percent gravity system because 1. In a pumped system, the problem begins in the slowing down of the rising water column when the pump is shut off (because of power failure or otherwise). Consideration must be given to the time required for the pump to stop and for the flow to come to a halt. This involves the inertia of the motor and any flywheel in the assembly. Provisions normally should be made for slow opening and closing of pump control valves on pump systems. In a gravity system, the hydraulic problem consists only of stopping the descending water column. 2. In a pumped system, the pipeline profile is usually irregular, with succes sive high and low points and variable slopes. These conditions may give rise to water column separation, causing severe surges and operational troubles. Surges from water column separation do not follow a standard pattern, and they have been measured at many times the calculated values. Sec. B.4.2 Alternative Layouts The design of a pumped system may involve the consideration of alternative layouts to keep surges and the consequent operational difficulties to a minimum. This work should be directed toward reducing the magnitude of surges and toward reducing the risk of water column separation that may be caused by the shutdown of a pump. 54 AWWA C403-89 Sec. B.4.3 Water Column Separation Water column separation can be serious because of the large magnitude of the surges developed when the water column rejoins. It can occur 1. At pump locations at the start of a steep main. 2. When the pressure at a high point falls below atmospheric and air enters the line through air valves that may be located at a high point. 3. When the pressure falls to below the vapor pressure of water. Sec. B.4.4 Entrapped Air Water column separation can cause difficulties not only because of the beforementioned surges set up by the rejoining of the water column, but because of the difficulties in getting air out of the line on subsequent start-up, even with air valves. Entrapped air can cause flow fluctuations and can seriously reduce the capacity of the system. SECTION B.5: METHODS OF CONTROL The two types of surge to be controlled are negative surge and positive surge. The type is determined, of course, by whether the surge pressures developed are below or above the normal static level. Sec. B.5.1 Negative Surges Negative surges in themselves are usually not dangerous, except when they cause water column separation. If this occurs, extremely high positive surges result when the cavity closes, and this frequently causes serious problems. The control of both negative and positive surges should be given consideration. Sec. B.5.2 Surge Control Devices Limiting negative and positive surges is accomplished by several types of surge control devices, as follows: 1. Controlled valves. This is one of the most effective means for controlling positive surges. As explained previously, the rate of opening and closing of a valve can be calculated to allow an acceptable level of surge. 2. Flywheel on pump motor. In the event of a power outage, the inertia of the flywheel will keep the pump running for a period of time, during which it will gradually slow to a stop. This means that the water column in the pipeline will also be brought to a gradual stop, thus reducing the risk of water column separation. 3. Standpipe. This is generally a tank with the surface of the water at atmo spheric pressure. Therefore, it is only practical at low heads. At a pump stoppage and consequent reduced pressure, the reserve of water in the tank flows into the pipe and reduces the risk of water column separation. For positive surge control, the tank provides an outlet for the built-up pressure in the system. 4. Air vessel or surge tank. This is an enclosed vessel containing air and water. It functions similarly to a standpipe, with water reentering the line during negative surge and leaving during positive surge. The major difference is that the air in the vessel is under pressure and much higher heads can be employed in the pipe system. ASBESTOS-CEMENT TRANSMISSION PIPE 55 5. One-way surge tank. This is an adaptation of the surge tank. It contains a check valve that permits water to enter the line during negative surge, but will not permit water to leave during positive surge. Therefore, it is only for control of nega tive surges and is very effective. 