ASTM D5365-23

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Designation: D5365 − 18 D5365 − 23
Standard Test Method for
Long-Term Ring-Bending Strain of “Fiberglass” (Glass-
Fiber-Reinforced Thermosetting-Resin) Pipe
This standard is issued under the fixed designation D5365; 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 test method covers a procedure for determining the long-term ring-bending strain (S ) of “fiberglass” pipe. Both
b
glass-fiber-reinforced thermosetting-resin pipe (RTRP) and glass-fiber-reinforced polymer mortar pipe (RPMP) are “fiberglass”
pipes.
1.2 The values stated in inch-pound units are to be regarded as the standard. The SI units given in parentheses are for information
only.
1.3 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. A specific warning statement is given in 9.5.
NOTE 1—There is no known ISO equivalent to this standard.
1.4 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:
D883 Terminology Relating to Plastics
D1600 Terminology for Abbreviated Terms Relating to Plastics
D3567 Practice for Determining Dimensions of “Fiberglass” (Glass-Fiber-Reinforced Thermosetting Resin) Pipe and Fittings
3. Terminology
3.1 Definitions:
3.1.1 General—Definitions are in accordance with Terminology D883 and abbreviations are in accordance with Terminology
D1600 unless otherwise indicated.
3.2 Definitions of Terms Specific to This Standard:
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.23 on Reinforced Plastic
Thermosetting Resin Piping Systems and Chemical Equipment.
Current edition approved Aug. 1, 2018July 1, 2023. Published August 2018July 2023. Originally approved in 1993. Last previous edition approved in 20122018 as
D5365 - 12.D5365 - 18. DOI: 10.1520/D5365-18.10.1520/D5365-23.
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.
*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
D5365 − 23
3.2.1 end point—the failure of the test specimen. The failure mode may be catastrophic, characterized by a sudden fracture through
the pipe wall in the area of greatest strain.
3.2.2 fiberglass pipe—tubular product containing glass-fiber reinforcements embedded in or surrounded by curing thermosetting
resin. The composite structure may contain aggregate, granular or platelet fillers, thixotropic agents, pigments, or dyes;
thermoplastic or thermosetting liners or coatings may be included.
3.2.3 reinforced polymer mortar pipe (RPMP)—fiberglass pipe with aggregate.
3.2.4 reinforced thermosetting resin pipe (RTRP)—fiberglass pipe without aggregate.
4. Summary of Test Method
4.1 This test method consists of subjecting submerged-pipe ring specimens to various increasing deflections induced by a constant
load and monitoring the time to failure. A minimum of 18 samples are required. Test temperatures are obtained by testing in a fluid
environment where the temperature is controlled.
4.2 The long-term ring-bending strain is obtained by an extrapolation to 50 years of a log-log linear regression line for failure
strain versus time.
NOTE 2—It is the consensus of Subcommittee D20.23 that the log-log linear regression analysis of test data is a conservative approach and is representative
of standard industry practice.
5. Significance and Use
5.1 This test method determines the long-term ring-bending strain of pipe when deflected under constant load and immersed in
a chemical environment. It has been found that effects of chemical environments can be accelerated by strain induced by deflection.
This information is useful and necessary for the design and application of buried fiberglass pipe.
NOTE 3—Pipe of the same diameter but of different wall thicknesses will develop different strains with the same deflection. Also, pipes having the same
wall thickness but different constructions making up the wall may develop different strains with the same deflection.
6. Apparatus
6.1 Loading Device—The testing apparatus shall be suitable for maintaining a constant load on the test specimen.
6.2 Load Application—The load shall be applied to the test specimens using any of three alternative pairs of parallel loading
surfaces; flat plates, rods or bars of a length at least as long as the pipe ring and of sufficient strength and stiffness to ensure a
straight loading surface throughout the test. The same type of loading device shall be used for each specimen in a test series. In
order to achieve uniform strain along the pipe, use 0.25-in. (6-mm) thick elastomeric pads between the parallel loading surfaces
and the pipe ring (see Note 4).
