ASTM C585-22

Standard Practice for Inner and Outer Diameters of Thermal Insulation for Nominal Sizes of Pipe and Tubing

SIGNIFICANCE AND USE
4.1 The purpose of this practice is to ensure satisfactory fit on standard sizes, to accommodate radial expansion of pipes and tubes which are heated after being insulated, and to minimize the number of insulation sizes and thicknesses to be manufactured and stocked.  
4.2 While it is possible to manufacturer insulation to these recommended dimensions, exercise care in attempting to nest layers of different materials, or layers supplied by different manufacturers. Individual manufacturing processes will operate at slightly different tolerances. While the product will fit the pipe, it is possible that it will not readily nest as the outer layer between the different materials, or with a different manufacturer, and possibly the same manufacturer. Exercise care to determine these differences before specifying or ordering nesting sizes.  
4.3 The wide range of outer diameter dimensional tolerances will prevent many pipe and tube insulations from nesting for staggered joints or double layered applications, or both unless specified when ordered from the manufacturer, distributor, or fabricator.  
4.4 Dimensions in accordance with this practice do not necessarily permit application of one thickness of pipe insulation over another (Nesting or Simplified Dimensional System) to obtain total thicknesses greater than those manufactured as single layer, or for multilayer application when desired.  
FIG. 3 Hinged Section Measurement Location
SCOPE
1.1 This practice is intended as a dimensional standard for preformed thermal insulation for pipes and tubing.  
1.2 This practice covers insulation supplied in cylindrical sections and lists recommended single layer inner and outer diameters of insulation having nominal wall thicknesses from 1/2 to 5 in. (13 to 127 mm) to fit over standard sizes of pipe and tubing.  
1.3 The values stated in inch-pound units are to be regarded as the standard. The values stated in SI units are provided for information only.  
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Apr-2022
• ICS: 27.220 - Heat recovery. Thermal insulation
• Technical Committee: C16 - Thermal Insulation
• Drafting Committee: C16.20 - Homogeneous Inorganic Thermal Insulations

Relations

• Refers: ASTM C168-24 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 15-Apr-2024
• Refers: ASTM C168-18 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 15-Apr-2018
• Refers: ASTM C168-17 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 01-Jun-2017
• Refers: ASTM C168-15a - Standard Terminology Relating to Thermal Insulation
• Effective Date: 15-Oct-2015
• Refers: ASTM C168-15 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 01-Jun-2015
• Refers: ASTM C302-13 - Standard Test Method for Density and Dimensions of Preformed Pipe-Covering-Type Thermal Insulation
• Effective Date: 01-Nov-2013
• Refers: ASTM C168-13 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 01-Apr-2013
• Refers: ASTM C168-10 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 01-Jan-2010
• Refers: ASTM C168-08b - Standard Terminology Relating to Thermal Insulation
• Effective Date: 15-Dec-2008
• Refers: ASTM C168-08a - Standard Terminology Relating to Thermal Insulation
• Effective Date: 01-Sep-2008
• Refers: ASTM C168-08 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 01-Jun-2008
• Refers: ASTM C302-95(2007) - Standard Test Method for Density and Dimensions of Preformed Pipe-Covering-Type Thermal Insulation
• Effective Date: 01-Mar-2007
• Refers: ASTM C168-05a - Standard Terminology Relating to Thermal Insulation
• Effective Date: 01-Nov-2005
• Refers: ASTM C168-05 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 01-Jun-2005
• Refers: ASTM C168-03 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 10-Apr-2003

Overview

ASTM C585-22 is an internationally recognized standard practice developed by ASTM International for the specification of inner and outer diameters of preformed thermal insulation used on nominal pipe and tubing sizes. This standard provides a dimensional framework for insulation manufacturers, distributors, and specifiers to ensure satisfactory fit over standard pipe and tubing, accommodate thermal expansion, and support efficient inventory management by reducing the number of insulation sizes and thicknesses that need to be manufactured or stocked.

Suitable for use with a variety of insulation materials including calcium silicate, cellular foam plastics, cellular glass, mineral fiber, perlite, flexible elastomeric, and polyolefin, ASTM C585-22 ensures industry-wide consistency and compatibility in thermal insulation for piping systems across commercial, industrial, and institutional facilities.