6. Reservoir of water. This is similar to the one-way surge tank, but provides some control of positive surge by permitting the slow entrance of water into the reservoir during a positive surge. 7. Suction pipe. This is a bypass around the pump from the suction side. It contains a check valve to prevent backflow into the reservoir. It effectively reduces negative pressure adjacent to the pump. 8. Surge relief valve. This is used for controlling positive and negative surges. The valve opens at a certain pressure and discharges water to relieve a surge--posi tive or negative. It must be carefully designed and controlled to be effective. 9. Nonreturn valve. This is a check, strategically placed in a line, that can bring a small measure of relief to positive pressure. However, unless properly placed, it can lead to higher rather than lower surge. 10. Reversal of pump. At pump stoppage, the column of water reverses itself. If the pump will not run backwards to permit water to flow back through it, then positive surges will be developed by the sudden stopping of the backflowing column of water. The pump should be designed to run reversed without damage to itself. Design of pumps that can run reversed without damage is a significant problem. Other measures may have to be taken. Sec. B.5.3 Economic Considerations From an economic standpoint, it is usually worthwhile to properly evaluate the surge potential in a system under design. The cost of control devices may be balanced against the added strength of pipe, valves, and other equipment that will be needed if surges are not controlled, and the most advantageous conclusion reached. Manufacturers of surge control equipment or consultants in this field should be sought for advice in complex situations. SECTION B.6: SURGE CALCULATION EXAMPLE The following example problem shows the calculation that may be followed to determine valve closing time for the control of surge within prescribed limits. Problem. A 24-in. gravity transmission line is to operate at a pressure of 100 psi. Velocity in the line is to be 5 ft/s. A valve is to be included in the line at a distance of 5000 ft from the reservoir. If positive surge pressure is to be controlled within 50 psi, determine the minimum time for valve closure. Assume that the effective closing time is one half of the actual valve stem travel time. (E for asbestos-cement pipe = 3.4 x 106, wall thickness is 1.5 in., k for water = 3 x 105.) Solution. 1. Determine surge wave velocity a Vs Vl+M Ee 56 AWWA C403-89 4660 a/1 3 x 105 x 24 3.4 x 10b x 1.5 = 3000 ft/s 2. Determine maximum surge pressure if the valve closes within the critical time aV h IT 3000 x 5 32^2 465 ft of water (200 psi) 3. Determine the critical time 2L _ a 2 x 5000 3000 3.33 s 4. Determine constant Kfor use in graph 2 (Figure B.l) aV 2gh0 3000 x 5 2 x 32.2 x 231 ,,, 5. Determine percent of maximum surge pressure that should not be exceeded in the system 50 x 100 = 25% 200 6. Enter graph 2 (Figure B.l) with percent of hmax (25 percent). Go horizon tally to the curves where K = 1.0. Read the effective closing time along the horizontal axis. This value is 2.6 and is given in units of 2L/a s. The effective closing time in seconds would be 2L/a x 2.6 = 3.33 x 2.6 = 8.7 s. The actual valve stem travel time would be twice this amount, or 17.4 s. Therefore, this calculated time (17.4 s) represents the fastest allowable time the valve can be closed to keep the surge pressure below the desired control level of 50 psi. SECTION B.7: AIR IN PIPELINES Air in pipelines can cause serious operational difficulties, including reduction in capacity because of reduced cross-sectional area and fluctuation in flow caused by expanding and contracting air in the line. These fluctuations in flow cause sudden movements of the air from one location to another, followed by slugs of water, and