6.2.1 Flat Plates—The plates shall have a minimum 6-in. (152-mm) width.
6.2.2 Bars—The bars shall have a flat contact surface of 0.75 6 0.25 in. (19 6 6 mm).
6.2.3 Rods—The rod diameter shall be 2 6 0.25 in. (51 6 6 mm) for pipe rings 12 in. (305 mm) and greater in diameter. For
smaller pipes, the rod diameter shall be 1 6 0.25 in. (25 6 6 mm).
6.3 Environment Containment—A test enclosure of sufficient size to fully immerse the test specimens shall be used to contain the
test solution. The enclosure shall not chemically affect the test solution.
NOTE 4—Elastomeric pads with a hardness of Shore A40 to 70 have been used successfully.
D5365 − 23
7. Test Specimens
7.1 The test specimens shall be ring sections taken from a sample(s) of pipe selected at random from a normal production run.
The test specimens shall have a minimum length of one nominal pipe diameter or 12 in. (305 mm) 6 5 %, whichever is less. Treat
the cut edges of the specimens by the same procedure as production products.
8. Test Conditions
8.1 The standard temperature shall be 23 6 5°C (73.4 6 9°F).
9. Procedure
9.1 Test Specimen Measurements:
9.1.1 Wall Thickness—Determine in accordance with Test Method D3567.
9.1.2 Inside Diameter—Determine in accordance with Test Method D3567 at both ends prior to deflection and average the
measurements.
NOTE 5—It is recommended that the inside diameter be measured with the axis vertical.
9.2 Place the test apparatus into the test enclosure.
9.3 Place the pipe ring in the test apparatus (see Fig. 1) and apply force to deflect the specimen at a rate not to exceed 10 % of
its diameter per minute while keeping the top and bottom loading devices (plates, bars, or rods) of the apparatus as near parallel
as practical. When the desired deflection is obtained cease adding load to the apparatus.
NOTE 6—Alignment of the specimen within the loading devices is critical. The loading devices should not only be parallel with the load points 180°
opposite, but the pipe ring should also be centered between the load-application guides. Additionally, the load-application guides should permit complete
vertical freedom of movement, so the specimen remains under constant load.
9.4 Measure the vertical inside diameter of the deflected pipe specimen at both ends to the nearest 0.01 in. (0.25 mm). Average
the measurements and determine the initial deflection by subtracting the average vertical inside diameter after loading from the
measurement determined in 9.1.2.
NOTE 7—Deflections in excess of 28 % of diameter may cause local flattening of the pipe and lead to erratic test results. For deflections approaching 28 %,
Side View Front View
1 Load-Application Guides 5 Submerged Test Specimen
2 Load-Application Device 6 Test Solution
3 0.25 in (6 mm) Rubber Pad 7 0.25 in. (6 mm) Rubber Pad
4 Test Enclosure 8 Load-Applicatiion Device
FIG. 1 Long-Term Ring Bending Test Apparatus
D5365 − 23
improved accuracy is obtained by use of strain gages or by establishing, for each pipe product, a calibration of deflection versus measured strain. This
calibration technique may also be useful at all deflection levels.
9.5 Introduce the test solution to completely submerge the pipe ring. ring as quickly as possible after loading. The solution may
be added prior to loading the pipe ring and shouldshall be added within 30 min of loading the pipe ring. Testing time commences
only after both specimen loading (deflection) and the addition of solution are complete. (Warning—Since the failure mode could
be catastrophic, take precautions to prevent or contain splashing or spilling of the test solution or other damages resulting from
the sudden collapse of the pipe specimen.)
9.6 Periodically check and maintain the test solution within 65 % of the specified strength or concentration for the duration of
the test. The test specimen must remain completely submerged.
NOTE 8—As some solutions become more concentrated with the evaporation of water, care must be exercised in replenishment to prevent a build-up in
strength. It may be necessary, with some reagents, to periodically clean the deflected specimen and replace the test solution with a fresh mixture. The
use of plastic film, cut carefully to fit around the test apparatus and floated on the top of the test solution, has been found helpful in reducing evaporation.
