THE MISUNDERSTOOD CHECK VALVE DFT Valves（误解了止回阀DFT阀门）.pdf

AS SEEN IN THE SUMMER 2006 ISSUE OF... Back to Back to BASICS: BASICS: TOO OFTEN THIS VALVE IS UNJUSTLY BLAMED WHEN PROBLEMS OCCUR,BUT THE REAL CULPRIT THE MISUNDERSTOOD IS THE APPLICATION. BY MIKE JOHNSON CHECK VALVE heck valves are probably the most they continue to work even if the plant facility loses air, electricity, or the human Cmisunderstood valves ever being that might manually cycle them. invented. If you mention check valves to As with other types of valves, check valves are found in a full range of sizes, most plant personnel, the typical materials, and end connections. The line sizes range from 1/8 inch or smaller to 50 response is “they don’t work.” In fact, inches and larger. They are made of bronze, cast iron, plastics, carbon steel, and those personnel may well have taken various grades of stainless steel, alloys such as Hastelloy, Inconel, Monel, and tita- out the internals or repiped the system nium. End connections include threaded, socket weld, butt weld, flanged, Victaulic, to avoid check valves. In other words, wafer, and insert type. these valves are the least popular valve Check valves are found everywhere, including the home. If you have a sump in use today. pump in the basement, a check valve is probably in the discharge line of the pump. This article will explore the basics Outside the home they are found in industries such as automotive, desalination, avi- of check valves, how they work, what ation, commercial construction, water and waste, chemical, colleges and universi- types there are, how to select and ties, food and beverage, geothermal, hospitals, mining, oil and gas, pharmaceutical, install them, how to solve their prob-