ASTM C1129-89(1994)e1
(Practice)Standard Practice for Estimation of Heat Savings by Adding Thermal Insulation to Bare Valves and Flanges
Standard Practice for Estimation of Heat Savings by Adding Thermal Insulation to Bare Valves and Flanges
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
1.3.3 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 the standard. The SI units in parentheses are provided for information only.
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.
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e1
Designation: C 1129 – 89 (Reapproved 1994)
Standard Practice for
Estimation of Heat Savings by Adding Thermal Insulation to
Bare Valves and Flanges
This standard is issued under the fixed designation C 1129; 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 (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Keywords were added editorially in March 1994.
1. Scope 1.7 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 The mathematical methods included in this practice
responsibility of the user of this standard to establish appro-
provide a calculational procedure for estimating heat loss or
priate safety and health practices and determine the applica-
heat savings when thermal insulation is added to bare valves
bility of regulatory limitations prior to use.
and flanges.
1.2 Questions of applicability to real systems should be
2. Referenced Documents
resolved by qualified personnel familiar with insulation sys-
2.1 ASTM Standards:
tems design and analysis.
C 168 Terminology Relating to Thermal Insulating Materi-
1.3 Estimated accuracy is limited by the following:
als
1.3.1 The range and quality of the physical property data for
C 450 Practice for Prefabrication and Field Fabrication
the insulation materials and system,
Fitting Covers for NPS Piping, Vessel Lagging, and Dished
1.3.2 The accuracy of the methodology used in calculation
Head Segments
of the bare valve and insulation surface areas, and
C 680 Practice for Determination of Heat Gain or Loss and
1.3.3 The quality of workmanship, fabrication, and installa-
the Surface Temperatures of Insulated Pipe and Equipment
tion.
Systems by the Use of a Computer Program
1.4 This procedure is considered applicable both for
C 1094 Guide for Removable Insulation Covers
conventional-type insulation systems and for removable/
2.2 American National Standards Institute Standard:
reuseable covers. In both cases, for purposes of heat transfer
ANSI B16.5 Fittings, Flanges, and Valves
calculations, the insulation system is assumed to be homog-
enous.
3. Terminology
1.5 This practice does not intend to establish the criteria
3.1 Definitions—For definitions of terms used in this prac-
required in the design of the equipment over which thermal
tice, refer to Terminology C 168.
insulation is used, nor does this practice establish or recom-
3.2 Symbols:Symbols—The following symbols are used in
mend the applicability of thermal insulation over all surfaces.
the development of the equations for this practice. Other
1.6 The values stated in inch-pound units are to be regarded
symbols will be introduced and defined in the detailed descrip-
as the standard. The SI units in parentheses are provided for
tion of the development. See Figs. 1 and 2.
information only.
This practice is under the jurisdiction of Committee C-16 on Thermal
Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal Annual Book of ASTM Standards, Vol 04.06.
Measurement. Available from American National Standards Institute, 11 W. 42nd St., 13th
Current edition approved June 30, 1989. Published August 1989. Floor, New York, NY 10036.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
C 1129
to it). This practice is used to estimate the heat loss per unit
surface area for the particular conditions and for all configu-
rations.
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 bare valve or flange,
4.3.2 Service and ambient temperatures,
4.3.3 Wind speed,
4.3.4 Surface emittances,
4.3.5 Insulation thickness and type, and
4.3.6 Number of service hours per year.
4.4 System Description—Insulation thickness, insulation
FIG. 1 Equation 1 for a Bare Valve, A 5 [D (L +2L +(C − D /
B P V F P
V
2 2 type, bare valve or flange surface emittance, insulation surface
2)−6T) + 1.5(D − D )+6 D T] p
F P F
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 C 680 for the
appropriate diameter. For bare gate valves, the particular
surface area can be taken from a look-up table. Table 1 gives
these areas for typical (ANSI Class 150, 300, 600, and 900)
flanged gate valves and flanges. If these valves are not
considered sufficiently accurate, they can be calculated using
FIG. 2 Equation 2 for a Bare Flange, A 5 [D
B P
F Eq 1 (see Fig. 1) and Eq 2 (see Fig. 2). Similar equations can
2 2
(L +2L −4T)+(D − D )+4 D T] p
V F F P F
be developed for other types of valves and flanges. For the
insulation, the outer surface area may be obtained from the
insulation fabricator or contractor.