this can cause serious surges. Sec. B.7.1 Entrance of Air Air can enter a pipeline in many ways. It may enter at the intake. Entry may be caused by release of air from water because of temperature and pressure varia tion, or it may be caused by draining the line, or by draining parts of the line during normal shutdown. Negative surges may cause air to enter at air valves. Air should be prevented from entering the line in the first place. This is very important to reduce operational difficulties. Suggested solutions for control are as follows: ASBESTOS-CEMENT TRANSMISSION PIPE 57 1. Intake. Correct design procedures, provide low water-level pump cutoff. 2. Release of air. Air is entrained in the water at intake and its release cannot be prevented. However, the quantities are not large, and provisions for exhausting can be made by means of air valves. There are various types of air valves with different functions, and the selection of the proper type and location for installation is essential. 3. Draining the line. Air cannot be prevented from entering the line on drain ing, of course. Large orifice air valves should be provided for exhausting the air during refilling. Draining and then refilling does not occur often. Therefore, long filling times may be satisfactory. 4. Drainage during shutdown. This can be a serious problem. Open standpipes can be provided for air entry and exhaust. Sweeping air out by using high velocities is another method. 5. Negative surges. The best way to prevent air from entering under these conditions is to design out the possibility of water column separation. Large volumes of air may be involved here and can cause serious problems. Any one of the negative surge control devices described in Sec. B.5.2 will normally be adequate. Sec. B.7.2 Recommendations to Combat Air Entrapment Colorado State University* has conducted studies to determine the effect of air entrapment in pipelines. The result of the studies proved that suddenly released entrapped air, under apparently static conditions, creates a situation similar to that of classic water hammer. Pressures are generated that may be on the order of 15 times the pipeline test pressure. Any pipeline material is seriously affected by this rapid magnitude of load increase. Hydrostatic failure because of defective pipe may, in all probability, be traced to suddenly released entrapped air. The initial filling and testing of a pipeline is often the most critical period of its service life. Recom mendations to combat air entrapment were made as follows: 1. Pipeline should be laid to grade wherever possible. 2. Automatic continual-acting air release valves should be used at all high points. 3. Air should be bled from pipeline slowly. 4. Limit filling velocity in the pipeline to 1 ft/s (0.3 m/s) or less. 5. Use Where: d/D = l/io to l/ioo d = diameter of air release valve D = pipe diameter The results of this study, together with the recommendations, have been found to be most useful to contractors in performing pipeline tests. Such recommendations also have been found to be useful to engineers from the standpoint of designing pipelines to minimize air problems. *Colorado State University, Fort Collins, Colo. APPENDIX C Frictional Power Requirements This appendix is for information only and is not a part ofAWWA C403. The chart shown in Figure C.l permits rapid calculations of the yearly power costs to overcome friction loss of head. This chart is based on continuous pumping operation (24 hours per day and 365 days per year), a power cost of $0.01 per kW-h, and a motor-pump efficiency of 100 percent. For actual operating conditions and local power costs, appropriate factors must be applied to the values shown in the chart. By calculating power costs to overcome friction in two pipe sizes or for two different types of pipe having different flow coefficients, an annual power cost savings can be determined. Economic justification for going to a larger pipe diameter with lower annual power costs can be determined by establishing the present worth of the annual savings using Table C.l (pages 60-65), which is based on the dis counted cash flow method. If the present worth of the annual savings based on established interest rates exceeds the added costs for the installation of a different size or type of material, then economic justification exists for the added capital expenditure. Nomograph values for Figure C.l are based on the following: 1. Cost per 1000 ft of pipe per year, in dollars. 