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): * *- >/ i0 '( `t' ,Ay O t '1 .1 i : ' f;'RAI, WOUiNH D DESIGN CRITERIA BULLETIN 171 1971 Fim Edition Catalog: F le x it a llic Gasket Co. 1-22-76 FLEXITALLIC GASKET COMPANY INC CAMDEN, NEW JERSEY 08101 U.S.A. FLEXITALLIC GASKETS (WOOD BROS.) LTD. STATION LANE, HECKMONDWIKE YORKSHIRE, ENGLAND LIATED COMPANIES IN AUSTRALIA, HOLLAND AND SOUTH AFRICA AFF 3 SPIRAL WOUND GASKETS DESIGN CRITERIA Copyright 1971, Flex*tallic Gasket Co. Inc. INTRODUCTION This paper has been prepared as the result of many requests received from design engineers, users and others for more detaiied information on the design and use of FLEXITALLIC spiral-wound gaskets. The concept of spiral-wound gasket construction was originated in 1912 by the FLEXITALLIC GASKET COMPANY. With the introduction of FLEXITALLIC gaskets, a new era in safe, effective sealing of joints was inaugurated. The versatility of this design concept is now attested by the wide range of successful applications, ranging from extremely high vacuums to pressures in excess of present flange standards of 2500 psi and from cryogenic temperatures to beyond 1500F and against virtually every known corrosive media. The FLEXITALLIC design has not only kept pace with modem trends, but has been constantly in advance of such progress that combines materials and construction techniques which result in effective sealing that could not be achieved by any other known type of gasket. Since 1912, the FLEXITALLIC GASKET COMPANY has had a record of steady growth and today is the largest organization in the world that exists solely to produce a spiral-wound gasket. Our entire efforts are directed toward producing for our customers, the highest quality and the most reliable gasket at competitive prices. I TABLE OF CONTENTS Page Introduction..................................................................................................................................................................................... 2 Available Styles................................................................................................................................................................................ 3 Criteria For Materials Used In Gasket Construction.................................................................................................................... 5 Available Gasket Sizes & Manufacturing Tolerances .................................................................................................................. 7 Sizing Spiral Wound Components For Flexitallic Gaskets......................................................................................................... 7 Flange Surface Finish ..................................................................................................................................................................... 9 ASME Boiler 8t Pressure Vessel Code Calculations.......................................... ............................................................................ 9 Flange Design For Flexitallic Gaskets..........................................................................................................................................11 Ordering Information -- Special Gasket Designs.........................................................................................................................11 Bolting-Up Procedures . . .................................................................................................................................................................12 Appendices: A -- Corrosives which can induce stress corrosion cracking inmetals ............................................................................................................................................... 14 B -- Corrosives which induce intergranular corrosion in Austenitic Stainless Steel . . .-..................................................................................................................... 15 C -- Properties of Asbestos Fibers............................................................................................................................................ 15 List of Tables Table No. I. -- Gasket Sizing Limitations................r............................................................................................................................ 7 II. - Gasket Manufacturing Tolerances IT............................................................................................................................. 7 III. -- Metal Ring Sizing Limitations........................................................................................................................................ 8 IV. -- Flange Surface Finishes................................................................................................................................................... 9 V. -- Gasket Seating Stresses................................................................................................................................................... 10 List of Charts and Sketches Chart No. I. -- Flange Width vs. Diameter.............................................................................................................................................. 8 Sketch No. I. -- Bolting Diagrams.............................................................................................................................................................. 10 "WHAT IS A FLEXITALLIC GASKET" Gaskets are essentially a packing designed for inclusion between rigid parts of a fluid container in an essentially stationary relationship. A FLEXITALLIC gasket consists of laminated, preformed metal strips and filler materials selected to meet the conditions of service required. Its construction provides internal resilience enabling it to follow flange movement within reasonable limits. Unfortu nately, gaskets are all too often simply accepted per se, that is, "just another gasket." The irony of this is that one of the most costly and serious industrial problems today is leaky joints resulting in explosions, fires, loss of production and soaring maintenance costs. Much of this is due to insufficient attention to the proper application and design of closures and the gaskets that are used to effect the seal. The FLEXITALLIC gasket is not "just another gasket." It is a specifically engineered product in the FLEXITALLIC program of continuous research and development in gasket design and production control to give you assurance of quality and safety. It is our objective in the preparation of this bulletin to help prevent, through greater knowledge of the FLEXITALLIC gasket, the serious and costly waste of time, money and resources resulting from joint leakage. We trust the information contained herein will prove worthwhile and will benefit the equipment manufacturer, design engineer, and the user in sealing closures, whether high or low pressure, high or low temperature, and regardless of the nature of the corrosive media to be sealed. HOW FLEXITALLIC GASKETS ARE MANUFACTURED" A FLEXITALLIC gasket is manufactured by spirally winding a preformed metal strip and a filler on the outer periphery of metal winding mandrels. The winding mandrel outside diameter forms the inner diameter of the gasket and the laminations are continually wound until the required outer diameter is attained. Normal practice is to reinforce the inner and outer diameters with several plies of metal with no soft fillers being introduced. Our method of manufacture includes custom designed devices which provide control of gasket density that permit compression to the operating thickness under a specified load. This engineered product is thus "tailor made" to be compatible with the flanged closure in which