subject: Suggestions of choosing a proper control valve [print this page] The function acted by the valve is generally becoming more and more necessary and important. And it is common to see that there is a chain of the various valves with various specifications in an industrial line to cooperate to achieve the machinery requirements. Sometimes, especially in some conditions with high requirements, the control valve should affect well at the stopping the flow. Thus, the performance of cutting off should be regarded as the indispensable indicator of the employment effect and internal quality. The failure of the cutting would lead to the unexpected leakage, even some worse consequences. As a result, it means a lot to have chosen a proper control valve. There are some favorable suggestions introduced in the following.
From the perspective of the structure, there are many good options. Previously, the double seal type valve was popular then. However, the leakage caused by this kind of valve was really great. Definitely, trails have been done to make up for this weakness. When the double seal type was changed into single seal type, the problem was perfectly solved. And as the industry develops, the working conditions are becoming more and more serious and complex. Within the developing requirements, rotary valve such as the three eccentric cut-off butterfly valve rises to be the better choice.
In terms of the sealing face, spherical seal is better than the face to face seal. As the face to face seal is made up with two cones, it is more or less influenced by the processing error like the concentricity, roundness or tilt. However, the contact of the spherical seal is called the linear contact. Thus, it does great favors at preventing the leakage, even achieving the zero leakage.
According to the sealing material, different materials hold their own strengths and weaknesses. Seals made of non-metallic materials are favorable except the corrosion resistant valve. But they are easy to get damaged by the medium in the pipe. And the hard seals endeavor to make compensate for the shortages of the soft seals. If it is out of the consideration of the reliability and service life, as well as the economic factor, the hard seal is the better choice.
No matter what, to select a proper control valve or a cut-off valve is to take an overall consideration on many aspects, such as the leakage rate, types and temperature of the media, flow coefficient and other parameters and the cost-effective. It is challenging to make a proper integration. But efforts would not in vain.
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