2. Power cost = $0.01 per kW-h. 3. Motor-pump efficiency (combined) = 100 percent. 4. Friction coefficient C = 140. 5. Continuous operation. NOTE: Yearly power cost values derived in Figure C.l are for coefficient of flow C = 140. They may be converted to yearly power cost values for other coefficients of flow by means of the following multiplying factors: 1.15 for C = 130 1.34 for C = 120 1.57 for C = 110 1.86 for C = 100 2.26 for C = 90 2.83 for C = 80 4.82 for C = 60 Diameters derived from Figure C.l are for coefficient of flow C = 140. These may be converted to other diameters for other coefficients of flow by means of the following multiplying factors: 1.033 for C = 130 1.063 for C = 120 1.100 for C = 110 1.142 for C = 100 1.185 for C = 90 1.261 for C = 80 1.365 for C = 60 58 ASBESTOS-CEMENT DISTRIBUTION PIPE 59 Figure C. 1 Yearly power cost to compensate for friction loss of head. 60 AWWA C403-89 Apply the following formula to Table C.l: (Vr)N- 1 rfl + r)^ Where: r = rate of yield in percent N = number of years from present Example: When using a 10 percent rate of yield, an income of $1.00 occurring each year for the next 5 years has a present worth of $3,791; for the next 7 years, $4,868; for the next 10 years, $6,145; and so forth. The present worth (PW) of a regular pattern of savings in the future is found as follows: Total years of operation--25 Amount of annual savings--$5000.00 PW factor at 10 percent--9.077 Total PW--$45,385.00 When expenditure, cash income, and life are known, and income is the same each year, the PW factor can be computed by dividing expenditure by annual cash income. Yield can then be determined by looking for the factor on the line or known life in Table C.l. Table C. 1 Present Worth of an Income of $1.00 per Year for the Next N Years Years 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 .5% .995 1.985 2.970 3.950 4.926 5.896 6.862 7.823 8.779 9.730 10.68 11.62 12.56 13.49 14.42 15.34 16.26 17.17 18.08 18.99 1.0% .990 1.970 2.941 3.902 4.853 5.795 6.728 7.652 8.566 9.471 10.37 11.26 12.13 13.00 13.87 14.72 15.56 16.40 17.23 18.05 1.5% .985 1.956 2.912 3.854 4.783 5.697 6.598 7.486 8.361 9.222 10.07 10.91 11.73 12.54 13.34 14.13 14.91 15.67 16.43 17.17 2.0% 2.5% .980 1.942 2.884 3.808 4.713 5.601 6.472 7.325 8.162 8.983 9.787 10.58 11.35 12.11 12.85 13.58 14.29 14.99 15.68 16.35 . .976 1.927 2.856 3.762 4.646 5.508 6.349 7.170 7.971 8.752 9.514 10.26 10.98 11.69 12.38 13.06 13.71 14.35 14.98 15.59 3.0% .971 1.913 2.829 3.717 4.580 5.417 6.230 7.020 7.786 8.530 9.253 9.954 10.64 11.30 11.94 12.56 13.17 13.75 14.32 14.88 3.5% .966 1.900 2.802 3.673 4.515 5.329 6.115 6.874 7.608 8.317 9.002 9.663 10.30 10.92 11.52 12.09 12.65 13.19 13.71 14.21 4.0% .962 1.886 2.775 3.630 4.452 5.242 6.002 6.733 7.435 8.111 8.760 9.385 9.986 10.56 11.12 11.65 12.17 12.66 13.13 13.59 4.5% .957 1.873 2.749 3.588 4.390 5.158 5.893 6.596 7.269 7.913 8.529 9.119 9.683 10.22 10.74 11.23 11.71 12.16 12.59 13.01 5.0% Years .952 1.859 2.723 3.546 4.329 5.076 5.786 6.463 7.108 7.722 1 2 3 4 5 6 7 8 9 10 8.306 8.863 9.394 9.899 10.38 10.84 11.27 11.69 12.09 12.46 11 12 13 14 15 16 17 18 19 20 Table continued next page. This table is reprinted by permission of the Johns-Manville Sales Corporation, from their publication "Discounted Cash Row Method of Investment Appraisal." ASBESTOS-CEMENT DISTRIBUTION PIPE 61 Table C. 1 (continued) Years 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 .5% 19.89 20.78 21.68 22.56 23.45 24.32 25.20 26.07 26.93 27.79 28.65 29.50 30.35 31.20 32.04 32.87 33.70 34.53 35.35 36.17 36.99 37.80 38.61 39.41 40.21 41.00 41.79 42.58 43.36 44.14 1.0% 18.86 19.66 20.46 21.24 22.02 22.80 23.56 24.31 25.07 25.81 26.54 27.27 27.99 28.70 29.41 30.11 