There are
many types of valves, each with its own advantages and disadvantages. Below is an analysis of six major valves, including gate valves, butterfly valves, ball valves, check valve, globe valves, and plug valves. We hope this will be helpful to you.
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gate valve is the valve where the closing member (gate) moves perpendicular to the axis of the pipeline. It is mainly used to cut off the medium, i.e., for fully open or fully closed operation. Generally, gate valves are not used for flow regulation. They can be applied to low-temperature and low-pressure systems as well as high-temperature and high-pressure systems, but are typically not used in pipelines conveying media such as mud.
Advantages:
① Low fluid resistance;
② Requires less torque to open and close;
③ Can be used in loop pipelines where the medium flows in both directions, i.e., the flow direction of the medium is not restricted;
④ When fully open, the sealing surface is less eroded by the working medium compared to globe valves;
⑤ Simple in structure and good in manufacturability;
⑥ Short structural length.
Disadvantages:
① Large external dimensions and opening height, requiring more installation space;
② During opening and closing, the sealing surfaces rub against each other, causing significant wear, and are prone to galling at high temperatures;
③ Most gate valves have two sealing surfaces, increasing the difficulty of processing, grinding, and maintenance;
④ Long opening and closing time.
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butterfly valve is a valve where a disc-shaped closing member rotates approximately 90° to open, close, and regulate the fluid.
Advantages:
① Simple structure, small volume, light weight, and material-saving;
② Quick opening and closing with low flow resistance;
③ Can be used for media with suspended solid particles, and depending on the strength of the sealing surface, it can also be used for powdery and granular media. Suitable for two-way opening/closing and regulation of ventilation and dust removal pipelines, widely used in gas pipelines and waterways in metallurgy, light industry, power, petrochemical systems, etc.
Disadvantages:
① Narrow flow regulation range – when opened to 30%, the flow rate is already over 95%;
② Due to structural and sealing material limitations, it is not suitable for high-temperature and high-pressure pipeline systems. Generally, the working temperature is below 300°C, and the pressure rating is below PN40;
③ Relatively poor sealing performance compared to ball valves and globe valves, so it is used in places with less strict sealing requirements.
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ball valve evolved from a plug valve, with a spherical closing member that rotates 90° around the valve stem axis to achieve opening and closing. Ball valves are mainly used in pipelines to cut off, distribute, and change the flow direction of the medium. Ball valves designed with a V-shaped opening also have good flow regulation capabilities.
Advantages:
① Extremely low flow resistance (practically zero);
② Reliably applicable to corrosive media and low-boiling liquids as it does not get stuck (when used without lubricant);
③ Achieves complete sealing over a wide pressure and temperature range;
④ Enables fast opening and closing – some structures can open/close in only 0.05–0.1 seconds, making them suitable for automated systems in test benches. No impact during fast operation;
⑤ The spherical closing member automatically positions at the extreme positions;
⑥ Reliable double-sided sealing for the working medium;
⑦ When fully open or closed, the sealing surfaces of the ball and seat are isolated from the medium, so high-velocity media passing through the valve does not erode the sealing surfaces;
⑧ Compact structure and light weight, making it a reasonable valve structure for low-temperature medium systems;
⑨ Symmetrical valve body, especially welded structures, can well withstand stresses from the pipeline;
⑩ The closing member can withstand high pressure differences during closing.
⑪ Fully welded ball valves can be directly buried underground, protecting internal components from corrosion, with a maximum service life of 30 years. They are ideal for oil and natural gas pipelines.
Disadvantages:
① The main seat sealing material for ball valves is polytetrafluoroethylene (PTFE), which is inert to almost all chemicals and has comprehensive properties such as low friction coefficient, stable performance, resistance to aging, wide temperature range, and good sealing. However, PTFE's physical properties – including high expansion coefficient, sensitivity to cold flow, and poor thermal conductivity – require the seat seal design to accommodate these characteristics. Therefore, when the sealing material hardens, sealing reliability is compromised. Additionally, PTFE has a low temperature rating and can only be used below 180°C. Beyond this temperature, the sealing material ages. For long-term use, it is generally limited to 120°C.
② Its regulation performance is inferior to that of globe valves, especially for pneumatic (or electric) valves.
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check valve, also known as a non-return valve or one-way valve, is designed to allow fluid (liquid or gas) to flow in one direction only, preventing backflow.
Advantages:
① The primary function of a check valve is to prevent media backflow, ensuring that fluids in the specified direction and avoiding equipment damage, process abnormalities, and other issues caused by backflow.
② Check valves have a relatively simple design, making installation and maintenance more convenient.
③ They are suitable for various fluid media, such as gases and liquids, and are widely used in both industrial and civil applications.
④ By preventing backflow, check valves reduce pressure fluctuations inside pipelines, extend pipeline service life, and lower maintenance frequency.
⑤ In water supply systems, check valves can reduce the risk of water quality contamination and safeguard household water safety.
⑥ By preventing reverse flow, they reduce waste and losses, offering energy-saving effects.
Disadvantages:
① Check valves generate significant resistance when closing, which may affect fluid flow efficiency.
② In some cases, the sealing performance of check valves may be less than ideal, leading to fluid leakage.
5. Globe Valve.
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globe valve is a type of valve where the closing member (disc) moves along the centerline of the seat. Due to this movement pattern, the change in the seat opening is directly proportional to the disc stroke. As the valve stem has a relatively short opening/closing stroke and provides a reliable shut-off function, and the seat opening is proportional to the disc stroke, this valve is highly suitable for flow regulation. Therefore, this type of valve is ideal for cutting off, regulating, and throttling.
Advantages:
① During opening and closing, the friction between the disc and the valve body sealing surface is smaller than that of gate valves, making it more wear-resistant;
② The opening height is generally only 1/4 of the seat channel, much smaller than that of gate valves;
③ Usually has only one sealing surface on the valve body and disc, making it better in manufacturability and easier to maintain;
④ The packing is typically a mixture of asbestos and graphite, giving it a high temperature rating. Globe valves are commonly used for steam systems.
Disadvantages:
① Due to the change in the medium's flow direction through the valve, the globe valve has a higher minimum flow resistance than most other valve types;
② Slower opening speed compared to ball valves due to the longer stroke.
6. Plug Valve.
A plug valve is a rotary valve with a plunger-shaped closing member that opens or closes by rotating 90° to align or disconnect the channels on the plug and the valve body. Also known as a cock or stopcock, the plug can be cylindrical or conical. It comes in various types, such as straight-through, three-way, and four-way. Its principle is basically similar to that of a ball valve.
Advantages:
① Suitable for frequent operation, with quick and effortless opening/closing;
② Low fluid resistance;
③ Simple structure, relatively small size, light weight, and easy to maintain;
④ Good sealing performance;
⑤ Unaffected by installation direction – the medium can flow in any direction;
⑥ No vibration and low noise.
Disadvantages:
①Large sealing surface area, resulting in high torque and reduced flexibility;
② Limited by body weight, the valve size is restricted;
③In practical use, large-diameter valves must use a backseat plug structure, which easily affects sealing performance.