it is to be used. For example, a closure designed for vacuum service may require a gasket of exactly the same dimensions as a closure designed for 1500 psi service. The closure designed for the vacuum service would have relatively light bolting indicating the necessity for a soft gasket, whiie the 1500 psi application would have heavy bolting indicating a relatively dense gasket. It is usually within our capability to satisfy both requirements. Refer to paragraph on "Flange Design for Flexitallic Gaskets." "AVAILABLE STYLES OF FLEXITALLIC GASKETS" i. > 1. Style R-------This designates a round spiral-wound gasket with no accessory devices added. The notations, Rl, R3, and R4 in our catalog, apply to our standard gaskets only, so indicated for use on standard flanges. If a Style R gasket is to be used on a special flange design (other than ANSI or BS flange specification), the gasket is usually termed a Special Style R. 3. Style CG------ A Style CG gasket is a round, spiralwound gasket with a solid metal outer ring forming a complete assembly. The outer ring serves as a compression stop, anti-blowout device, and to properly center the gasket on the flange. >> 2. Style RIR-------This is a round spiral-wound gasket fitted with an inner metal ring used to provide inner confinement to tire gasket, to act as a compression stop if of the proper thickness, and to be used to fill the annular space between the flange bore and the gasket I.D. to minimize turbulence of process Quids and erosion of flange faces. 4. Style CGI Gasket------ This designates a CG gasket as above with the addition of an inner metal ring. The inner ring thickness is normally the same as the outer ring and serves to prevent material build-up between tire flange bore and the gasket I.D., as a protection against excessive heat, to reduce process fluid turbulence and to minimize erosion of flange facings. Style CGI gaskets are frequently 3 used on vacuum service. This style eliminates costly machining in one of the flange faces if a totally contained gasket is required. A Style CGI gasket will effectively provide a totally contained gasket without the additional costly machining. S. Style CG-RJ-------This style designates a Special CG gasket sized to be used on standard ring joint flanges as noted in our catalog. The outer ring is dimensioned to cover the ring joint grooves and .to prevent the_spiral-wound portion from entering the groove. The spiral-wound portion of the gasket is sized to fit between the flange bore and the ring joint groove. This type of gasket should be used only as a maintenance repair item and should not be used on new construction. If FLEXITALL1C gaskets are to be used in new construction, it is advisable to use standard raised face flanges and our Style CG gasket. Please note Style T gaskets rely on internal pressure in the boiler to properly seat the gasket. This means, when a hydrostatic test is performed on the gasket, the pressure exerted against the plate will further compress the gasket -- and it is necessary to tighten each nut to compensate for the additional compression of the gasket under load. ROJ'ID OBROUND OR FLAT-SIDED OR STRAIGHT-SIDED VJ SQUARE OR rectangular 6. Style D------- This consists of a spiral-wound gasket with loops (usually 2) added to the O.D. of the gasket and dimensioned to fit over two diametrically opposite flange bolts for centering purposes. Style D gaskets are not generally recommended for use in applications where pressures are in excess of 600 psi. It is not as widely used or as popular as the Style CG gasket, with its outer metal ring functioning as a centering, anti-blowout device as well as a compression stop. The Style D gasket does lend itself to ease of assembly in areas of congested piping plus the fact that the standard Style D's are less expensive than the CG for the equivalent size and pressure rating. When Style D gaskets are required and are not standard catalog items, special winding mandrels must be purchased. It should be noted, the spiral-wound portion of the Style D gasket is identical to the spiral-wound portion of a Style CG gasket in the same size and pressure series. 8. Style M & MC------- These styles are designed for boiler manhole cover assemblies. They are usually of round, obround or oval shape, depending, of course, upon the manhole plate configuration. Style MC gaskets have a preformed spiral-wound centering ring snapped into the inner groove of the gasket proper. This centering guide permits the gasket to assume its correct position and to compensate for inequalities in plate contours and fillets in cold-pressed plates as well as to prevent shouldering and pinching caused by radial misplacement. ROUND OBRO'JND OVAL 9. Style HE------ Style HE gaskets are for heat exchangers where pass ribs are required. The outer portion is of standard spiral-wound construction, whereas the rib portion is normally of single or double-jacketed style, securely fastened to the I.D. of the spiral-wound portion. 7. Style T-------This designates gaskets for boiler handhole and tube cap assemblies. They are available in round, oval, obround, square, pear and diamond shapes. Refer to our general catalog for standard Style T gaskets. 10. Style HE-CG-------This style is identical to the Style HE above, except that it is fitted with an outer ring on the O.D. Note-------Style HE and Style HE-CG gaskets have a primary seal of spiral-wound construction with its inherent resiliency and excellent sealing quality. It is necessary that cimensiona. drawings locating rhe pass ribs and the configurations be submitted for all inquiries and orders for these style gaskets. ( I 11. Style HX*------ Style HX gaskets are suitable for standard heat exchanger flanges designed in accordance with BS 3274 and TEMA standards. The primary seal is a spiral wound gasket construction which is fitted with a stainless steel outer wound guide so as to correctly locate the gasket in the flange recess. An inner compression stop ring is fitted and for the tubeplate to channel connection, a compressed asbestos fibre insert with pass partition bars is incorporated. Where working conditions demand it, the compressed asbestos fibre insert can be dispensed with and the pass partition bars can be supplied in metal asbestos or solid metal as part of the inner compression stop ring. Note------- Not available in U. S. A. 12. Style 625 -------Similiar to Style R gaskets, except narrow flange widths. Most frequently used on clamp-type closures where an extremely thin gasket is required. 13. Miscellaneous-------- On rare occasions, applications for FLEXJTALL1C gaskets arise where it is necessary to utilize a spiral-wound inner and/or outer ring. The spiral-wound inner or outer rings are used primarily as centering devices and are chosen in lieu of a solid metal ring, because of lower cost or because of limited space when the use of a solid metal ring would be prohibited because of the difficulty in fabrication. Refer to our General Catalog for FLEX1TALLIC gaskets available for standard flanges and common boiler handhole and manhole fittings. original thickness is .0625". Limited to small diameters and "CRITERIA FOR MATERIAL!' The selection of materials of construction for FLEXITALLIC gaskets requires consideration of the following aspects: 1. The corrosive nature and concentration of the' fluid to be confined. 2. The operating temperature. 3. The expected life of the installation. 