Key Topics

• Dimensional Guidance: Specifies recommended single-layer inner and outer diameters for pipe and tubing insulation ranging from 1/2 to 5 inches (13 to 127 mm) nominal wall thickness.
• Fit and Expansion: Designed to ensure a proper fit on standard pipe and tubing sizes and to accommodate the radial expansion that occurs when pipes are heated.
• Tolerance and Measurement: Details methods and tolerances for measuring inner and outer diameters, including requirements for half and hinged insulation sections.
• Nesting Considerations: Addresses potential challenges with nesting or layering insulation from different materials or manufacturers, emphasizing the need for careful specification if multi-layer applications are involved.
• Units of Measurement: Values are provided in inch-pound units as the standard, with SI units included for reference.
• Material Applicability: Applies to numerous insulation types commonly used in mechanical and process piping applications.

Applications

ASTM C585-22 is essential in industries and applications where precise thermal insulation aids in energy conservation, temperature control, and equipment protection:

• HVAC and Plumbing Systems: Ensures accurate selection and installation of pipe insulation for hot and cold water, steam, and chilled water systems.
• Industrial Facilities: Supports insulation for process piping in power plants, chemical plants, refineries, and food processing plants.
• Commercial Buildings: Used in mechanical rooms and piping runs to maintain energy efficiency and protect building systems.
• Multilayer Insulation Systems: While not inherently intended for nesting or multilayer builds, the standard highlights the need for explicit specification if such applications are required.
• Project Specifications: Provides a uniform reference point for engineers, contractors, and facility managers when specifying insulation products for bids and submittals.

Related Standards

The guidance provided by ASTM C585-22 complements a range of other ASTM and industry standards related to thermal insulation:

• ASTM C168 - Terminology Relating to Thermal Insulation
• ASTM C302 - Test Method for Density and Dimensions of Preformed Pipe-Covering-Type Thermal Insulation
• ASHRAE Standards - Pertaining to insulation performance in HVAC applications
• ASTM C335 / C518 - Related to thermal conductivity testing of insulation materials

By adhering to ASTM C585-22, stakeholders in construction, manufacturing, and facility management can ensure dimensional compatibility, optimize thermal insulation performance, and maintain regulatory and industry best practices for piping insulation systems.

