2023/12/22 09:08

Advantages and disadvantages of several types of valves

Advantages and disadvantages of several types of valves

Gate valve:

Gate valve is the closing member (gate) along the axis of the channel in the vertical direction of the _ move the valve, in the pipeline mainly as a cut off the medium with, that is, full open or full closed use. Generally, the gate valve can not be used as a flow adjustment. It can be applied to low temperature pressure can also be applied to high temperature and high pressure, and can be based on different materials of the valve. But the gate valve is generally not used in the pipeline to transport slurry and other media.

Advantages: ① fluid resistance is small; ② opening and closing torque required is small; ③ can be used in the medium to the two directions of the flow of the ring network pipeline, that is to say, the direction of flow of the medium is not restricted; ④ open, the sealing surface by the work of the media erosion than the cut-off valve is small; ⑤ shape and structure is relatively simple, manufacturing process is better; ⑥ structure length is relatively short.

Disadvantages: ① external dimensions and open height is larger, the space required for installation is also larger; ② in the process of opening and closing, the sealing surface of the relative friction, wear and tear, and even at high temperatures can easily cause abrasion phenomenon; ③ the general gate valve have two sealing surfaces, to the processing, grinding and maintenance added some difficulties; ④ opening and closing time is long.

Butterfly valve:

Butterfly valve is a kind of valve with disc-type opening and closing parts reciprocating about 90 ° to open, close and adjust the fluid channel.

Advantages: ① simple structure, small size, light weight, consumables, suitable for large diameter valves; ② rapid opening and closing, small flow resistance; ③ can be used for media with suspended solid particles, based on the strength of the sealing surface can also be used for powder and granular media. It can be used for two-way opening and closing and adjustment of ventilation and dust removal pipelines, and is widely used in metallurgy, light industry, electric power, petrochemical systems, gas pipelines and waterways.

Disadvantages: ① flow adjustment range is not large, when open up to 30%, the flow will be more than 95%. ② due to the structure of the butterfly valve and sealing material limitations, should not be used for high temperature, high pressure piping system. General operating temperature below 300 ℃, PN40 below. ③ sealing performance relative to the ball valve, globe valve is poor, so it is used for sealing requirements are not very high.

Ball valve:

Is evolved from the plug valve, its opening and closing member is a sphere, the use of the sphere around the axis of the valve stem rotated 90 ° to achieve the purpose of opening and closing. Ball valve in the pipeline is mainly used to cut off, distribution and change the direction of media flow, designed as a V-shaped opening of the ball valve also has a good flow regulation function.

Advantages: ① has a low flow resistance (actually 0); ② because in the work will not be stuck (in the absence of lubricant), it can be applied to corrosive media and low boiling point liquid; ③ in the larger pressure and temperature range, can realize the complete _ full seal; ④ can be realized quickly open and close, the opening and closing time of some structures is only 0.05 ~ 0.1s to ensure that it can be used for the test bench automation system. When opening and closing the valve quickly, the operation is shockless. ⑤ spherical closing member can be automatically positioned in the boundary position; ⑥ double-sided sealing; ⑦ in the fully open and fully closed, the sealing surface of the sphere and the valve seat and the media isolation, so the high speed through the valve medium will not cause the sealing surface of the erosion; ⑧ compact structure, light weight, can be considered as a reasonable valve structure for the system of cryogenic media; ⑨ symmetry of the valve body, in particular the welded valve structure, can well withstand the pipeline from the Stress; ⑩ Closing parts can withstand the high pressure difference when closing. (11) fully welded body ball valve, can be buried directly in the ground, so that the valve internal parts are not subject to erosion, high service life of up to 30 years, is the ideal valve for oil, natural gas pipelines.

Disadvantages: ① because the main valve seat sealing ring material is PTFE, it is inert to almost all chemicals, and has a small coefficient of friction, stable performance, not easy to aging, temperature range and excellent sealing performance of the comprehensive characteristics. However, the physical properties of PTFE, including a high coefficient of expansion, sensitivity to cold flow and poor thermal conductivity, requiring the design of the valve seat seal around these characteristics. Therefore, when the sealing material hardens, the seal is damaged. Furthermore, PTFE has a low temperature resistance rating and can only be used at temperatures less than 180°C. Above this, the sealing material will deteriorate. Above this temperature, the sealing material will deteriorate. Considering the long-term use, it is generally not used at 120℃. ② Its regulating performance is worse than that of globe valve, especially pneumatic valve (or electric valve).


Pneumatic valve working principle and failure analysis

The so-called pneumatic valve, specifically refers to the cylinder as an actuator, compressed air as a power source to realize the drive of the valve, in order to achieve the switch to regulate.

Advantages and disadvantages of several types of valves

Advantages and disadvantages of several types of valves

Plumbing fittings classification method

Plumbing fittings in the elbow fittings classification: elbow fittings according to the radius of curvature to points, can be divided into long radius elbow and short radius elbow. Long radius elbow means that its radius of curvature is equal to 1.5 times the outside diameter of the pipe