1、Designation: C 1129 89 (Reapproved 2008)Standard Practice forEstimation of Heat Savings by Adding Thermal Insulation toBare Valves and Flanges1This standard is issued under the fixed designation C 1129; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 The mathematical methods included in this practiceprovide a calculational procedure fo
3、r estimating heat loss orheat savings when thermal insulation is added to bare valvesand flanges.1.2 Questions of applicability to real systems should beresolved by qualified personnel familiar with insulation sys-tems design and analysis.1.3 Estimated accuracy is limited by the following:1.3.1 The
4、range and quality of the physical property data forthe insulation materials and system,1.3.2 The accuracy of the methodology used in calculationof the bare valve and insulation surface areas, and1.3.3 The quality of workmanship, fabrication, and installa-tion.1.4 This procedure is considered applica
5、ble both forconventional-type insulation systems and for removable/reuseable covers. In both cases, for purposes of heat transfercalculations, the insulation system is assumed to be homog-enous.1.5 This practice does not intend to establish the criteriarequired in the design of the equipment over wh
6、ich thermalinsulation is used, nor does this practice establish or recom-mend the applicability of thermal insulation over all surfaces.1.6 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided f
7、or information onlyand are not considered standard.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of
8、regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 168 Terminology Relating to Thermal InsulationC 450 Practice for Fabrication of Thermal Insulating FittingCovers for NPS Piping, and Vessel LaggingC 680 Practice for Estimate of the Heat Gain or Loss andthe Surface Temp
9、eratures of Insulated Flat, Cylindrical,and Spherical Systems by Use of Computer ProgramsC 1094 Guide for Flexible Removable Insulation Covers2.2 American National Standards Institute Standard:ANSI B16.5 Fittings, Flanges, and Valves33. Terminology3.1 DefinitionsFor definitions of terms used in this
10、 prac-tice, refer to Terminology C 168.3.2 Symbols:The following symbols are used in the de-velopment of the equations for this practice. Other symbolswill be introduced and defined in the detailed description of thedevelopment. See Figs.1 and 2.AB= outer surface area of the bare valve or flange (do
11、esnot include the wheel and stem of the valve), ft2(m2).AI= surface area of the insulation cover over the valve orflange, ft2(m2).C = distance from the center-line axis of the pipe (towhich the valve is attached) to the uppermost posi-tion of the valve that is to be insulated (recommendedto be below
12、 the gland seal), ft (m).DF= the valve flange and the bonnet flange outer diameter(assumed equal), ft (m).DP= the actual diameter of the pipe, ft (m).LV= overall length of the valve, flange to flange, ft (m).T = thickness of the valve flange and of the bonnet flange,ft (m).1This practice is under th
13、e jurisdiction of Committee C16 on Thermal Insulationand is the direct responsibility of Subcommittee C16.30 on Thermal Measurement.Current edition approved Dec. 1, 2008. Published February 2009. Originallyapproved in 1989. Last previous edition approved in 2001 as C112989 (2001).2For referenced AST
14、M standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th
15、 Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.qB= time rate of heat loss per unit area from the bare valveor flange surface, Btu/hft2(W/m2).qI= time rate of heat loss per unit area fro
16、m the insulationsurface, Btu/hft2) (W/m2).QB= time rate of heat loss from the bare valve or flangesurface, Btu/h (W).QI= time rate of heat loss from the insulated surface,Btu/h (W).4. Summary of Practice4.1 The procedures for estimating heat loss used in thispractice are based upon standard steady-s
17、tate heat transfertheory as outlined in Practice C 680 (or programs conformingto it). This practice is used to estimate the heat loss per unitsurface area for the particular conditions and for all configu-rations.4.2 The procedures for estimating surface areas used in thispractice are based on stand
18、ard geometric logic: for a bare valveor flange, the contours of the metal surface are considered. Foran insulated valve or flange, the fabricated shape of the finishedinsulation system is considered.4.3 Data Input:4.3.1 Total bare surface area and total insulation surfacearea of the bare valve or fl
19、ange,4.3.2 Service and ambient temperatures,4.3.3 Wind speed,4.3.4 Surface emittances,4.3.5 Insulation thickness and type, and4.3.6 Number of service hours per year.4.4 System DescriptionInsulation thickness, insulationtype, bare valve or flange surface emittance, insulation surfaceemittance.4.5 Ana
