ASTM C1129-17

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Designation: C1129 − 12 C1129 − 17
Standard Practice for
Estimation of Heat Savings by Adding Thermal Insulation to
Bare Valves and Flanges
This standard is issued under the fixed designation C1129; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 The mathematical methods included in this practice provide a calculational procedure for estimating heat loss or heat
savings when thermal insulation is added to bare valves and flanges.
1.2 Questions of applicability to real systems should be resolved by qualified personnel familiar with insulation systems design
and analysis.
1.3 Estimated accuracy is limited by the following:
1.3.1 The range and quality of the physical property data for the insulation materials and system,
1.3.2 The accuracy of the methodology used in calculation of the bare valve and insulation surface areas, and the quality of
workmanship, fabrication, and installation.
1.4 This procedure is considered applicable both for conventional-type insulation systems and for removable/reuseable covers.
In both cases, for purposes of heat transfer calculations, the insulation system is assumed to be homogenous.
1.5 This practice does not intend to establish the criteria required in the design of the equipment over which thermal insulation
is used, nor does this practice establish or recommend the applicability of thermal insulation over all surfaces.
1.6 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
C168 Terminology Relating to Thermal Insulation
C450 Practice for Fabrication of Thermal Insulating Fitting Covers for NPS Piping, and Vessel Lagging
C680 Practice for Estimate of the Heat Gain or Loss and the Surface Temperatures of Insulated Flat, Cylindrical, and Spherical
Systems by Use of Computer Programs
C1695 Specification for Fabrication of Flexible Removable and Reusable Blanket Insulation for Hot Service
2.2 ASTM Adjuncts:
ADJC0450A Recommended Dimensional Standards for Fabrication of Thermal Insulating Fitting Covers for NPS Piping and
Vessel Lagging
2.3 American National Standards Institute Standard:
ANSI B16.5 Fittings, Flanges, and Valves
3. Terminology
3.1 Definitions—For definitions of terms used in this practice, refer to Terminology C168.
3.2 Symbols:
This practice is under the jurisdiction of ASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal Measurement.
Current edition approved May 1, 2012March 1, 2017. Published July 2012March 2017. Originally approved in 1989. Last previous edition approved in 20082012 as
C1129–89C1129 – 12. (2008). DOI: 10.1520/C1129-12. 10.1520/C1129-17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from ASTM International Headquarters. Order Adjunct No. ADJADJC0450A. Original adjunct produced in 1976. Adjunct last revised in 2002.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1129 − 17
3.2.1 The following symbols are used in the development of the equations for this practice. Other symbols will be introduced
and defined in the detailed description of the development. See Fig. 1 and Fig. 2.
2 2
A = outer surface area of the bare valve or flange (does not include the wheel and stem of the valve), ft (m ).
B
2 2
A = surface area of the insulation cover over the valve or flange, ft (m ).
I
C = distance from the center-line axis of the pipe (to which the valve is attached) to the uppermost position of the valve that
is to be insulated (recommended to be below the gland seal), ft (m).
D = the valve flange and the bonnet flange outer diameter (assumed equal), ft (m).
F
D = the actual diameter of the pipe, ft (m).
P
L = overall length of the valve, flange to flange, ft (m).
V
T = thickness of the valve flange and of the bonnet flange, ft (m).
2 2
q = time rate of heat loss per unit area from the bare valve or flange surface, Btu/h·ft (W/m ).
B
2 2
q = time rate of heat loss per unit area from the insulation surface, Btu/h·ft ) (W/m ).
I
Q = time rate of heat loss from the bare valve or flange surface, Btu/h (W).
B
Q = time rate of heat loss from the insulated surface, Btu/h (W).
I
4. Summary of Practice
4.1 The procedures for estimating heat loss used in this practice are based upon standard steady-state heat transfer theory as
outlined in Practice C680 (or programs conforming to it such as 3E Plus ). Practice C680 and 3E plus are used to estimate the heat
loss per unit surface area for the particular conditions and for all configurations, both bare and insulated.
4.2 The procedures for estimating surface areas used in this practice are based on standard geometric logic: for a bare valve or
flange, the contours of the metal surface are considered. For an insulated valve or flange, the fabricated shape of the finished
insulation system is considered.
4.3 Data Input:
4.3.1 Total bare surface area and total insulation surface area of the valve or flange,
4.3.2 Service and ambient temperatures,
4.3.3 Wind speed,
4.3.4 Surface emittance values
4.3.5 Insulation thickness and type, and
4.3.6 Number of service hours per year.
4.4 System Description—Insulation thickness, insulation type, bare valve or flange surface emittance, insulation surface
emittance.