4. The relative cost of alternative materials. Specific recommendations for materials of construction are beyond the scope of this paper. The resistance to corrosive attack by the various materials used in FLEXITALLIC gaskets fluctuates widely, depending upon the concentration of the corrosive agent, presence of other contaminates and the operating variables of temperature and pressure. Lacking specific experience with the corrosive nature of any particular agent and those materials that would have sufficient corrosion resistance to the media, designers are recommended to contact the manufacturers of alloyed materials, who have available extensive information on the chemical resistivity of their products to various corrosive media. Another excellent source of corrosion resistance is contained in "Corrosion Data Survey" pub lished by the Association of Corrosion Engineers, Houston, Texas. It is frequently necessary to conduct laboratory corrosive tests and/or pilot plant operations in order to obtain factual and reliable information. When considering the choice of materials for FLEXITALLIC gaskets, designers should be guided by the following general comments: 1. Stress Corrosion -- FLEX1TALL1C gaskets, when installed, are highly stressed, particularly in the area of the engineered wire formation, and adjacent to the flange seating surfaces. The 18-8 stainless steels are particularly subject to stress corrosion or stress corrosion cracking when exposed to certain media. Corrosive materials that induce stress coirosion cracking in metals are included in Appendix A In such cases, alternative materials must be .->U-Tpr! that are less susceptible to stress corrosion cracking. Dll G r,1 2. Integranular Corrosion -- When austenitic stainless steels are subjected to temperatures in the range of 800 to 1500F, carbides are precipitated along the grain boundaries. When exposed to certain chemicals, inter granular corrosion will occur. A list of corrosives which induce intergranular corrosion are included in Appendix B. When handling these media, special attention to material selection is necessary. 3. Expected life of the Installation -- The trend in industry today is to lengthen the time between overhauls and consequendy, the best possible material, regardless of initial cost, is frequently the most economical. Gaskets are relatively low cost items when compared to labor costs to install, downtime on equipment and loss of productivity, should premature failure occur. Hence, for "permanent" installations, the cost of special gasketing materials should be equated against increased productivity and reliability. The FLEX1TALUC GASKET COMPANY maintains a substantial inventory of a wide variety of metals and filler materials to meet specific operating conditions and requirements. T-y, r;r-iCi it; The following materials are normally inventoried to insure prompt delivery: Type 304 Stainless Steel -- This 18-8 Chromium-Nickel Steel is the most common metal used in the fabrication of FLEX1TALL1C gaskets. It has excellent corrosion resistance to a wide variety of chemicals. It is, however, subject to stress corrosion cracking when exposed to certain media, and to intergranular corrosion at temperatures between 800F and 1500F in the presence of certain media. Under these conditions, alternative materials should be selected. Due to the precipitation of carbides alcr.g grain boundaries, its use is normally limited to a maximum continuous temperature of 800 F if any danger of the materials that would cause intergranular corrosion are expected to be present. Type 347 Stainless Steel -- The addition of coiumbium to this 18-10 Chromium-Nickel Steel serves to keep carbides in solution, and hence, inhibits carbide precipitation along the grain boundaries. Type 347 Stainless Steel has corrosion resistant qualities comparable to Type 304 Stainless Steel. It is not as subject to intergranular corrosion as is Type 304 Stainless Steel, and can be used at continuous temperatures up to the 1400--1500F range. Type 347 is subject to stress corrosion cracking, however, as is Type 304. Type 316L Stainless Steel -- The 2% molybdenum added to this 18-12 Chromium-Nickel alloy increases its creep strength at elevated temperatures. Carbon content is held at a maximum of .03% which inhibits the tendency toward carbide precipitation. Type 316L is subject to stress corrosion cracking and also to intergranular corrosion, but to a lesser degree than Type 304 Stainless Steel. Its continuous maximum temperature exposure would be in the range of 1400--1500F. Type 309SCb Stainless Steel -- This 25-12 ChromiumNickel steel has excellent corrosion resistance due to the high Chromium-Nickel content. It is not as subject to stress corrosion cracking as are the 18-8 stainless steels. The presence of Coiumbium inhibits carbide precipitation. Maximum continuous temperatures would be in the range of 1600F--1700 F. Type 304L Stainless Steel -- This 18-8 stainless steel alloy has the same excellent corrosion resistance as does Type 304, but its carbon content is maintained at a maximum of .03%, which tends to reduce the precipitation of carbides along grain boundaries, and as a consequence, would be less subject to intergranular corrosion than is the Type 304 stainless steel. It is, however, subject to stress corrosion cracking. Plated Low Carbon Steel -- In FLEXITALLIC gasket construction, the use of this metal is normally limited to low pressure steam applications at maximum temperatures in the range of 500F. Monel Metal -- This Nickel base alloy contains 67% Nickel and 30% Copper. It is widely used as a gasketing material due to its excellent resistance to most acids and alkalis, except the strong oxidizing acids. In combination with PTFE, it is widely used in FLEXITALLIC gaskets for hydrofluoric acid service. Maximum upper temperature limit for Monel metal is in the range of 1500F. Monel metal is subject to stress corrosion cracking when exposed to fluorosilic acid, mercuric-chloride and mercury, and should not be used with these media. Inconel 600 -- This metal is a Nickel base alloy containing 77% Nickel, I 5% chromium and 7% iron. It Eas excellent high temperature strength and can be used at temperatures up to the 2000F range. Inconel 600 has little tendency toward stress corrosion cracking and is frequently used as a gasketing material to overcome this problem. AVAILABLE" MATERIAL MAX/TEMPERATURE* 321 S. S.......... :.................................................. 1400; 1 500 'F 430 S. S............................................................... 14(J0/I500jF Carpenter 20 .....................................................1400/1500 F Phosphor Bronze......................................................... 500F Nickel ......................................................................... I400F Titanium.................................................................... 2000F Hastelloy C&B......................................................... 2000F Inconel X.................................................................... 2000F Copper........................................................................... 500F 310 S. S....................................................................... 1900F On special order, gaskets can be fabricated from gold, zirconium, platinum, aluminum and tantalum. * Maximum temperature ratings are based upon hot air at constant temperatures. The presence of contaminating fluids and cyclic conditions may drastically affect the maximum temperature range. " c IL1E R MATERIALS" 1. Canadian Asbestos Paper (Chrysotile) -- Canadian Asbestos Paper is the most common filler material used in the fabrication of FLEXITALLIC gaskets. Canadian Asbestos is a hydrated magnesium-silicate. The form, as we use it, is composed of approximately 90% Canadian Chrysotile Asbestos, 7% vegetable rubber latex binder and 3% water-proofing binder. This material has poor acid resistance and strong mineral acids dissolve out all magnesia, leaving a residue of nearly pure insoluble silica. It does, however, show excellent resistance against alkaline solutions, such as sodium-hydroxide or caustic soda and can be used against solvents, aqueous and salt solutions, and gases (except oxygen). Canadian Asbestos has a very high melting point fusing at approximately 2770F. However, it loses 11% by weight of water at 1100F and about 13.5% at 1400F. From this point to the fusion temperature, it has turned to a powder with very little tensile strength left. In spite of this, if it is still confined, it can continue to produce a satisfactory seal since it is completely confined between the metal windings of the gasket and the seating surfaces of the flange. Our standard Canadian asbestos paper contains .1% blue vegetable dye for identification purposes. This material is available without the dye added if the possibility of color contamination is a problem. Note: Alt asbestos paper used by FLEXITALLIC GASKET COMPANY is tested for teachable chlorides and meets the 200 parts per million requirements for total soluble chlorides. 