Gaskets are materials used to seal one compartment of a device ...

Fibrous glass packings are usually divided into two groups, “E” glass
packings, and “S” glass packings, depending upon the type of glass fiber used
in the formulation. “E” glass is one of the more common glass fibers, and is
often manufactured into a packing which is used as a jacket around a plastic
core of carbon or aramid fibers, and other materials (OGJ 1986).
“E” glass packings are suitable for applications where the operating
temperature is below 1000°F. Above this temperature, the packing loses 50
percent of its tensile strength. Also, the material can be used with most
fluids except strong caustics.
The second type of fiber, ~ glass, was developed by NASA and is
recognized as the superior glass fiber in use today (OGJ 1986). This material
is generally used as a jacket around a core of graphite and other fibers. The
packing is caustic resistant and can be used in applications with operating
temperatures of 1500°F(OGJ 1986).
One disadvantage of glass packings is the abrasive nature of the material.
In high shaft-speed applications, the abrasiveness of glass wears down the
shaft stem requiring frequent replacement of the stem.
Glass packings will
capture 30 percent of the total asbestos packing market and will cost twice as
much as the asbestos material. Thus, the price will be $60.40 per pound
(Palmetto Packing,
ICF 1986a).
John Crane-Houdaille, previously one of the major producers of asbestos
packings, offers an “S”-glass yarn packing replacement that it claims is
better than the asbestos packings it replaces. It has a higher temperature
limit, good service life in caustics, steam, oil, liquid petroleum, and
chemicals, a high pressure limit of 7700 psi and will not score valve stems or
other pieces of equipment in which it is used (John-Crane 1987).
3. PBI Mixtures
PBI (polybenzimidazole) is produced by Celanese Engineering. It has a
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