4.5 Analysis—Once input data is entered, the program calculates the surface coefficients (if not entered directly), the insulation
resistance, the bare metal heat loss per unit area, and the insulation surface heat loss per unit area. The rate of heat loss per unit
area is computed by Practice C680 for the appropriate diameter. For bare gate valves, the particular surface area can be taken from
a look-up table. Table 1 and Table 2 give these areas for typical (ANSI Class 150, 300, 600, and 900) flanged gate valves and
Available from the North American Insulation Manufacturers Association for a free download. http//:www.pipeinsulation.org.
2 2
FIG. 1 Equation 1 for a for the Surface Area of Bare Valve, A = [D (L + 2L + (C − D /2) − 6T) + 1.5(D − D ) + 6D T] π (Ref. 3)
B P V F P F P F
V
C1129 − 17
2 2
FIG. 2 Equation 2 for the surface area of a Bare Flange, A [D 2L + (D – D )/ 2 + 2 D T]
BF P F F P F
flanges. If these valves are not considered sufficiently accurate for the particular valves or flanges being considered, those areas
can be calculated using Eq 1 (see Fig. 1) for bare flanges and Eq 2 (see Fig. 2) for bare gate valves. Similar equations can be
developed for other types of valves and flanges. For the insulation on the valves and the flanges, the outer surface area can be
obtained either from Table 3 and Table 4 for insulation thickness up to 4 in. or from the insulation fabricator or contractor.
5. Significance and Use
5.1 Manufacturers of thermal insulation for valves typically express the performance of their products in charts and tables
showing heat loss per valve. These data are presented for both bare and insulated valves of different pipe sizes, ANSI classes,
insulation types, insulation thicknesses, and service temperatures. Additional information on effects of wind velocity, jacket
emittance, bare valve emittance, and ambient conditions are also required to properly select an insulation system. Due to the infinite
combination of pipe sizes, ANSI classes, insulation types and thicknesses, service temperatures, insulation cover geometries,
surface emittance values, and ambient conditions, it is not possible to publish data for each possible case.
5.2 Users of thermal insulation for piping systems faced with the problem of designing large systems of insulated piping,
encounter substantial engineering costs to obtain the required thermal information. This cost can be substantially reduced by both
the use of accurate engineering data tables, or by the use of available computer analysis tools, or both.
5.3 The use of this practice by the manufacturer, contractor, and users of thermal insulation for valves and flanges will provide
standardized engineering data of sufficient accuracy and consistency for predicting the savings in heating energy use by insulating
bare valves and flanges.
5.4 Computers are now readily available to most producers and consumers of thermal insulation to permit use of this practice.
5.5 The computer program in Practice C680 has been developed to calculate the heat loss per unit length, or per unit surface
area, of both bare and insulated pipe. With values for bare valve or flange surface areas, heat loss can be estimated. By estimating
the outer insulation surface area from an insulation manufacturer’s or contractor’s drawings, the heat loss from the insulation
surface can likewise be calculated by taking the product of heat loss per unit area (from programs conforming to Practice C680)
and the valve or flange insulation surface area. The area of the uninsulated surfaces also will need to be considered.
5.6 The use of this practice requires that the valve or flange insulation system meets either Specification C1695 for
removeable/reuseable or the Adjunct to Practice C450 for insulation fabricated from rigid board and pipe insulation.
6. Calculation
6.1 This calculation of heat gain or loss requires the following:
6.1.1 The thermal insulation shall be assumed to be homogenous as outlined by the definition of thermal conductivity in
Terminology C168.
6.1.2 The valve or flange size and operating temperature shall be known.
6.1.3 The insulation thickness shall be known.
6.1.4 Values of wind speed and surface emittance shall be available to estimate the surface coefficients for both the bare surface
and for the insulation.
6.1.5 The surface temperature in each case shall be assumed to 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 be estimated from drawings or field measurements.
6.1.8 Practice C680 or other comparable methodology shall be used to estimate the heat loss from both bare and insulated
surfaces.
6.2 Estimation of Rate of Heat Loss from the Bare Surface—Since Practice C680 needs to perform iterations in calculating heat
flow across an insulation surface, an uninsulated surface must be simulated. To do this, select a thin insulation (with a thickness
of 0.02 in. (0.5 mm)) and a thermal curve giving a high thermal conductivity. It is recommended that Type 1 be selected for which
the following constants are assigned: a = 10 Btu·in. ⁄h·ft ·F (1.44 W/m·c), b = 0, and c = 0. 3E Plus has the capability of
calculating heat loss from bare surfaces so this step is unnecessary.
C1129 − 17
TABLE 1 Calculated Surface Areas of Bare Valves using Eq 1 (Ref 3 )
ANSI Class
150 300 600 900
NPS, in.
