1. What is the working mechanism of globe valves?

The main engineering principle behind the globe valve lies in its design. A globe valve consists of a body, seat, stem, disc, sealing ring and so on. The disc inside the valve is movable whereas the seat is stationary and is in a spherical body. 

The disc is attached to a stem that is operated by a handwheel or an actuator to move the disc up and down so that flow is under control. The body of the valve is spherical, hence the name “shut-off valve”, and the inlet and outlet are located on opposite sides, allowing for an effective change in flow direction. When a handwheel or actuator is turned to open the valve, the valve disc is lifted, allowing fluid to pass through the annular space between the disc and the seat.

Conversely, when the valve is closed, the valve disc is lowered to shut off the flow. This design allows for precise flow control and throttling, making globe valves suitable for applications that require precise flow regulation.

Key engineering principles that are at work in globe valves include the use of linear motion to control flow, the shape of the valve body to facilitate directional changes, and the precise alignment of the valve disc and seat for tight closure at closing.

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2. What is the application of globe valves?

●High-temperature or high-pressure media pipeline or device is appropriate to use the globe valves, such as thermal power plants, nuclear power plants, petrochemical systems, high-temperature and high-pressure pipelines.

●Pipelines that are not strict with the flow resistance requirement, that is, the pressure loss is not considered a place where you can prioritize using of globe valves.

●Globe valves are good choices for food processing, pharmaceutical, petrochemical, chemical industries, used to control the flow of steam, gas, and liquid.

●Flow regulation or pressure regulation, but the requirements of the regulation accuracy are not high, and the pipeline diameter is relatively small, such as the nominal size of the pipeline is not greater than DN50, so it is appropriate to use throttling type globe valves.

●In the chemical sector, globe valves are essential for managing the flow of diverse fluids such as acids, alkalis, and solvents. They are extensively utilized in chemical processing plants to control chemical flow in pipelines, reactors, and storage tanks. Globe valves also regulate steam and gas flows in chemical processes.

●Globes valves can be used in city construction in the water supply, heating projects and the nominal size of the smaller pipeline.

●Globe valves are used in HVAC systems to control and balance the flow of steam, hot and cold water, or glycol mixtures.

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3. What should be considered when choosing the right globe valves?

●Understanding the application area

Fluid characteristics: Identify the type of fluid liquid, gas, corrosive, toxic, etc) the valve will handle.

Pressure and temperature: Determine the operating pressure and temperature range. This information is crucial for selecting a valve that can withstand the system’s conditions without failure.

Flow requirements: Consider the flow rate and the necessity for flow regulation or throttling.

●Select the appropriate valve size

Pipe size: The valve size should correspond to the pipe size in the system to ensure proper fit and avoid unnecessary pressure drops.

Cv value: Calculate the valve's flow coefficient (Cv required based on the flow rate,fluid density, and the pressure drop across the valve.

●Selection of valve body material

Compatibility: The valve material must be compatible with the fluid to prevent corrosion. Common materials include carbon steel, stainless steel, bronze and special alloys for corrosive applications

●Determine the valve end connection

Connection type: Globe valves are available with flanged, threaded, butt-welded and welded end connections. The choice depends on the piping system design, pressure rating, and ease of installation or maintenance.

Standards compliance: Ensure that the selected end connections comply with industry standards, such as ASME B16.5 for flanged connections, to ensure piping system compatibility and integrity.

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4. How could you maintain globe valves?

Regular maintenance is essential to extend the globe valve lifespan and ensure optimal performance. Maintenance tasks include:

Inspection: Conduct regular visual inspections of the valve for signs of wear, corrosion, or leakage. Check the valve’s packing gland for any leaks and adjust or replace the packing material as needed. Check the motion of the stem, which is often the threaded piece exposed to the elements and can easily become dirty or gritty. Lubricate it often to ensure smooth function of the valve. If any of the external hardware (nuts, washers, bolts) show signs of wear, replace them. Tighten the hardware during regular maintenance. Those components tend to loosen with frequent use of the valve. Clean the outer surfaces with a cleaning solution and scrape away any buildup. Ensure that there’s no grease on the handwheel to prevent it from slipping when turned. Lubrication: Regularly lubricate the valve stem, threads, and moving parts according to the manufacturer’s recommendations. Use a lubricant compatible with the valve’s material and operating conditions.

Cleaning: Keep the valve and surrounding area clean and free of debris to prevent contamination and ensure smooth operation.

Replacement parts: Use only manufacturer-recommended replacement parts for repairs to maintain the valve’s performance and safety standards.

Scheduled maintenance: Follow a regular maintenance schedule based on the manufacturer’s recommendations and the valve’s operating conditions.

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5. What are the advantages of globe valves?

The vertical movement of the valve disc and seat promotes good throttling of the globe valve. When the valve is closed, the space between the valve disc and seat decreases over a short distance, contributing to good flow regulation.

Globe valves are simpler in construction than gate valves. Globe valves have one sealing surface and a minimum sealing area, which reduces construction costs and saves on production materials.

It is easy to maintain globe valves and the valve saves cost and material, so it provides better production process.

There is little or no sliding between the seat and disc surfaces, which reduces friction between the two surfaces. As a result, the sealing surfaces are subjected to less wear over a long period of time and provide good sealing operation.

In addition, globe valves have a longer service life than some valves because the seat and disc are less susceptible to wear.

Installation of globe valves does not require much height as the valves have a thicker construction.

Globe valves have different patterns and types so you have a wider selection of suitable valves. Globe valves have less seat leakage than gate valves.

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