ASTM D3681-96
(Test Method)Standard Test Method for Chemical Resistance of "Fiberglass" (Glass-Fiber-Reinforced Thermosetting-Resin) Pipe in a Deflected Condition
Standard Test Method for Chemical Resistance of "Fiberglass" (Glass-Fiber-Reinforced Thermosetting-Resin) Pipe in a Deflected Condition
SCOPE
1.1 This test method covers the procedure for determining the chemical-resistant properties of fiberglass pipe in a deflected condition for diameters 4 in. (102 mm) and larger. Both glass-fiber-reinforced thermosetting resin pipe (RTRP) and glass-fiber-reinforced plastic mortar pipe (RPMP) are fiberglass pipes.
Note 1—For the purposes for this standard, polymer does not include natural polymers.
1.2 Inch-pound units are to be regarded as the standard. The values 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 and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in 9.5.
Note 2—There is no similar or equivalent ISO standard.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 3681 – 96
Standard Test Method for
Chemical Resistance of “Fiberglass”
(Glass–Fiber–Reinforced Thermosetting-Resin) Pipe in a
1 2
Deflected Condition ,
This standard is issued under the fixed designation D 3681; 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.
1. Scope wall in the area of greatest strain, parallel to the axis of the
pipe, with the fiber reinforcement cleanly broken at the edge of
1.1 This test method covers the procedure for determining
the fracture. Visual evidence of surface etching or pitting may
the chemical-resistant properties of fiberglass pipe in a de-
or may not be present.
flected condition for diameters 4 in. (102 mm) and larger. Both
3.2.2 fiberglass pipe—tubular product containing glass
glass–fiber–reinforced thermosetting resin pipe (RTRP) and
fiber reinforcements embedded in or surrounded by cured
glass–fiber–reinforced plastic mortar pipe (RPMP) are fiber-
thermosetting resin. The composite structure may contain
glass pipes.
aggregate, granular or platelet fillers, thixotropic agents, pig-
1.2 Inch-pound units are to be regarded as the standard. The
ments, or dyes. Thermoplastic or thermosetting liners or
values given in parentheses are for information only.
coatings may be included.
1.3 This standard does not purport to address all of the
3.2.3 reinforced plastic mortar pipe—fiberglass pipe with
safety concerns, if any, associated with its use. It is the
aggregate.
responsibility of the user of this standard to establish appro-
3.2.4 reinforced thermosetting resin pipe—fiberglass pipe
priate safety and health practices and determine the applica-
without aggregate.
bility of regulatory limitations prior to use. Specific precau-
3.2.5 strain-corrosion—the failure of the pipe wall caused
tionary statements are given in 9.5.
by the exposure of the inside surface, while in a strained
NOTE 1—There is no similar or equivalent ISO standard.
condition, to a corrosive environment for a period of time.
2. Referenced Documents
4. Summary of Test Method
2.1 ASTM Standards:
4.1 This test method consists of exposing the interior of a
D 883 Terminology Relating to Plastics
minimum of 18 specimens of pipe to a corrosive test solution
D 1600 Terminology for Abbreviated Terms Relating to
while the pipe is constantly maintained in a deflected condition
Plastics
at differing induced initial ring flexural strain levels, and
measuring the time to failure for each strain level. Test
3. Terminology
temperatures are obtained by testing in an air environment
3.1 Definitions:
where the temperature is controlled.
3.1.1 General—Definitions are in accordance with Termi-
4.2 The long-term resistance of the pipe to the test solution
nology D 883 and abbreviations are in accordance with Termi-
is obtained by an extrapolation to 50 years of a log-log linear
nology D 1600 unless otherwise indicated.
regression line for initial strain level versus time.
3.2 Definitions of Terms Specific to This Standard: Descrip-
NOTE 2—It is the consensus of Subcommittee D20.23 that the log–log
tions of Terms Specific to This Standard:
linear regression analysis of test data is a conservative approach and is
3.2.1 end point—the passage of the fluid through the pipe
representative of standard industry practice. However, a task group has
wall unless otherwise stated. The failure mode may be cata-
been formed to evaluate alternative non-linear analysis methods.
strophic, characterized by a sudden fracture through the pipe
5. Significance and Use
1 5.1 This test method evaluates the effect of a chemical
This test method is under the jurisdiction of ASTM Committee D-20 on Plastics
environment on pipe when in a deflected condition. It has been
and is the direct responsibility of Subcommittee D20.23 on Reinforced Plastic
Piping Systems and Chemical Equipment.
found that effects of chemical environments can be accelerated
Current edition approved April 10, 1996. Published June 1996. Originally
by strain induced by deflection. This information is useful and
published as D 3681 – 78. Last previous edition D 3681 – 95.
necessary for the design and application of buried fiberglass
This revision includes changes to 4.2, 9.10, 9.12, 9.13, 9.14, 10.3, 10.4.1,
10.4.2, 10.5.1, 10.7.1, 10.7.2, and Section 13. Paragraphs 11.1.9, 11.1.10, Note 15, pipe.
