ASTM F948-94(2001)e1
(Test Method)Standard Test Method for Time-to-Failure of Plastic Piping Systems and Components Under Constant Internal Pressure With Flow
Standard Test Method for Time-to-Failure of Plastic Piping Systems and Components Under Constant Internal Pressure With Flow
SCOPE
1.1 This test method covers the determination of the time-to-failure of plastic piping products under constant internal pressure and flow.
1.2 This test method provides a method of characterizing plastics in the form of pipe, components, and systems under any reasonable combination of internal and external temperatures and environments, under the procedures described.
1.3 This test method can be used to characterize the tested plastic materials or products, or both, on the basis of pressure-, or stress-rupture data developed under the conditions prescribed.
1.4 The values stated in inch-pound units are to be regarded as the standard.
1.5 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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An American National Standard
e1
Designation:F 948 – 94 (Reapproved 2001)
Standard Test Method for
Time-to-Failure of Plastic Piping Systems and Components
Under Constant Internal Pressure With Flow
This standard is issued under the fixed designation F 948; 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 added editorially in November 2003.
1. Scope E 177 Practice for Use of the Terms Precision and Bias in
ASTM Test Methods
1.1 This test method covers the determination of the time-
2.2 PPI Documents:
to-failure of plastic piping products under constant internal
TR-2 Policies and Procedures for the Listing of Thermo-
pressure and flow.
plastic Pipe, Fittings, and Fixture Materials When Evalu-
1.2 This test method provides a method of characterizing
ated Under Constant Internal Pressure With Flow
plastics in the form of pipe, components, and systems under
TR-3 Policies and Procedures for Developing Recom-
any reasonable combination of internal and external tempera-
mended Hydrostatic Design Stresses for Thermoplastic
tures and environments, under the procedures described.
Pipe Materials
1.3 This test method can be used to characterize the tested
plastic materials or products, or both, on the basis of pressure-,
3. Terminology
or stress-rupture data developed under the conditions pre-
3.1 Definitions:
scribed.
3.1.1 failure—bursting, cracking, splitting, or weeping
1.4 The values stated in inch-pound units are to be regarded
(seepage of test fluid through the wall of the product) during
as the standard.
the test, which results in the inability of the specimen to
1.5 This standard does not purport to address all of the
maintain pressure or contain the internal test fluid, shall
safety concerns, if any, associated with its use. It is the
constitute failure of the test specimen. Failure may sometimes
responsibility of the user of this standard to establish appro-
occur by ballooning, an excessive extension leading to struc-
priate safety and health practices and determine the applica-
tural failure. When failure occurs by ballooning the degree of
bility of regulatory limitations prior to use.
distension should be recorded. Assemblies may also fail to
2. Referenced Documents joint leakage or separation.
2.1 ASTM Standards:
NOTE 1—Overall distension, which results from creep caused by
D 543 Test Method for Resistance of Plastics to Chemical long-term stress, is not considered to be a ballooning failure.
Reagents
3.1.2 hoop stress—thetensilestressinthewallofthepiping
D 2122 Test Method for Determining Dimensions of Ther-
product in the circumferential direction due to internal pres-
moplastic Pipe and Fittings
sure. Units will be reported as pounds per square inch (psi) or
D 2837 Test Method for Obtaining Hydrostatic Design
mega pascals (MPa). Hoop stress will be calculated by the
Basis for Thermoplastic Pipe Materials
following ISO equation:
D 2992 Practice for Obtaining Hydrostatic or Pressure De-
S 5 P ~D 2 t!/2t
sign Basis for “Fiberglass’’ (Glass–Fiber–Reinforced
Thermosetting Resin) Pipe and Fittings
where:
D 3567 Practice for Determining Dimensions of “Fiber-
S = hoop stress, psi (MPa),
glass’’ (Glass–Fiber–Reinforced Thermosetting-Resin)
D = average outside diameter, in. (mm),
Pipe and Fittings
P = internal pressure, psig (MPag), and
t = mimimum wall thickness in. (mm).
NOTE 2—Hoop stress should only be determined on straight hollow
This test method is under the jurisdiction of ASTM Committee F17 on Plastic
Piping Systems and is the direct responsibility of Subcommittee F17.40 on Test
Methods.
Current edition approved April 15, 1994. Published June 1994. Originally
published as F 948 – 85. Last previous edition F 948 – 85. Annual Book of ASTM Standards, Vol 14.02.
