ASTM F38-00(2006)
(Test Method)Standard Test Methods for Creep Relaxation of a Gasket Material
Standard Test Methods for Creep Relaxation of a Gasket Material
SIGNIFICANCE AND USE
These test methods are designed to compare related materials under controlled conditions and their ability to maintain a given compressive stress as a function of time. A portion of the torque loss on the bolted flange is a result of creep relaxation. Torque loss can also be caused by elongation of the bolts, distortion of the flanges, and vibration; therefore, the results obtained should be correlated with field results. These test methods may be used as a routine test when agreed upon between the consumer and the producer.
Note 1—Test Method B was developed using asbestos gasket materials and at issuance substantiating data were not available for other gasket materials.
FIG. 1 Relaxometer, Test Method A
SCOPE
1.1 These test methods provide a means of measuring the amount of creep relaxation of a gasket material at a predetermined time after a compressive stress has been applied.
1.1.1 Test Method A Creep relaxation measured by means of a calibrated strain gauge on a bolt.
1.1.2 Test Method B Creep relaxation measured by means of a calibrated bolt with dial indicator.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
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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Designation: F38 − 00(Reapproved 2006)
Standard Test Methods for
Creep Relaxation of a Gasket Material
ThisstandardisissuedunderthefixeddesignationF38;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 2.2 ASTM Adjuncts:
Relaxometer, Method A (F38)
1.1 These test methods provide a means of measuring the
Relaxometer, Method B (F38)
amount of creep relaxation of a gasket material at a predeter-
mined time after a compressive stress has been applied.
3. Summary of Test Methods
1.1.1 Test Method A—Creep relaxation measured by means
of a calibrated strain gauge on a bolt.
3.1 In both test methods the specimen is subjected to a
1.1.2 Test Method B—Creep relaxation measured by means
compressivestressbetweentwoplatens,withthestressapplied
of a calibrated bolt with dial indicator.
by a nut and bolt.
1.2 The values stated in SI units are to be regarded as
3.2 InTestMethodA,normallyrunatroomtemperature,the
standard. The values given in parentheses are for information
stress is measured by a calibrated strain gauge on the bolt. In
only.
running the test, strain indicator readings are taken at intervals
of time, beginning at the loading time, to the end of the test.
1.3 This standard does not purport to address all of the
The strain indicator readings are converted to percentages of
safety concerns, if any, associated with its use. It is the
the initial stress which are then plotted against the log of time
responsibility of the user of this standard to establish appro-
in hours. The percentage of initial stress loss or relaxation can
priate safety and health practices and determine the applica-
be read off the curve at any given time, within the limits of the
bility of regulatory limitations prior to use.
total test time.
2. Referenced Documents
3.3 InTestMethodB,runatroomorelevatedtemperatures,
2.1 ASTM Standards:
the stress is determined by measuring the change in length of
A193/A193MSpecification for Alloy-Steel and Stainless
the calibrated bolt with a dial indicator. The bolt length is
Steel Bolting for High Temperature or High Pressure
measured at the beginning of the test and at the end of the test;
Service and Other Special Purpose Applications
from this the percentage of relaxation is calculated.
B637Specification for Precipitation-Hardening and Cold
Worked Nickel Alloy Bars, Forgings, and Forging Stock
4. Significance and Use
for Moderate or High Temperature Service
4.1 These test methods are designed to compare related
D3040Practice for Preparing Precision Statements for Stan-
materials under controlled conditions and their ability to
dards Related to Rubber and Rubber Testing (Withdrawn
3 maintain a given compressive stress as a function of time. A
1987)
portion of the torque loss on the bolted flange is a result of
F104Classification System for Nonmetallic Gasket Materi-
creep relaxation. Torque loss can also be caused by elongation
als
of the bolts, distortion of the flanges, and vibration; therefore,
the results obtained should be correlated with field results.
These test methods are under the jurisdiction of ASTM Committee F03 on
These test methods may be used as a routine test when agreed
Gaskets and are the direct responsibility of Subcommittee F03.20 on Mechanical
upon between the consumer and the producer.