Annex A1 and Annexes A 2, and Appendixes X 1 and X 2 were deleted. A new
NOTE 3—Pipe of the same diameter but of different wall thicknesses
paragraph 11.1.10 and Annex A1 were added.
Annual Book of ASTM Standards, Vol 08.01. will develop different strains with the same deflection. Also, pipes having
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 3681
the same wall thickness but different constructions making up the wall
9.2.1.2 Measure the vertical inside diameter to the nearest
may develop different strains with the same deflection.
0.01 in. (0.25 mm) at both ends prior to deflection and average
the measurements.
6. Apparatus
NOTE 6—It is recommended that the vertical inside diameter be
6.1 Use parallel plate apparatus suitable to maintain a
measured with the axis vertical.
constant deflection on the pipe. In order to achieve uniform
9.2.1.3 Place the pipe specimen in the test apparatus (Fig. 1)
strain along the pipe, use 0.25-in. (6-mm) thick elastomeric
with the measured wall thicknesses at the bottom and apply
pads between the parallel plate (channel) surfaces and the pipe
force to the apparatus to deflect the specimen while keeping the
ring (see Note 4). Foil type, single element strain gages suitable
top and bottom plates (channels) of the apparatus as near
for strain levels to 1.50 % strain and a length appropriate to the
parallel as possible. When the desired deflection is obtained,
diameter of the pipe are required when initial strain is to be
lock the apparatus to maintain the specimen in the deflected
determined by Procedure B (see Note 5). An example of the
condition.
apparatus required is shown in Fig. 1.
NOTE 7—Alignment of the specimen within the channels is critical. The
NOTE 4—Elastomeric pads with a hardness of Shore A 15 to 70 have
channels must not only be parallel with the load points 180° opposite, but
been used successfully.
1 1 the pipe must be centered between the rods.
NOTE 5—Strain gages of ⁄4 and ⁄2-in. (6 and 13-mm) length have been
found to be effective for pipe diameters 12 through 24 in. (305 through
9.2.1.4 Measure the vertical inside diameter of the deflected
610 mm). Consult the strain gage manufacturer for gage length recom-
pipe specimen at both ends to the nearest 0.01 in. (0.25 mm).
mendations for other pipe diameters.
Average the measurements and determine the deflection by
subtracting the average vertical inside diameter after deflection
7. Test Specimens
from the measurement determined in 9.2.1.2.
7.1 The test specimens shall be ring sections taken from a
9.2.1.5 Calculate the initial strain level using the following
sample of pipe selected at random from a normal production
equation which includes compensation for increased horizontal
run. The test specimens shall have a minimum length of one
diameter with increasing deflection.
nominal pipe diameter or 12 in. (300 mm), whichever is less.
e 5
T
428~t!~D!
8. Test Conditions
D
8.1 The standard temperature shall be 73.4 6 3.6°F (23 6
D 1
S m D
2°C).
where:
9. Procedure
e 5 initial strain, %,
T
9.1 General—Determine the initial strain level induced in
t 5 average wall thickness at bottom, in. (mm),
the pipe by calculation, or strain gage measurement, or both.
D5 average deflection, in. (mm),
¯
Procedure A describes the determination of initial strain by
D 5 mean diameter, in. (mm) D +t,and
m
¯
calculation; Procedure B describes the determination of initial D 5 average inside pipe diameeter, free state, in. (mm).
strain as obtained by use of foil-type resistance strain gages.
NOTE 8—The calculation assumes that the neutral axis is at the pipe
9.2 Determination of Test Level:
wall midpoint. For pipe wall constructions that produce an altered neutral
9.2.1 Test Procedure A:
axis position, it may be necessary to evaluate results substituting 2 y¯ for
9.2.1.1 Measure the wall thickness to the nearest 0.001 in.
t.( y¯ is the distance from the inside pipe surface to the neutral axis.)