2 5
Annual Book of ASTM Standards, Vol 08.01. Available from Plastics Pipe Institute, Division of The Society of the Plastics
Annual Book of ASTM Standards, Vol 08.04. Industry, 250 Park Avenue, New York, NY 10017.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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F 948 – 94 (2001)
cylindrical specimens. Products of more complex shape may be evaluated
long-term performance of piping products, and therefore
by Option 2 of Appendix X1 based on pressure.
should be taken into consideration during any evaluation (see
Appendix X2).
3.1.3 make-up fluid—an exchange of internal fluid with
5.4 Specimens used must be representative of the piping
fresh fluid at a minimum rate of 10 % of the total system
product or material under evaluation (see Appendix X2).
volume per week.
3.1.4 maximum internal surface temperature—that tem-
6. Apparatus
perature attained when increased fluid velocity results in no
further increase in the outside surface temperature of the
6.1 Constant-Temperature System:
specimen (see X2.7).
6.1.1 Controlling the Internal Environment of Test
3.1.5 pressure—the force per unit area exerted by the test
Specimens—Any system that will ensure that the test fluid
fluidinthepipingproduct.Unitswillbereportedaspoundsper
entering and exiting the test specimen is maintained at a
square inch gage (psig) or mega pascals gage (MPag).
constant temperature within6 3.6°F (62°C) throughout the
3.1.6 test assembly—components (such as, pipe, fittings,
duration of the test.
valves, etc.) tested separately or together in an array that may
6.1.2 Controlling the External Environment of Test
simulate an actual field system that might include joints,
Specimens—Any system that will ensure constant external
fusions, plastic-to-metal transitions, etc.
environment temperature within 63.6°F (62°C) throughout
the duration of the test.
4. Summary of Test Method
6.2 Dynamic Flowing Pressure System—Any device that is
capable of continuously applying a constant internal pressure
4.1 This test method consists of exposing specimens of
within the tolerance limits defined in Table 1, while allowing a
extruded, molded, or otherwise manufactured pipe or compo-
continuous flow through the test specimens. The flow rate
nents (such as fittings, valves, assemblies, etc.) to a constant
should be substantial enough to control the internal tempera-
internal pressure by a flowing test fluid of controlled tempera-
ture of each test specimen. The device shall be capable of
ture and composition, while in a controlled external environ-
reaching the test pressures without exceeding it, and holding
ment. Time-to-failure and specimen surface temperature
the pressures within the tolerances listed in Table 1 for the
should be measured during exposure under the test conditions.
duration of the test.
Unless otherwise specified the internal fluid shall be water and
the external environment will be air.
NOTE 4—Pressure variations from pumps may exceed the tolerance
limits. (See X2.6.)
5. Significance and Use
6.3 Pressure Gage—A pressure measuring instrument ca-
5.1 The data obtained by this test method are useful for
pable of determining the internal pressure of the test speci-
establishing pressure, or hoop stress where applicable, versus
men(s) within the limits as required in Table 1.
failure-time relationships, under independently controlled in-
6.4 Timing Device—Any timing device or system capable
ternal and external environments that simulate actual antici-
of determining the time-to-failure for each test specimen,
pated product end-use conditions, from which the design basis
within the tolerances listed in Table 1.
(DB) for piping products or materials, or both, can be deter-
6.5 Specimen Holder—Any device that will support the
mined.(RefertoTestMethodD 2837andPracticeD 2992,and
specimens, but will minimize externally induced stresses.
Appendix X1 of this test method.)
Provisions shall be made to allow for normal bidirectional
thermal expansion of the test specimen.
NOTE 3—Reference to design basis (DB) in this test method refers to
6.6 Feed-and-Bleed System—Provisions shall be made to
the hydrostatic design basis (HDB) for material in straight hollow
cylindrical shapes where hoop stress can be easily calculated, or is based introduce fresh make-up fluid to the system while bleeding off
on applied pressure design basis (PDB) for complex-shaped products or
an equivalent amount necessary to maintain a constant volume
systems where complex stress fields seriously prohibit the use of hoop
and ensure constant composition of the test fluid. This system
stress.
should be designed to maintain composition of the internal
5.2 In order to characterize plastics as piping products, it is
fluid within prescribed limits.
necessary to establish the stress-to-rupture-time, or pressure- 6.7 Other Provisions—Additional provisions may be neces-
to-rupture-time relationships over two or more logarithmic
sary to maintain constant composition.
