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<DIV STYLE="text-align:Left;"><P STYLE="font-size:16ptmargin:7 0 7 0;"><SPAN><SPAN>A system valve is a facility that is fitted to a pipeline or orifice in which the closure member is either rotated or moved transversely or longitudinally in the waterway so as to control or stop the flow. System valves are used to regulate pressure, isolate, throttle flow, revent backflow, and relieve pressure. System valve types include Gate, Plug, Ball, Cone, and Butterfly. These specific types may be classified as isolation valves. Isolation valves are designed to start and stop the flow of water within the distribution network (and isolate portions of the network for maintenance or repair). Isolation valves are the predominant type of SystemValve installed in a distribution network. They are commonly intended to be either fully open or fully closed. They are not intended to throttle flow by being partially open.</SPAN></SPAN></P><P STYLE="font-size:16ptmargin:7 0 7 0;"><SPAN><SPAN>A gate valve is an isolation valve (which is modeled here as a system valve) that is used to prevent water flow via a simple gate mechanism. Gate valves may be motorized (and remotely controlled), and they may also have small bypass valves. Gate valves are not installed in locations where they need to be frequently operated due to the time required to open and close them. </SPAN></SPAN></P><P STYLE="font-size:16ptmargin:7 0 7 0;"><SPAN><SPAN>A butterfly valve is similar to a gate valve but uses a disk that is rotated ninety degrees to control the flow of water. Butterfly valves operate easier under</SPAN></SPAN></P><P STYLE="font-size:16ptmargin:7 0 7 0;"><SPAN><SPAN>large pressures and volumes of water than standard gate valves, and are thus found on larger pipes. However, because the butterfly valve disk stays in the water path even when the valve is open, the valve creates a higher resistance to flow (i.e., pressure loss) than a gate valve. Additionally, if it becomes necessary to clean a main by using pigs or swabs, the butterfly valve would block the operation. Butterfly valves can be operated quickly, increasing the risk of serious water hammer.</SPAN></SPAN></P><DIV><P><SPAN /></P></DIV></DIV> |