2. Blue African Asbestos (Crocidolite) -- Blue African Asbestos is a complex silicate of iron and sodium. Blue African Asbestos has excellent acid and alkaline resistance. It was originally developed particularly for use against strong mineral acids such as sulphuric, nitric and hydro chloric. For this reason, it is frequently used as a filler material for hot strong mineral acids in FLEXITALLIC gasket construction. Blue African asbestos has a fusion point of approximately 2180F. However, because of the very small loss in weight due to water loss, it may perform excellently as a seal up to 1900 to 2000F. Note: 1 -- Blue African Asbestos is not available m U. K. 2 -- When Blue African Asbestos is required, always specify "Blue African" to eliminate any confusion with our ''blue-dyed" Canadian Asbestos. 3. Canadian Asbestos paper with an Inorganic Binder -- This is a Canadian Asbestos paper that contains an inorganic binder lor applications where Canadian Asbestos is saiistactorv bui where jiiv ui aanic materials cannof be tolerated. 4. Compressed Asbestos Fibre Type Special -- This is a grade of compressed asbestos fibre specially developed for use in spiral wound gaskets. The homogeneous structure of the material allows it to more readily conform to the spiral wound steel profile than conventional compressed asbestos fibre materials. The material contains an asbestos content' of 70% and a binder content of 12%, this being a blend of NR and SBR. The material shows good performance in steam and hydrocarbon service at high temperatures. 5. Polyteirafluoroethylene IPTFE) -- PTFE-ls used as a filler material in FLEXJTALLIC gaskets where extreme chemical inertness is required for temperatures ranging from cryogenic to 500F. PTFE is unaffected by any known chemicals except molten alkali metals and fluorine precursors. Because of its low permeability, PTFE is also frequently used as a filler material on FLEXITALLIC gaskets in vacuum applications. 6. FLEX1CARB -- This material is a pure pyrolitic graphite tape and does not melt, rather it sublimates at 660QF. This material shows promise as being as excellent filler material for extremely high temperature in reducing atmospheres. 7. Other Materials -- FLEXITALLIC'gaskets are also available.,with various compressed asbestos sheet packings utilizing T^urta S., Neoprene, or Buna N as a binder or a PTFE Impregnation for special applications. Note: Refer to Appendix C for prdperties of Canadian and Blue African Asbestos. "AVA'LABLE GASKET SIZES i\ND MANOFACTURI MG TOLERANCES" TABLE I Gasket Thickness Max. I.D. Max. Flange Width Recommended Compressed Thkns.' .0625 .0625 .100 .125 125 .125 .175 .175 .175 .175** .175** .175** .175 .250 .250 .285 .285 Up to 6" 3/8" .050/ 055 6 to 9" 1/4" 050/.055 10" 3/4" .075/.080 Up to 20" 1" .090/100 20" to 40" 3/4'" 090/.100 Over 40" Convert to .1 75" thickness Up to 1 2" 1 -1/2" .125/.135 12" to 20" 1 -3/8" .125/. 135 20" to 40" 1-1/8" .125/.135 40" to 60" 1" .125/135 60" to 70" 7/8" .125/. 135 70" to 75" 3/4" .125/. 135 Over 75" Convert to .250 or .285" thickness Up to 90" 1-1/4" .180/. 200 90" to 150" 1" .180/. 200 Up to 90" M/4" .200/ 220 90" to 150" r* .200/.220 Notes: *The recommended compressed thickness is what experience has indicated to be the optimum range in order to achieve maximum resiliency of the gasket. An additional spread of .010 in either direction can be tolerated on all gasket thicknesses with the exception of the .0625 and the .100" thick gasket. This is on the assumption that the flange surface finishes are relatively smooth. Refer to "Flange Surface Finish" on page 9. **PTFE filled FLEXITALLIC gaskets in this size range are unstable and are subject to "springing apart" in shipping and handling. A .285" thick gasket should be specified in order to minimize this problem. FLEXITALLIC gaskets are available in sizes from 1/2" l.D. to approximately 150" I.D. depending upon gasket thickness. Table I indicates size ranges available in various thicknesses, maximum flange widths and the recommended compressed thickness. FLEXITALLIC gaskets are subject to standard manu facturing tolerances listed in Table II. If tighter tolerances are required, consult our Engineering Department. Gasket Diameter Up to 24" 24" to 36" 36" to 60" 60" & Above TABLE II l.D. + 1/64 + 1/32 + 3/64 + 1/16 O.D. + 1/32 * 1/16 + 1/16 1/16 Tolerance on gasket thickness is + .005" on all thicknesses except as follows where standard tolerance becomes plus .010", minus .005". Gaskets with less than 1" I.D. Gaskets using PTFE fillers Gaskets using compressed asbestos sheet filler. Gaskets with flange widths greater than 1". "S'Z'NG SPIRAL WOUND COMPONENTS FOR FLEX'TAL.'C GASKETS" Regardless of the type of flange facing in use, FLEXI TALLIC gaskets must be sized to insure the spiral-wound element is seated against a flat surface. This is of utmost importance. If the spiral-wound element protrudes into the flange bore or extends beyond a raised face, mechanical damage will occur to the g3sket during initial compression, and ultimate failure will result. In addition, should the gasket protrude into the flange bore, the windings can possibly enter the process stream with severe damage to other equipment resulting. With recessed flange facings, limiting dimensions of the gasket are established by dimen sions of the groove. On flat or raised face flanges, considerable leeway is available. The following rules will be generally applicable for limiting dimensions of spiralwound components. (See Chart I for nominal flange widths.) 1. Gasket confined on both l.D. & O.D, -- This is the type facing encountered in tongue and groove joints, and groove to smooth joints. Standard practice is to allow a 1/16 " diametrical clearance between the I.D. of the groove and the l.D. of the gasket and 1/16" diametrical clearance between the O.D. of the gasket and O.D. of the groove. \ 2. Gasket confined on O.D. only -- This is the type of facing encountered with male and female facings and female to flat facings. Standard practice is to allow a 1/16" diametrical clearance between the O.D. of the gasket and the O.D. of the groove. If possible, allow a minimum 1/4" diametrical clearance between the I.D. of the seating surface and the I.D. of the gasket. Cr'ART iMO. I Nominal Gasket Flange Width vs. Diameter (Refer to Table I for Maximum Flange Width for Various Thicknesses! Maint ain Same Widths __ for Larger ' Gaskets I/A 1/2 3/4 I FLANGE WIDTH - INCHES 1 H/4 3. Gasket unconfined on both the ID. & O.D. -- Allow a minimum 1/4" diametrical clearance between the gasket I.D, and the I.D. of the seating surface. The O.D. should be kept as close as possible to the bolt circle to minimize flange bending moments. If the gasket is used with raised face flanges, allow a minimum 1/4" diametricaLcIearance between the gasket O.D. and the raised face. O.D. and determine the I.D. on the basis of the desired flange width. Important -- Please note the above rules establish