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392 CHAPTB? 22 1965 Guide And Data Book uniform width of air space (usually } in. in walls and f in. or more in foiling ami floors) adjoining the reflective surface. Forms in which the product is available include (1) blankets fabricated to provide a number of air spaces when installed between framing, and (2) large sheets, adhered to insulating batts, blankets, and to other building materials, such as interior finish panels. In applying reflective type insulations, it is important that the manufacturer's specifications and instructions be fol lowed. If a particular insulation product is provided with a nailing flange, it must be placed and stapled in a manner that will assure a permanent, uniform air space. The ends of the product should also be stapled and sealed to prevent openings. If tears or punctures occur during application, they must be repaired with tape or suitable pieces of vapor barrier material to assure adherence to the reflective surface. The insulation should be trimmed tightly around electric outlet boxes, -plumbing, etc., and taped tight. Since condensation may occur on a single piece of reflective material used alone in the center of a stud space, a separate vapor barrier should be used on the warm aide of the wall or two or more single sheets of reflective material or insulation with multiple layers of reflective surfaces may be applied. When irregularities of stud or joist spacing exoeed the dimen sional tolerances of the reflective blanket involved, other forms of should be used. FORMED-IN-PLACE INSULATIONS Formed-in-place insulations include sprayed and plastic foam types. Sprayed tni>latmn is usually inorganic fibrous material which is blown against a clean surface to which has been applied a coat of adhesive to assure a good bond. A special spray gun is used where the adhesive is mixed with the fibers as they are blown against the surface to the desired thickness which may be up to 2 in. The surface is lightly tamped to provide uniformity and obtain a proper density from 1 to 1M lb per board foot. This type of product is often left exposed to the room to provide acoustical treatment as well as insulation value. Polystyrene and urethane plastic foams may be molded or foamed-in-pkce. Urethane insulation may also be applied by spraying. The application of expandable polystyrene requires the use of steam boilers as a source of heat and heavy molds. Thus, it will probably not be used directly as a building insu lation but is finHmg application in panels. Foamed-in-place and spray techniques for urethane require special equipment for correctly metering and miring the liquid components. These materials, however, can be used in the field and are. being applied as roof, wall, and floor insulation. Since the methods of handling expandable polystyrene and urethane foams are undergoing rapid changes in technology, the recommendations of the manufacturers of these materials should be consulted before attempting to use them as building insulations. PART V: GENERAL PRACTICE FOR INDUSTRIAL INSULATION The applications of industrial insulation to be discussed ini this section include: (1) pipes; (2) tanks, vessels, and equip ment; (3) ducts; (4) refrigerated rooms or buildings; (5), dnmewttc. and commercial refrigerators; (6) mobile equip ment; and (7) environmental spaces. PIPES Rmull pipes are ingflatad with sectional insulation which is furnished with factory applied canvas jackets that form a hinge and lap. Small pipes and tubes are also insulated with flogpd roll elastomeric tubing that is slipped over the pipe or tnhing before joints are made. Lorge piping is insulated with Bpgrwpntal blocks, wired or branded in place, or with sectional insulation, particularly where removal for frequent servicing of the pipe is necessary. Indoors, sectional insulation is ap plied with the lap cemented. Outdoors, it is necessary to provide a weatherproof finish. Fittings and bends are insulated with portions of standard preformed insulation, or insulating cements. Fitting insulation should be consistent with the pipe insulation. Surfaces maintainpd at temperatures lower than the sur rounding air are insulated to reduce heat gain and to prevent condensation. Prevention of moisture accumulation is par ticularly important in the insulationof surfaces that are below the dew point of the surrounding air, since moisture sub stantially increases the effective conductivity of the insu lating material. In such cases, it is necessary to seal the sur face of the insulation against the penetration of water vapor which would condense within the material and cause a serious increase in heat flow, possible breakdown of the material, and corrosion of the metal surfaces. There are a number of systems for accomplishing vapor sealing, some of which have been darigneH by manufacturers to suit their products, and others by applicators and users. Vapor barrier treatment should be that which is recommended by the insulation or vapor barrier manufacturer and selected on performance rating as a basis. Good practice demands that the insulation should be pro tected from inclement elements prior to application and applied as dry as possible. Wherever the pipe is interrupted by fittingB, valves or Hangup the pipe insulation should be carefully sealed with a vapor barrier tape, mastic or sealer to prevent the entrance of moisture. Vapor barrier adhesive mud be used for fastening laps of sheet vapor barriers. Tapes of adequate width or strips of vapor barrier sheets should be cemented over the joints between sections to completely seal the joint. In some casesfor long runs of piping, the ends of permeable insulation sec tions should be sealed with vapor harrier compounds at inter vals of from 15 to 20 feet to limit the extent of water penetra tion in tiie event of physical damage. Vapor barrier protective ermting may be reinforced with glass fabric or other rot proof strong membranes for additional protection from damage. Where impermeable or low permeance insulations are used, all butt and longitudinal joints should be filled and sealed with Table 3 .... Minimum Insulated Pipe Spacing (For Propor Appficortoo end Sooting of Pipe luulotioa) bmstafioo TWcEmo Space porafM pqw*. in. Spec* bnfnoM pip* cad adjacent turfoeu,. IH in. to 2 in. Up to 6-in. pipe--screwed fittings Larger than 6-in.