20、lysisOnce input data is entered, the programcalculates the surface coefficients (if not entered directly), theinsulation resistance, the bare metal heat loss per unit area, andthe insulation surface heat loss per unit area. The rate of heatloss per unit area is computed by Practice C 680 for theappr
21、opriate diameter. For bare gate valves, the particularsurface area can be taken from a look-up table. Table 1 givesthese areas for typical (ANSI Class 150, 300, 600, and 900)flanged gate valves and flanges. If these valves are notconsidered sufficiently accurate, they can be calculated usingEq 1 (se
22、e Fig. 1) and Eq 2 (see Fig. 2). Similar equations canbe developed for other types of valves and flanges. For theinsulation, the outer surface area may be obtained from theinsulation fabricator or contractor.TABLE 1 Calculated Surface Areas of Bare ValvesANSI ClassNPS, in.150 300 600 900ft2(m2)ft2(m
23、2)ft2(m2)ft2(m2)2 2.21 (0.205) 2.94 (0.273) 2.94 (0.273) 5.20 (0.483)212 2.97 (0.276) 3.51 (0.326) 3.91 (0.363) 6.60 (0.613)3 3.37 (0.313) 4.39 (0.408) 4.69 (0.436) 6.50 (0.604)4 4.68 (0.435) 6.06 (0.563) 7.64 (0.710) 9.37 (0.870)6 7.03 (0.653) 9.71 (0.902) 13.03 (1.210) 15.80 (1.468)8 10.30 (0.957)
24、 13.50 (1.254) 18.40 (1.709) 23.80 (2.211)10 13.80 (1.284) 18.00 (1.672) 26.50 (2.462) 32.10 (2.982)12 16.10 (1.496) 24.10 (2.239) 31.90 (2.964) 41.90 (3.893)14 22.80 (2.118) 32.50 (3.019) 39.70 (3.688) 48.20 (4.978)16 27.60 (2.564) 39.30 (3.651) 50.50 (4.691) 57.00 (5.295)18 31.70 (2.945) 49.40 (4.
25、589) 59.80 (5.555) 69.70 (6.475)20 37.70 (3.502) 59.10 (5.490) 71.30 (6.624) 24 49.10 (4.561) 83.50 (7.757) 95.10 (8.835) 30 72.20 (6.707) 123.30 (11.46) 141.70 (13.6) 36 107.30 (9.968) 164.00 (15.24) 199.00 (18.49) FIG. 1 Equation 1 for a Bare Valve, ABV=DP(LV+2LF+(C DP/2)6T)+1.5(DF2 DP2)+6DFT pFIG
26、. 2 Equation 2 for a Bare Flange, ABF=DP(LV+2LF4T)+(DF2 DP2)+4DFT pC 1129 89 (2008)25. Significance and Use5.1 Manufacturers of thermal insulation for valves typicallyexpress the performance of their products in charts and tablesshowing heat loss per valve. These data are presented for bothbare and
27、insulated valves of different pipe sizes, ANSI classes,insulation types, insulation thicknesses, and service tempera-tures.Additional information on effects of wind velocity, jacketemittance, bare valve emittance, and ambient conditions mayalso be required to properly select an insulation system. Du
28、e tothe infinite combination of pipe sizes, ANSI classes, insulationtypes and thicknesses, service temperatures, insulation covergeometries, surface emittances, and ambient conditions, it isnot possible to publish data for each possible case.5.2 Users of thermal insulation for piping systems facedwi
29、th the problem of designing large systems of insulatedpiping, encounter substantial engineering costs to obtain therequired thermal information. This cost can be substantiallyreduced by both the use of accurate engineering data tables, orby the use of available computer analysis tools, or both.5.3 T
30、he use of this practice by the manufacturer, contractor,and users of thermal insulation for valves and flanges willprovide standardized engineering data of sufficient accuracyand consistency for predicting the savings in heating energyuse by insulating bare valves and flanges.5.4 Computers are now r
31、eadily available to most producersand consumers of thermal insulation to permit use of thispractice.5.5 The computer program in Practice C 680 has beendeveloped to calculate the heat loss per unit length, or per unitsurface area, of both bare and insulated pipe. With values forbare valve or flange s
32、urface areas, heat loss can be estimated.By estimating the outer insulation surface area from aninsulation manufacturers or contractors drawings, the heatloss from the insulation surface can likewise be calculated bytaking the product of heat loss per unit area (from programsconforming to Practice C
33、 680) and the valve or flange insula-tion surface area. The area of the uninsulated surfaces may alsoneed to be considered.5.6 The use of this practice requires that the valve or flangeinsulation system meets Guide C 1094 and Practice C 450,where applicable.6. Calculation6.1 This calculation of heat
34、 gain or loss requires thefollowing:6.1.1 The thermal insulation shall be assumed to be homog-enous as outlined by the definition of thermal conductivity inTerminology C 168.6.1.2 The valve or flange size and operating temperatureshall be known.6.1.3 The insulation thickness shall be known.6.1.4 Val
