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Old 10-14-2009, 01:08 PM   #14
RickB
Scraping Paint
 
City: Fort Lauderdale
Vessel Model: CHB 48 Zodiac YL 4.2
Join Date: Oct 2007
Posts: 3,804
RE: Stuffing box question/can of worms

Quote:
Marin wrote:

PS-- Okay, did some research on the web and carbon graphite and ceramic are two different things entirely.

Sort of an Europa vs**Sedan thing*I guess*but the following description sure sounds like a ceramic to me.


"SUBJECT : How the Carbon/ Graphite seal face is manufactured ...

Seal companies purchase carbon/ graphite molded faces from one of several carbon manufacturers. The seal companies pay for the necessary molds and then retain the exclusive use of them. A good seal face would be a mixture of carbon, graphite and nothing else. The carbon is purchased as a by-product of a manufacturing process while the graphite is mined with the main sources being in Canada and Madagascar. The cost of these elements is determined by two things:
<ul>[*]How finely is the product milled? A fine talc is desirable.[*]How pure is the product?[/list]A good mixture would be 80% carbon and 20% graphite. Graphite is a good conductor of heat, a natural lubricant, and has a laminar grain structure similar to a deck of cards, allowing the individual grains to slide over one another. It is this laminar structure that allows the graphite to release from the carbon/ graphite face and deposit on the hard face in the same manner a graphite pencil will write on a sheet of paper.

To manufacture the finished product we place this mixture in an oversized mold using a hydrocarbon as the glue to hold the powder together. Years ago "pitch" from a tree, was used for the same purpose. The mixture is then compressed and placed in an oven at 2000° Fahrenheit (1000° C) for a period of thirty to sixty days. The hydrocarbon will convert to carbon at this temperature. The piece must be heated slowly or otherwise the carbon will combine with oxygen to form carbon monoxide, or carbon dioxide which will, in either case, ruin it."

http://www.mcnallyinstitute.com/04-html/4-7.html

Ceramic materials are inorganic, nonmetallic materials. Most ceramics are compounds between metallic and nonmetallic elements for which the interatomic bonds are either totally ionic or predominantly ionic but having some covalent character. The term ceramic comes from the Greek word keramikos, which means burnt stuff, indicating that desirable properties of these materials are normally achieved through a high-temperature heat treatment process called firing.

http://www.engr.sjsu.edu/wofmate/ceramics.htm



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