There is no doubt that common control valves can easily handle an array of control applications. Certainly, corrosiveness and viscosity associated with the fluid, leakage rates, and a lot of other factors demand consideration even for standard applications. Throughout addition to typically the standard ones, presently there are also many special kinds which usually can be undoubtedly used for specific applications.
High potential control valve is definitely one of essential ones. Generally, globe-style valves larger than 12-inch, ball valves over 24-inch and great performance butterfly valves larger than 48-inch all belong to be able to the special valve category. As control device sizes increase arithmetically, static pressure tons at shutoff enhance geometrically. Consequently, base strength, bearing loads, unbalance forces, in addition to available actuator thrust all become more substantial with increasing device size.
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Normally utmost allowable pressure lose is reduced upon large valves to keep design and actuator requirements in reasonable limits. Despite lowered working stress ratings, the stream capacity of a few large-flow valves continues to be tremendous. Naturally, actuator requirements are serious, and long-stroke, dual acting pneumatic aide is typically particular for large-flow software. The physical dimension and weight of the valve and even actuator components confuse installation repairs and maintanance treatments. Installation of typically the valve body assembly into the pipeline and removal plus replacing major trim parts require heavy-duty hoists.
High-temperature handle valves are various other special valve varieties. Those valves which usually are used for service at conditions above 450�F (232�C) has to be designed plus specified with typically the temperature conditions in mind. At raised temperatures, such because could possibly be encountered inside boiler feed drinking water systems and super-heater bypass systems, typically the standard materials regarding control valve construction might be not enough. For instance, plastic materials and standard mechanical seals generally prove faulty and must end up being replaced by even more durable materials. Metal-to-metal seating materials are usually used. Semi-metallic or even laminated flexible graphite packing materials may also be commonly used.
Apart from for the aforementioned two types, low movement control valves also deserve our focus. Many applications can be found where control involving extremely low move rates is essential. In addition to the very low moves, these specialty handle valves are lightweight and light bodyweight because they are often used found in laboratory environments where very light schedule piping/tubing is applied. These types of control valves are specially designed for the particular accurate control over really low flowing liquefied or gaseous fluid applicati