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Keywords: pipe thermal insulation diameter, pipe insulation standards, tubing insulation dimensions, insulation dimensional tolerance, thermal insulating materials, ASTM C585-22, pipe insulation fit, HVAC insulation standards, mechanical piping insulation specifications.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C585 − 22
Standard Practice for
Inner and Outer Diameters of Thermal Insulation for
Nominal Sizes of Pipe and Tubing
This standard is issued under the fixed designation C585; 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 4. Significance and Use
1.1 This practice is intended as a dimensional standard for
4.1 The purpose of this practice is to ensure satisfactory fit
preformed thermal insulation for pipes and tubing.
on standard sizes, to accommodate radial expansion of pipes
and tubes which are heated after being insulated, and to
1.2 This practice covers insulation supplied in cylindrical
minimize the number of insulation sizes and thicknesses to be
sections and lists recommended single layer inner and outer
manufactured and stocked.
diameters of insulation having nominal wall thicknesses from
⁄2 to 5 in. (13 to 127 mm) to fit over standard sizes of pipe and
4.2 While it is possible to manufacturer insulation to these
tubing.
recommended dimensions, exercise care in attempting to nest
layers of different materials, or layers supplied by different
1.3 The values stated in inch-pound units are to be regarded
manufacturers. Individual manufacturing processes will oper-
as the standard. The values stated in SI units are provided for
ate at slightly different tolerances.While the product will fit the
information only.
pipe, it is possible that it will not readily nest as the outer layer
1.4 This standard does not purport to address all of the
between the different materials, or with a different
safety concerns, if any, associated with its use. It is the
manufacturer, and possibly the same manufacturer. Exercise
responsibility of the user of this standard to establish appro-
care to determine these differences before specifying or order-
priate safety, health, and environmental practices and deter-
ing nesting sizes.
mine the applicability of regulatory limitations prior to use.
4.3 The wide range of outer diameter dimensional toler-
1.5 This international standard was developed in accor-
ances will prevent many pipe and tube insulations from nesting
dance with internationally recognized principles on standard-
for staggered joints or double layered applications, or both
ization established in the Decision on Principles for the
unless specified when ordered from the manufacturer,
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical distributor, or fabricator.
Barriers to Trade (TBT) Committee.
4.4 Dimensions in accordance with this practice do not
necessarily permit application of one thickness of pipe insula-
2. Referenced Documents
tion over another (Nesting or Simplified Dimensional System)
2.1 ASTM Standards:
to obtain total thicknesses greater than those manufactured as
C168 Terminology Relating to Thermal Insulation
single layer, or for multilayer application when desired.
C302 Test Method for Density and Dimensions of Pre-
formed Pipe-Covering-Type Thermal Insulation
5. Summary of Practice
3. Terminology 5.1 This practice provides for each pipe and tubing sizes the
inner diameters with tolerances for calcium silicate, cellular
3.1 Definitions—Definitions pertaining to insulation are de-
foam plastics, cellular glass, mineral fiber, and perlite pre-
fined in Terminology C168.
formed pipe and tubing insulation identified by Table 1 and
Table 2.
This practice is under the jurisdiction of ASTM Committee C16 on Thermal
5.2 This practice provides for each pipe and tubing sizes the
InsulationandisthedirectresponsibilityofSubcommitteeC16.20onHomogeneous
Inorganic Thermal Insulations.
