Advantages and Disadvantages of Various Valves

Advantages and Disadvantages of Various Valves

● Gate Valve

A gate valve is a type of valve in which the closing element (the gate) moves perpendicular to the axis of the flow passage. It is primarily used in pipelines for on/off (isolation) service—i.e., fully open or fully closed—and is generally not suitable for flow regulation. Gate valves can be used in both low-temperature/low-pressure and high-temperature/high-pressure applications, depending on the materials selected. However, they are typically not recommended for pipelines conveying slurry or similar media.

Advantages:

① Low fluid resistance.

② Requires relatively low torque to open or close.

③ Suitable for bidirectional flow in looped pipeline systems—flow direction is unrestricted.

④ When fully open, the sealing surfaces are less eroded by the working medium compared to globe valves.

⑤ Simple body structure with good manufacturability.

⑥ Short face-to-face (structure) length.

Disadvantages:

① Large overall dimensions and high opening height require considerable installation space.

② During operation, the sealing surfaces experience relative sliding friction, leading to significant wear—especially prone to galling at high temperatures.

③ Most gate valves have two sealing surfaces, complicating machining, lapping, and maintenance.

④ Long opening/closing time.

● Butterfly Valve

A butterfly valve uses a disc-shaped closure member that rotates approximately 90° to open, close, or regulate fluid flow.

Advantages:

① Simple structure, compact size, light weight, and material-efficient—particularly suitable for large-diameter applications.

② Quick operation and low flow resistance.

③ Can handle media containing suspended solids; depending on seal material strength, it may also be used for powdery or granular media. Widely used for bidirectional on/off and throttling in ventilation/dust collection systems, as well as in metallurgy, light industry, power generation, and petrochemical gas and water pipelines.

Disadvantages:

① Limited flow control range: when opened to about 30%, flow already reaches over 95% of maximum.

② Due to structural and sealing material limitations, butterfly valves are unsuitable for high-temperature/high-pressure systems. Typical operating limits: ≤300°C and ≤PN40.

③ Sealing performance is inferior to ball and globe valves, so they are best used where tight shutoff is not critical.

● Ball Valve

Derived from the plug valve, a ball valve uses a spherical closure element that rotates 90° around the stem axis to open or close. It is primarily used for isolation, distribution, and flow direction change in pipelines. Ball valves with a V-port design also offer excellent flow regulation capabilities.

Advantages:

① Extremely low flow resistance (practically zero).

② Unlikely to jam during operation (even without lubrication), making it reliable for corrosive media and low-boiling-point liquids.

③ Capable of achieving bubble-tight sealing over a wide pressure and temperature range.

④ Fast opening/closing—some designs actuate in just 0.05–0.1 seconds, ideal for automated test benches. Operation is smooth with no hydraulic shock.

⑤ The spherical closure element self-aligns at end positions.

⑥ Provides reliable bidirectional sealing.

⑦ In fully open or closed positions, the ball and seat sealing surfaces are isolated from the medium, preventing erosion by high-velocity flow.

⑧ Compact and lightweight—considered the most suitable valve design for cryogenic service.

⑨ Symmetrical body design, especially welded bodies, effectively withstands pipeline stresses.

⑩ The closure element can withstand high differential pressure during shut-off.

⑪ Fully welded ball valves can be buried directly underground, protecting internal components from corrosion; service life can reach up to 30 years—making them ideal for oil and gas pipelines.

Disadvantages:

① The primary seat seal material is PTFE (polytetrafluoroethylene), which is chemically inert, has low friction, stable performance, wide temperature tolerance, and excellent sealing properties. However, its physical characteristics—such as high thermal expansion coefficient, susceptibility to cold flow, and poor thermal conductivity—require careful seat design. When PTFE hardens over time, sealing reliability degrades. Moreover, PTFE has a limited temperature rating: usable only below 180°C. Above this, the material ages rapidly. For long-term service, continuous use is typically limited to ≤120°C.

② Flow control performance is inferior to globe valves, especially in pneumatic or electric actuated versions.

● Globe Valve

In a globe valve, the closure member (disc or plug) moves along the centerline of the seat. The flow area through the seat changes in direct proportion to the disc travel. Due to its short stroke and highly reliable shut-off capability—and because flow area varies linearly with disc position—it is well-suited for flow regulation, throttling, and isolation.

Advantages:

① Lower friction between disc and seat during operation compared to gate valves, resulting in better wear resistance.

② Opening height is typically only about 1/4 of the seat bore—much smaller than gate valves.

③ Usually features only one sealing surface on the body and disc, simplifying manufacturing and maintenance.

④ Packing is often a mixture of asbestos and graphite, offering high-temperature resistance. Hence, globe valves are commonly used for steam service.

Disadvantages:

① Flow direction changes within the valve, resulting in higher minimum flow resistance compared to most other valve types.

② Longer stroke leads to slower opening speed compared to ball valves.

● Plug Valve

A plug valve uses a cylindrical or conical plug-shaped closure element that rotates 90° to align or block ports between the plug and body, thereby opening or closing the flow path. Its operating principle is similar to that of a ball valve—indeed, the ball valve evolved from the plug valve. Plug valves are primarily used in oilfield production and also in petrochemical applications.

● Safety Valve

A safety valve is a pressure-relief device installed on pressurized vessels, equipment, or pipelines to protect against overpressure. When system pressure exceeds the allowable limit, the valve automatically opens fully to discharge excess pressure and prevent further pressure rise. Once pressure drops back to the set reseating value, the valve automatically closes to ensure safe operation.

● Steam Trap (Condensate Drain Valve)

When steam, compressed air, or similar media are transported, condensate forms. To maintain system efficiency and safe operation, this unwanted and potentially harmful condensate must be promptly removed. Steam traps serve three key functions:

① Rapidly discharge generated condensate.

② Prevent live steam leakage.

③ Vent air and other non-condensable gases.

● Pressure Reducing Valve

A pressure reducing valve automatically reduces inlet pressure to a desired outlet pressure and maintains this reduced pressure steadily by utilizing the energy of the flowing medium itself.

● Check Valve (Non-Return Valve, Reflux Valve, Back Pressure Valve)

Check valves are automatic valves that open and close in response to the force generated by the flowing medium itself. They are used in piping systems primarily to:

Prevent backflow of fluid,

Avoid reverse rotation of pumps and driving motors,

Prevent unintended discharge from vessels.

They may also be used in auxiliary systems where pressure could exceed the main system pressure, allowing make-up flow. Main types include:

Swing check valves (pivot about a hinge or trunnion),

Lift check valves (move linearly along the flow axis).

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