general limits for sizing FLEXITALLIC gaskets. It is frequently necessary to adjust dimensions in order to achieve a proper balance between gasket area and bolt area to maintain a reasonable compressive force on the gasket and a minimum gasket factor "m" of three. Please refer to section covering ASME Boiler and Pressure Vessel Code. 4. Metal Gauge Rings -- When FLEXITALLIC gaskets are required to be equipped with outer metal ring? or with inner metal rings, limitations on the minimum flange widths of the solid metal ring are necessary due to the availability of machining facilities and rigidity of completed assemblies. Table III indicates the minimum flange width for solid metal rings based on the ring I.D. TABLE III Diameter of Ring UP to 10" I.D. 10" to 24" I.D. 24" to 50" I.D. 50" to 70" I.D. 70" and Larger Minimum Flange Width* 3/8" 7/16" 1/2" 5/8" 3/4" *Note: Where space is limited and narrower flange widths are necessary, it may be possible to supply inner and outer spacer rings of solid metal spiral-wound construction. Consult our Engineering Department for advice. Standard practice is to size outer rings with the outside diameter equal to diameter of the bolt circle less the diameter of one bolt. Inner rings are normally sized with an inside diameter equal to the flange bore. 5. Non-Circular Gaskets -- FLEXITALLIC gaskets can be fabricated in non-circular shapes within limitations. As a general rule, if the ratio of the long I.D. to the short I.D. exceeds 3 to I and should any of th-se sides approach a straight line, it may not be possible to manufacture a FLEXITALLIC gasket that would be suitable. Our product requires a definite radius or curvature to give it inherent strength and stability and to prevent it from springing apart. Any application requiring a non-circular gasket should be submitted to our Engineering Department for review to determine the feasibility of producing a satis factory gasket as early as possible in the design stage. The comments above relating to availability of sizes and recommended clearances for proper sizing of FLEXITALLIC gaskets are general in nature. Many applications will arise where the recommended clearances are impractical due to space limitation on the flange. Frequently, clearances between gasket sealingmemberand grooves must be reduced in order to effectively maintain a seal under operating conditions, particularly when the higher pressures are encountered. Under such circumstances, FLEXITALLIC GASKET COMPANY engineers should be consulted prior to finalizing designs. "FLANGE SURFACE FINISH" FLEX1TALLIC gaskets rely on the combined reaction of the metal and filler material to effect a seal. When the gasket is compressed, the filler material flows into minute imperfections and the metal serves to completely trap the filler material and provide the necessary strength and resilience to the gasket assembly. Obviously, the deeper the serrations, or the rougher the flange surface finish, the higher the force required to'flow the gasket mto the imper fections. Although FLEX1TALL1C gaskets will seal against virtually any commercial flange surface finish, abnormally high bolt loads may be required to obtain a seal against rough flange finishes. For this reason, flanges to be used with FLEXITALLIC gaskets should be specified with surface finishes specified in Table IV. TABLE IV Serv.ro Flange Surface Finish in Micro Inches General Purpose Hazardous Service and Hard to Hold Fluids Vacuum Service 125 to 200 RMS 125 RMS 80 RMS Important -- Under no circumstances, xdnould flange sealing surfaces be machined in a manne/that tool marks would extend radially across the seating surface. Such tool marks are practically impossible to seal, regardless of the type of gasketing material used. A phonographic or concentric serrated finish is preferred for FLEXITALLIC gasket applications. "ASME BO'LER AND PRESSURE VESSEL CODE CALCULATIONS" Section VIII, of the ASME Boiler & Pressure Vessel Code, establishes criteria for flange design and suggests values of "m" (gasket factor) and "y" (minimum gasket seating stress) as applied to spiral-wound gaskets. For the most part, the defined values have proven successful in actual applications. However, much confusion exists regarding these values, primarily due to a misunderstanding of the definitions of the terms and their significance in practical applications. Mandatory Appendix II, in Section VIII of the Boiler Code, requires in the design of a bolted flange connection, complete calculations shall be made for two separate and independent sets of conditions. 1. Operating Conditions Condition one (1) requires a minimum load be determined in accordance with the following equation: 0) Wml =-144P--+ 2b 3.14GmP This equation states the minimum required bolt load for operating conditions is the sum of the hydrostatic end force plus a residual gasket load on the contact area of the gasket times a factor times internal pressure. Stated another way, this equation requires the minimum bolt load be such that it will maintain a residual unit compressive load on the gasket area that is greater than internal pressure when the total load is reduced by the hydrostatic end force. It should be noted that Table UA-49.1 suggests a gasket factor "m" for a spiral-wound gasket of 2.5 for carbon steel and 3.0 for stainless or monel. It is important to note the gasket factor "m" is suggested and is not mandatory. (Note: See paragraph on gasket factor "m" on page 10 for a more detailed discussion.) 2. Gasket Seating Condition two (2) requires a minimum bolt load be determined to seat the gasket regardless of internal pressure and utilizes a formula: (2) Wm2 = 3.14bGy The "b" in this formula is defined as the effective gasket width and "y" is defined as the minimum seating stress in psi that depends upon the type of gasket material. Table UA49.1 suggests a minimum "y" value for a spiralwound gasket of 2900 psi for carbon steel and 4500 psi for stainless or monel. These design values are suggested and are not mandatory. The term "b" is defined as: b = bQ when bQ = 1/4" b=/ when bQ >1/4" In the case of a spiral-wound gasket, b0 = N in all cases where N is the radial flange width of the spiral-wound portion of the gasket. Our experience has been that the suggested values for "y" using the effective seating width as defined in the Code is too low. The minimum design seating stress for a FLEXITALLIC gasket is subject to variables. (Note: See paragraph on Minimum Seating Stress -- "v" an page 10.) After Wmi and Wm2 are determined, the minimum required bolt area, Am is determined as follows: \ymi A-ml = ~p-- where Sfo is the allowable bolt stress at b _ wm2 operating temperature, and Am2 = -where Sa is the allowable bolt stress at atmospheric temperature. Then Am is equal to the greater of Aml or Am2. Bolts are then selected so the actual bolt area, Ab, is equal to or greater than Am. At this point, it is important to realize the gasket must be capable of carrying the entire compressive force applied / the bolts when prestressed unless provisions are madejo utilize a compression stop in the flange design or by the use of a compression gauge ring. For this reason, FLEXITALLIC'S standard practice is to assume W is equal to Ab Sa.