The performance of a gasket depends on its ability to withstand internal pressure, endure in all temperatures and mediums, compress and compact in flange loading while
being easy to design into all applications. EGC Thermafoil¨ meets these challenges with infinite make-ups and capabilities.
EGC excels in problem solving and provides the best possible performance
under the most adverse conditions. Gasket configurations range from
standard I.D./O.D. flange gaskets to complex, close tolerance composite
sealing structures. From prototype to production, all engineering
and manufacturing is provided by EGC personnel. In addition,
EGC also carries a complete line of standard ANSI flange gaskets
from 1/2" to 32", Boilerwater level gauge gaskets, and
many man-hole, hand-hole gaskets. Each of these can be produced
from a variety of gasket materials, to suit your application.
DESIGN CRITERIA
Gasket performance is directly related to the base materials used in construction and
the ability of the material to withstand creep. Creep is defined as the continued plastic flow of a material under constant load. Should creep continue long enough to reduce gasket load below its sealing requirements,
leakage, wire drawing, and even blowout will occur. Thermafoil flexible graphite is a no-creep gasket material and is the base from which all EGC gaskets are manufactured.
This catalog section is intended as an aid in
designing flanged, gasketed joints and as a guide for solving your field gasketing problems. Our technical service engineers will be glad to discuss your particular application.
DESIGN FACTORS
When designing a gasket and selecting the proper gasket material, the goal is "zero leakage". EGC delivers with "High Technology Fluid Sealing" and Thermafoil flexible graphite.
Gasket Performance vs. Medium
EGC Thermafoil flexible graphite has performed in some of the most
abusive environments known, providing an extra margin of safety
for refining, petrochemical and power generating companies.
Refer to your chemical compatibility chart before choosing a gasket type or style for your particular application, or call our design hot line at 1-800-342-0211 for specific design
criteria on your application. Many liquids and gasses which come into contact with the gasket may be safe at ambient temperature, but elevating the temperature even slightly may cause leakage, potentially dangerous
situations, or violation of EPA fugitive emission laws.
Gasket Design vs. Flange Design
When designing a flange gasket, the surface finish, flatness, bolt loading, and deflection of
the flanges under load should always be considered.
Surface Finish
No correlation has been found between surface finishes and leak pressure vs. load as indicated in graph number 1. The
surface finish of Thermafoil gaskets may range anywhere from 5 to 125 rms.
Flatness
Flange flatness is a critical item with all gaskets. When gasket flanges are brought together, a
.001" feeler gauge should not be able to pass between the flanges at any point. Flanges that are larger can be checked with a straight edge. In these cases a .001" feeler gauge should not fit between the
straight edge and the flange at any point.
Bolt Loading
To achieve minimum "Y" stress, and/or correlate to graph
number 1 "Leak pressure vs. unit load", bolt loading should
always be considered. In addition, the bolt spacing, or tightening
sequence, may also affect the gasket load. A good pressure paper
test should always be performed on new designs to ensure adequate
gasket load.
EGC can supply this pressure paper, called "Laserfilm", at no additional charge. Refer to the Diagnostic pressure chart on the previous page to determine the proper flange load.
Flange Deflection
Flange deflection can be affected by many factors including bolt spacing, bolt material, internal pressure, and temperatures. The end result is stress relaxation and gasket failure. Consult with
your EGC engineer if you have any design questions.
For More Information
Any additional questions, Call EGC at 1-800-EGC-0211. A plethora of information on Flange Gasket Design is
available our Interactive Design Kit, now available on CD-ROM.
