Energy dissipation inside a large diameter pipeline or at dam outlet works is one of thernimportant design and operations and maintenance issues for water supply and hydropowerrnfacilities. For water supply, flow regulation is also required to meet project specific operatingrnrequirements. In the early 1900's, the first needle valve was installed at a dam to controlrnreservoir's free discharge; about 30 years after that, the plunger valve was developed forrnfacilities such as transmission pipelines, dam outlet works, or hydropower stations. The plungerrnvalve design has introduced a number of unique features that have performed extremely well inrna variety of flow conditions.rnThis paper presents the plunger valve development history and main design features includingrncompact valve design, linear flow characteristics, and custom outlet configurations. All of whichrnhave contributed to the successful application of plunger valves to date in the water andrnhydropower industries. This paper also includes a comparison of technical and operationalrncharacteristics between the plunger valve and other energy dissipation and control valves, suchrnas the plug, ball, sleeve, and fixed cone valves. Finally, this paper documents threernrepresentative installations showing that the plunger valve has performed superbly over otherrnvalves in the areas of anti-cavitation, noise and vibration reduction, debris passage, closurerntightness, operational reliability, durability, and life-cycle cost efficiency. Clearly the plunger valve is a better choice in terms of technical soundness, operations and maintenancernrequirements, and valve economics for handling energy dissipation and/or flow regulation,rnparticularly under severe flow conditions.
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