decades of time (hours) within controlled environmental pa- 6.8 Flow Control—Provisions shall be made to ensure that
rameters. Because of the nature of the test and specimens
the internal fluid velocity shall be adequate to ensure constant
employed, no single line can adequately represent the data. internaltemperatureinthespecimenwithin 63.6°F(62°C).In
Therefore, the confidence limits should be established. the special case of hot water inside/ambient air outside,
5.3 Results obtained at one set of environmental conditions
should not be used for other conditions, except that higher
TABLE 1 Tolerances for Testing Thermoplastic Piping Products
temperature data can be used for a design basis assignment for
lower application temperatures, provided that it can be dem-
Test Periods, h Pressure, % Time, %
onstratedthattheapplicationconditionspresentalessstringent
0to10 60.5 60.5
environment. The design basis should be determined for each
10 to 100 60.5 61.0
specificplasticmaterialandeachdifferentsetofenvironmental
100+ 61.0 62.0
constraints. Design and processing can significantly affect the
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F 948 – 94 (2001)
provision shall be made to ensure maximum internal surface 9. Procedure
temperature of the specimen within 63.6°F (62°C).
9.1 Attach the specimens or assemblies to the system
supported in a manner that will minimize externally induced
7. Test Specimens
stresses and minimize entrapment of gas in the specimen when
7.1 Material—Material evaluation shall be done on cylin- the internal fluid is a liquid.
drical test specimens molded or formed by the same process as 9.2 After conditioning the specimens as specified in Section
the actual product. Unless otherwise specified the part shall
8, adjust the pressure to produce the desired loading.Apply the
meet the specimen requirements as follows: pressure to the specimens and make sure the timing devices
7.1.1 Injection Molded—The test specimens shall be injec- have started after reaching the assigned pressure. Pressures
tion molded tubes with as uniform a wall as technically should be preset prior to loading test specimens in order to
possible. The mold shall be side-gated so that a bond line is avoid overstressing the specimens during pressure setting
created lengthwise along the tubular test specimens (see Note procedure.
5). The working exposed length of the specimen in the test 9.3 Periodically, measure the surface temperature of each
shallhaveaminimumlengthtoactualoutsidediameterratioof
test specimen (see X2.7) and the air temperature near the test
5to1. specimen’s surface.
9.3.1 Any failure occurring within one pipe diameter of the
NOTE 5—The PPI Hydrostatic Stress Board is currently evaluating the
joining system of the test assembly to test apparatus should be
question of side versus end gating as part of a broad study of the
examined carefully. If there is any reason to believe that the
forecasting of the long-term strength of fittings.
failure was attributable to the joining system, this data point
7.1.2 Extrusion—The specimen length between end clo-
should not be used in the regression equation computations.
sures shall be not less than 5 times the nominal outside
9.3.2 All data must be reported, whether employed in the
diameter of the pipe, but in no case less than 12 in. (300 mm).
regression analysis or not. Widely scattered failures may be
7.1.3 Others—For manufacturing processes other than
indicative of performance to be expected in the field. If
those specified, straight hollow cylindrical shapes produced by
circumstances can be determined for inconsistent test perfor-
the process should be used as specimens for evaluating the
mance, the reason should be so noted with the failure time.
material. Restriction of 7.1.2 should apply.
7.2 End-Use Products—Actual commercial designs simu-
10. Report
lating end-use products shall be representative of the final
10.1 Report the following information:
product design and manufacturing process (seeAppendix X2).
10.1.1 Complete identification of the sample, including
7.3 Systems and Assemblies—System or subsystem designs
material type, source, manufacturer’s name and code number,
that include joints or other assembly techniques which repre-
and previous significant history, if any.
sent field installations, or both, may be tested.
10.1.2 Specimen dimensions, including nominal size and,
7.4 Measurements—Dimensions shall be determined in ac-
when applicable, average and minimum wall thickness, aver-
cordance with Test Method D 2122 or Practice D 3567, where
age outside diameter and length to diameter ratio.
applicable.
10.1.3 Asketch of the test specimen shall be included in the
report.
8. Conditioning
10.1.4 Fluid temperatures inside and outside the specimen.
8.1 If the external environment is gaseous, test specimens
10.1.4.1 For Water Inside/Ambient Air Outside—Report
shall be conditioned in the external air or gaseous environment
fluid temperatures entering and leaving the specimen, air
for a minimum of 16 h before pressurizing the internal test
temperature around the specimens, minimum external surface
fluid. If the external environment is a liquid, test specimens
temperature of the specimens, and method used to measure
shall be conditioned for a minimum of 1 h. This conditioning
surface temperature of the specimens.
period may be concurrent with internal conditioning using
10.1.5 Test environments inside and outside the specimen.
flowing internal test fluid. Refer to Table 2.
10.1.6 A table of pressures or stresses, or both, and the
8.2 The internal test fluid shall be circulated through the test
respective time-to-failure in hours for all the specimens tested.
specimens for a minimum of1hif liqu
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