[Science Post] Analysis of the advantages and disadvantages of the five major valves, you may not know all of them (part 1)!

​Five kinds of valves

Advantages and disadvantages 

The butterfly valve is a valve that uses a disc-type opening and closing member to reciprocate about 90° to open, close and adjust the fluid channel.

advantage:

①Simple structure, small size, light weight, less consumables, suitable for large-diameter valves;

②Rapid opening and closing, small flow resistance;

③It can be used for media with suspended solid particles, and it can also be used for powder and granular media depending on the strength of the sealing surface. It can be applied to the two-way opening and closing and adjustment of ventilation and dust removal pipelines, and is widely used in gas pipelines and water channels in metallurgy, light industry, electric power, and petrochemical systems.

Disadvantages:

① Due to the limitation of the structure of the butterfly valve and the sealing material, it is not suitable to be used in the high temperature and high pressure pipeline system.

②The sealing performance is worse than that of ball valves and stop valves, so it is used in places where the sealing requirements are not very high.

The ball valve is evolved from the plug valve. Its opening and closing part is a sphere, which uses the sphere to rotate 90° around the axis of the valve stem to achieve the purpose of opening and closing. The ball valve is mainly used to cut off, distribute and change the direction of the medium flow in the pipeline.

advantage:

①Has the lowest flow resistance;

②Because it will not get stuck when working (when there is no lubricant), it can be reliably used in corrosive media and low boiling point liquids;

③It can be completely sealed in a larger pressure and temperature range;

④ Fast opening and closing can be realized, and it is suitable for the automation system of the test bench. When opening and closing the valve quickly, there is no shock in operation;

⑤The spherical closure can be automatically positioned on the boundary position;

⑥The working medium is reliably sealed on both sides;

⑦When fully open and fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, so the medium passing through the valve at high speed will not cause the erosion of the sealing surface;

⑧Compact structure, light weight, the most reasonable valve structure suitable for medium and low temperature medium system;

⑨The valve body is symmetrical, especially the overall structure, which can withstand the stress from the pipeline well;

⑩The closing piece can withstand the high pressure difference when it is closed. It is the most ideal valve for petroleum and chemical pipelines.

Disadvantages:

①Because the main valve seat sealing ring material of the ball valve is PTFE, it is inert to almost all chemical substances, and has a small friction coefficient, stable performance, not easy to age, wide temperature application range and excellent sealing performance The comprehensive characteristics. However, the physical properties of PTFE, including high expansion coefficient, sensitivity to cold flow and poor thermal conductivity, require the design of valve seat seals to focus on these characteristics. Therefore, when the sealing material becomes hard, the reliability of the seal is impaired. Moreover, PTFE has a low temperature resistance rating and can only be used at less than 180°C. Above this temperature, the sealing material will deteriorate. In the case of long-term use, it will generally only be used at 120°C.

② Its adjustment performance is worse than that of the stop valve, especially the pneumatic valve (or electric valve).

We have introduced the advantages and disadvantages of the two valves above, and the next issue will be more exciting.