ASTM F948-94(2006)
(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
SIGNIFICANCE AND USE
The data obtained by this test method are useful for establishing pressure, or hoop stress where applicable, versus failure-time relationships, under independently controlled internal and external environments that simulate actual anticipated product end-use conditions, from which the design basis (DB) for piping products or materials, or both, can be determined. (Refer to Test Method D 2837 and Practice D 2992, and Appendix X1 of this test method.)
Note 3—Reference to design basis (DB) in this test method refers to the hydrostatic design basis (HDB) for material in straight hollow cylindrical shapes where hoop stress can be easily calculated, or is based on applied pressure design basis (PDB) for complex-shaped products or systems where complex stress fields seriously prohibit the use of hoop stress.
In order to characterize plastics as piping products, it is necessary to establish the stress-to-rupture-time, or pressure-to-rupture-time relationships over two or more logarithmic decades of time (hours) within controlled environmental parameters. Because of the nature of the test and specimens employed, no single line can adequately represent the data. Therefore, the confidence limits should be established.
Results obtained at one set of environmental conditions should not be used for other conditions, except that higher temperature data can be used for a design basis assignment for lower application temperatures, provided that it can be demonstrated that the application conditions present a less stringent environment. The design basis should be determined for each specific plastic material and each different set of environmental constraints. Design and processing can significantly affect the long-term performance of piping products, and therefore should be taken into consideration during any evaluation (see Appendix X2).
Specimens used must be representative of the piping product or material under evaluation (see Appendix X2).
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.
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
Designation:F948– 94 (Reapproved 2006)
Standard Test Method for
Time-to-Failure of Plastic Piping Systems and Components
Under Constant Internal Pressure With Flow
ThisstandardisissuedunderthefixeddesignationF948;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E177 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
D543 Practices for Evaluating the Resistance of Plastics to long-term stress, is not considered to be a ballooning failure.
Chemical Reagents
3.1.2 hoop stress—thetensilestressinthewallofthepiping
D2122 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
D2837 TestMethodforObtainingHydrostaticDesignBasis
mega pascals (MPa). Hoop stress will be calculated by the
forThermoplastic Pipe Materials or Pressure Design Basis
following ISO equation:
for Thermoplastic Pipe Products
S 5 P ~D 2 t!/2t
D2992 Practice for Obtaining Hydrostatic or Pressure De-
sign Basis for “Fiberglass” (Glass-Fiber-Reinforced
where:
Thermosetting-Resin) Pipe and Fittings
S = hoop stress, psi (MPa),
D3567 Practice for Determining Dimensions of “Fiber-
D = average outside diameter, in. (mm),
glass” (Glass-Fiber-Reinforced Thermosetting Resin) Pipe
P = internal pressure, psig (MPag), and
and Fittings t = mimimum wall thickness in. (mm).
NOTE 2—Hoop stress should only be determined on straight hollow
cylindrical specimens. Products of more complex shape may be evaluated
This test method is under the jurisdiction of ASTM Committee F17 on Plastic
by Option 2 of Appendix X1 based on pressure.
Piping Systems and is the direct responsibility of Subcommittee F17.40 on Test
Methods.
Current edition approved Aug. 1, 2006. Published August 2006. Originally
´1 2
approved in 1985. Last previous edition approved in 2001 as F948 – 94(2001) . Available from Plastics Pipe Institute, Division of The Society of the Plastics
DOI: 10.1520/F0948-94R06. 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.
F948– 94 (2006)
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
6.1 Constant-Temperature System:
further increase in the outside surface temperature of the
6.1.1 Controlling the Internal Environment of Test
specimen (see X2.7).
Specimens—Any system that will ensure that the test fluid
3.1.5 pressure—the force per unit area exerted by the test
entering and exiting the test specimen is maintained at a
fluidinthepipingproduct.Unitswillbereportedaspoundsper
constant temperature within6 3.6°F (62°C) throughout the
square inch gage (psig) or mega pascals gage (MPag).
duration of the test.
3.1.6 test assembly—components (such as, pipe, fittings,
6.1.2 Controlling the External Environment of Test
valves, etc.) tested separately or together in an array that may
Specimens—Any system that will ensure constant external
simulate an actual field system that might include joints,
environment temperature within 63.6°F (62°C) throughout
fusions, plastic-to-metal transitions, etc.
the duration of the test.
