Published: 1967
Total Pages: 181
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Valves have been used for more than 4000 years. The Chinese are said to have used wood-plug valves in bamboo pipelines; arti-facts from the depths of the Mediterranean contain fragments of petcocks dating from before the time of Christ. Wooden valves of the Roman Empire bear a striking resemblance to the plug valves on wine casks and beer kegs today. Nearly every person in the civilized world now comes into daily contact with valves. They are controlling elements in fluid-handling systems, and system control can be no better than the valves being used. Valves serve five primary functions: to start and stop flow, to regulate and throttle flow, to prevent backflow, to regulate pressure, and to relieve excessive pressure. How well these functions are accomplished largely determines the performance of the system. Management is becoming more and more aware of the importance of valves in industrial plants and processes. In the hydrocarbon and natural gas industries, valves represent about 8 percent of new plant capital expenditures and 10 percent of the maintenance budget for replacement purchases. The price of valve failure and leakage increases as the cost of process fluids rises.
