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Thickness, Gasket
Garlock recommends the use of thinner gaskets wher-
ever possible. This not only lowers the cost of the gasket,
it increases the performance of the joint by lowering emis-
sions and product loss and increasing blowout resistance.
Thinner gaskets will not seal as many flange irregularities
as thicker gaskets, however, and require flatter flanges.
Experience with the particular flange system is often an
important guide when specifying a gasket thickness. A
more complete discussion of the subject is available.
Torques, Bolt
We realize many end users resist using a torque
wrench for installation. We have found the use of a torque
wrench to be the least painful way to gain a substantial
increase in performance. Any method which accurately
controls the compressive load on the gasket is acceptable.
See Bolt Torque Tables for ANSI/ASME B16.5 RF
flanges on page C-44. For non-standard flanges, contact
Applications Engineering.
The maximum torque values for flanges such as
glass-lined or PTFE-lined, FRP and PVC-type flanges are
established by the flange manufacturer to avoid damage
to the flanges. We recommend the use of the maximum
allowable torque for each size. These maximum torques
are usually lower, and often much lower, than we would
recommend.
Traced Lines (Heat Traced)
Heat traced lines pumping materials which are solid
at ambient temperature can present a number of problems
for gaskets:
1. The bolts are usually hotter than the flanges since the
heat is applied from outside the pipe. This causes the bolts
to expand more than the pipe, which lowers the compres-
sive stress on the gasket.
2. Any line which is shut down will freeze solid. When the
line is reheated on start-up, there is occasionally a plug of
solid material blocking a section of the pipe. The heating
may cause some areas of the material to liquefy and then
expand. The expansion can create extremely high pres-
sures inside the joint if the solid plug is blocking a section
of the line.
USDA
See FDA.
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