Test Methods.
Current edition approved Oct. 1, 2006. Published December 2006. Originally
approved in 1962. Last previous edition approved in 2000 as F38–00. DOI:
10.1520/F0038-00R06.
2 4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or AprintofthisapparatusisavailableatanominalcostfromASTMInternational
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Headquarters. OrderAdjunct No. ADJF003801. Original adjunct produced in 1965.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. Detailed working drawings of this apparatus are available from ASTM
The last approved version of this historical standard is referenced on International Headquarters. Order Adjunct No. ADJF003802. Original adjunct
www.astm.org. produced in 1965.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F38 − 00 (2006)
FIG. 1 Relaxometer, Test Method A
NOTE1—TestMethodBwasdevelopedusingasbestosgasketmaterials
6.2.1 Specimen size shall be 10.16 6 0.381 mm (0.400 6
and at issuance substantiating data were not available for other gasket
0.015in.)wideby31.75 60.381mm(1.250 60.015in.)long.
materials.
Four specimens are required per test.
2 2
6.2.2 An annular specimen with 1290-mm (2.0-in. ) sur-
5. Apparatus
face area may also be used. A size of 15.62-mm (0.615-in.)
5.1 Test Method A:
inside diameter by 43.56-mm (1.715-in.) outside diameter is
5.1.1 Strain Indicator.
recommended.
5.1.2 Timer.
6.2.3 For Type 4 Class 2 materials, specimen size shall be
5.1.3 Relaxometer, composed of two platens, upper and
one continuous length of 152.4 mm (6.0 in.).
lower; a bolt, with mounted strain gauge; and a thrust bearing
6.3 A minimum of three tests shall be conducted.
as shown in Fig. 1.
5.1.4 Strain Gauges, 120Ω resistance with a gauge factor
6.4 Nominal thickness of specimen shall be 0.8 mm
of 2.0 6 0.10%. The gauges shall be mounted to indicate
(0.03in.) unless otherwise agreed upon between the consumer
tensile strain and positioned to compensate for torque, tem-
andtheproducer.ForType4materialsthenominalthicknessof
perature, and bending. The gauges shall be mounted on the
the specimen shall be no greater than 1.78 mm (0.07 in.).
smalldiameteroftheboltabout50.8mm(2in.)fromthehead.
The bolt with mounted strain gauges must be calibrated. 7. Conditioning
5.2 Test Method B: 7.1 Condition cut specimens in accordance with their clas-
5.2.1 Relaxometer, composed of two platens, special drilled sification as required in Classification F104.
and calibrated bolt, washer and nut composed of Specification
8. Procedure
A193/A193M Grade B7 or Specification B637 Grade UNS
N07718 or other alloys of construction that would satisfy the
8.1 Test Method A:
calibration procedure (see Annex) for the test temperature
8.1.1 Clean all surfaces, platens, and specimen free of wax,
specified, and a dial indicator assembly as shown in Fig. 2.
mold release, and oils. (Remove with isooctane or other
5.2.2 Box End Wrench.
suitable solvent.) Lubricate bolt threads.
8.1.2 Use an initial stress of 13.8 6 0.3 MPa (2000 6
6. Test Specimen
50psi) unless otherwise specified.
6.1 Test Method A—The sample size shall be 33.02 6
8.1.3 Conduct the test at 20 to 30°C (70 to 85°F) unless
0.05mm (1.300 6 0.002 in.) in inside diameter and 52.32 6
otherwise specified.
0.05mm (2.0606 0.002 in.) in outside diameter.
8.1.4 Disassemble the relaxometer and place the specimen
between platens. The inside diameter of the specimen should
6.2 Test Method B:
be nearly concentric with the inside diameter of the platens.
