The difference between gate valves and ball valves

Los Angeles, California
August 28, 2014 2:28am CST
Gate and ball valves can in general be used interchangeably. Both are considered open/close valves and are seldom used for control. (There are some special ball valves that have a characterized flow profile that permit them to be used for control but they are a very special application.) Although some users believe ball valves have a tighter shut off but that is a function of the seat material and the service. Pressure limits are primarily set by the design of the specific valve. Ball valves may be considered to give better and more reliable leak resistance and therefore specified where this is most critical such as for gas or liquefied gas applications. Ball valves usually can be opened with a quarter turn of the handle except for very large ones that require a gear type or piston operator. Gate valves are good for isolation and avoiding a fast opening. By examining the cross section of the gate valve it will be seen that when it is fully open it offers very little resistance to flow. Also when it is just about fully closed, all the throttling is done on the bottom of the discs and seats, making for uneven wear by erosion. For these two reasons gate valves are recommended by China valve manufacturer for use when they are either fully open or closed. They offer little resistance when open and are not suited for throttling purposes when almost fully closed. Also note that the internal pressure always forces the downstream disc against its seat. For this reason gate valves only wear on the downstream side. This wear is eliminated by carefully guiding the disc to its seat. The wear is taken up by guides built into the body of the valve which accurately engage machined wings on the discs. Stainless steel ball valve is for high pressure and gate valve is for low pressure, the gate valves are used for pressure ratings of 2000 to 5000 psi. Both are generally used for shutoff or equipment isolation purposes.
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