outer diameters for calcium silicate, cellular foam plastics,
Current edition approved May 1, 2022. Published June 2022. Originally
cellular glass, mineral fiber, and perlite preformed pipe and
approvedin1966toreplaceC312andC521.Lastpreviouseditionapprovedin2016
tubing insulation identified by Table 3, Table 4, Table 5 and
as C585 – 10 (2016). DOI: 10.1520/C0585-22.
Table 6.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
5.3 This practice provides for a range of pipe and tubing
Standards volume information, refer to the standard’s Document Summary page on
theASTM website. sizes the outer diameter tolerances for calcium silicate and
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C585 − 22
perlitepreformedpipeandtubinginsulationidentifiedbyTable 6.2.2 Inner diameters and tolerances for nominal sizes of
3a, Table 4a, Table 5a, and Table 6a. tubing are shown in Table 2, Table 8. Table 8a Table 10 and
Table 10a.
5.4 This practice provides for a range of pipe and tubing
sizes the outer diameters tolerances for cellular foam plastics,
6.3 Recommended Outer Diameters:
cellular glass, and mineral fiber, preformed pipe and tubing
6.3.1 Outerdiametersfornominalsizesofpipeareshownin
insulations identified by Table 3b, Table 4b, Table 5b and Table
Table 3 and Table 4, Table 7 and Table 9 and tubing in Table
6b.
5 and Table 6, Table 8, and Table 10. All Tables 3-10 are not
5.5 This practice provides for each pipe and tubing sizes the
for nesting purposes. When a pipe or tubing insulation product
inner and outer diameters for flexible elastomeric cellular and
is to be nested, it shall be so stated on order.
polyolefin preformed pipe and tubing insulation identified by
6.3.2 There are no maximum outer diameter tables provided
Table 7, Table 8, Table 9, and Table 10.
for jacketing purposes because of the wide spread variations in
5.6 This practice provides for a range of pipe and tubing
the outside diameters with their plus or minus tolerances.
sizes the inner and outer diameter tolerances for flexible
NOTE 1—Previous versions of C585 contained Tables for jacketing
elastomeric and polyolefin cellular preformed pipe and tubing
purposes only.These tables have been removed from this practice with the
insulation identified by Table 7a, Table 8a, Table 9a, and Table
inclusion of variable outside diameters caused by the addition of outer
10a.
diameter (OD) tolerances. It is recommended in order to calculate the
maximum circumferences for jacketing purposes, determine the pipe or
6. Procedure
tube insulation’s maximum outer diameters from the manufacturer. An
6.1 Measurement: alternativemeasureforfindingthejacketingstretch-outnumbersistolook
up the outer diameter for the pipe or tubing insulation from the tables; add
6.1.1 Measurement of inner and outer diameters shall be
1 the applicable plus (+) outer diameter tolerance and twice the thickness of
made to the nearest ⁄32 in. (0.8 mm) using a steel tape or rule.
the jacketing to the insulation outer diameter number; multiply the added
6.1.1.1 Uneven Insulation Inner & Outer Circumferential
total times pī (3.14159) to arrive at the maximum circumference; add the
Surfaces—Use Test Method C302, Procedure C. This method
necessary longitudinal overlap dimension to the maximum circumference;
must be used, to duplicate fit for application on a pipe and
and the calculated answer will be the stretch-out requirement for cutting
the outer jacketing to be applied over / around the pipe or tubing
tubing and to determine the final outside diameter when an
insulation’s OD.
outer metal jacket system is snugly applied.
NOTE 2—NPS (Nominal Pipe Size) is a dimensionless designator that
6.1.1.2 Half Sections—The diameter reported for each half-
has been substituted in the customary units section for the previous term
section shall be the average of six measurements taken at three
inch nominal pipe size.
locations including two near the ends and one near the center