Screw on the nut and thrust bearing and tighten very slightly,
Thesolesourceofsupplyofstraingauges(TypeAB-7)knowntothecommittee
by hand, or just enough to hold the specimen in place during
at this time is Baldwin-Lima-Hamilton. If you are aware of alternative suppliers,
subsequent handling. Mount the head of the bolt in a clamp.
please provide this information to ASTM International Headquarters. Your com-
8.1.5 Hook up and balance the strain indicator. Record the
ments will receive careful consideration at a meeting of the responsible technical
committee, which you may attend. reading. Then set the reading on the strain indicator for the
F38 − 00 (2006)
8.2 Test Method B:
8.2.1 Clean all surfaces and lightly lubricate the washer and
bolt threads; graphite and molybdenum disulfide have been
found to be acceptable lubricants.
8.2.2 Place rectangular specimens between the platens in
accordancewithFig.2andmakingsuretheyarenocloserthan
2mm(0.078in.)totheotherpiecesandtheedgeoftheplatens.
If an annular specimen is used, center the specimen around the
bolt hole between the platens. If a Type 4 Class 2 specimen is
used, center the specimen around the bolt hole between the
platens, being certain that the two ends overlap by a minimum
of 6.35 mm (0.25 in.).
8.2.3 Place the washer in position and screw on the nut,
finger tight.
8.2.4 Screw on the dial indicator assembly, finger tight, and
set the dial indicator at the zero reading.
8.2.5 Apply stress to the specimens by tightening the nut
with a wrench until the desired dial indicator reading is
reached. Record the reading (D ). Apply the stress in one
continuousmotionwithamaximumloadingtimeof3s.Abolt
elongation of 0.1222 to 0.1270 mm (0.00481 to 0.00500 in.) is
typical for a compressive force of 26.7 kN (6000 lbf). Remove
the dial indicator assembly. (The calibration procedure is
outlined in Annex A1.)
NOTE 2—When testing materials thicker than 0.8 mm (0.03 in.), the
time to tighten the nut may be extended to 5 s maximum to allow for the
longer arc required to apply the test load.
8.2.6 Place the specimen unit in a hot air-circulating oven
for 22 h at 100 6 2°C (212 6 3.6°F), unless otherwise
specified. The maximum test temperature for Specification
A193/A193M Grade B7 shall not exceed 204.4°C (400°F) and
the maximum test temperature for Specification B637 Grade
UNS N07718 shall not exceed 482.2°C (900°F).
8.2.7 Remove from the oven and cool to room temperature.
8.2.8 Replace the dial indicator assembly, finger tight, and
set the dial indicator at the zero reading. Loosen the nut,
without disturbing the dial indicator assembly, and record the
dial reading (D).
f
8.2.9 Calculate the percentage relaxation as follows:
FIG. 2 Relaxometer and Dial Indicator Assembly, Test Method B
Relaxation, % 5 [~D 2 D !/D ] 3100 (1)
0 f 0
specified initial stress. (The microinches that are added to the
9. Report
above reading will vary the stress and the strain gauge bolt
9.1 Report the following information:
calibration.)
9.1.1 Identification and designation number of the material
8.1.6 Apply stress to the gasket by tightening the nut with a
solid wrench until the strain indicator reaches a balance. A tested,
torque of approximately 30 N·m (22 lbf·ft) is required for a 9.1.2 Test temperature,
compressive force of 17.8 kN (4000 lbf). The stress should be
9.1.3 Length of the test, in hours,
applied at uniform rate such that at the end of 10 6 2 s the
9.1.4 “Initial stress” used, and the specimen thickness,
specified stress is reached. This is called the “initial stress.”
9.1.5 Percentage stress loss for each specimen, and
8.1.7 Beginning at the time of “initial stress,” take strain
9.1.6 Average of all the results recorded in 9.1.5.
indicator readings at intervals of 10 s, 1 min, 6 min, 30 min,
1h, 5 h, 24 h, etc., or until the end of the test. (Check the zero
of the strain indicator after the test.)