* [f we equate Wm2 = W on the assumption we can develop in the gasket sufficient density to carry the entire bolt load and solve this equation for Dg_we have, Ab Sa (3) Dg = 3 ~j 3-~bG '^lere *g *s the actual load carrying capacity or density of the gasket. This is the gasket density used by FLEXITALLIC in assigning construction details for fabrication in our shops. Following this procedure, once Ab has been determined, we are no longer concerned with which is greater, Wm] or Wm2- We are concerned with actual values. If the values determined for Dg are within the density range indicated in Table V, a suitable gasket can be supplied. If the values determined are greater than those listed, either a wider gasket is required or a compression stop must be utilized. GASKET SEAT'VG STRESS -- "y" As indicated previously, our experience has indicated the minimum "y" value as defined in Table (JA49.I, Section VII], coupled with the effective gasket seating width "b" as defined in Table UA-49.2 is unrealistic. The "y" value should be in the 9000 psi range rather than the 4500 psi range suggested in the Code. (It is possible to reduce the minimum "y" value for a FLEXITALLIC gasket to the Code figure if an extremely narrow gasket is furnished in relationship to its I.D. However, to achieve such a low figure would result in a radial width of the gasket we believe to be inadequate for long term satisfactory service and would be below what we would recommend as a minimum gasket width.) If gasket proportions as indicated on Chart l are followed. Table V can be used as a guide to "y" (minimum seating stress) and Dg (actual density.) The minimum seating stress is a function of flange surface finish as well as gasket density. The rougher the surface finish, the higher the required forces to flow the gasket into the imperfections. Dg and "y" are normally considered to be the unit load required to compress the gasket to its optimum operating thickness. NOTATIONS Ab = Actual total cross-sectional root area of ttflris or section of least diameter under stress; square inches. Am Total required cross-sectional area of bolts, taken as greater of Ami, or Am2.' square inches. Ami * Total required cross-sectional area of bolts required for operating conditions; square inches. Arrt2 = Total required cross-sectional area of bolts required for gasket seating; square inches. b - Effective seating width; inches. 2b - Jomt-coniact-surface pressure width;inches, bo = Basic gasket seating width; inches. G = Diameter of location of gasket load reaction; inches, rn = Gasket factor. table v GASKET SEATING STRESSES "v" Dg (minimum seating stress! psi Canadian or Blue African asbestos filled 9000 TFE filled 10000 Flexicarb filled 10000 (actual density rangel psi 9000 to 30000 10000 to 13000 10000 to 20000 GASKET FACTOR "nV* Appendix II, Section VIII, of the Boiler Code under paragraph VA-49 makes the statement "the `m' factor is a function of the gasket material and construction.'' We do not agree entirely with this interpretation of "m". Actually, the gasket does not create any forces and can only react to external forces. We believe a more realistic interpretation of "m" would be "the residual compressive force exerted against the gasket contact area must be greater than internal pressure when the compressive force has been relieved by the hydrostatic end force." It is the ratio of residual gasket contact pressure to internal pressure and must be greater than unity otherwise leakage would occur. It follows then, the use of a higher value for "m" would result in a closure design with a greater factor of safety. Experience has indicated a value of 3 for "m" is satisfactory for flanged designs utilizing FLEXITALLIC gaskets regardless of the materials of construction. In order to maintain a satisfactory ratio of gasket contact pressure to internal pressure, two points must be considered. First, the flanges must be sufficiently rigid to prevent unloading the gasket due to flange rotation when internal pressure is introduced. Secondly, the bolts must be adequately prestressed. The Boiler Code recognizes the importance of pre stressing bolts sufficiently to withstand hydrostatic test pressure. Appendix S, in the Code, discusses this problem in detail. N = Radial flange width of spiral-wound component: inches. P = Design pressure: psi. Sa = Allowable bolt stress at atmospherictemperature; psi. Sb = Allowable bolt stress at designtemperature: psi. W = Flange design bolt load; pounds. Wml - Minimum required bolt load for operating conditions; pounds. Wm2 = Minimum required bolt load for gasket seating; pounds, y = Minimum gasket seating stress; psi. Dg = Actual gasket density; psi. |*Note: If a prestress greater than Sa is to be used (as is normal practice in order to successfully pass a hydrostatic testl the actual prestress value will be used in lieu of Sa in equation (3). F_AvGE DESIGN FDR FLEXiTALL C GAS 'STS 1. Determine the required bolt load for operating conditions Wmi, (Equation (1).) (Approximate gasket size by referring to Chart I and Table 1, and use an "m" value equal to three.) 2. Determine the required bolt load to effect a seal (Wm2) by solving equation (2). Use a minimum seating stress "y" per Table V. * _ 3. Determine the minimum bolt area by dividing Wmj by the allowable bolt stress at operating temperature and by dividing Wm2 by the allowable bolt stress at atmospheric temperature. The greater of these two values becomes Am. the minimum bolt area. Select the number and size of bolts that will give an actual total cross sectional area equal to or greater than Am. 4. If Wmj is greater than Wm2, equate Wmi =3.14bG Dg and solve for "Dg". If "Dg" falls within the ranges shown on Table V, a FLEXITALLIC gasket can be designed to carry the load. If the resulting value of Dg is greater than the maximum indicated in Table V, it is necessary to provide a compression stop either by utilizing a ring on the inside or the outside of the gasket or by designing into the flange, a compression stop that would bring the flanges metal to metal. 5. If Wm2 is substantially greater than Wm[ resulting in a greater bolt load than required for operating conditions, it is possible to reduce Wm2 by reducing the flange width of the gasket, if this is the case, we suggest you contact FLEXITALLIC engineers for recommendations as to minimum flange widths for the diameter and pressure/ temperature conditions. 6. Proceed strictly to the flange design procedures in Appendix II of the Boiler Code. 7. After all flange dimensions have been determined, determine flange rotation at the gasket interface at test conditions. If the flange rotation is excessive, extra ordinary precautions must be taken to insure a satisfactory hydrostatic test. (Refer to section covering "Bolting Up Procedures.") ORDERING FLEX1TA_L'C GASKETS FOR SPEC AL = LANGE DES'GNS In order for the FLEXITALLIC GASKET COMPANY to design a gasket suitable for the application, it is imperative that complete details be submitted for review. The information we require is the following: 1. Type of flange facing 2. Dimensions of the gasket seating surfaces 3. Number, size and material of bolts 4. Bolt circle diameter 5. Operating pressure & temperature (Process material if known) 6. Hydrostatic Test pressure 7. Initial bolt pre-stress 8. Customer preference on gasket materials FLEXITALLIC supplies engineering data sheets at no cost on which this information may be submitted. As a gasket manufacturer, it is impossible for us to review every flange design to make certain that flange rotation and flange stresses are within allowable limits defined in the Code. We proceed on the assumption the design engineer has followed the design criteria established by the ASME Boiler Code and that the flanges are sufficiently^igid under the most severe condition to preclude the possibility the gasket could become unloaded either during operating conditions or hydrostatic test conditions. We are aware that most flange designers do not take into consideration, flange rotation at test conditions. This is a very important aspect that is not normally considered, and we urge every flange designer to check out flange rotation at test conditions prior to finalizing his design. We also, of a practical necessity, must assume the bolt material being used is adequate for all conditions including operating pressure at operating temperature and hydrostatic