A 5 outer surface area of the bare valve or flange (does
B
2 2
not include the wheel and stem of the valve), ft (m ). 5. Significance and Use
A 5 surface area of the insulation cover over the valve or
I
5.1 Manufacturers of thermal insulation for valves typically
2 2
flange, ft (m ).
express the performance of their products in charts and tables
C 5 distance from the center-line axis of the pipe (to
showing heat loss per valve. These data are presented for both
which the valve is attached) to the uppermost posi-
bare and insulated valves of different pipe sizes, ANSI classes,
tion of the valve that is to be insulated (recommended
insulation types, insulation thicknesses, and service tempera-
to be below the gland seal), ft (m).
tures. Additional information on effects of wind velocity, jacket
D 5 the valve flange and the bonnet flange outer diameter
F
emittance, bare valve emittance, and ambient conditions may
(assumed equal), ft (m).
also be required to properly select an insulation system. Due to
D 5 the actual diameter of the pipe, ft (m).
P
the infinite combination of pipe sizes, ANSI classes, insulation
L 5 overall length of the valve, flange to flange, ft (m).
V
types and thicknesses, service temperatures, insulation cover
T 5 thickness of the valve flange and of the bonnet flange,
geometries, surface emittances, and ambient conditions, it is
ft (m).
not possible to publish data for each possible case.
q 5 time rate of heat loss per unit area from the bare valve
B
2 2
5.2 Users of thermal insulation for piping systems faced
or flange surface, Btu/h·ft (W/m ).
with the problem of designing large systems of insulated
q 5 time rate of heat loss per unit area from the insulation
I
2 2
piping, encounter substantial engineering costs to obtain the
surface, Btu/h·ft ) (W/m ).
required thermal information. This cost can be substantially
Q 5 time rate of heat loss from the bare valve or flange
B
reduced by both the use of accurate engineering data tables, or
surface, Btu/h (W).
by the use of available computer analysis tools, or both.
Q 5 time rate of heat loss from the insulated surface,
I
5.3 The use of this practice by the manufacturer, contractor,
Btu/h (W).
and users of thermal insulation for valves and flanges will
4. Summary of Practice
provide standardized engineering data of sufficient accuracy
4.1 The procedures for estimating heat loss used in this and consistency for predicting the savings in heating energy
practice are based upon standard steady-state heat transfer use by insulating bare valves and flanges.
theory as outlined in Practice C 680 (or programs conforming 5.4 Computers are now readily available to most producers
C 1129
TABLE 1 Calculated Surface Areas of Bare Valves
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) .
and consumers of thermal insulation to permit use of this insulation (with a thickness of 0.02 in. (0.5 mm)) and a thermal
practice. curve giving a high thermal conductivity. It is recommended
5.5 The computer program in Practice C 680 has been
that Type 1 be selected for which the following constants are
developed to calculate the heat loss per unit length, or per unit assigned: a 5 10 Btu·in./h·ft ·F (1.44 W/m·c), b 5 0, and c
surface area, of both bare and insulated pipe. With values for
5 0.
bare valve or flange surface areas, heat loss can be estimated.
6.2.1 Run Practice C 680 for either a horizontal or a vertical
By estimating the outer insulation surface area from an
pipe of the appropriate diameter, inputing the ambient air
insulation manufacturer’s or contractor’s drawings, the heat
temperature, wind speed, and bare valve surface emittance.
loss from the insulation surface can likewise be calculated by
Unless information is available for estimating the bare valve
taking the product of heat loss per unit area (from programs
surface emittance, it is suggested that a value of 0.9 be
conforming to Practice C 680) and the valve or flange insula-
selected. Select output in units of heat loss per unit surface
tion surface area. The area of the uninsulated surfaces may also
area. This value of heat loss per unit bare surface area is
need to be considered.
designated q .