NOTE 3—NTS (Nominal Tube Size) is a dimensionless designator that
(see Fig. 1a and Fig. 2a). Three of the six readings shall be
has been substituted in the customary units section for the previous term
taken in the longitudinal plane of the flat, cut surface: the other
inch nominal tube size.
three shall each be twice a half-diameter in the longitudinal
NOTE 4—DN (Diameter Nominal) is a dimensionless designator that
plane at right angles to that of the first three (see Fig. 1b and has been substituted in the customary units section for the previous term
SI (metric) system to describe millimeter nominal pipe or tube size.
Fig. 2b).
6.1.1.3 Hinged Sections—The diameter reported for each
7. Keywords
hinged section shall be the average of four measurements taken
at both ends of the section (two per end) (see Fig. 3). The two
7.1 pipe thermal insulation diameter; pipe thermal insula-
measurements at each end shall be at right angles.
tion dimension; pipe thermal insulation dimensional tolerance;
6.2 Recommended Inner Diameters: thermal insulating materials-pipe; thermal insulating materials-
tubing; thermal insulation; tubing thermal insulation diameter;
6.2.1 Inner diameters and tolerances for nominal sizes of
insulation for pipe are shown in Table 1, Table 7. Table 7a tubing thermal insulation dimension; tubing thermal insulation
Table 9 and Table 9a. dimensional tolerance
C585 − 22
Fig. 1a Three Meaurement Locations
Fig. 1b Diameter and Half-Diameter Measurement Locations
FIG. 1 Inner Diameter Measurement Location
Fig. 2a Three Measurement Locations
Fig. 2b Diameter and Half-Diameter Measurement Locations
FIG. 2 Outer Diameter Measurement Location
C585 − 22
FIG. 3 Hinged Section Measurement Location
TABLE 1 Nominal Pipe Sizes with Inner Diameters and Tolerances for
Calcium Silicate, Cellular Foam Plastics, Cellular Glass, Mineral Fiber, and Perlite Preformed Insulation
Customary and SI Units for Pipe Insulation
Tolerance
Outer Diameter Inner Diameter
NPS DN
Minus Plus
Note 2 Note 4
in. mm in. mm in. mm in. mm
⁄2 15 0.840 21.3 0.86 22 0 0 0.063 1.6
⁄4 20 1.050 26.7 1.07 27 0 0 0.063 1.6
1 25 1.315 33.4 1.33 34 0 0 0.063 1.6
1 ⁄4 32 1.660 42.2 1.68 43 0 0 0.063 1.6
1 ⁄2 40 1.900 48.3 1.92 49 0 0 0.063 1.6
2 50 2.375 60.3 2.41 61 0 0 0.094 2.4
2 ⁄2 65 2.875 73.0 2.91 74 0 0 0.094 2.4
3 80 3.500 88.9 3.53 90 0 0 0.094 2.4
3 ⁄2 90 4.000 101.6 4.03 102 0.031 0.8 0.094 2.4
4 100 4.500 114.3 4.53 115 0.031 0.8 0.094 2.4
4 ⁄2 115 5.000 127.0 5.03 128 0.031 0.8 0.094 2.4
5 125 5.563 141.4 5.64 143 0.031 0.8 0.094 2.4
6 150 6.625 168.3 6.70 170 0.031 0.8 0.094 2.4
7 175 7.625 193.7 7.70 196 0.031 0.8 0.094 2.4
8 200 8.625 219.1 8.70 221 0.031 0.8 0.094 2.4
9 225 9.625 244.5 9.70 246 0.031 0.8 0.094 2.4
10 250 10.750 273.0 10.83 275 0.031 0.8 0.094 2.4
11 275 11.750 298.4 11.83 300 0.031 0.8 0.094 2.4
12 300 12.750 323.8 12.84 326 0.063 1.6 0.094 2.4
14 350 14.000 355.6 14.09 358 0.063 1.6 0.156 4.0
C585 − 22
TABLE 2 Nominal Tube Sizes with Inner Diameter and Tolerances for
Calcium Silicate, Cellular Foam Plastics, Cellular Glass, Mineral Fiber, and Perlite Preformed Insulation
Customary and SI Units for Tube Insulation
Tolerance
Outer Diameter Inner Diameter
NTS DN
Minus Plus
Note 3 Note 4
in. mm in. mm in. mm in. mm
⁄8 10 0.500 12.7 0.52 13 0 0 0.063 1.6
⁄2 15 0.625 15.9 0.64 16 0 0 0.063 1.6
⁄4 20 0.875 22.2 0.89 23 0 0 0.063 1.6
1 25 1.125 28.6 1.14 29 0 0 0.063 1.6
1 ⁄4 32 1.375 34.9 1.39 35 0 0 0.063 1.6
1 ⁄2 40 1.625 41.3 1.64 42 0 0 0.063 1.6
2 50 2.125 54.0 2.16 55 0 0 0.063 1.6
2 ⁄2 65 2.625 66.7 2.66 68 0 0 0.063 1.6
3 80 3.125 79.4 3.16 80 0 0 0.063 1.6
3 ⁄2 90 3.625 92.1 3.66 93 0 0 0.063 1.6
4 100 4.125 104.8 4.16 106 0.031 0.8 0.094 2.4
5 125 5.125 130.2 5.16 131 0.031 0.8 0.094 2.4
6 150 6.125 155.6 6.20 157 0.031 0.8 0.094 2.4
TABLE 3 Outer Diameters for Nominal Pipe Sizes and Nominal Wall Thickness on
Calcium Silicate, Cellular Foam Plastics, Cellular Glass, Mineral Fiber, and Perlite Preformed Insulation, inches