30.80 31.49 32.16 32.84 33.50 34.16 34.81 35.46 36.09 36.73 37.35 37.97 38.59 39.20 1.5% 17.90 18.62 19.33 20.03 20.72 21.40 22.07 22.73 23.38 24.02 24.65 25.27 25.88 26.48 27.08 27.66 28.24 28.81 29.37 29.92 30.46 30.99 31.52 32.04 32.55 33.06 33.55 34.04 34.53 35.00 2.0% 17.01 17.66 18.29 18.91 19.52 20.12 20.71 21.28 21.84 22.40 22.94 23.47 23.99 24.50 25.00 25.49 25.97 26.44 26.90 27.36 27.80 28.24 28.66 29.08 29.49 29.89 30.29 30.67 31.05 31.42 2.5% 16.19 16.77 17.33 17.89 18.42 18.95 19.46 19.97 20.45 20.93 21.40 21.85 22.29 22.72 23.15 23.56 23.96 24.35 24.73 25.10 25.47 25.82 26.17 26.50 26.83 27.15 27.47 27.77 28.07 28.36 3.0% 15.42 15.94 16.44 16.94 17.41 17.88 18.33 18.76 19.19 19.60 20.00 20.39 20.77 21.13 21.49 21.83 22.17 22.49 22.81 23.12 23.41 23.70 23.98 24.25 24.52 24.78 25.03 25.27 25.50 25.73 3.5% 14.70 15.17 15.62 16.06 16.48 16.89 17.29 17.67 18.04 18.39 18.74 19.07 19.39 19.70 20.00 20.29 20.57 20.84 21.10 21.36 21.60 21.84 22.06 22.28 22.50 22.70 22.90 23.09 23.28 23.46 4.0% 14.03 14.45 14.86 15.25 15.62 15.98 16.33 16.66 16.98 17.29 17.59 17.87 18.15 18.41 18.67 18.91 19.14 19.37 19.58 19.79 19.99 20.19 20.37 20.55 20.72 20.89 21.04 21.20 21.34 21.48 4.5% 13.41 13.78 14.15 14.50 14.83 15.15 15.45 15.74 16.02 16.29 16.54 16.79 17.02 17.25 17.46 17.67 17.86 18.05 18.23 18.40 18.57 18.72 18.87 19.02 19.16 19.29 19.42 19.54 19.65 19.76 5.0% Years 12.82 13.16 13.49 13.80 14.09 14.38 14.64 14.90 15.14 15.37 21 22 23 24 25 26 27 28 29 30 15.59 15.80 16.00 16.19 16.37 31 32 33 34 35 16.55 16.71 16.87 17.02 17.16 17.29 17.42 17.55 17.66 17.77 17.88 17.98 18.08 18.17 18.26 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 Years 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 5.5% .948 1.846 2.698 3.505 4.270 4.996 5.683 6.335 6.952 7.538 8.093 8.619 9.117 9.590 10.04 10.46 10.87 11.25 11.61 11.95 6.0% .943 1.833 2.673 3.465 4.212 4.917 5.582 6.210 6.802 7.360 7.887 8.384 8.853 9.295 9.712 10.11 10.48 10.83 11.16 11.47 6.5% .939 1.821 2.648 3.426 4.156 4.841 5.485 6.089 6.656 7.189 7.689 8.159 8.600 9.014 9.403 9.768 10.11 10.43 10.74 11.02 7.0% .935 1.808 2.624 3.387 4.100 4.767 5.389 5.971 6.515 7.024 7.499 7.943 8.358 8.745 9.108 9.447 9.763 10.06 10.34 10.59 7.5% .930 1.796 2.601 3.349 4.046 4.694 5.297 5.857 6.379 6.864 7.315 7.735 8.126 8.489 8.827 9.142 9.434 9.706 9.959 10.19 8.0% .926 1.783 2.577 3.312 3.993 4.623 5.206 5.747 6.247 6.710 7.139 7.536 7.904 8.244 8.559 8.851 9.122 9.372 9.604 9.818 8.5% .922 1.771 2.554 3.276 3.941 4.554 5.119 5.639 6.119 6.561 6.969 7.345 7.691 8.010 8.304 8.575 8.825 9.055 9.268 9.463 9.0% .917 1.759 2.531 3.240 3.890 4.486 5.033 5.535 5.995 6.418 6.805 7.161 7.487 7.786 8.061 8.313 8.544 8.756 8.950 9.129 9.5% .913 1.747 2.509 3.204 3.840 4.420 4.950 5.433 5.875 6.279 6.647 6.984 7.291 7.572 7.828 8.062 8.276 8.471 8.650 8.812 10.0% Years .909 1.736 2.487 3.170 3.791 4.355 4.868 5.335 5.759 6.145 6.495 6.814 7.103 7.367 7.606 7.824 8.022 8.201 8.365 8.514 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Table continued next page 62 AWWA C403-89 Table C. 1 (continued) Years 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 5.5% 12.28 12.58 12.88 13.15 13.41 13.66 13.90 14.12 14.33 14.53 14.72 14.90 15.08 15.24 15.39 15.54 15.67 15.81 15.93 16.05 16.16 16.26 16.36 16.46 16.55 16.63 16.71 16.79 16.86 16.93 6.0% 11.76 12.04 12.30 12.55 12.78 13.00 13.21 13.41 13.59 13.77 13.93 14.08 14.23 14.37 14.50 14.62 14.74 14.85 14.95 15.05 15.14 15.23 15.31 15.38 15.46 15.52 15.59 15.65 15.71 15.76 6.5% 11.29 11.54 11.77 11.99 12.20 12.39 12.58 12.75 12.91 13.06 13.20 13.33 13.46 13.58 13.69 13.79 13.89 13.98 14.07 14.15 14.22 14.29 14.36 14.42 14.48 14.54 14.59 14.64 14.68 14.73 7.0% 10.84 11.06 11.27 11.47 11.65 11.83 11.99 12.14 12.28 12.41 12.53 12.65 12.75 12.85 12.95 13.04 13.12 13.19 13.27 13.33 13.39 13.45 13.51 13.56 13.61 13.65 13.69 13.73 13.77 13.80 7.5% 10.41 10.62 10.81 10.98 11.15 11.30 11.44 11.57 11.70 11.81 11.92 12.02 12.11 12.19 12.27 12.35 12.42 12.48 12.54 12.59 12.65 12.69 12.74 12.78 12.82 12.86 12.89 12.92 12.95 12.98 8.0% 10.02 10.20 10.37 10.53 10.68 10.81 10.94 11.05 11.16 11.26 