Some laboratories have found Alloy A-286 meets the calibration standard at
8.1.8 Convert the strain indicator readings of 8.1.7 to a
temperaturesupto482.2°C(900°F).Theusermayspecifyanyalloyofconstruction
percentage of “initial stress.” Then plot this percentage on
as long as the alloy meets the calibration standard for the desired test temperature.
semilog paper against the log of time in hours.
F38 − 00 (2006)
TABLE 1 Precision of Creep Relaxation Test of Gasket Materials, Using Coefficient of Variation Method of Presenting Results
NOTE 1—
S =standard deviation.
CV=% coefficient of variation=(S×100)/(average).
LSD=% least significant difference between two individual test results based on a 95% confidence level,52 2 sCVd.
œ
NOTE2—AnannularspecimencanbeusedinplaceofrectangularspecimensforType1,Class2;Type5,Class1;Type7,Class1;andType7,Class2.
An annular specimen cannot be used in place of rectangular specimens for Type 1, Class 1 because of the statistically significant difference in results.
Material Type and
Relaxation Values, % Repeatability Reproducibility
Class, Classification
Range Average S CV, % LSD,% S CV, % LSD,%
F104
Type 1, Class 1 11.5–15.4 13.3 1.22 9.4 26.5 1.58 11.9 33.7
Type 1, Class 2 27.2–33.7 30.9 1.87 6.2 17.6 2.52 8.2 23.1
Type 5, Class 1 4.0–8.9 6.3 1.27 18.1 51.2 2.01 31.9 90.1
Type 7, Class 1 14.2–24.5 18.1 1.33 8.0 22.7 3.93 21.8 61.5
Type 7, Class 2 20.7–28.5 26.0 0.97 4.2 11.8 3.10 11.9 33.7
10. Precision and Bias B, with an initial stress of 20.68 MPa (3000 psi) applied on a
2 2
1290-mm (2-in. ) sample area, total of 26.7-kN (6000-lb)
10.1 These precision and bias statements have been pre-
compressive force.The tests were conducted for 22 h at 100°C
pared in accordance with Practice D3040. Please refer to this
(212°F).Thetestswereconductedintriplicateoneachmaterial
practice for terminology and other testing and statistical
using the A193 Grade B7 Fixture.
concept explanations.
10.2 Seven laboratories tested the following five gasket 10.3 The precision results for the Specification A193/
materials (Classification F104 material designations) for creep
A193M Grade B7 Fixture are given in Table 1.
relaxation: Type 1, Class 1; Type 1, Class 2; Type 5, Class 1;
10.4 Additional F38 Round Robin test data regarding the
Type 7, Class 1; Type 7, Class 2. Test Method B, Type 1
evaluation of Specification B637 UNS N07718 is provided in
conditioning was used by all laboratories. Rectangular test
Appendix X1.
specimens were prepared from gasket sheets by cutting them
with the long dimension in the machine direction. Tests were
11. Keywords
conducted in accordance with Test Methods F38, Test Method
11.1 creep relaxation; deflection; gasket material; platens;
8 relaxometer;strain;stress;temperature;torquebolt;torqueloss
Supporting data have been filed atASTM International Headquarters and may
be obtained by requesting Research Report RR:F03-1009.
ANNEX
(Mandatory Information)
A1. TEST METHOD B CREEP RELAXATON APPARATUS: BOLT CALIBRATION PROCEDURE
A1.2.2 Spacer, washer-shaped, 0.80 6 0.13 mm (0.031 6
A1.1 Purpose
0.005 in.) thick.
A1.1.1 To precondition (strain relieve) the bolts at elevated
temperature prior to calibration.
A1.2.3 Tensile Testing Machine, capable of obtaining and
recording a load of 26.7 kN (6000 lbf). The maximum
A1.1.2 To calibrate the bolts after preconditioning, and on a
allowable system error equals 0.5% of the applied load.
periodicbasisafteruse.Boltsusedattemperaturesgreaterthan
205°C (401°F) should be recalibrated more often than bolts
A1.2.4 Calib
...
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