What kind of valve is fireproof valves do? Abroad mentioned fire valve (fire-safe valve), the definition of valve fire resistance abroad a lot and not unified, this definition is still a lack of clearly defined industrial. So far, still no single test or definition clearly determine whether a valve of fire. Many Industrial Society, oil companies, insurance companies, the valve manufacturer, as well as the United Kingdom, the United States agency already provides a variety of testing methods. However, the measured type of valves and the main test specification with the test method varies. Combustion valve test debate continues, some tried integrating two or more methods is a complete way, but still not conclusive. This is what we have to study the problem should first study the problem of soft valve seat.
Some people think that will not melt in the fire, metal gate valve and ball valve (globe valve) is the fire dampers. The design and structure of these valves can guarantee before and after it in a fire, are metal and the metal contact (metal-to-metal), which avoids the flammable fluids into the fire this. However, the metal seat before ignition, sealing is not good. The leak is very small, in most of the developed fire safety standards is allowed. User requirements both good seal valve in normal operation, but also has a fire resistance. Many valve manufacturers as early as 15 to 20 years ago, trying to solve this complex problem, they have developed a variety of "soft," "hard" sealing elements, these two types of components fire this can keep the metal surface contacting seal. Hard seat is made with the metal or alloy itself can withstand high temperatures. Soft seat of the elastic material of rubber, plastic or melting point lower than 700 ° F (about 370 ℃), soft seat can be burned after the fire, and then by virtue of the pressure of the system, the rotation of the valve plate, the spring force of its own gravity role holding the metal surface contact. However, the many soft seat valve combustion security is not ideal. If these resilient seat can not be totally destroyed in the blaze, will not be able to form the metal surface contact. The following table summarizes the various combustion tests including soft seat valve test specifications from the table, a variety of test standard for analysis and comparison, will be able to understand which of the five standard is more stringent. It must be pointed out, the American Petroleum Institute standard API607 "soft SealBall combustion test (1977) is a tentative standard applicable to all 16 inches below the ball valve. Later, the second edition of the standard API RP6F modified, more stringent requirements. However, the valve can only be provided by different manufacturers to meet fire safety standards introduced in one or both of the following table, for example, Rockwell (Rock well) fire plunger valves and ball valves can only comply with API607, and API RP6F two kinds standard, some other company valve only meet some other criteria.
In order to ensure that the valve body fire performance, many manufacturers have been various attempts. For example, they bandage on the valve cover of layers of felt refractory brick box of the valve and the outside world. However, the above methods are not very satisfactory, because every repair of the valve must be disassembled, build. Since the the valve installation location restrictions, this method may not be used. A more satisfactory method is with a fireproof bags, it can be within a few minutes, put on, maintenance is also easy to uncover. The material of the bag containing the multilayer ceramic fibers (eramic fiber) or glass fiber (fiberglass) with nylon tied tightly, and coated with a stainless steel wire of the vinyl resin is tied in the device. In general a question, does not need to change the pipeline location, a small installation space, through the test in 2000 ℉ flame to burn for 30 minutes, the valve is still not damaged, the performance is satisfactory.
Executive agency directly controls the position of the valve, so need more careful study. Steel (iron) of the valve will remain closed in a timely manner, easy to ignite occasions are often used in spring pneumatic diaphragm actuator, using patch melting point low. Fire, quickly damaged due to the diaphragm low melting point and therefore the spring movement, so that the valve is in the closed position. The use of heat-sensitive fusible hole plugs to reduce the pressure of the pneumatic system, especially suitable for the piston reciprocating spring actuator.
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