under specific operating conditions.
Whichever gasket material or type is selected, ensure it is correct for the
application!
1. Gasket Materials
Beater Addition Compressed Fiber Sheet Gasketing
The Beater Addition process incorporates a range of natural or synthetic fiber (i.e. cellulose, aramid, etc.) for strength.
Additionally, binders (i.e. NBR, SBR, etc.) and resins are added for flexibility, strength, heat or chemical resistance.
Gaskets manufactured per this method can also be laminated to support materials such as stainless steel for
increased strength. Fluid compatibility and acceptable application temperature range will be a function of the
material utilized and material thickness. The manufacturing process is outlined in Appendix B. 27
Compressed Fiber Sheet Gasketing
Compressed sheets have been around since the 1890's. It is a composition of fibers, elastomers and fillers that is
formed into sheets of finite dimensions with the process dictating maximum sheet width and maximum sheet length.
This manufacturing method is outlined in detail in Appendix B.
Fluid compatibility and acceptable application temperature range will be a function of the material utilized and
material thickness. Different compressed sheets are available that can function over an extensive range of fluids,
temperatures and pressures. End users should ensure they provide complete application service conditions to
optimize in-service effectiveness and life.
Cork Gaskets
Although there are many new materials available today, cork gaskets may continue to be used in some applications
where minimal bolt load is available such as stamped metal flanges or easily damaged materials (i.e. glass or
ceramics). Cork is impervious to water, lubricating oil and other petroleum derivatives.
Cork gaskets are primarily used for low internal pressures up to 345 kPa (50 psi), where sustained fluid temperature
does not exceed 120°C (250°F). Cork has a tendency to stick to flanges and also has limited shelf life due to humidity.
It should not be used to seal inorganic acids, alkalis or oxidizing solutions. See Appendix B for additional information.
Flexible Graphite
Flexible graphite refers to natural graphite flake that has been expanded and then compressed. It is a material with
the essential characteristics of graphite and complementary properties of flexibility and resilience, as well as an
ability to compress and conform. The manufacturing process is described in Appendix B.
A sheet density of 1.12 g/cm3 (70 lbs/ft3) is often typical of the processed material in the US, while a density of 1.0
g/cm3 (62.4 lbs./ft3) is typical in Europe and is widely used for the majority of industrial gasket applications. While
this density is approximately fifty percent (50%) of the theoretical maximum density of graphite, the through-
thickness sheet permeability to fluids, as measured by the helium admittance test, is extremely low. Characteristics of
the flexible graphite can be tailored for specific gasket applications simply by changing the starting density of the
sheet. Additional details related to flexible graphite are described in Appendix B.
Effective sealability is inherent in the flexible graphite by virtue of its conformability to the flange surfaces under load
and once in place because of its low creep relaxation and stability under a wide range of compressive
load/temperature conditions. Since the tensile strength of flexible graphite is significantly lower than that of binder
containing products, a reinforcement material is commonly employed to improve handleability of the flexible graphite
for many applications. Gasket reinforcement can be either metallic or non-metallic material. There are many
variables and options for consideration when selecting the gasket reinforcement and construction of flexible graphite
gaskets.
Considerations for Reinforcements:
• Non-metallic materials, such as fiberglass cloth and polyester film, can be used to produce the laminate or
composite gasket material. The benefits of these inserts are chemical resistance and ease of cutting.