Pipe Customary Units for Insulation, Nominal Thickness
1 1 1 1
in. 1 1 ⁄2 22 ⁄2 33 ⁄2 44 ⁄2 5
NPS
Outer Diameter, in.
Note 2
⁄2 2.88 4.00 5.00 6.62 7.62 8.62 9.62 10.75 11.75
⁄4 2.88 4.00 5.00 6.62 7.62 8.62 9.62 10.75 11.75
1 3.50 4.50 5.56 6.62 7.62 8.62 9.62 10.75 11.75
1 ⁄4 3.50 5.00 5.56 6.62 7.62 8.62 9.62 10.75 11.75
1 ⁄2 4.00 5.00 6.62 7.62 8.62 9.62 10.75 11.75 12.75
2 4.50 5.56 6.62 7.62 8.62 9.62 10.75 11.75 12.75
2 ⁄2 5.00 6.62 7.62 8.62 9.62 10.75 11.75 12.75 14.00
3 5.56 6.62 7.62 8.62 9.62 1
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C585 − 10 (Reapproved 2016) C585 − 22
Standard Practice for
Inner and Outer Diameters of Thermal Insulation for
Nominal Sizes of Pipe and Tubing
This standard is issued under the fixed designation C585; 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 This practice is intended as a dimensional standard for preformed thermal insulation for pipes and tubing.
1.2 This practice covers insulation supplied in cylindrical sections and lists recommended single layer inner and outer diameters
of insulation having nominal wall thicknesses from ⁄2 to 5 in. (13 to 127 mm) to fit over standard sizes of pipe and tubing.
1.3 The values stated in inch-pound units are to be regarded as the standard. The values stated in SI units are provided for
information only.
1.4 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
C168 Terminology Relating to Thermal Insulation
C302 Test Method for Density and Dimensions of Preformed Pipe-Covering-Type Thermal Insulation
3. Terminology
3.1 Definitions—Definitions pertaining to insulation are defined in Terminology C168.
4. Significance and Use
4.1 The purpose of this practice is to ensure satisfactory fit on standard sizes, to accommodate radial expansion of pipes and tubes
which are heated after being insulated, and to minimize the number of insulation sizes and thicknesses to be manufactured and
stocked.
This practice is under the jurisdiction of ASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.20 on Homogeneous
Inorganic Thermal Insulations.
Current edition approved May 1, 2016May 1, 2022. Published May 2016June 2022. Originally approved in 1966 to replace C312 and C521. Last previous edition approved
in 20102016 as C585 – 10.C585 – 10 (2016). DOI: 10.1520/C0585-10R16.10.1520/C0585-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C585 − 22
4.2 While it is possible to manufacturer insulation to these recommended dimensions, exercise care in attempting to nest layers
of different materials, or layers supplied by different manufacturers. Individual manufacturing processes will operate at slightly
different tolerances. While the product will fit the pipe, it is possible that it will not readily nest as the outer layer between the
different materials, or with a different manufacturer, and possibly the same manufacturer. Exercise care to determine these
differences before specifying or ordering nesting sizes.
4.3 The wide range of outer diameter dimensional tolerances will prevent many pipe and tube insulations from nesting for
staggered joints or double layered applications, or both unless specified when ordered from the manufacturer, distributor, or
fabricator.
4.4 Dimensions in accordance with this practice do not necessarily permit application of one thickness of pipe insulation over
another (Nesting or Simplified Dimensional System) to obtain total thicknesses greater than those manufactured as single layer,
or for multilayer application when desired.
5. Summary of Practice
5.1 This practice provides for each pipe and tubing sizes the inner diameters with tolerances for calcium silicate, cellular foam
plastics, cellular glass, mineral fiber, and perlite preformed pipe and tubing insulation identified by Table 1 and Table 2.
5.2 This practice provides for each pipe and tubing sizes the outer diameters for calcium silicate, cellular foam plastics, cellular
