Page 114 - GarlockFluidSealing2010

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 fuid is nitrogen gas. Internal pres-
sures can be varied from atmospheric to approximately
5,000 psig (345 bar). The fanges 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 feld 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 fange irregularities such as minor faws or nicks,
non-parallelism, corrosion and variations in groove depth.
Voids must be flled 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 defned 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 fuid 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 fange is a result
of creep relaxation. Creep relaxation is defned 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,
fange distortion and vibration. Therefore, results obtained
in lab conditions should be correlated with feld 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 specifed fuids un-
der defned conditions of time and temperature. The types
of materials covered are those included in the frst numeral
described in Classifcation F104. They are not applicable
to the testing of vulcanized rubber, a method described in
Test Method D471.
The test fuids 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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