- For the main applicability of plug valves, there are the following application advantages:
1. The valve body is an integrated, top-mounted design with simple structure, convenient online maintenance, no valve body leakage points, and supports higher pipeline system strength.
2. The medium in the chemical process is very corrosive. At the chemical industry 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 resistance to corrosion. Intergranular corrosion, the valve body of the plug valve is a high-grade casting, the casting quality is level II, and the accuracy is level V.
3. Minimalist internal parts. The opening and closing parts, that is, the cock, are completely covered by the bushing. There is no wear on the valve body and cock. Simple and economical replacement of the bushing and top seal can complete the maintenance and update of the valve, which can reach 300℃. With long-term use requirements, it has considerable competitive advantages compared with metal hard-sealed ball valves belonging to the same application range.
4. The entire machining surface of the plug valve is only the top surface and flange. All other parts are cast and formed at 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 It has obvious price advantages when it comes to special materials such as alloys.
5. Plug valves can be added with a variety of designs to achieve specific functions according to user needs. Plug valves are the leader in customer-customized valve products. Plug valves are easy to customize for customer processes and can be made into three-way, four-way, five-way, six-way, double or multi-valve groups, and various jacket requirements. Etc., for example, the six-way distribution valve used in the polyester industry is a plug valve customized according to the patentee's requirements, but it is more difficult to use a ball valve to make a customized valve.
6. No gap and face seal are still the unique characteristics of plug valves. Although there are designs of gapless ball valves, the ball valve design only reduces the gap between the valve ball and the valve body to 1~3 mm as much as possible, which cannot be achieved. The application advantages of the covering surface seal and this feature of the plug valve make the plug valve suitable for handling many harsh media, such as fluids that are easy to crystallize, are viscous, contain catalyst particles and have sedimentation corrosion.
7. The covered bushing provides surface sealing characteristics and can strictly control the "zero leakage" test requirements of API 598 soft-sealing valve seats, and can meet the valve stem sealing requirements of TA-Luft or ISO 15848.
The comprehensive characteristics of the plug valve are its 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 application in the chemical industry. applicability.
- The disadvantages of plug valves are as follows:
1. The face seal design increases the requirements for driving torque. When it is necessary to equip a pneumatic actuator, larger actuators and accessories are required compared with ball valves, which will increase the user's cost. For example, in the PP process, the main shut-off valve uses a plug valve instead of a ball valve, but the high-frequency switching valve uses a ball valve, so basically pneumatic plug valves are used in key shut-off positions. Plug valves are not entirely recommended for use in regulating applications. High-frequency switching is not the advantage of plug valves. It is a highly reliable shut-off valve.
2. In some applications, incorrect selection of bushing material or improper design of the valve body for the bushing deformation release area will cause the PTFE material bushing to swell, causing the required driving torque of the valve to change several times. This situation can basically be avoided if the materials are correct and targeted.