6.2 Dynamic Flowing Pressure System—Any device that is
4. Summary of Test Method
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. (Refer to Test Method D2837 and Practice D2992, and
specimens, but will minimize externally induced stresses.
Appendix X1 of this test method.)
Provisions shall be made to allow for normal bidirectional
NOTE 3—Reference to design basis (DB) in this test method refers to
thermal expansion of the test specimen.
the hydrostatic design basis (HDB) for material in straight hollow
6.6 Feed-and-Bleed System—Provisions shall be made to
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
stress.
and ensure constant composition of the test fluid. This system
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
provision shall be made to ensure maximum internal surface
should not be used for other conditions, except that higher
temperature of the specimen within 63.6°F (62°C).
temperature data can be used for a design basis assignment for
lower application temperatures, provided that it can be dem-
onstratedthattheapplicationconditionspresentalessstringent
TABLE 1 Tolerances for Testing Thermoplastic Piping Products
environment. The design basis should be determined for each
specificplasticmaterialandeachdifferentsetofenvironmental
Test Periods, h Pressure, % Time, %
constraints. Design and processing can significantly affect the
0to10 60.5 60.5
long-term performance of piping products, and therefore
10 to 100 60.5 61.0
should be taken into consideration during any evaluation (see
100+ 61.0 62.0
Appendix X2).
F948– 94 (2006)
7. Test Specimens stresses and minimize entrapment of gas in the specimen when
the internal fluid is a liquid.
7.1 Material—Material evaluation shall be done on cylin-
9.2 After conditioning the specimens as specified in Section
drical test specimens molded or formed by the same process as
8, adjust the pressure to produce the desired loading.Apply the
the actual product. Unless otherwise specified the part shall
pressure to the specimens and make sure the timing devices
meet the specimen requirements as follows:
have started after reaching the assigned pressure. Pressures
7.1.1 Injection Molded—The test specimens shall be injec-
should be preset prior to loading test specimens in order to
tion molded tubes with as uniform a wall as technically
avoid overstressing the specimens during pressure setting
possible. The mold shall be side-gated so that a bond line is
procedure.
created lengthwise along the tubular test specimens (see Note
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
forecasting of the long-term strength of fittings. examined carefully. If there is any reason to believe that the
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
product design and manufacturing process (seeAppendix X2).
10.1 Report the following information:
7.3 Systems and Assemblies—System or subsystem designs
10.1.1 Complete identification of the sample, including
that include joints or other assembly techniques which repre-
material type, source, manufacturer’s name and code number,
sent field installations, or both, may be tested.
and previous significant history, if any.
7.4 Measurements—Dimensions shall be determined in ac-
10.1.2 Specimen dimensions, including nominal size and,
cordance with Test Method D2122 or Practice D3567, where
when applicable, average and minimum wall thickness, aver-
applicable.
age outside diameter and length to diameter ratio.
10.1.3 Asketch of the test specimen shall be included in the
8. Conditioning
report.
8.1 If the external environment is gaseous, test specimens
10.1.4 Fluid temperatures inside and outside the specimen.
shall be conditioned in the external air or gaseous environment
10.1.4.1 For Water Inside/Ambient Air Outside—Report
for a minimum of 16 h before pressurizing the internal test
fluid temperatures entering and leaving the specimen, air
fluid. If the external environment is a liquid, test specimens
temperature around the specimens, minimum external surface
shall be conditioned for a minimum of 1 h. This conditioning
temperature of the specimens, and method used to measure
period may be concurrent with internal conditioning using
surface temperature of the specimens.
flowing internal test fluid. Refer to Table 2.
8.2 The internal test fluid shall be circulated through the test 10.1.5 Test environments inside and outside the specimen.
specimens for a minimum of1hif liquid, or 16 h if gaseous,
10.1.6 A table of pressures or stresses, or both, and the
before applying test pressure. Refer to Table 2.
respective time-to-failure in hours for all the specimens tested.
10.1.6.1 In those cases where pressure variations could
9. Procedure
affect the life performance, pressure variations should be
9.1 Attach the specimens or assemblies to the system
r
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