B
5.6 The use of this practice requires that the valve or flange
6.3 Use of Practice C 680 for the Insulated Valve or
insulation system meets Guide C 1094 and Practice C 450,
Flange—Since Practice C 680 is designed to calculate heat
where applicable.
loss for insulated flat surfaces and for pipes, it is necessary to
treat the insulated valve as an insulated pipe. It is recom-
6. Calculation
mended that the diameter of the pipe, to which the valve fits, or
6.1 This calculation of heat gain or loss requires the
the diameter of the flanges be selected for the calculation. Input
following:
the same ambient air temperature and wind speed as in 6.1 and
6.1.1 The thermal insulation shall be assumed to be homog-
estimate the insulation surface emittance. For a removable
enous as outlined by the definition of thermal conductivity in
insulation cover, this would be the emittance of the fabric or
Terminology C 168.
metal jacket. For conventional insulation, this is either the
6.1.2 The valve or flange size and operating temperature
emittance of that material or of the jacketing, if jacketing is
shall be known.
used. The value of heat loss per unit insulation surface area is
6.1.3 The insulation thickness shall be known.
designated q .
I
6.1.4 Values of wind speed and surface emittance shall be
6.4 Surface Area of the Bare Valve or Flange—Fig. 1 gives
available to estimate the surface coefficients for both the bare
a diagram of a gate valve with the dimensions D , L , T, L ,
P V F
surface and for the insulation.
D , and C as indicated. Eq 1 (see Fig. 1) gives a method for
6.1.5 The surface temperature in each case shall be assumed F
estimating the surface area of valves, and Eq 2 (see Fig. 2)
to be uniform.
gives a method for estimating the surface area of flanges. Table
6.1.6 The bare surface dimensions or area shall be known.
1 gives the results of calculating the surface area for 2-in.
6.1.7 The outer surface area of the insulation cover can be
through 36-in. NPS gate valves for ANSI classes of 150, 300,
estimated from drawings or field measurements.
600 and 900. The value of a bare valve or flange is designated
6.1.8 Practice C 680 or other comparable methodology shall
A .
be used to estimate the heat loss from both bare and insulated B
surfaces. 6.5 Surface Area of the Insulated Valve or Flange—The
6.2 Estimation of Rate of Heat Loss from the Bare estimation of the outer insulation surface area is best performed
Surface—Since Practice C 680 needs to perform iterations in by the manufacturer or the insulation contractor. This surface
calculating heat flow across an insulation surface, an uninsu- area will depend on the dimensions of the valve or flange being
lated surface must be simulated. To do this, select a thin insulated, the thickness of the insulation, and the extent of
C 1129
coverage to either side of the valve or flange. This practice does 8.2 There are a number of factors which influence the
not recommend a specific method for arriving at this area, estimation of heat loss savings, however. The result of a
which would be designated as A . savings estimate is far more dependent upon the calculated heat
I
6.6 Calculation of Bare Valve or Flange Heat Loss—This loss from the bare surface than from the insulated surface. The
value is determined by taking the product of the bare valve or calculated heat loss from the bare surface, in turn, is highly
flange heat loss per unit surface area and of the bare surface dependent on the values of valve or flange service temperature,
area. It will be designated as Q : ambient temperature, wind speed, and surface area, with a
B
lesser dependence on surface emissivity.
Q 5 q A (1)
B B B
8.3 Since the service temperature should be reasonably well
6.7 Calculation of Insulated Valve or Flange Heat Loss—
known, the person performing this estimation is advised to
This value is determined by taking the product of the insulated
perform Practice C 680 calculations on the bare surface under
valve or flange heat loss per unit surface area and of the
extreme environmental conditions. This may not be necessary
insulation outer surface area. It would be designated as Q :
I
if the piping system is located indoors in a controlled environ-
Q 5 q A (2)
I I I ment, but it is strongl
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