ASTM F1948-20

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: F1948 − 19 F1948 − 20 An American National Standard
Standard Specification for
Metallic Mechanical Fittings for Use on Outside Diameter
Controlled Thermoplastic Gas Distribution Pipe and Tubing
This standard is issued under the fixed designation F1948; 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 specification covers requirements and test methods for the qualification of metallic mechanical fittings for use with
outside diameter controlled thermoplastic gas distribution pipe and tubing as specified in Specification D2513, F2785, or F2945.
1.2 The test methods described are not intended to be routine quality control tests.
1.3 This specification covers the types of mechanical fittings described in 3.3.
1.4 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.
1.5 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes
(excluding those in tables and figures), shall not be considered as requirements of the standard.
1.6 The following safety hazards caveat pertains only to the test method portion, Section 7, of this specification. 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.
1.7 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:
D638 Test Method for Tensile Properties of Plastics
D1598 Test Method for Time-to-Failure of Plastic Pipe Under Constant Internal Pressure
D1600 Terminology for Abbreviated Terms Relating to Plastics
D2513 Specification for Polyethylene (PE) Gas Pressure Pipe, Tubing, and Fittings
E515 Practice for Leaks Using Bubble Emission Techniques
F412 Terminology Relating to Plastic Piping Systems
F1588 Test Method for Constant Tensile Load Joint Test (CTLJT)
F2785 Specification for Polyamide 12 Gas Pressure Pipe, Tubing, and Fittings
F2897 Specification for Tracking and Traceability Encoding System of Natural Gas Distribution Components (Pipe, Tubing,
Fittings, Valves, and Appurtenances)
F2945 Specification for Polyamide 11 Gas Pressure Pipe, Tubing, and Fittings
2.2 ASME Standard:
ASME B 31.8 Gas Transmission and Distribution Piping Systems
This specification is under the jurisdiction of ASTM Committee F17 on Plastic Piping Systems, and is the direct responsibility of Subcommittee F17.60 on Gas.
Current edition approved Nov. 1, 2019Feb. 1, 2020. Published January 2020February 2020. Originally published in 1999. Last previous edition approved in 20152019
as F1948–15.–19. DOI: 10.1520/F1948-19.10.1520/F1948-20
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 American Society of Mechanical Engineers (ASME), ASME International Headquarters, Three Park Ave., New York, NY 10016-5990, http://
www.asme.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1948 − 20
2.3 Federal Specification:
OPS Part 192 Title 49, Code of Federal Regulations
2.4 Other Document:
PPI TR-4 Recommended Hydrostatic Strengths and Design Stresses for Thermoplastic Pipe and Fitting Compounds
3. Terminology
3.1 Definitions are in accordance with Definitions F412 unless otherwise specified. Abbreviations are in accordance with
Abbreviations D1600 unless otherwise specified.
3.1.1 The gas industry terminology used in this specification is in accordance with ASME/ANSI B31.8 or United States CFR
49 Part 192 unless otherwise indicated.
3.1.2 The term “pipe” used herein refers to both pipe and tubing unless specifically stated otherwise. The term “fitting” refers
to a mechanical connecting device as described in 3.2.5 and 3.2.7.
3.2 Definitions:
3.2.1 Category 1 mechanical fitting, n—fitting for assembling pipe, which includes a compression zone(s) to provide for
pressure integrity, leak tightness, and resistance to end loads sufficient to cause no less than 25 % elongation of the piping, as
described in this standard.
3.2.2 Category 2 mechanical fitting, n—fitting for assembling pipe, which includes a compression zone(s) to provide for
pressure integrity and leak tightness; Category 2 fittings do not provide for resistance to end loads.
3.2.3 Category 3 mechanical fitting, n—fitting for assembling pipe, which includes a compression zone(s) for pressure integrity,
leak tightness, and resistance to end loads; the nominal size of the fitting shall be 4 and larger in diameter.
3.2.3.1 Discussion—
Resistance to end loads shall be equal to or greater than the maximum thermal stress that would be produced by a temperature
change of 100 °F (55 °C) (for formula, see Annex A1).
3.2.4 joint, n—the location at which two or more pieces of pipe, or a pipe and a fitting, are connected (an installed coupling has
two joints).
3.2.5 joint, mechanical, n—a connection between piping components employing physical force to develop a seal or produce
alignment.
3.2.6 maximum allowable operating pressure, MAOP, n—of the fuel gas piping system, in psig, as determined in accordance
with US DOT CFR, Title 49, Part 192.121, and as represented in the following:
MAOP 5 P 5 23S/~R 2 1!xf (1)
where:
S = the pipe material’s HDB as published in PPI TR 4,
R = the pipe’s dimension ratio determined by dividing the pipe’s specified nominal outside diameter by the pipe’s specified
nominal wall thickness, and
f = design (derating) factor for thermoplastic fuel gas piping as set by the authority having jurisdiction. In the United States,
the design factor is cited in CFR, Title 49, Part 192.121.
3.2.7 mechanical fitting, n—fitting for making a mechanical joint to provide for pressure integrity, leak tightness, and, depending
on category, as defined in this standard, resistance to end loads.
3.3 Types of Mechanical Fittings:
3.3.1 clamped insert fitting, n—mechanical fitting used to make a mechanical joint that utilizes external clamps, or other
mechanical devices, to form a pressure seal between the reinforcing tubular stiffener and the surface of the pipe.
3.3.2 compression fitting, n—mechanical fitting used to make a mechanical joint by compressing either externally, internally, or
radially to form a pressure seal between the fitting and the surface of the pipe.
