Analysis of the advantages and disadvantages of the five common valves

There are many types of valves, each with its own advantages and disadvantages. Below are five advantages and disadvantages of valves, including gate valves, butterfly valves, ball valves, globe valves, and plug valves, hoping to be helpful to you.

1. Gate valve

Gate valve refers to a valve whose closing element (gate) moves vertically along the channel axis, mainly used for cutting off the medium in pipelines, that is, fully open or fully closed. Generally, gate valves cannot be used to regulate flow. It can be used for both low temperature and high temperature and high pressure, but gate valves are generally not used in pipelines for transporting mud and other media.

1.1 Advantages

① Low fluid resistance;

② The required torque for opening and closing is relatively small;

③ It can be used on ring network pipelines where the medium flows in both directions, which means that the flow direction of the medium is not restricted;

④ When fully open, the sealing surface is less eroded by the working medium than the globe valve;

⑤ The body structure is relatively simple and the manufacturing process is good;

⑥ The structural length is relatively short.

1.2 Disadvantages

① The external dimensions and opening height are relatively large, and the required installation space is also large;

② During the opening and closing process, the sealing surface will experience relative friction and wear, and may even cause abrasion at high temperatures;

③ Generally, gate valves have two sealing surfaces, which adds some difficulties to processing, grinding, and maintenance;

④ Long opening and closing time.

2. Butterfly valve

Butterfly valve is a type of valve that uses a disc type opening and closing element to rotate back and forth about 90 degrees to open, close, and regulate fluid channels.

2.1 Advantages

① Simple structure, small size, light weight, and low consumables consumption;

② Quick opening and closing, low flow resistance;

③ It can be used in media with suspended solid particles, and can also be used in powder and granular media depending on the strength of the sealing surface. Suitable for bidirectional opening, closing, and adjustment of ventilation and dust removal pipelines, widely used in gas pipelines and waterways in metallurgy, light industry, power, and petrochemical systems.

2.2 Disadvantages

① The range of flow regulation is not large. When the opening reaches 30%, the flow reaches nearly 95% or more;

② Due to the limitations of the structure and sealing materials of butterfly valves, they are not suitable for use in high-temperature and high-pressure pipeline systems. The general working temperature is below 300 ℃ and PN40;

③ The sealing performance is relatively poor compared to ball valves and globe valves, so it is used in places where sealing requirements are not very high.

3. Ball valve

Ball valves evolved from plug valves, and their opening and closing components are a sphere that rotates 90 ° around the axis of the valve stem to achieve the purpose of opening and closing. Ball valves are mainly used on pipelines to cut off, distribute, and change the direction of medium flow. Ball valves designed with V-shaped openings also have good flow regulation functions.

3.1 Advantages

① Has the lowest flow resistance (actually 0);

② Because it does not get stuck during work (in the absence of lubricants), it can be reliably applied to corrosive media and low boiling point liquids;

③ Complete sealing can be achieved within a wide range of pressure and temperature;

④ It can achieve fast opening and closing, with some structures having an opening and closing time of only 0.05~0.1 seconds, to ensure its application in the automation system of the test bench. When quickly opening and closing the valve, there is no impact during operation;

⑤ The spherical closure can automatically locate at the boundary position;

⑥ The working medium is reliably sealed on both sides;

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

⑧ Compact structure and light weight make it the most reasonable valve structure for low-temperature medium systems;

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

⑩ The closure component can withstand the high pressure difference during closure;

The ball valve with a fully welded valve body can be directly buried underground to prevent corrosion of the valve components. Its maximum service life can reach 30 years, making it the most ideal valve for oil and gas pipelines.

3.2 Disadvantages

① Because the main sealing ring material for ball valves is polytetrafluoroethylene, which is inert to almost all chemicals and has comprehensive characteristics such as low friction coefficient, stable performance, low aging, wide temperature applicability, and excellent sealing performance. However, the physical properties of polytetrafluoroethylene, including its high coefficient of expansion, sensitivity to cold flow, and poor thermal conductivity, require that the design of valve seat seals must revolve around these characteristics. So, when the sealing material becomes hard, the reliability of the seal is compromised. Moreover, polytetrafluoroethylene has a lower temperature resistance rating and can only be used below 180 ℃. Beyond this temperature, the sealing material will age. When considering long-term use, it is generally only used at 120 ℃.

② Its regulating performance is relatively poor compared to globe valves, especially pneumatic valves (or electric valves).

4. Globe valve

A globe valve refers to a valve in which the closing element (valve disc) moves along the centerline of the valve seat. According to the movement of the valve disc, the change in the valve seat opening is directly proportional to the stroke of the valve disc. Due to the relatively short opening or closing stroke of the valve stem and its highly reliable shut-off function, as well as the proportional relationship between the change in the valve seat opening and the stroke of the valve disc, this type of valve is very suitable for regulating flow. Therefore, this type of valve is very suitable for cutting off, regulating, and throttling purposes.

4.1 Advantages

① During the opening and closing process, the friction between the valve disc and the sealing surface of the valve body is smaller than that of a gate valve, making it wear-resistant;

② The opening height is generally only 1/4 of the valve seat channel, so it is much smaller than gate valves;

③ Usually, there is only one sealing surface on the valve body and disc, so the manufacturing process is relatively good and easy to maintain;

④ Due to its filler being a mixture of asbestos and graphite, its temperature resistance level is relatively high. Generally, steam valves use globe valves.

4.2 Disadvantages

① Due to the change in flow direction of the medium passing through the valve, the minimum flow resistance of the globe valve is also higher than that of most other types of valves;

② Due to the longer travel, the opening speed is slower than that of a ball valve.

5. Plug valve

A plug valve refers to a rotary valve with a plunger shaped closure, which opens or closes by rotating 90 ° to connect or separate the channel port on the valve plug with the channel port on the valve body. Also known as a plug, cork, or revolving valve, the shape of the valve plug can be cylindrical or conical, and there are many types, including straight through, three-way, and four-way. Its principle is basically similar to that of a ball valve.

5.1 Advantages

① High frequency of operation, quick and easy opening and closing;

② Low fluid resistance;

③ Simple structure, relatively small volume, light weight, and easy maintenance;

④ Good sealing performance;

⑤ Unrestricted by installation direction, the flow direction of the medium can be arbitrary;

⑥ No vibration, low noise.

5.2 Disadvantages

① The sealing surface is too large, resulting in excessive torque and lack of flexibility;

② Due to its own weight, the caliber size is limited;

③ In practical use, if large-sized valves are used, a reverse plug structure must be used, which can easily affect the sealing effect.