SEALING SENSE

Are the symptoms, causes, and correctiveactions for failure of mechanical seals by thermal attack? symptom of thermal attack is the appear-ance of fine-to-large radial cracks that emanate fromthe center of the metal or ceramic ring. Character-ized asheat checking,these cracks act as cuttingedges on the carbon-graphite and other seal facematerials, and the consequent scraping action rapid-ly wears out the causes of heat checking include: (1)insufficient lubrication; (2) vaporization at the sealfaces; (3) inadequate cooling; and (4) excessive pres-sures and velocities. Any one or a combination ofthese factors can result in higher friction and heat atthe seal faces. The excessive thermal stresses thatdevelop will result in fine Actions include: Checking operating conditions to ensure theyare within the prescribed limits for the seal. Confirming adequate coolant flow at the sealfaces to carry away seal-generated heat; guide-lines are that (a) the temperature rise of thefluid flowing through the seal cavity should notexceed 40 F (22 C); and (b) pressure of theseal cavity product should be maintained 25 PSI ( bar) above the vapor pressure of theseal cavity fluid to avoid vaporization.

Q.What are the symptoms, causes, and corrective actions for failure of mechanical seals by thermal attack? A. One symptom of thermal attack is the appear-

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  Mechanical, Leasing, Senses, Sealing sense

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