3.3.3 compression gasket fitting, n—mechanical fitting used to make a mechanical joint that utilizes a compression nut,
tightening ring, bolts, or any other device to compress gasketing onto the surface of the pipe to form a pressure seal.
3.3.4 stab-type fitting, n—mechanical fitting used to make a mechanical joint in which a seal is achieved by radial compression
of a gasket between; the outside diameter (OD) of the pipe and the inside diameter (ID) of the fitting; the inside diameter (ID) of
the pipe with the insert stiffener; or both.
Available from the Office of Pipeline Safety, Research and Special Programs Administration, U.S. Department of Transportation, 400 Seventh Street, S.W., Washington,
DC, 20006-1301.
Available from Plastics Pipe Institute (PPI), 105 Decker Court, Suite 825, Irving, TX 75062, http://www.plasticpipe.org.
F1948 − 20
4. Material
4.1 The physical properties of each material used to produce the fitting shall be available from the fitting manufacturer upon
request.
4.2 Specifications outlining the physical and chemical properties of all fitting materials shall be available from the fitting
manufacturer upon request.
NOTE 1—Materials in long-term contact with natural gas of line quality and LP gas vapor should be demonstrated to not adversely effect the
performance of the fitting.
NOTE 2—Materials should have a demonstrated resistance to environmental stress cracking when exposed, under stress, to chemical compounds
encountered in or external to gas piping systems, and a demonstrated resistance to bacteriological decomposition. Such compounds include, but are not
limited to, ice thawing chemicals, fertilizers, insecticides, herbicides, leak detection fluids, acids, bases and antifreeze solutions used to thaw frozen lines.
5. Dimensions
5.1 The dimensions and tolerances shall be determined by the manufacturer.
6. Qualification Requirements
6.1 General—Unless otherwise specified, each nominal size of fitting shall be tested. Testing the fitting with the thickest wall
pipe for which the fitting is designed qualifies that type of fitting for use with pipe of lesser wall thickness.
6.1.1 Mechanical joint qualification shall be performed on assembled joints using the fitting manufacturer’s joining procedure.
All mechanical fittings offered by the manufacturer shall be capable of meeting the requirements of this standard when:
6.1.1.1 Connecting thermoplastic gas piping complying with applicable ASTM thermoplastic gas piping standards, as listed in
Section 2, Referenced Documents, either same to same (for example, PE to PE) or transitioning (for example, PE to PA).
6.1.1.2 Transitioning between thermoplastic gas piping complying with applicable ASTM thermoplastic gas piping standards,
in Section 2, Referenced Documents, and metal piping. It is not the intent of this standard to require the testing of all fitting
configurations (that is, tee, ells, etc.) but each fitting joint design in each size.
6.1.2 All mechanical fittings described in 3.3 shall have an internal pipe reinforcing tubular stiffener that extends at least under
the seal and gripping device (where used). Exception: When the fitting is used to transition from plastic to metal, only the plastic
end of the fitting is required to have a stiffener employed.
6.1.3 In the case of fittings designed to transition between different thermoplastic materials, between different wall thicknesses
(SDRs), or different diameters of the same thermoplastic material, the pipe requiring the lowest force to elongate to yield shall fail
before any joint fails. For example, when transitioning between PE and PA of the same wall thickness (same DR) and diameter,
failure of the PE before the joint fails, qualifies the fitting in this transition scenario. Another example is a fitting used to transition
1 1
between 1CTS PE and ⁄2 CTS PE piping, of the same DR, qualifies if the ⁄2 CTS tubing fails before the joint fails.
6.1.4 In the case of fittings designed to transition between metallic piping and thermoplastic piping, the fitting shall be qualified
as Category 1 under this standard only if the joint between the fitting and the metallic piping has been tested to provide axial tensile
restraint strength of 1.5 times the tensile strength at yield of the thermoplastic piping joined to the opposite end.
6.1.4.1 The metallic piping shall not pull out of the fitting when tested to the following pull-out forces and tested in accordance
with 7.2.
(1) For PE 3770 psi
(2) For PA11 8700 psi
(3) For PA12 7614 psi
6.2 Performance Requirements:
6.2.1 Tensile Strength—The fitting shall provide a thermoplastic pipe joint design capable of accommodating the following
tensile loads, when tested in accordance with 7.2.
6.2.1.1 Category 1—A fitting that, when properly installed and meeting the qualification requirements of 6.1.1, 6.1.2 and 6.1.3,
shall provide for joints in thermoplastic piping that resist pull-out to a force on the thermoplastic pipe equal to or greater than that
which will cause no less than 25% elongation of the plastic pipe, or which causes the plastic pipe to fail outside the joint area when
tested in accordance with 7.2. Furthermore, a fitting designed to transition between metallic piping and thermoplastic piping that,
when properly installed, shall meet the qualification requirements of 6.1.4 when tested in accordance with 7.2.
6.2.1.2 Category 2—Fitting that, when properly installed, creates a joint that provides only a seal. A mechanical joint designed
for this category excludes any provisions in the design of the joint to resist axial pullout forces; therefore, tensile tests are not
required.
6.2.1.3 Category 3—Fittings of nominal pipe size 4 and larger in diameter that, when properly installed provides a pull-out
resistance to a force on the thermoplastic pipe joint equal to or greater than the maximum thermalstress that would be produced
by a temperature change of 100 °F (55 °C)(for (55 °C) (for formula, see Annex A1).
NOTE 3—Category 3 has a manufacturer’s rated pipe end restraint less than the value required t
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