test pressure at ambient temperature. The use of the optimum material -J&xtkU&fc gasket engineering data -irwi-j nu ._ _______ ___ _0* - ______ - sewer co**0>no cum*** rnirmucr irKTINir irr/T jhn; gCj/n; njQn irrT~]W idZbnu EOn "0 for bolts is a very complex subject and we suggest ASME paper, number 53-BET-7 entitled "Modern Steel Bolting for Piping & Pressure Vessels", authored by C. M. Vogrtn, Frank S. G. Williams and John S. Worth, be consulted for guidance in the proper selection of boiling maierial fur piping and pressure vessel applications. BOLTING-UP PROCEDURES FLEXJTALLIC GASKET COMPANY supplies thousands of different gaskets for special flange designs that must successfully pass a hydrostatic test and maintain a satis factory seal under operating conditions. Our experience has indicated that virtually every time a leaky joint is encountered, the actual cause of failure relates to some thing other than the gasket design. These causes are itemized below: - -- 1. On low pressure applications, flange designers have followed the Code suggestions for a minimum seating stress (y value) that we know from experience are impractical and hence, neither the bolting nor the rigidity of the flanges, are adequate to initially seat the gasket to obtain a seal. 2. Flange designers do not take into consideration, the rotation of the flanges and the necessity for the flanges and the bolting to maintain a sufficiently high residual unit load on the gasket contact surface to contain internal pressure. These two conditions contribute to a vast majority of complaints on joint leakage. 3. The insistence of some inspection personnel that hydro static test conditions must be carried out at stress values for initial pretensioning of bolts at the allowable design stresses specified in the Code. Appendix S, in the Code, specifically covers this area and must be taken into cognizance anytime a hydrostatic test is to be performed. From a practical standpoint, when a flange is designed for pressure conditions of 600 psi and the hydrostatic test pressure is to be performed at 900 psi, it is obvious that a higher prestress must be applied to the bolts is a satisfactory test is to be applied. 4. The use of low yield bolting material, such as the austenitic stainless steels or ordinary carbon steel machine bolts. With both of these materials, it is relatively easy to stress the bolts beyond their yield point with eventual failure occurring using a standard wrench for the nominal bolt diameter. In order to successfully pass a hydrostatic test, it is often desirable and permissible to utilize a high strength alloy bolt for hydrostatic testing purposes. When this procedure is followed, the following steps are recommended: a. For hydrostatic testing, use ASTM B 193, Grade B 7 bolting material, or equivalent, to initially seat the gasket and perform the hydrostatic test.,. b. .After achieving a successful hydrostatic test, relieve the tension on the bolts to approximateiy"50% of the allowable bolt stress and replace the bolts one at a time with the required bolting material. c. When replacement is made, the bolts should be stressed to the allowable stress for operating conditions. ft should be pointed out a bolt initially prestressed to 20,000 psi will very rapidly relax to approximately 50% of the initial applied stress due to creep and relaxation in the bolt material. Bolting that is stressed to 30,000 psi initially will relax to approximately 75% of its initial prestress over a short period of time. This indicates it is essential to prestress the bolt to a level that will guarantee maintenance of a stress level at operating conditions that will insure a safe joint. Thermal Expansion When bolts are initially prestressed to compensate for relaxation plus the usual hydrostatic end load, plus a residual gasket load, consideration must be given to stresses induced by thermal expansion under operating conditions. This can be caused by differential expansion of the flanges and the bolt material due to different coefficients of expansion or a temperature gradient that is present between the flange and the bolt material. In many installations, stresses developed by thermal expansion can adversely affect both the ability of the gasket to carry the applied forces and/or the ability of the bolt material to remain in an elastic state without being over-stressed. When thermal expansion is a serious problem and excessive bolt stresses or gasket loading can result, it is recommended the gasket be compressed only to a point that will permit further compression of the gasket as the loading due to thermal expansion is applied. In the case of a gasket with a compression stop, it is recommended initial compression be limited to within 8 to 10 thousandths of the final compressed range that is controlled by the thickness of the compression gauge ring or by the depth of the groove. By doing so, the build up of excessive stresses in the bolts can be eliminated. In the case where a compression stop is not provided, the additional stresses can be absorbed by the gasket providing the stresses resulting from thermal expansion will not crush the gasket beyond its elastic limit. Developing Prestresses in Bolting The only completely satisfactory method for closing the flange and developing uniform stresses in each bolt at a controlled bolt stress is by measuring bolt elongation. This is an impractical approach, since the cost of bolting up using this procedure becomes excessive. An alternate means must be considered. The most frequent method is by utilizing torque wrenches. The use of torque wrenches, however, introduces many variables, and are not normally reliable methods of determining the actual bolt stress developed. Some of the factors that enter into the actual developed bolt stress are: 1. The class of fit of the bolt and nut 2. Presence of burrs 3. The degree of lubrication achieved 4. The presence of grit, chips and dirt in the threads in the bolt and nut 5. Nicks 6. The relative condition of the seating surface on the flange against which the nut is rotated All of these variables have a marked effect on the amount of torque required to produce a given stress. Where conditions are fairly constant and reasonably controlled, it is possible to give nuts a certain torque value and obtain stresses that are consistent within reasonable limits. The required torque value can be obtained by tightening a sample bolt to a desired elongation while measuring the torque or by calculating it by means of formula. If this, procedure is not followed, the actual developed stress in a stud can be completely unrealistic. Field tests have indicated that the use of torque wrenches in attempting to develop required bolt stressescan vary as much as 100% due to the variables present that have been previously mentioned. It is a requirement, particularly in the use of a FLEX1TALLIC gasket, that a reasonably, even compressive force, be applied. From a practical standpoint, in order to achieve this, a very definite bolt up procedure must be followed. This procedure is detailed as follows: 1. Install the gasket on the gasket seating surface and bring the cover flange in contact with the gasket. 2. Install all bolts, making sure they are free of dirt and grit, and are well lubricated. 3. Run up all nuts finger tight. 