9.7 Continuously monitor the decreasing pipe-ring inside vertical diameter versus time or inspect the loaded specimen at least at
the frequency given below and measure the pipe specimen inside vertical diameter:
Hours Inspect at Least
0 to 20 Every hour
20 to 40 Every 2 h
40 to 60 Every 4 h
60 to 100 Every 8 h
100 to 600 Every 24 h
600 to 6000 Every 48 h
After 6000 Every week
Determine the deflection by subtracting the inside vertical diameter from the measurement determined in 9.1.2.
NOTE 9—Decreasing diameter of the pipe ring (deflection change) may be monitored with an appropriate indicator on the apparatus above the solution
and submerged specimen.
9.8 Calculate the end point (failure time and failure deflection) in accordance with 10.1.
9.9 Record the following data:
9.9.1 Average pipe-wall thickness,
9.9.2 Average inside pipe diameter before deflection,
9.9.3 Average inside pipe diameter after deflection,
9.9.4 Initial deflection,
9.9.5 Type of loading device,
9.9.6 Type, location and time of any distress of the pipe wall,
9.9.7 Failure deflection and time at the end point, and
9.9.8 Type of failure.
9.10 To determine the regression line and the lower confidence level, a minimum of 18 samples is required. Distribution of data
points shall be as follows:
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Hours Failure Points
10 to 1000 At least 4
1000 to 6000 At least 3
After 6000 At least 3
After 10 000 At least 1
9.10.1 Those specimens that have not failed after more than 10 000 h may be included as failures to establish the regression line.
Use of these data points may result in a higher or lower extrapolated value.
NOTE 10—Non-failed specimens may be left under test and the regression line recalculated as failures are obtained.
10. Calculation
10.1 Determine the failure time and deflection:
10.1.1 The failure deflection and failure time shall be the last values noted prior to the fracture occurrence.
10.2 Long-Term Ring-Bending Strain:
10.2.1 Compute the failure strain for each failed specimen as given in 10.2.1.1 and 10.2.1.2.
10.2.1.1 Crown and invert failures:
4.28 e Δ
~ !~ !
f
ε 5
f 2
~D1Δ /2!
f
where:
ε = failure strain in inches per inch (millimetres per millimetre),
f
e = wall thickness in inches (millimetres) in accordance with 9.1.1 (see Note 11),
D = mean diameter in inches (millimetres) (ID in accordance with 9.1.2 plus e in accordance with 9.1.1 or OD minus e), and
Δ = failure deflection in accordance with 10.1.
f
10.2.1.2 Springline failures:
2.44~e!~Δ !
f
ε 5
f
D1Δ /2
~ !
f
NOTE 11—The S calculations assume that the neutral axis is at the pipe-wall midpoint. For pipe-wall constructions that produce an altered neutral-axis
b
position, it shall be necessary to evaluate results by substituting 2y¯ for e. (y¯ is the distance from the appropriate pipe surface to the neutral axis.)
Neutral-axis position shall be determined with strain-gage couples.
10.2.2 Use for each specimen in the series, the log of the failure strain and the log of the failure time in hours as described in
A1.4.1. Calculate S , the strain at 50 years (438 000 h).
b
10.2.3 If Sxy > 0 (see Annex A1.4.2.2), consider the data unsuitable.
10.2.4 Calculate r in accordance with A1.4.3.1. If r is less than the applicable minimum value given in Table A1.1, consider the
data unsuitable.
10.2.5 Prepare a graph on a log-log diagram showing time to failure versus failure strain, with time plotted on the horizontal (x)
axis and strain on the vertical (y) axis.
11. Reconfirmation of the S Regression Line
b
11.1 When a piping product has an existing S regression line, any change in material, manufacturing process, construction or liner
b
will necessitate a screening evaluation (reconfirmation) as described in 11.2, 11.3, 11.4, and 11.5.
D5365 − 23
11.2 Calculate and plot the 95 % confidence limits and the 95 % prediction limits of the original regression line in accordance with
A1.4.6.2 using only data obtained prior to the change.
NOTE 12—Prediction limits define the bounds for single observations, whereas confidence limits define the bounds for the regression line.
NOTE 13—For 95 % confidence limits, there
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