11.35 11.44 11.51 11.59 11.66 11.72 11.78 11.83 11.88 11.93 11.97 12.01 12.04 12.08 12.11 12.14 12.16 12.19 12.21 12.23 8.5% 9.0% 9.644 9.810 9.963 10.10 10.23 10.35 10.47 10.57 10.66 10.75 10.83 10.90 10.97 11.03 11.09 9.292 9.442 9.580 9.707 9.823 9.929 10.03 10.12 10.20 10.27 10.34 10.41 10.46 10.52 10.57 11.14 11.19 11.24 11.28 11.32 11.35 11.38 11.41 11.44 11.47 11.49 11.51 11.53 11.55 11.57 10.61 10.65 10.69 10.73 10.76 10.79 10.81 10.84 10.86 10.88 10.90 -10.92 10.93 10.95 10.96 9.5% 8.961 9.097 9.221 9.334 9.438 9.532 9.618 9.697 9.769 9.835 9.895 9.950 10.00 10.05 10.09 10.13 10.16 10.19 10.22 10.25 10.27 10.29 10.31 10.33 10.35 10.36 10.38 10.39 10.40 10.41 10.0% Years 8.649 8.772 8.883 8.985 9.077 9.161 9.237 9.307 9.370 9.427 9.479 9.526 9.569 9.609 9.644 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 9.677 9.706 9.733 9.757 9.779 9.799 9.817 9.834 9.849 9.863 9.875 9.887 9.897 9.906 9.915 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 Years 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 10.5% .905 1.724 2.465 3.136 3.743 4.292 4.789 5.239 5.646 6.015 6.348 6.650 6.923 7.170 7.394 7.596 7.779 7.945 8.095 8.231 11.0% .901 1.713 2.444 3.102 3.696 4.231 4.712 5.146 5.537 5.889 6.207 6.492 6.750 6.982 7.191 7.379 7.549 7.702 7.839 7.963 11.5% .897 1.701 2.423 3.070 3.650 4.170 4.637 5.056 5.431 5.768 6.070 6.341 6.583 6.801 6.997 7.172 7.329 7.470 7.596 7.710 12.0% .893 1.690 2.402 3.037 3.605 4.111 4.564 4.968 5.328 5.650 5.938 6.194 6.424 6.628 6.811 6.974 7.120 7.250 7.366 7.469 12.5% .889 1.679 2.381 3.006 3.561 4.054 4.492 4.882 5.228 5.536 5.810 6.053 6.270 6.462 6.633 6.785 6.920 7.040 7.147 7.241 13.0% .885 1.668 2.361 2.974 3.517 3.998 4.423 4.799 5.132 5.426 5.687 5.918 6.122 6.302 6.462 6.604 6.729 6.840 6.938 7.025 13.5% .881 1.657 2.341 2.944 3.475 3.943 4.355 4.718 5.038 5.320 5.568 5.787 5.979 6.149 6.299 6.431 6.547 6.649 6.739 6.819 14.0% .877 1.647 2.322 2.914 3.433 3.889 4.288 4.639 4.946 5.216 5.453 5.660 5.842 6.002 6.142 6.265 6.373 6.467 6.550 6.623 14.5% .873 1.636 2.302 2.884 3.392 3.836 4.224 4.562 4.858 5.116 5.341 5.538 5.710 5.861 5.992 6.106 6.206 6.294 6.370 6.437 15.0% Years .870 1.626 2.283 2.855 3.352 1 2 3 4 5 3.784 4.160 4.487 4.772 5.019 5.234 5.421 5.583 5.724 5.847 6 7 8 9 10 11 12 13 14 15 5.954 6.047 6.128 6.198 6.259 16 17 18 19 20 Table continued next page ASBESTOS-CEMENT DISTRIBUTION PIPE 63 Table C. 1 (continued) Years 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 10.5% 8.345 8.465 8.566 8.657 8.739 8.814 8.881 8.942 8.997 9.047 9.093 9.134 9.171 9.204 9.235 9.262 9.287 9.309 9.330 9.348 9.365 9.380 9.394 9.406 9.417 9.427 9.437 9.445 9.452 9.459 Years 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 15.5% .866 1.615 2.264 2.826 3.313 3.734 4.099 4.415 4.688 4.925 5.130 5.307 5.461 5.594 5.709 5.808 5.895 5.969 6.034 6.090 11.0% 8.075 8.176 8.266 8.348 8.422 8.488 8.548 8.602 8.650 8.694 8.733 8.769 8.801 8.829 8.855 8.879 8.900 8.919 8.936 8.951 8.965 8.977 8.989 8.999 9.008 9.016 9.024 9.030 9.036 9.042 11.5% 7.811 7.903 7.984 8.058 8.124 8.183 8.236 8.283 8.326 8.364 8.398 8.429 8.456 8.481 8.503 8.523 8.541 8.557 8.571 8.584 8.595 8.606 8.615 8.623 8.631 8.637 8.643 8.649 8.654 8.658 12.0% 7.562 7.645 7.718 7.784 7.843 7.896 7.943 7.984 8.022 8.055 8.085 8.112 8.135 8.157 8.176 8.192 8.208 8.221 8.233 8.244 8.253 8.262 8.270 8.276 8.283 8.288 8.293 8.297 8.301 8.304 12.5% 7.326 7.401 7.467 7.526 7.579 7.626 7.667 7.704 7.737 7.766 7.792 7.815 7.836 7.854 7.870 7.885 7.898 7.909 7.919 7.928 7.936 7.943 7.949 7.955 7.960 7.965 7.968 7.972 7.975 7.978 13.0% 7.102 7.170 7.230 7.283 7.330 7.372 7.409 7.441 7.470 7.496 7.518 7.538 7.556 7.572 7.586 7.598 7.609 7.618 7.627 7.634 7.641 7.647 7.652 7.657 7.661 7.664 7.668 7.671 7.673 7.675 13.5% 6.889 6.951 7.005 7.053 7.095 7.132 7.165 7.194 7.219 7.242 7.261 7.279 7.294 7.307 7.319 7.330 7.339 7.347 7.354 7.361 7.366 7.371 7.375 7.379 7.383 7.386 7.388 7.390 7.392 7.394 14.0% 6.687 6.743 6.792 6.835 6.873 6.906 6.935 6.961 6.983 7.003 7.020 7.035 7.048 7.060 7.070 7.079 7.087 7.094 7.100 7.105 7.110 7.114 7.117 7.120 7.123 7.126 