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Test Procedures
Blowout of Gasket Products
(No ASTM Designation)
Garlock developed the equipment and test procedure
used for testing the blowout resistance of gaskets at vary-
ing pressures and temperatures.
This test method and procedure enable us to compare
the blowout resistance of all types of non-metallic gasket-
ing products. The test fluid is nitrogen gas. Internal pres-
sures can be varied from atmospheric to approximately
5,000 psig (345 bar). The flanges and gaskets can be
exposed to temperatures up to 1,000°F (540°C).
Garlock blowout tests are primarily used to compare
various products, and do not represent results that can
be expected under actual field conditions. The experience
gained over many years in blowout testing provides part of
the technical backup of our data on longer term P (psig or
bar) x T (°F or °C) values.
Compressibility and Recovery of Gasket
Material
ASTM Designation: F36
This method covers determination of the short-time
compressibility and recovery at room temperature of sheet
gasket materials.
This test method is not intended as a test for com-
pressibility under prolonged stress applications, generally
referred to as "creep", or for recovery following such pro-
longed stress applications, the inverse of which is gener-
ally referred to as "compression set".
Some initial compressibility is essential for proper
installation of a gasket and is required to compensate
for any flange irregularities such as minor flaws or nicks,
non-parallelism, corrosion and variations in groove depth.
Voids must be filled to obtain proper seating of the gasket
or premature failure will occur.
In addition, good recovery upon release of load is
indicative of torque retention of a gasketed joint.
Compressibility and recovery as defined by ASTM are
two worthwhile physical property criteria for supplier and
purchaser to agree upon as routine tests.
Creep Relaxation of Gasket Material
ASTM Designation: F38 Method B
Measured by means of a calibrated bolt with dial
indicator, ASTM F38 provides a means for measuring the
amount of creep relaxation of a gasket material at a stated
time after a compressive stress has been
applied. There is no fluid involved.
This method is designed to compare related products
under controlled conditions in regard to 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. Creep relaxation is defined by ASTM
as: "A transient stress-strain condition in which the strain
increases concurrently with the decay of stress." The
result of creep relaxation is loss of thickness of a gasket,
which causes bolt torque loss, resulting in leakage.
Torque loss also can be caused by elongation of bolts,
flange distortion and vibration. Therefore, results obtained
in lab conditions should be correlated with field results.
Also see Torque Retention Test for further
information.
Fluid Resistance of Gasket Materials
ASTM Designation: F146
These methods provide a standardized procedure for
measuring the effect of immersion on physical properties
of non-metallic gasketing materials in specified fluids un-
der defined conditions of time and temperature. The types
of materials covered are those included in the first numeral
described in Classification F104. They are not applicable
to the testing of vulcanized rubber, a method described in
Test Method D471.
The test fluids and conditions outlined were selected
as typical for the purposes of comparing different materi-
als, and can be used as a routine test when agreed upon
between the supplier and purchaser. The results of immer-
sion tests are not intended to give any direct correlation
with service conditions in view of the wide variations in
temperature and special uses encountered in gasket ap-
plications.
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