glass, mineral fiber, and perlite preformed pipe and tubing insulation identified by Table 3, Table 4, Table 5 and Table 6.
5.3 This practice provides for a range of pipe and tubing sizes the outer diameter tolerances for calcium silicate and perlite
preformed pipe and tubing insulation identified by Table 3a, Table 4a, Table 5a, and Table 6a.
5.4 This practice provides for a range of pipe and tubing sizes the outer diameters tolerances for cellular foam plastics, cellular
glass, and mineral fiber, preformed pipe and tubing insulations identified by Table 3b, Table 4b, Table 5b and Table 6b.
5.5 This practice provides for each pipe and tubing sizes the inner and outer diameters for flexible elastomeric cellular and
polyolefin preformed pipe and tubing insulation identified by Table 7, Table 8, Table 9, and Table 10.
5.6 This practice provides for a range of pipe and tubing sizes the inner and outer diameter tolerances for flexible elastomeric and
polyolefin cellular preformed pipe and tubing insulation identified by Table 7a, Table 8a, Table 9a, and Table 10a.
6. Procedure
6.1 Measurement:
6.1.1 Measurement of inner and outer diameters shall be made to the nearest ⁄32 in. (0.8 mm) using a steel tape or rule.
6.1.1.1 Uneven Insulation Inner & Outer Circumferential Surfaces—Use Test Method C302, Procedure C. This method must be
used, to duplicate fit for application on a pipe and tubing and to determine the final outside diameter when an outer metal jacket
system is snugly applied.
6.1.1.2 Half Sections—The diameter reported for each half-section shall be the average of six measurements taken at three
locations including two near the ends and one near the center (see Fig. 1a and Fig. 2a). Three of the six readings shall be taken
in the longitudinal plane of the flat, cut surface: the other three shall each be twice a half-diameter in the longitudinal plane at right
angles to that of the first three (see Fig. 1b and Fig. 2b).
6.1.1.3 Hinged Sections—The diameter reported for each hinged section shall be the average of four measurements taken at both
ends of the section (two per end) (see Fig. 3). The two measurements at each end shall be at right angles.
6.2 Recommended Inner Diameters:
C585 − 22
6.2.1 Inner diameters and tolerances for nominal sizes of insulation for pipe are shown in Table 1, Table 7. Table 7a Table 9 and
Table 9a.
6.2.2 Inner diameters and tolerances for nominal sizes of tubing are shown in Table 2, Table 8. Table 8a Table 10 and Table 10a.
6.3 Recommended Outer Diameters:
6.3.1 Outer diameters for nominal sizes of pipe are shown in Table 3 and Table 4, Table 7 and Table 9 and tubing in Table 5 and
Table 6, Table 8, and Table 10. All Tables 3-10 are not for nesting purposes. When a pipe or tubing insulation product is to be
nested, it shall be so stated on order.
6.3.2 There are no maximum outer diameter tables provided for jacketing purposes because of the wide spread variations in the
outside diameters with their plus or minus tolerances.
NOTE 1—Previous versions of C585 contained Tables for jacketing purposes only. These tables have been removed from this practice with the inclusion
of variable outside diameters caused by the addition of outer diameter (OD) tolerances. It is recommended in order to calculate the maximum
circumferences for jacketing purposes, determine the pipe or tube insulation’s maximum outer diameters from the manufacturer. An alternative measure
for finding the jacketing stretch-out numbers is to look up the outer diameter for the pipe or tubing insulation from the tables; add the applicable plus
(+) outer diameter tolerance and twice the thickness of the jacketing to the insulation outer diameter number; multiply the added total times pī (3.14159)
to arrive at the maximum circumference; add the necessary longitudinal overlap dimension to the maximum circumference; and the calculated answer
