Application advantages of plug valve
The plug valve is an integrated top mounted valve body design, which has certain comparability with one piece top mounted ball valve. Compared with two-piece or three-piece ball valve, it is a product of completely different types and different application occasions. Next, I will check the advantages and disadvantages of the cock valve for you. For the main applicability of plug valve, there are the following application advantages:
1. The valve body is one-piece, top mounted design, simple structure, convenient online maintenance, no valve body leakage point, supporting higher pipeline system strength.
2. The medium in the chemical process has strong corrosiveness. In the chemical site, it is often seen that the valve body is corroded by the medium. Therefore, the valve body used in the chemical process must have strong resistance to permeability and intergranular corrosion. The valve body of the plug valve is a high-grade casting with a casting quality of class II and a precision of class v.
3. The simple internal parts, the opening and closing parts, that is, the cock is completely covered by the bushing, the valve body and the cock are not worn, and the simple and economic replacement of the bushing and the top seal can complete the maintenance and renewal of the valve, which can meet the long-term use requirements of 300 ℃, and has a considerable competitive advantage compared with the metal hard seal ball valve in the same application range.
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4. The whole processing surface of the plug valve is only the top surface and flange. All other parts are cast in one time. There is no processing inside the valve body. Compared with the ball valve, it has the advantage of low machining allowance. When the material is Inconel, Monel, Hastelloy and other special materials, it has obvious price advantage.
5. The plug valve can achieve specific functions by adding multiple designs according to the users requirements. Plug valve is the leader of customized valve products. It is easy to realize customized process for customers. It can be made into three-way, four-way, five-way, six-way, double valve group or multi valve group, various jacket requirements, etc. for example, the six-way distribution valve applied in polyester industry is the plug valve customized according to the requirements of the patent manufacturer, while it is difficult to use the ball valve as the customized valve.
6. Clearance free and face sealing are still the unique characteristics of the plug valve. Although there is a design of clearance free ball valve, it is only to reduce the clearance between the ball and the valve body to 1-3mm as far as possible, which can not achieve the application advantages of the enveloping face sealing. This feature of the plug valve makes the plug valve suitable for handling many harsh media, such as crystallization, viscosity It contains catalyst particles and fluid with deposition corrosion.
7. The cladding bushing provides face sealing characteristics, which can strictly control the zero leakage test requirements of API 598 soft seal valve seat, and can meet the stem sealing requirements of TA Luft or ISO 15848.
Plug valve is characterized by long service life and high reliability. It is a good choice for many corrosive, abrasive, highly toxic, continuous operation and other media and devices. It has application advantages and wide applicability in chemical industry.
Disadvantages of plug valve
1. The design of face seal improves the requirement of driving torque. In the case that pneumatic actuator is required, the users use cost will be increased if larger actuator and accessories are required compared with ball valve. For example, in PP process, the main shut-off valve is a plug valve, not a ball valve, but the high-frequency switching valve is a ball valve, so basically pneumatic plug valves are used in key shut-off positions. The plug valve is not fully recommended for regulating applications. High frequency switching is not the advantage of the plug valve. It is a high reliability shut-off valve.
2. In some applications, improper selection of sleeve material or improper design of valve body for sleeve deformation release area will cause swelling of PTFE material sleeve, resulting in several times change of driving torque required by the valve, which is basically avoided under the condition of correct and targeted materials.
3. The one-time investment of the plug valve is higher than that of the ball valve, but with the advantages of the plug valve, such as the reliability and the total cost of the service cycle, etc., gradually accepted by the domestic users, more and more users will continue to use the plug valve required by the original process design, and gradually reduce the decision to change it into the ball valve.