MECHANICAL SEALS FOR HIGH-SPEED BOILER FEED PUMPS IN ULTRA-PURE WATER

摘要

Since 2007, the hot-filament Chemical Vapor Depositionrn(CVD) technology for crystalline diamond thin-film coatingsrnhas found its way into the mechanical seal market to combat thernproblems of dry running, corrosion and abrasion. This newrntechnology has proved successful in hundreds of pumpingrnapplications in a wide range of services and duties. Thernreliability and lifetime of mechanical seals are improved byrnusing diamond-coated faces.rnOne such application involved the sealing of large boilerrnfeed and steam generator pumps in power plants. The dutyrnconditions for the pump’s seals can be as high as pressures uprnto 580 psig (40 bar), shaft RPMs up to 6,500 and temperaturesrnup to 400?F (200?C). Consequently, the mechanical seal facesrnare highly loaded in a fluid with far less than ideal lubricatingrnqualities. It is evident, therefore, that these applications arerntechnologically challenging for mechanical seal manufacturersrnnot only from a tribological perspective, but also from arncorrosion viewpoint when the feed water has a low electricalrnconductivity or is free of impurities.rnThis paper discusses a new seal-face treatment using hotfilamentrnCVD manufacturing technology tested in a lab forrn16,000 hours and currently used in feed pump operations inrnseveral power stations in the USA and Europe.