will be the stretch-out requirement for cutting the outer jacketing to be applied over / around the pipe or tubing insulation’s OD.
NOTE 2—NPS (Nominal Pipe Size) is a dimensionless designator that has been substituted in the customary units section for the previous term inch
nominal pipe size.
NOTE 3—NTS (Nominal Tube Size) is a dimensionless designator that has been substituted in the customary units section for the previous term inch
nominal tube size.
NOTE 4—DN (Diameter Nominal) is a dimensionless designator that has been substituted in the customary units section for the previous term SI (metric)
system to describe millimeter nominal pipe or tube size.
7. Keywords
7.1 pipe thermal insulation diameter; pipe thermal insulation dimension; pipe thermal insulation dimensional tolerance; thermal
insulating materials-pipe; thermal insulating materials-tubing; thermal insulation; tubing thermal insulation diameter; tubing
thermal insulation dimensiondimension; tubing thermal insulation dimensional tolerance
C585 − 22
Fig. 1a Three Meaurement Locations
Fig. 1b Diameter and Half-Diameter Measurement Locations
FIG. 1 Inner Diameter Measurement Location
Fig. 2a Three Measurement Locations
Fig. 2b Diameter and Half-Diameter Measurement Locations
FIG. 2 Outer Diameter Measurement Location
C585 − 22
FIG. 3 Hinged Section Measurement Location
TABLE 1 Nominal Pipe Sizes with Inner Diameters and Tolerances for
Calcium Silicate, Cellular Foam Plastics, Cellular Glass, Mineral Fiber, and Perlite Preformed Insulation
Customary and SI Units for Pipe Insulation
Tolerance
Outer Diameter Inner Diameter
NPS DN
Minus Plus
Note 2 Note 4
in. mm in. mm in. mm in. mm
⁄2 15 0.840 21.3 0.86 22 0 0 0.063 1.6
⁄4 20 1.050 26.7 1.07 27 0 0 0.063 1.6
1 25 1.315 33.4 1.33 34 0 0 0.063 1.6
1 ⁄4 32 1.660 42.2 1.68 43 0 0 0.063 1.6
1 ⁄2 40 1.900 48.3 1.92 49 0 0 0.063 1.6
2 50 2.375 60.3 2.41 61 0 0 0.094 2.4
2 ⁄2 65 2.875 73.0 2.91 74 0 0 0.094 2.4
3 80 3.500 88.9 3.53 90 0 0 0.094 2.4
3 ⁄2 90 4.000 101.6 4.03 102 0.031 0.8 0.094 2.4
4 100 4.500 114.3 4.53 115 0.031 0.8 0.094 2.4
4 ⁄2 115 5.000 127.0 5.03 128 0.031 0.8 0.094 2.4
5 125 5.563 141.4 5.64 143 0.031 0.8 0.094 2.4
6 150 6.625 168.3 6.70 170 0.031 0.8 0.094 2.4
7 175 7.625 193.7 7.70 196 0.031 0.8 0.094 2.4
8 200 8.625 219.1 8.70 221 0.031 0.8 0.094 2.4
9 225 9.625 244.5 9.70 246 0.031 0.8 0.094 2.4
10 250 10.750 273.0 10.83 275 0.031 0.8 0.094 2.4
11 275 11.750 298.4 11.83 300 0.031 0.8 0.094 2.4
12 300 12.750 323.8 12.84 326 0.063 1.6 0.094 2.4
14 350 14.000 355.6 14.09 358 0.063 1.6 0.156 4.0
C585 − 22
TABLE 2 Nominal Tube Sizes with Inner Diameter and Tolerances for
Calcium Silicate, Cellular Foam Plastics, Cellular Glass, Mineral Fiber, and Perlite Preformed Insulation
Customary and SI Units for Tube Insulation
Tolerance
Outer Diameter Inner Diameter
NTS DN
Minus Plus
Note 3 Note 4
in. mm in. mm in. mm in. mm
⁄8 10 0.500 12.7 0.52 13 0 0 0.063 1.6
⁄2 15 0.625 15.9 0.64 16 0 0 0.063 1.6
⁄4 20 0.875 22.2 0.89 23 0 0 0.063 1.6
1 25 1.125 28.6 1.14 29 0 0 0.063 1.6
1 ⁄4 32 1.375 34.9 1.39 35 0 0 0.063 1.6
1 ⁄2 40 1.625 41.3 1.64 42 0 0 0.063 1.6
2 50 2.125 54.0 2.16 55 0 0 0.063 1.6
2 ⁄2 65 2.625 66.7 2.66 68 0 0 0.063 1.6
3 80 3.125 79.4 3.16 80 0 0 0.063 1.6
3 ⁄2 90 3.625 92.1 3.66 93 0 0 0.063 1.6
4 100 4.125 104.8 4.16 106 0.031 0.8 0.094 2.4
5 125 5.125 130.2 5.16 131 0.031 0.8 0.094 2.4
6 150 6.125 155.6 6.20 157 0.031 0.8 0.094 2.4
TABLE 3 Outer Diameters for Nominal Pipe Sizes and Nominal Wall Thickness on
Calcium Silicate, Cellular Foam Plastics, Cellular Glass, Mineral Fiber, and Perlite Preformed Insulation, inches
Pipe Customary Units for Insulation, Nominal Thickness
1 1 1 1
in. 1 1 ⁄2 2 2 ⁄2 3 3 ⁄2 4 4 ⁄2 5
NPS
Outer Diameter, in.
Note 2
⁄2 2.88 4.00 5.00 6.62 7.62 8.62 9.62 10.75 11.75
⁄4 2.88 4.00 5.00 6.62 7.62 8.62 9.62 10.75 11.75
1 3.50 4.50 5.56 6.62 7.62 8.62 9.62 10.75 11.75
1 ⁄4 3.50 5.00 5.56 6.62 7.62 8.62 9.62 10.75 11.75
1 ⁄2 4.00 5.00 6.62 7.62 8.62 9.62 10.75 11.75 12.75
2 4
...