7.128 7.130 7.131 7.133 14.5% 6.495 6.546 6.590 6.629 6.663 6.693 6.718 6.741 6.761 6.778 6.793 6.806 6.817 6.827 6.836 6.844 6.851 6.856 6.861 6.866 6.870 6.873 6.876 6.879 6.881 6.883 6.885 6.886 6.887 6.889 15.0% Years 6.312 6.359 6.399 6.434 6.464 6.491 6.514 6.534 6.551 6.566 21 22 23 24 25 26 27 28 29 30 6.579 6.591 6.600 6.609 6.617 31 32 33 34 35 6.623 6.629 6.634 6.638 6.642 6.645 6.648 6.650 6.652 6.654 6.656 6.657 6.659 6.660 6.661 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 16.0% .862 1.605 2.246 2.798 3.274 3.685 4.039 4.344 4.607 4.833 5.029 5.197 5.342 5.468 5.575 5.668 5.749 5.818 5.877 5.929 16.5% .858 1.595 2.228 2.770 3.236 3.636 3.980 4.274 4.527 4.745 4.931 5.091 5.228 5.346 5.447 5.534 5.609 5.673 5.728 5.775 17.0% .855 1.585 2.210 2.743 3.199 3.589 3.922 4.207 4.451 4.659 4.836 4.988 5.118 5.229 5.324 5.405 5.475 5.534 5.584 5.628 17.5% .851 1.575 2.192 2.716 3.163 3.543 3.866 4.142 4.376 4.575 4.745 4.889 5.012 5.117 5.206 5.281 5.346 5.401 5.447 5.487 18.0% .847 1.566 2.174 2.690 3.127 3.498 3.812 4.078 4.303 4.494 4.656 4.793 4.910 5.008 5.092 5.162 5.222 5.273 5.316 5.353 18.5% .844 1.556 2.157 2.664 3.092 3.453 3.758 4.015 4.232 4.415 4.570 4.700 4.810 4.903 4.982 5.048 5.104 5.151 5.191 5.224 19.0% .840 1.547 2.140 2.639 3.058 3.410 3.706 3.954 4.163 4.339 4.486 4.611 4.715 4.802 4.876 4.938 4.990 5.033 5.070 5.101 19.5% .837 1.537 2.123 2.613 3.024 3.367 3.655 3.895 4.096 4.265 4.406 4.523 4.622 4.705 4.774 4.832 4.880 4.921 4.954 4.983 20.0% Years .833 1.528 2.106 2.589 2.991 3.326 3.605 3.837 4.031 4.192 4.327 4.439 4.533 4.611 4.675 4.730 4.775 4.812 4.843 4.870 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Table continued next page 64 AWWA C403-89 Table C. 1 (continued) Years 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 15.5% 6.139 6.181 6.217 6.249 6.276 6.299 6.320 6.337 6.353 6.366 6.378 6.387 6.396 6.404 6.410 6.416 6.420 6.425 6.428 6.431 6.434 6.436 6.438 6.440 6.442 6.443 6.444 6.445 6.446 6.447 16.0% 5.973 6.011 6.044 6.073 6.097 6.118 6.136 6.152 6.166 6.177 6.187 6.196 6.203 6.210 6.215 6.220 6.224 6.228 6.231 6.233 6.236 6.238 6.239 6.241 6.242 6.243 6.244 6.245 6.246 6.246 16.5% ' 17.0% 5.815 5.850 5.880 5.905 5.927 5.946 5.962 5.976 5.988 5.999 6.007 6.015 6.021 6.027 6.032 5.665 5.696 5.723 5.746 5.766 5.783 5.798 5.810 5.820 5.829 5.837 5.844 5.849 5.854 5.858 6.036 6.039 6.042 6.045 6.047 6.049 6.051 6.052 6.053 6.054 6.055 6.056 6.057 6.057 6.058 5.862 5.865 5.867 5.896 5.871 5.873 5.874 5.875 5.876 5.877 5.878 5.879 5.879 5.880 5.880 17.5% 5.521 5.550 5.574 5.595 5.613 5.628 5.641 5.652 5.661 5.669 5.676 5.681 5.686 5.691 5.694 5.697 5.700 5.702 5.704 5.705 5.707 5.708 5.709 5.710 5.710 5.711 5.711 5.712 5.712 5.712 18.0% 5.384 5.410 5.432 5.451 5.467 5.480 5.492 5.502 5.510 5.517 5.523 5.528 5.532 5.536 5.539 5.541 5.543 5.545 5.547 5.548 5.549 5.550 5.551 5.552 5.552 5.553 5.553 5.554 5.554 5.554 18.5% 5.252 5.276 5.296 5.313 5.328 5.340 5.350 5.359 5.366 5.372 5.377 5.382 5.385 5.389 5.391 5.393 5.395 5.397 5.398 5.399 5.400 5.401 5.402 5.402 5.403 5.403 5.404 5.404 5.404 5.404 19.0% 5.127 5.149 5.167 5.182 5.195 5.206 5.215 5.223 5.229 5.235 5.239 5.243 5.246 5.249 5.251 5.253 5.255 5.256 5.257 5.258 5.259 5.260 5.260 5.261 5.261 5.261 5.262 5.262 5.262 5.262 19.5% 5.007 5.026 5.043 5.057 5.069 5.078 5.086 5.093 5.099 5.104 5.108 5.111 5.114 5.116 5.118 5.120 5.121 5.122 5.123 5.124 5.125 5.125 5.126 5.126 5.127 5.127 5.127 5.127 5.127 5.128 20.0% Years 4.891 4.909 4.925 4.937 4.948 4.956 4.964 4.970 4.975 4.979 4.982 4.985 4.988 4.990 4.992 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 4.993 4.994 4.995 4.996 4.997 4.997 4.998 4.998 4.998 4.999 4.999 4.999 4.999 4.999 4.999 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 Years 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21% .826 1.509 2.074 2.540 2.926 3.245 3.508 3.726 3.905 4.054 4.177 4.278 4.362 4.432 4.489 4.536 4.576 4.608 4.635 4.657 22% .820 1.492 2.042 2.494 2.864 3.167 3.416 3.619 3.786 3.923 4.035 4.127 4.203 4.265 4.315 4.357 4.391 4.419 4.442 4.460 23% .813 1.474 2.011 2.448 2.803 3.092 3.327 3.518 