Page 160 - GarlockFluidSealing2010

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In a fanged connection, all components must be
correct to achieve a seal. The most common cause of
leaky gasketed joints is improper installation proce-
dures.
Bolting Procedures
¦Place the gasket on the fange surface to be sealed.
¦Bring the opposing fange into contact with the gasket.
¦Clean the bolts and lubricate them with a quality lubri-
cant, such as an oil and graphite mixture.
¦Place the bolts into the bolt holes.
¦Finger-tighten the nuts.
¦Follow the bolting sequence in the diagrams above.
¦During the initial tightening sequence, do not tighten
any bolts more than 30% of the recommended bolt
stress. Doing so will cause cocking of the fange and
the gasket will be crushed.
¦Upon reaching the recommended torque require­
ments, do a clockwise bolt-to-bolt torque check to
make certain that the bolts have been stressed evenly.
¦Due to creep and stress relaxation, it is essential to
prestress the bolts to ensure adequate stress load
during operation.
Hydrostatic Testing Precautions
¦If hydrostatic tests are to be performed at pressures
higher than those for which the fange was rated,
higher bolt pressures must be applied in order to get
a satisfactory seal under the test conditions.
Gasket Installation
¦Use high-strength alloy bolts (ASTM B 193 Grade
B7 is suggested) during the tests. They may be
removed upon completion. Higher stress values
required to seat the gasket during hydrostatic tests
at higher than fange rated pressures may cause
the standard bolts to be stressed beyond their yield
points.
¦Upon completion of hydrostatic testing, relieve all
bolt stress by 50% of the allowable stress.
¦Begin replacing the high-strength alloy bolts (sug-
gested for test conditions) one by one with the stan-
dard bolts while maintaining stress on the gasket.
¦After replacing all the bolts, follow the tightening
procedure recommended in the bolting sequence
diagrams.
Prestressing Bolts for
Thermal Expansion
Bolts should be prestressed to compensate for
thermal expansion as well as for relaxation, creep,
hydrostatic end pressure and residual gasket loads.
A difference in the coeffcient of thermal expansion
between the materials of the fange and the bolts may
change loads. In cases of serious thermal expansion,
it may be necessary to apply a minimum of stress to
the bolts and allow the pipe expansion to complete the
compression of the gasket.
A gasket with a centering guide ring should be
compressed to the guide ring. A gasket without a
centering guide ring must be installed with precautions
taken to prevent thermal expansion from crushing the
gasket beyond its elastic limit.
4-Bolt Flange 8-Bolt Flange 16-Bolt Flange
WARNING:
Properties/applications shown throughout this brochure are typical. Your specifc applica-
tion should not be undertaken without independent study and evaluation for suitability.
For specifc application recommendations consult Garlock. Failure to select the proper
sealing products could result in property damage and/or serious personal injury.
Performance data published in this brochure has been developed from feld testing,
customer feld reports and/or in-house testing.
While the utmost care has been used in compiling this brochure, we assume no respon-
sibility for errors. Specifcations subject to change without notice. This edition cancels
all previous issues. Subject to change without notice.