In an apparatus using fluid, the flow of the fluid is normally controlled by using various kinds of valves.Check Valves For intercepting lines of fluid, a solenoid valve is often used as a valve for controlling opening and closing of the fluid lines, while as a valve for intercepting a backflow of fluid, a check valve is provided in most cases. These valves are each selected depending on equipment for use or conditions of pipes.

For example, in the pipes for fuel system such as boilers, there is provided a valve for controlling supply of fuel. Since boiler fuel is a light fuel or a gas fuel in nature, it is necessary to take all possible measures against leakage of the boiler fuel to ensure safety. Accordingly, in order to prevent leakage of fuel, there have conventionally been made efforts including combining various types of valves and disposing a plurality of valves in series.

In a feedwater pipe for use in feedwater system for boilers and the like, there is provided a check valve for preventing the backflow of feedwater and boiler water. Since the boiler water is high in pressure and high in temperature, it is necessary to take all possible measures against the backflow of the boiler water to ensure safety.CHECK VALVES Accordingly, in order to prevent leakage in the check valve, more specifically, to prevent the backflow, there have conventionally been made efforts including combining various types of check valves and disposing a plurality of check valves in series.

Also in a valve element that comes into contact with a valve seat of each type of valve, various materials are used to prevent leakage and a backflow. For example, as the valve element, there are used an elastic member such as rubbers and a metal member (inelastic member) generally called a metal seal. The valve made only from the elastic member is low in withstanding pressure and short of durability.

In the case of using only the metal seal, there is a problem that a small dust being interposed between the valve sheet and the valve element made from an inelastic member, which is so-called dust clogging, easily damages sealing, and tends to cause leakage and a backflow.Check Valves Also, if the dust clogging occurs in the valve with metal seal structure, the dust may be washed away by the next flow of fluid, which eliminates reproducibility of leakage or the backflow, thereby disturbing examination of the cause of leakage and the backflow. Further in the metal seal structure, impact at the time of closing the valve is large, and there are also problems of durability and noise.

Further, the tendency of occurrence of damage on the functions of the valve, i.e., the leakage or the backflow, is predicted by detection of the leakage and the backflow with use of pressure gauges and the like before the function of the valve are actually damaged. However, it is difficult to predict the tendency by every valve unit.

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2011-12-21

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