Neutral axis position must be determined with strain gage couples. See
(0.025 mm) in at least five equally spaced places along the
also Note 10.
bottom of the pipe specimen on a line parallel with the pipe
axis, and average the measurements. 9.2.2 Procedure B:
FIG. 1 Strain-Corrosion Test Apparatus
D 3681
The use of spacers (such as, wooden blocks) under the apparatus is
9.2.2.1 Carefully align and attach three strain gages on the
suggested to reduce attack of the apparatus after failure of the sample.
inside bottom surface of the pipe specimen in the circumfer-
ential direction to measure initial circumferential strains. Place 9.6 Periodically check and maintain the test solution within
65 % of the specified strength or concentration for the
the gages perpendicular to the pipe axis as follows: one in the
middle and the other two at the quarter points along the invert duration of the test. Maintain the level at a depth of not less
than 1 in. (25.4 mm) during the period of the test.
of the specimen. The adhesive used to attach the gages shall not
cover more than 37 % of the pipe specimen length along the
NOTE 13—As some solutions become more concentrated with the
invert. Zero-in the gages while the pipe is circular in shape.
evaporation of water, care must be exercised in replenishment to prevent
a build-up in strength. It may be necessary, with some reagents, to
NOTE 9—It is recommended that the pipe specimen be placed with its
periodically clean the deflected specimen and replace the test solution with
axis vertical to maintain roundness when the bridge is balanced to “zero”
a fresh mixture. The use of plastic film, cut carefully to fit between the
the instrument.
dams and floated on the top of the test solution, has been found helpful in
9.2.2.2 After installing the strain gages, place the specimen
reducing evaporation.
in the test apparatus (see Fig. 1) with the strain gages at the
9.7 Record the following data:
bottom. Extreme care should be taken to ensure that the gages
9.7.1 Average pipe wall thickness,
are located at the point of maximum strain (6 o’clock position).
9.7.2 Average inside pipe diameter before deflection,
NOTE 10—Alignment of the specimen within the channels is critical. 9.7.3 Average inside pipe diameter after deflection,
The channels must not only be parallel with the load points 180° opposite,
9.7.4 Percent deflection,
but the pipe must be centered between the rods.
9.7.5 Initial strain and method of determination,
9.2.2.3 Apply force to the apparatus to deflect the specimen
9.7.6 Type, location, and time of any distress of the pipe
while keeping the top and bottom plates (channels) of the wall, and
apparatus as parallel as possible. When the desired strain level
9.7.7 Time to end point. Times are measured from the
is reached, lock the apparatus to maintain the specimen in the addition of solution.
deflected condition. Read the gages as soon as the apparatus is
9.8 To determine the regression line and the lower confi-
locked. Initial strain should be recorded within 2 min after dence level for the report, a minimum of 18 samples is
locking the apparatus. At least two gages shall read within 5 %
required. Distribution of data points should be as follows:
of each other for a valid experiment. If any gage reads more
Hours Failure Points
10 to 1000 at least 4
than 5 % from the average of the other two gages, disregard the
1000 to 6000 at least 3
indication unless thickness verification implies the strain gage
After 6000 at least 3
reading was accurate. Average the valid gage indications, and
After 10 000 at least 1
record as initial (indicated) strain. In addition, measure and
9.9 Perform inspection of the test samples as follows:
record the deflection.
Hours Inspect at Least
9.3 When using Procedure A, verify the strain level by using
10 to 20 every 1 h
strain gages as described in Procedure B for at least one
20 to 40 every 2 h
40 to 60 every 4 h
specimen in every nine. Conversely, when using Procedure B,
60 to 100 every 8 h
verify the strain level by measurement and calculation as
100 to 600 every 24 h
described in Procedure A for at least one specimen in every
600 to 6000 every 48 h
After 6000 every week
nine. If the calculated strain and the indicated strain do not vary
more than 10 %, consider the strain levels accurate within
Record the time to end point for each specimen.
normal experimental error.
NOTE 14—The use of electronic timers is considered highly desirable in
NOTE 11—Deflections in excess of 28 % of diameter may cause local
monitoring failure time particularly on short term tests.
flattening of the pipe and lead to erratic strain distribution. For deflections
9.10 Analyze the test results by using for each specimen, the
approaching 28 % improved accuracy is obtained by use of strain gages or
logarithm of the strain in percent and the logarithm of the
by establishing, for a typical pipe, a calibration of deflection versus
time-to-failure in hours as described in Annex A1. Calculate
measured strain. This calibration technique is also useful at all deflection
the strain at 50 years (YL).
levels as a check of the calculations by 9.2.1.5 which assumes neutral axis
at pipe wall midpoint. 9.11 Those specimens that have not failed after more than
10 000 h may be included as failures to establish the regres-
9.4 After the initial strain is obtained using Procedure A or
sion line. Use of these data points may result in a lower or
B, install chemically inert dams using a flexible sealant so that
higher extrapolated strain. In either case the requirements of
only the interior surface of the pipe will be exposed to the test
9.14 must be satisfied.
environment. The dams shall not add support to the pipe
specimen.
NOTE 15—Non–failed specimens may be left under test and the
9.5 Place the apparatus containing the specimen in a chemi-
regression line recalculated as failures are obtained.
cally resistant trough or pan and introduce the test solution. The
9.12 Determine the final line for extrapolation to 50 years
solution should be added within 30 min of locking the
by the method of least squares given in Annex A1, using all end
apparatus and the time should be recorded from t
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.