--screwed fittings All pipe --flanged fittings 7 11 5 2 in. to 3 in. Up to 6-in. pipe--screwed fittingB Larger than 6-in. pipe--screwed fittings All pipe rises--flanged fittingB 9 15 16 9 3 in. to 4 in. Up to 3-in. pipe--screwed fittings Larger than 3-in. pipe--screwed fittings All pipe sizes flanged fittings 11 19 20 9 13 14 Thermal Insulation and Water Vapor Barriers vapor barrier compound. Where multiple layer construction is 0^ joints in the outer layer must be sealed and the insula tion must be applied with staggered joints. Fire resistive vapor barrier material should be used in hazardous areas. For dual temperature service where the pipe is alternately cold and hot, vapor barrier finish as well as all flashing and compound must be selected to withstand movement of the pipe without permitting water vapor leakage. The barriers and sealers must be able to withstand the highest and lowest temperature to which they are subjected without softening, melting, or otherwise deteriorating. * The piping must be carefully protected against corrosion caused by condensation of water vapor or environmental con ditions. Table 3 shows the minimum spacing that must be allowed to permit proper application and sealing of pipe insulation. Heat gains for pipes insulated' with a material having a conductivity of 0.30 Btu per (hr) (sq ft) (F deg per in.) are given in Table 28, Chapter 24, which may be used as a guide many of the commercial insulations offered for this purpose have conductivities very near the 0.30 value used, fig. 6 is used to determine the thickness of insulation required to prevent condensation. Insulation of Pipes to Prevent Freezing If the surrounding cur temperature remains sufficiently low for an ample period of time, insulation cannot prevent the freezing of still water, or of water flowing at such a velocity that the quantity of heat carried in the water is not sufficient to take care of the resulting heat losses that will cause the tem perature of the water to be lowered to the-freezing point. Insulation can materially prolong the time required for the water to give up its heat, and if the velocity of the water flowing in the pipe is maintained at a sufficiently high rate, freezing will be prevented. Table 4 may be used for making estimates of the thickness of insulation necessary to take care of still water in pipes at various water and surrounding air temperature nonHitinn* Because of the damage and service interruptions which may result from frozen water in pipes, it is essential that an effi cient insulation be utilized. Table 4 is based on the use of a material having a conductivity of 0.30. The initial water tem- Table 4 .... Data for Estimating Requirements to Prevent Freezing of Water in Pipes with Surrounding Air at -- 18 F 393 perature is assumed to be 10 F deg above, and the surrounding air temperature 50 F deg below, the freezing point of water (temperature difference, 60 F deg). The last column of Table 4 gives the minimnni quantity of water at initial temperature of 42 F which should be supplied every hour for each linear foot of pipe, in order to prevent the temperature of the water from being lowered to the freezing point The weights given in this column should be multiplied by the total length of the exposed pipe line expressed in feet As an additional factor of safety, *nd in onder to provide against temporary reductions in flow occasioned by reduced pressure, it is advisable to double the rates of flow listed in Table 4. It must be emphasized that the flow rates *nH periods of time designated apply only for tire conditions stated. To estimate for other service conditions, the following procedure may be used. If. water enters (he pipe at any temperature other than 42 F, the time required to cool it to the freezing point will be equal to (<--32)/10 times that given in Table 4, or the rate of flow of water may be changed to l0/((--32) times the indicated flow rate in the last columns of Table 4. For r*tmp1; if the water enters the pipe at 34 F, it will be cooled to 32 F in onefifth of the time given in Table 4. It will (hen be necessary to increase the rate of flow so that five times the specified quan tity of water will have to be supplied in order to prevent freezing. If the minimum air temperature is -- 38 F (temperature difference 80 F deg) instead of --18 F, the tinw required to cool the water to the freezing point will be 60/80 of the tims given in Table 4, or the necessary quantity of water to be supplied will be 80/60 of that given. In making calculations to arrive at the values given in Table 4, the los of heat stored in the insulation, the effect of a varying temperature difference due to the cooling of pipe and water, and the resistance of the outersurface of the insulation to the transfer of heat to the air, have all been n^ected When these factors enter into the computations it is necessary to enlarge the factor of safety. Also as stated, the time shown in Table 4 is that required to lower the water to the freezing point. A longer period would be required to freeze the water; but the danger point is reached when freezing starts. The flow of water will stop and the entire line, will be in danger as woon as the water freezes across the section of the pipe at any point.' It is is necessary to calculate the time required for the water to cool to 32 F, the following equation may be gapd - g_ - 32) *(i x ri) (3) Cr = Capacity of pipe, lb water/Iin. ft -- C, may be obtained from Tables 1 :and 2, Chapter 58 or from manufacturers' catalogs and handbooba. `tm- 9. ---------------------------------r* log, -- rt H *= time for water to oool to 32 F, hours. - q, -- Btu per (hour) (square footof outer surface of insulation). n = Inside radius of pipe, inches. ri = outer radius Of pipe or inner radius of insulation, inches, rt " outer radius of insulation, inches. k TM thermal conductivity of insulation, Btu per (hour) (square foot) (Fahrenheit degree per inch). ti = initial water temperature, Fahrenheit degrees. -