What is the difference between a check valve and a globe valve?

When it comes to industrial valves, two commonly used types are check valves and globe valves. As a Check Valve supplier, I often encounter inquiries about the differences between these two valve types. In this blog post, I'll delve into the distinct features, functions, and applications of check valves and globe valves to help you make informed decisions for your specific needs.

Basic Definitions and Working Principles

Check Valve

A Check Valve is a type of valve that allows fluid (liquid or gas) to flow in only one direction. It operates automatically, relying on the pressure of the fluid to open and close. When the fluid flows in the forward direction with sufficient pressure, it pushes the valve disc open, allowing the fluid to pass through. Conversely, when the fluid tries to flow in the reverse direction, the pressure difference causes the valve disc to close, preventing backflow.

The simplicity of its design and operation makes check valves highly reliable and suitable for a wide range of applications where backflow prevention is crucial. For example, in a water supply system, a check valve can prevent water from flowing back into the main supply when the pressure in the distribution network drops.

Globe Valve

A globe valve, on the other hand, is designed to control the flow rate of fluid in a pipeline. It consists of a movable disc that can be adjusted to vary the size of the flow passage. The disc is connected to a stem, which is operated either manually or automatically (e.g., by an actuator). By turning the stem, the disc can be moved up or down, thereby increasing or decreasing the flow area and regulating the flow rate.

Globe valves are known for their excellent throttling capabilities, making them ideal for applications where precise flow control is required. For instance, in a chemical processing plant, a globe valve can be used to control the flow of reactants into a reactor, ensuring the correct reaction conditions are maintained.

Structural Differences

Check Valve

Check valves typically have a simple and compact structure. They usually consist of a valve body, a valve disc, and a seat. The valve disc is the movable part that opens and closes the valve. Depending on the type of check valve, the disc can be a swing disc, a lift disc, or a ball.

Swing check valves have a disc that pivots on a hinge. When the fluid flows in the forward direction, the disc swings open, and when the flow reverses, the disc swings back to close the valve. Lift check valves, on the other hand, have a disc that moves linearly along the valve axis. The disc is lifted off the seat by the forward flow and drops back onto the seat to prevent backflow. Ball check valves use a ball as the closing element, which is pushed away from the seat by the forward flow and returns to the seat to block reverse flow.

Globe Valve

Globe valves have a more complex structure compared to check valves. They consist of a valve body, a bonnet, a disc, a stem, and a seat. The valve body has an S-shaped or Z-shaped flow path, which causes the fluid to change direction as it passes through the valve. This design helps to reduce the velocity of the fluid and provides better flow control.

The disc of a globe valve is usually flat or convex and is attached to the stem. The stem extends through the bonnet and is connected to an operating mechanism, such as a handwheel or an actuator. By turning the handwheel or activating the actuator, the stem moves the disc up or down, adjusting the flow area between the disc and the seat.

Performance Characteristics

Flow Resistance

Check valves generally have lower flow resistance compared to globe valves. Since check valves are designed to allow fluid to flow freely in one direction, they have a relatively straight flow path with minimal obstruction. This results in less pressure drop across the valve, which is beneficial for applications where energy efficiency is important.

Globe valves, on the other hand, have a more tortuous flow path due to their S-shaped or Z-shaped design. This increases the flow resistance and causes a higher pressure drop across the valve. However, the higher pressure drop is often acceptable in applications where precise flow control is required, as the benefits of accurate flow regulation outweigh the energy loss.

Sealing Performance

Both check valves and globe valves can provide good sealing performance, but their sealing mechanisms are different. Check valves rely on the pressure of the fluid to keep the valve disc in contact with the seat, creating a seal to prevent backflow. In some cases, additional sealing elements, such as gaskets or O-rings, may be used to enhance the sealing performance.

Globe valves, on the other hand, achieve sealing by pressing the disc against the seat. The tightness of the seal depends on the design of the disc and seat, as well as the force applied by the stem. Globe valves can provide a very tight seal, making them suitable for applications where leakage must be minimized, such as in high-pressure or high-temperature systems.

Flow Control Capability

As mentioned earlier, check valves are primarily designed for one-way flow and do not provide any flow control capabilities. Once the valve is open, the fluid flows freely in the forward direction until the pressure drops or the flow reverses.

Globe valves, on the other hand, are specifically designed for flow control. They can be adjusted to vary the flow rate from fully open to fully closed, allowing for precise regulation of the fluid flow. This makes globe valves suitable for applications where the flow rate needs to be adjusted based on changing process conditions.

Applications

Check Valve

Check valves are widely used in various industries for backflow prevention. Some common applications include:

• Water and wastewater treatment: Check valves are used in water supply systems, sewage treatment plants, and pumping stations to prevent backflow of water and contaminants.
• Oil and gas industry: Check valves are used in pipelines, refineries, and offshore platforms to prevent backflow of oil, gas, and other fluids.
• Power generation: Check valves are used in steam turbines, boilers, and cooling systems to prevent backflow of steam, water, and other working fluids.
• Chemical processing: Check valves are used in chemical reactors, storage tanks, and pipelines to prevent backflow of chemicals and ensure the safety of the process.

Globe Valve

Globe valves are commonly used in applications where precise flow control is required. Some common applications include:

• Chemical processing: Globe valves are used in chemical reactors, distillation columns, and heat exchangers to control the flow of reactants, products, and heat transfer fluids.
• Power generation: Globe valves are used in steam turbines, boilers, and feedwater systems to control the flow of steam, water, and other working fluids. They are also used in control systems to regulate the pressure and temperature of the fluids.
• HVAC systems: Globe valves are used in heating, ventilation, and air conditioning systems to control the flow of hot and cold water, refrigerant, and air.
• Water and wastewater treatment: Globe valves are used in water treatment plants, pumping stations, and distribution networks to control the flow of water and chemicals.

Conclusion

In summary, check valves and globe valves are two distinct types of valves with different functions, structures, and applications. Check valves are designed for one-way flow and backflow prevention, while globe valves are designed for flow control. When choosing between a check valve and a globe valve, it is important to consider the specific requirements of your application, such as flow direction, flow rate control, pressure drop, and sealing performance.

As a Check Valve supplier, I can provide you with high-quality check valves that are suitable for a wide range of applications. If you have any questions or need assistance in selecting the right valve for your project, please feel free to contact me for a procurement discussion. I look forward to working with you to meet your valve needs.

References

• Valve Handbook, 4th Edition, by J. E. Tompkins
• Industrial Valves: Selection and Sizing, by William W. Lyons
• Valve Technology and Application, by C. S. Jog