1、Designation: C 1129 89 (Reapproved 2001)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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 The mathematical methods included in this practiceprovide a calculational procedure f
3、or 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 applic
5、able 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 w
6、hich 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 the standard. The SI units in parentheses are provided forinformation only.1.7 This standard does no
7、t 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 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standard
8、s:C 168 Terminology Relating to Thermal Insulation2C 450 Practice for Prefabrication and Field Fabrication ofThermal Insulation Fitting Covers for NPS Piping, VesselLagging, and Dished Head Segments2C 680 Practice for Determination of Heat Gain or Loss andthe Surface Temperatures of Insulated Pipe a
9、nd EquipmentSystems by the Use of a Computer Program2C 1094 Guide for Removable Insulation Covers22.2 American National Standards Institute Standard:ANSI B16.5 Fittings, Flanges, and Valves33. Terminology3.1 DefinitionsFor definitions of terms used in this prac-tice, refer to Terminology C 168.3.2 S
10、ymbols: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 (doesnot include the wheel and stem of the valv
11、e), 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 the gland seal), ft (m).DF= the valve flang
12、e 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).qB= time rate of heat loss per unit area from the bare valveor flange
13、surface, Btu/hft2(W/m2).qI= time rate of heat loss per unit area from 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).1This practice is under the jurisdiction of Committ
14、ee C16 on Thermal Insulationand is the direct responsibility of Subcommittee C16.30 on Thermal Measurement.Current edition approved June 30, 1989. Published August 1989.2Annual Book of ASTM Standards, Vol 04.06.3Available from American National Standards Institute, 11 W. 42nd St., 13thFloor, New Yor
15、k, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Practice4.1 The procedures for estimating heat loss used in thispractice are based upon standard steady-state heat transfertheory as outlined in Practice C 680
16、 (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 standard geometric logic: for a bare valveor flange, the co
17、ntours 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 flange,4.3.2 Service and ambient temperatures,4.3.3 Wind
18、 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 AnalysisOnce input data is entered, the programcalculates
19、 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 theappropriate diameter. For bare gate valves, the particular
20、surface 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 (see Fig. 1) and Eq 2 (see Fig. 2). Similar equations can
21、be developed for other types of valves and flanges. For theinsulation, the outer surface area may be obtained from theinsulation fabricator or contractor.5. Significance and Use5.1 Manufacturers of thermal insulation for valves typicallyexpress the performance of their products in charts and tabless
22、howing heat loss per valve. These data are presented for bothbare and 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 con
23、ditions mayalso be required to properly select an insulation system. Due tothe infinite combination of pipe sizes, ANSI classes, insulationTABLE 1 Calculated Surface Areas of Bare ValvesANSI ClassNPS, in.150 300 600 900ft2(m2)ft2(m2)ft2(m2)ft2(m2)2 2.21 (0.205) 2.94 (0.273) 2.94 (0.273) 5.20 (0.483)
24、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) 13.50 (1.254) 18.40 (1.709) 23.80 (2.211)10 13.80 (1.284) 18.00 (1.6
25、72) 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 (4.589) 59.80 (5.555) 69.70 (6.475)20 37.70 (3.502) 59.10 (5.490) 71.30
26、(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. 2 Equation 2 for a Bare Flange, ABF=DP(LV+2LF4T)+(DF2 DP2)+4DFT p
27、C 1129 89 (2001)2types 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 facedwith the problem of designing large systems of insula
28、tedpiping, 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 The use of this practice by the manufacturer, contra
29、ctor,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 readily available to most producersand consumers of
30、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 surface areas, heat loss can be estimated.By estimat
31、ing 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 680) and the valve or flange insula-tion surface a
32、rea. 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 gain or loss requires thefollowing:6.1.1 The therm
33、al 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 Values of wind speed and surface emittance shall beava
34、ilable 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 area of the insulation cover can beestimated from draw
35、ings 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 iterations incalculating heat flow across an insul
36、ation 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 following constants areassigned: a = 10 Btuin./hft2F (1.4
37、4 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 the bare valvesurface emittance, it is suggested th
38、at 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 calculate heatloss for insulated flat surfaces and
39、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 temperature and wind speed as in 6.1 andestimate the insula
40、tion 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 loss per unit insulation surface area isdesignated
41、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 method for estimating the surface area of flanges. Ta
42、ble1 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 FlangeTheestimation of the outer insulation surface area is best per
43、formedby 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 practice doesnot recommend a specific method for arrivi
44、ng 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 designated as QB:QB5 qBAB(1)6.7 Calculation of Insulated V
45、alve 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 of Heat Loss SavingsThis value is deter-mined by taking the differen
46、ce between the values of heat lossfor the bare and the insulated valve or flange. It would bedesignated as QB-I:QB2I5 QB2 QI(3)C 1129 89 (2001)37. Report7.1 The results of calculations performed in accordancewith this practice may be used to estimate heat loss savings forspecific job conditions, or
47、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. These referencesshould include:7.1.1 Name and iden
48、tification 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 an
49、d 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 coefficient).7.1.8 The estimate for the outer surface area of the valve orflange insulation system.7.1.9 The calculated values of QBand QI.7.1.10 The estimation of heat loss savings, QB-I.7.1.11 Either tabular or graphical representation of theresults of the calculations may be used. No attempt is made torecommend the format of this presentation of results