35、ues of wind speed and surface emittance shall beavailable to estimate the surface coefficients for both the baresurface and for the insulation.6.1.5 The surface temperature in each case shall be assumedto be uniform.6.1.6 The bare surface dimensions or area shall be known.6.1.7 The outer surface are
36、a of the insulation cover can beestimated from drawings or field measurements.6.1.8 Practice C 680 or other comparable methodology shallbe used to estimate the heat loss from both bare and insulatedsurfaces.6.2 Estimation of Rate of Heat Loss from the BareSurfaceSince Practice C 680 needs to perform
37、 iterations incalculating heat flow across an insulation surface, an uninsu-lated surface must be simulated. To do this, select a thininsulation (with a thickness of 0.02 in. (0.5 mm) and a thermalcurve giving a high thermal conductivity. It is recommendedthat Type 1 be selected for which the follow
38、ing constants areassigned: a = 10 Btuin./hft2F (1.44 W/mc), b = 0, and c=0.6.2.1 Run Practice C 680 for either a horizontal or a verticalpipe of the appropriate diameter, inputing the ambient airtemperature, wind speed, and bare valve surface emittance.Unless information is available for estimating
39、the bare valvesurface emittance, it is suggested that a value of 0.9 beselected. Select output in units of heat loss per unit surfacearea. This value of heat loss per unit bare surface area isdesignated qB.6.3 Use of Practice C 680 for the Insulated Valve orFlangeSince Practice C 680 is designed to
40、calculate heatloss for insulated flat surfaces and for pipes, it is necessary totreat the insulated valve as an insulated pipe. It is recom-mended that the diameter of the pipe, to which the valve fits, orthe diameter of the flanges be selected for the calculation. Inputthe same ambient air temperat
41、ure and wind speed as in 6.1 andestimate the insulation surface emittance. For a removableinsulation cover, this would be the emittance of the fabric ormetal jacket. For conventional insulation, this is either theemittance of that material or of the jacketing, if jacketing isused. The value of heat
42、loss per unit insulation surface area isdesignated qI.6.4 Surface Area of the Bare Valve or FlangeFig. 1 givesa diagram of a gate valve with the dimensions DP, LV, T, LF,DF, and C as indicated. Eq 1 (see Fig. 1) gives a method forestimating the surface area of valves, and Eq 2 (see Fig. 2)gives a me
43、thod for estimating the surface area of flanges. Table1 gives the results of calculating the surface area for 2-in.through 36-in. NPS gate valves for ANSI classes of 150, 300,600 and 900. The value of a bare valve or flange is designatedAB.6.5 Surface Area of the Insulated Valve or FlangeTheestimati
44、on of the outer insulation surface area is best performedby the manufacturer or the insulation contractor. This surfacearea will depend on the dimensions of the valve or flange beinginsulated, the thickness of the insulation, and the extent ofcoverage to either side of the valve or flange.This pract
45、ice doesnot recommend a specific method for arriving at this area,which would be designated as AI.6.6 Calculation of Bare Valve or Flange Heat LossThisvalue is determined by taking the product of the bare valve orflange heat loss per unit surface area and of the bare surfacearea. It will be designat
46、ed as QB:QB5 qBAB(1)C 1129 89 (2008)36.7 Calculation of Insulated Valve or Flange Heat LossThis value is determined by taking the product of the insulatedvalve or flange heat loss per unit surface area and of theinsulation outer surface area. It would be designated as QI:QI5 qIAI(2)6.8 Calculation o
47、f Heat Loss SavingsThis value is deter-mined by taking the difference between the values of heat lossfor the bare and the insulated valve or flange. It would bedesignated as QB-I:QB2I5 QB2 QI(3)7. Report7.1 The results of calculations performed in accordancewith this practice may be used to estimate
48、 heat loss savings forspecific job conditions, or may be used in general form topresent the effectiveness of insulating valves or flanges for aparticular product or system. For the purpose of decisionmaking, it is recommended that reference be made to thespecific constants used in the calculations.
49、These referencesshould include:7.1.1 Name and identification of insulation products orcomponents and the valve or flange products.7.1.2 Identification of the NPS valve or flange sizes andtheir ANSI class ratings.7.1.3 The surface temperatures of the piping system.7.1.4 The estimated surface emittance used in the calcula-tions.7.1.5 The equations and constants selected for the thermalconductivity versus mean temperature relationship.7.1.6 The insulation thickness used for the calculations.7.1.7 The ambient temperature and the wind speed (orsurface coe
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