Mechanical Seals.NetA Division of Steadman & Associates, Inc.
Mechanical Seals - Carbon
Carbon: resin-impregnated carbon graphite. The best seal grades are machined to near final shape, then baked to improve physical properties. The final resin impregnation is only used to make the carbon gas-tight, and only penetrates the surface of the part. Pure Carbon Company P-658RC is the preferred grade and is standard in all ASP seals. “Machinable” grades often used by seal repair shops are manufactured to be porous throughout so that the resin impregnation penetrates the entire part. This allows a carbon part to be machined from tube stock. These grades wear rapidly and run poorly.
Carbon is not acceptable in the presence of a strong oxidizing agent.
Here is a list of the most common chemicals that will attack P-658RC:
Aqua Regia (nitric and hydrochloric acid)--used for dissolving metals.
Oleum (fuming sulfuric acid)--used in the manufacture of detergents and explosives.
Perchioric Acid--used in the manufacture of medicine, explosives and esters.
Fluorine - used as an oxidizer or rocket fuel.
Sulfur Trioxide - used in paper bleaching, oxygen generation and dyeing.
Nitric Acid in concentrations greater than 20% and over 250°F - used in fertilizer, dyeing, explosives, etching, drugs and medicine.
Sulfuric Acid greater than 75% and over 250°F -the most widely used industrial chemical.
Iodine greater than 5% and over 200° F - used in dyes, soap, salt, medicine and some lubricants.
Chioric Acid greater than 10% and over 200°F -ignites organic material on contact.
Chiorous Acid - greater than 10% and over 200°F.
•Ferric Chloride greater than 50% and over 200°F used for sewage treatment, etching, photography, oxidizing disinfectant, medicine and feed additives.
Hydrofluoric Acid greater than 40% and over 200°F - used for etching, pickling, cleaning stone and brick, purification, fermentation, dissolving ores and cleaning castings.
Calcium Chlorate greater than 5% - used in photography and pyrotechnics.
Sodium Chlorate greater than 5% - used as a bleach for paper pulp, medicine, textiles and tanning leather.
Sodium Hypo~chlorite greater than 5% - used in bleaching pulp and paper, textiles and water purification.
The following chemicals will not attack P-658RC
but can cause severe abrasive wear:
--Chromic Oxide (Aqueous)
--Chrome Plating Solutions
Carbon graphite running against Silicon carbide has a low coefficient of friction, and is the best choice for most applications. Silicon carbide is the hardest of all seal face materials.
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