3.673 3.799 3.902 3.985 4.053 4.108 4.153 4.189 4.219 4.243 4.263 4.279 24% .806 1.457 1.981 2.404 2.745 3.020 3.242 3.421 3.566 3.682 3.776 3.851 3.912 3.962 4.001 4.033 4.059 4.080 4.097 4.110 25% .800 1.440 1.952 2.362 2.689 2.951 3.161 3.329 3.463 3.571 3.656 3.725 3.780 3.824 3.859 3.887 3.910 3.928 3.942 3.954 26% .794 1.424 1.923 2.320 2.635 2.885 3.083 3.241 3.366 3.465 3.543 3.606 3.656 3.695 3.726 3.751 3.771 3.786 3.799 3.808 27% .787 1.407 1.896 2.280 2.583 2.821 3.009 3.156 3.273 3.364 3.437 3.493 3.538 3.573 3.601 3.623 3.640 3.654 3.664 3.673 28% .781 1.392 1.868 2.241 2.532 2.759 2.937 3.076 3.184 3.269 3.335 3.387 3.427 3.459 3.483 3.503 3.518 3.529 3.539 3.546 29% .775 1.376 1.842 2.203 2.483 2.700 2.868 2.999 3.100 3.178 3.239 3.286 3.322 3.351 3.373 3.390 3.403 3.413 3.421 3.427 30% Years .769 1.361 1.816 2.166 2.436 2.643 2.802 2.925 3.019 3.092 3.147 3.190 3.223 3.249 3.268 3.283 3.295 3.304 3.311 3.316 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Table continued next page ASBESTOS-CEMENT DISTRIBUTION PIPE 65 Table C.l (continued) Years 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 21% 4.675 4.690 4.703 4.713 4.721 4.728 4.734 4.739 4.743 4.746 4.749 4.751 4.753 4.755 4.756 4.757 4.758 4.759 4.759 4.760 4.760 4.760 4.761 4.761 4.761 4.761 4.761 4.761 4.761 4.762 22% 4.476 4.488 4.499 4.507 4.514 4.520 4.524 4.528 4.531 4.534 4.536 4.538 4.539 4.540 4.541 4.542 4.543 4.543 4.544 4.544 4.544 4.544 4.545 4.545 4.545 4.545 4.545 4.545 4.545 4.545 23% 4.292 4.302 4.311 4.318 4.323 4.328 4.332 4.335 4.337 4.339 4.341 4.342 4.343 4.344 4.345 4.345 4.346 4.346 4.346 4.347 4.347 4.347 4.347 4.347 4.347 4.348 4.348 4.348 4.348 4.348 24% 4.121 4.130 4.137 4.143 4.147 4.151 4.154 4.157 4.159 4.160 4.161 4.162 4.163 4.164 4.164 4.165 4.165 4.165 4.166 4.166 4.166 4.166 4.166 4.166 4.166 4.166 4.166 4.167 4.167 4.167 25% 3.963 3.970 3.976 3.981 3.985 3.988 3.990 3.992 3.994 3.995 3.996 3.997 3.997 3.998 3.998 3.999 3.999 3.999 3.999 3.999 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 26% 3.816 3.822 3.827 3.831 3.834 3.837 3.839 3.840 3.841 3.842 3.843 3.844 3.844 3.845 3.845 3.845 3.845 3.846 3.846 3.846 3.846 3.846 3.846 3.846 3.846 3.846 3.846 3.846 3.846 3.846 27% 3.679 3.684 3.689 3.692 3.694 3.696 3.698 3.699 3.700 3.701 3.701 3.702 3.702 3.703 3.703 3.703 3.703 3.703 3.703 3.703 3.703 3.704 3.704 3.704 3.704 3.704 3.704 3.704 3.704 3.704 28% 3.551 3.556 3.559 3.562 3.564 3.566 3.567 3.568 3.569 3.569 3.570 3.570 3.570 3.571 3.571 3.571 3.571 3.571 3.571 3.571 3.571 3.751 3.571 3.571 3.571 3.571 3.571 3.571 3.571 3.571 29% 3.432 3.436 3.438 3.441 3.442 3.444 3.445 3.446 3.446 3.447 3.447 3.447 3.448 3.448 3.448 3.448 3.448 3.448 3.448 3.448 3.448 3.448 3.448 3.448 3.448 3.448 3.448 3.448 3.448 3.448 30% Years 3.320 3.323 3.325 3.327 3.329 3.330 3.331 3.331 3.332 3.332 3.332 3.333 3.333 3.333 3.333 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 3.333 3.333 3.333 3.333 3.333 3.333 3.333 3.333 3.333 3.333 3.333 3.333 3.333 3.333 3.333 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 21 March 1990 for AWWA C403-89 1 November 1989 SUPERSEDING AWWA C403-84 31 January 1985 Department of Defense Acceptance Notice AWWA C403-89 was adopted on 21 March 1990 and is approved for use by the Department of Defense (DoD). AWWA has furnished the clearance required by existing regulations. Copies of this document are stocked by the DoD Single Stock Point, Military Specifications and Standards, Bldg. 40, 700 Robbins Ave., Philadelphia, PA 19111-5094, for issue to DoD activities only. All other requestors must obtain documents from AWWA, 6666 West Quincy Ave., Denver, CO 80235. Title of Document: American Water Works Association Standard for the Selection of Asbestos-Cement Transmission and Feeder Main Pipe, Sizes 18 In. Through 42 In. (450 mm Through 1050 mm) Date of Specific Issue Adopted: November 1,1989 Releasing Nongovernment Standards Body: American Water Works Association Custodians: Army--ME Navy--YD Air Force--99 Military Coordinating Activity: Navy--YD User Activity: Navy--MC Project No. 5630-0189 FSC 5630 1 P-12M-43403-10/89-MG