2 2 2 2 2 2 2 2
ft (m ) ft (m ) ft (m ) ft (m )
2 2.21 (0.205) 2.94 (0.273) 2.94 (0.273) 5.20 (0.483)
2 ⁄2 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 (1.672) 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 (4.589) 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) . . . . . .
TABLE 2 Calculated Flange Pair Surface Areas using Eq 2
Bare surface areas in square feet (square meters) for ANSI Classes 150, 300, 600, and 900
150 300 600 900
NPS, in.
2 2 2 2 2 2 2 2
ft (m ) ft (m ) ft (m ) ft (m )
2 0.71 0.066 0.84 0.078 0.88 0.081 1.54 0.143
3 1.06 0.099 1.32 0.122 1.36 0.127 1.85 0.172
4 1.44 0.133 1.83 0.170 2.23 0.208 2.64 0.245
6 2.04 0.190 2.72 0.252 3.60 0.334 4.37 0.406
8 2.92 0.271 3.74 0.348 4.89 0.454 6.40 0.595
10 3.68 0.342 4.80 0.446 6.93 0.643 8.47 0.787
12 5.01 0.465 6.34 0.589 7.97 0.740 10.43 0.969
14 6.15 0.571 7.90 0.734 9.16 0.851 11.59 1.077
16 7.19 0.668 9.25 0.859 11.49 1.067 13.34 1.239
20 9.40 0.873 12.50 1.161 15.18 1.411 19.12 1.776
24 11.82 1.099 16.23 1.507 19.30 1.793 28.18 2.618
6.2.1 Run Practice C680 or 3E Plus for either a horizontal or a vertical pipe of the appropriate diameter, inputing the ambient
air temperature, wind speed, and bare valve surface emittance. Unless information is available for estimating the bare valve surface
emittance, it is suggested that a value of 0.9 be selected. Select output in units of heat loss per unit surface area. This value of heat
loss per unit bare surface area is designated q .
B
6.3 Use of Practice C680 for the Insulated Valve or Flange—Since Practice C680 is designed to calculate heat loss for insulated
flat surfaces and for pipes, it is necessary to treat the insulated valve as an insulated pipe. It is recommended that the diameter of
the pipe, to which the valve fits, or the diameter of the flanges be selected for the calculation. Input the same ambient air
temperature and wind speed as in 6.1 and estimate the insulation surface emittance. For a removable insulation cover, this would
be the emittance of the fabric or metal jacket. For conventional insulation, this is either the emittance of that material or of the
jacketing, if jacketing is used. The value of heat loss per unit insulation surface area is designated q .
I
6.4 Surface Area of the Bare Valve or Flange—Fig. 1 gives a diagram of a gate valve with the dimensions D , L , T,L , D ,
P V F F
and C as indicated. Eq 1 (see Fig. 1) gives a method for estimating the surface area of valves, and Eq 2 (see Fig. 2) gives a method
for estimating the surface area of flanges. Table 1 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 designated A .
B
6.5 Surface Area of the Insulated Valve or Flange—The estimation of the outer insulation surface area has been done for
insulation thicknesses from 1 to 4 in. and NPS sizes 2 through 24 inches, for ANSI Classes 150, 300, 600, and 900, using
dimensions taken from the ADJC0450A. An alternative, to using the values in Table 3 and Table 4, is to get dimensions from the
manufacturer or the insulation contractor and then perform calculations on the surface area. This surface area will depend on the
dimensions of the valve or flange being insulated, the thickness of the insulation, and the extent of coverage to either side of the
valve or flange.
6.6 Calculation of Bare Valve or Flange Heat Loss—This value is determined by taking the product of the bare valve or flange
heat loss per unit surface area and of the bare surface area. It will be designated as Q :
B
Q 5 q A (1)
B B B
6.7 Calculation of Insulated Valve or Flange Heat Loss—This value is determined by taking the product of the insulated valve
or flange heat loss per unit surface area and of the insulation outer surface area. It would be designated as Q :
I
C1129 − 17
TABLE 3 Calculated Insulated Gate Valve Surface Areas
Table 3A - 150 psi gate valves - insulated Surface Area, sf (sm) for four different insulation thicknesses
NPS, in. 1 in. 25 mm 2 in. 51 mm 3 in. 76 mm 4 in. 102 mm
2 4.21 0.392 4.64 0.43 6.31 0.59 8.25 0.77
3 5.24 0.487 5.73 0.53 7.30 0.68 9.30 0.86
4 7.15 0.664 7.72 0.72 8.60 0.80 10.60 0.99
6 9.67 0.898 10.29 0.96 11.70 1.09 14.18 1.32
8 12.49 1.160 12.29 1.14 15.89 1.48 17.26 1.60
10 15.03 1.396 15.85 1.47 17.41 1.62 19.99 1.86
12 20.80 1.932 21.58 2.01 23.39 2.17 25.50 2.
...