4. Develop the required bolt stress in a minimum of three steps, following a tightening up procedure as recommended in Sketch I. It is important to make certain that no more than 50% of the required bolt stress is achieved on the initial set. Should this occur, serious damage can be done to the FLEXITALLIC gasket and subsequent tightening cannot offset the damage. Once a complete cycle of stressing has been achieved, it is not necessary to follow the exact bolting sequence recommended. However, we cannot emphasize the importance for following the sequence in the first application of pre-tightening. CONCLUSION In summary, the FLEXITALLIC gasket is a carefully engineered, precisely made, quality product capable of providing industry with the optimum in closure sealing when used judiciously in accordance with good engineering practice. Beyond the horizon of today, FLEXITALLIC will maintain its leadership by providing for industry's needs as we face tomorrow's technological advances. The information contained in this bulletin is not to be taken as a warranty or representation for which we assume legal responsibility. It is offered solely for your consideration, investigation and verification. ~- Comments, criticism and discussion on its contents are cordially invited. Please write, Flexitallic Gasket Co., Inc., P.O. Box 6K0, Camden. New Jersey 0SI01 U.S.A. or Flexitallic Gaskets (Wood Bros.) Ltd. Station Lane Heckmondwike. Yorkshire, England. The authors are appreciative of ihe assistance freely given by their co-workers and oihers outside the company in preparing - this bulletin and the extremely helpful suggestions and criticisms ottered. BOLTING UP SEQUENCE SKETCH I 13 appendix a Repimed from 1967 Corros on Data Survey. NACE, 24Q3 W. Loop S., Houston, Tx. 77027 CORROSIVES WHICH CAN INDUCE STRESS CORROSION CRACKING IN METALS Monel N ickel Inconel T ita n iu m 1 A lum inum 1 Leigend: I - Intergranular Cracks T - TrShsgranular Cracks IT - Intergranular and/or Transgranular Cracks l l ac *<3u W a>i aa e i Ammonium Chloride................................................................. Amines............... Ammonia (pure) Ammonia (Dilute) Ammonium Nitrate................................................................. Butane + Sulfur Dioxide.......................................................... Cadmium .... Calcium Bromide Chloride salts (see Inorganic and Organic Chlorides) Chromic Acid . . IT I Ii | T IT I T T T I Cresylic Acid (vapors).............................................................. Cyanogen .... Fluosilicic Acid . Hydrogen Chloride (some water)....................................... Hydrogen Cyanide (some water)....................................... Hydrogen sulfide (some water)........................................... Hydrofluoric Acid HN03, HC1, HF Pickling Acids........................................... Inorganic Chlorides (same water present).................... Inorganic Nitrates I T (7) TT T 1 IT IT T T I IT IT! a) I<a; Mercurous Nitrate Mercury................ Metal chlorides (see Inorganic chlorides) Mixed Acids (H3S0 . + HNOu) ........................................... Nitrate salts (see Inorganic nitrates) I IT IT IT IT Nitric Acid + Manganese Chloride................................... Nitric Acid (Bed Fuming)...................................................... Nitric Acid (vapors) ............................................................. Oleum................... Organic Chlorides some water present) .................... I IT T T I I (*) Potassium Hydroxide .......................................................... Potassium Permanganate.................................................. Salt Water + Oxygen.............................................................. Silicofluoride Salts Sodium hydroxide -ir.............................................................. Steam....................... -- Sulfate Liquor (white).......................................................... Sulfide Liquor . . Sulfur Compounds Uranyl Sulfate . . IT I I T I I IT IT I I ( Ojt * (5) (5) (6) T IT IT C 3> JI (1) Acid attack on steels containing martensite can cause cracking by hydrogen absorption in many media. (2) Heating to temperatures of 475 C and above after exposure to sulfur compounds. (3) (vapor) (6) Stress Cracks Inconel, 1500 F. (4) (alloyed) (7) Stress Cracks Monel. (5) Stress Cracks Si-Bronze 400 F; Monel, 600 F. appendix b Reprinted ftorr 1967 Corrosion Deta Survey. MACE, 2400 W. Loop S,, Houston. Tx. 77C27 CORROSIVES WHICH INDUCE INTERGRANULAR CORROSION IN AUSTENITIC STAINLESS STEEL Acetic Acid Acetic Acid + Salicylic Acid Ammonium Nitrate Ammonium Sulfate Ammonium Sulfate H2SO4 Beet Juice Calcium Nitrate Chromic Acid Chromium Chloride Copper Sulfate Crude Oil Fatty Acids Ferric Chloride Ferric Sulfate Formic Acid Hydrocyanic Acid Hydrocyanic Acid + Sulfur Dioxide Hydrofluoric Add + Ferric Sulfate Lactic Acid Lactic Acid + Nitric Acid Maleic Acid Nitric Acid Nitric Acid + Hydrochloric Acid Nitric Acid + Hydrofluoric Acid Oxalic Acid Phenol + Naphthenic Acid Phosphoric Acid Phthalic Acid Salt Spray Sea Water Silver Nitrate + Acetic Acid Sodium Bisulfate Sodium Hydroxide + Sodium Sulfide Sodium Hypochlorite Sulfite Cooking Liquor Sulfite Solution Sulfite Digester Acid (Calcium Bisulfite + Sulfur Dioxide) Sulfamic Acid Sulfur Dioxide (Wet) Sulfuric Acid Sulfuric Acid + Acetic Acid Sulfuric Acid + Copper Sulfate Sulfuric Acid + Ferrous Sulfate Sulfuric Acid + Methanol Sulfuric Acid + Nitric Acid Sulfurous Acid Water + Starch + Sulfur Dioxide Water + Aluminum Sulfate APPENDIX C PROPERTIES OF ASBESTOS FIBRES % Si 02 Mg 0 Fe O Fe 2 03 At2 03 H2O Ca O Na2 O Chemical Composition of Asbestos Fibers Canadian Asb. (Chrysotile) Blue African (Crocidolite) 37-44 39-44 0.0 - 6.0 0.1 - 5.0 0.2 - 1.5 12.0 - 15.0 Tr - 5.0 49 - 53 0-3 13-20 17-20 2.5 -4.5 4.0 - 8.5 EFFECT OF HEAT ON LOSS IN WEIGHT OF ASBESTOS FIBRES It has been found that with the corresponding loss in weight, proportional reduction in tensile strength of the fibres takes place. When the loss in weight on exposure to heat of "blue" crocidolite asbestos fibres is compared with that of chrysotile it may be seen that at 800F., crocidolite asbestos loses a great part of its combined water (and becomes brittle), whilst chrysotile loses 1 /6th only. Further, crocidolite asbestos completely gives off its water content at 1,200F., whilst chrysotile asbestos loses the last trace at 1,800F. Effect of temperature on percent loss m weight of asbestos fibers. Temp. F. 400 600 700 800 900 1,000 1,100 1,200 1.400 1,500 1.600 1,700 1,800 Time 2 hrs. 2 hrs. 2 hrs. 2 hrs. 2 hrs. 2 hrs. 2 hrs. 2 hrs. 2 hrs. 2 hrs. 2 hrs. 2 hrs. 2 hrs. Chrysotile 0.30 0.85 1.78 2.17 2.83 3.99 10.38 12.75 13.43 -- 13.62 -- 13.77 Crocidolite 0.08 0.25 0.49 0.73 0.83 Q.86 1.00 1.04 1.03 -- 0.93 -- 0.77- CHEMICAL RESISTANCE The varieties of asbestos vary considerably in their chemical resistance. Chrysotile asbestos is essentially a basic magnesium silicate, with a magnesia-silica ratio of approximately 1:1. This means that there is an excess of magnesia over the chemically equivalent quantity of silica. As might be expected from the composition, the acid resistance of chrysotile is poor. Strong mineral acids dissolve out all the magnesia leaving an insoluble residue of nearly pure silica. The silica residue retains the fibrous form of the asbestos but practically all the original strength is lost. In crocidolite asbestos, the basic constituents and the silica are in almost chemically equivalent proportions, and the acid resistance is good. M.S. Badollet has published the following tables showing the effect of chemicals on asbestos:------ Solubility of Asbestos Percent loss in weight due to refluxing for two hours _________ in 25 percent acid or Caustic Soda_________ HCI CH3COOH H3PO4 H2SO4 NaOH Chrysotile............. 55.69 Crocidolite........... 4.38 23.42 0.91 55.18 55.75 4.37 3.69 0.99 1.35 Percent loss 1in weight due to exposure at 26C. for 528 hours in 25 percent Acid or Caustic Soda Chrysotile............. 56.00 Crocidolite........... 3.14 24.04 1.02 56.45 56.00 3.91 3.48 1.03 1.20 HCL -- Hydrochloric Acid. CH3COOH -- Acetic Acid. H3PO4 -- Phosphoric Acid. H2SO4 -- Sulfuric Acid. NaOH -- Sodium Hydroxide. Fusion Point F. 2.770 2.180 'Iron changing in weight caused by oxidation. 1