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What is a stainless steel globe valve?

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Stainless steel globe valve is a type of globe valve that is made of stainless steel. This type of valve is meant for throttling, opening or closing fluid flow. The stainless steel globe valve manufacturers mostly use stainless steel material to make the body, bonnet, disc and stem. This helps to make the valve very strong and resistant to impact damage as well as able to withstand high pressure and high temperatures. Other parts of the stainless steel globe valves such as seats can be made of other materials such as plastic and or rubber. Stainless steel globe valves can be either soft seated or metallic seated valves. Metallic seated valves are the ones in which the seat is made of soft material like rubber and or plastic. Metallic seated stainless steel globe valves are the ones in which the seat is made of metallic material like stainless steel. Stainless steel globe valves use linear motion when closing or opening fluid flow. The closing member of a stainless steel globe valve is known as a disc. The disc fits on the seat to block fluid flow when the valve is closed. Stainless steel globe valve manufacturers design these valves to be either manual or automatic.

Figure: Stainless steel globe valve.

How does a stainless steel globe valve work?

A stainless steel globe valve is a type of unidirectional valve that is fluid flow can take place in one direction only. A stainless steel globe valve works by using a handwheel or actuator. The handwheel is used for manual stainless steel globe valves so that the valve operator can apply force on the handwheel to turn the stem. The stem connects the handwheel and the valve disc. The stainless steel globe valve with an actuator is automatic. The actuator is used to determine when the stainless steel globe valve opens and closes as well as to provide the force needed to open or close the fluid flow. To open a stainless steel globe valve, the handwheel is rotated in the anticlockwise direction. This makes the stem that is connected to the disc move in the same anticlockwise direction. As the stem rotates, it moves linearly upwards. This makes the disc move upwards which then opens fluid flow. To close a stainless steel globe valve, the handwheel is rotated in the clockwise direction. This makes the stem start rotating in the same direction as it moves linearly downwards until it closes fluid flow. To throttle the valve, the handwheel is turned slightly in the anticlockwise direction to make the disc partially open fluid flow.

Figure: Working of a stainless steel globe valve.

Stainless steel globe valve manufacturers employ two designs of this valve. The two designs are:

Disc closing opposite to the direction of fluid flow. In this design of a stainless steel globe valve, the kinetic energy of the fluid assists in opening the fluid flow. However, this design of a stainless steel globe valve becomes a challenge when closing the valve. As such, this design is suitable for use when the stainless steel globe valve is needed for rapid opening applications.
The other design is the one in which the disc closes in the same direction as the fluid flow. In this design of a stainless steel globe valve the kinetic energy of the fluid assists in closing the disc quickly. However, a valve with this design becomes hard to open. As such, stainless steel globe valve manufacturer recommend this design where the valves are needed for quick closing of the fluid flow.

Figure: Designs of the stainless steel globe valves (left: disc closes against fluid flow, right: disc closes in the same direction to the fluid flow).

Types of stainless steel globe valves

T-pattern stainless steel globe valve

This is a stainless steel globe valve that has a T-shaped body. This valve is also known as the standard pattern stainless steel globe valve. This is the most common type of stainless steel globe valve. Stainless steel globe valve manufacturers design these valves with a horizontal setting of the valve seat so that the disc and the stem can move perpendicular to the direction of fluid flow. This type of stainless steel globe valve has a flow passage that has twisting and which is known for causing fluid flow resistance in all T pattern valves. The design of a T-pattern globe valve has a high-pressure drop relative to other valves. As such, stainless steel globe valve manufacturers recommend these valves for use in harsh throttling applications and in applications where pressure loss is not a major technical concern.

Figure: T-pattern stainless steel globe valve.

Y-pattern stainless steel globe valve

This type of stainless steel globe valve is also known as oblique pattern stainless steel globe valve. Stainless steel globe valve manufacturers design this valve such that the stem and seat are oriented at an angle of 45^o degrees to the pipeline axis. Such orientation helps to provide straight fluid flow when the valve is fully opened and which results to low pressured drop unlike in the T-pattern stainless steel globe valve. This is the valve that is used as the best alternative to the T-pattern stainless steel globe valve in case of a high-pressure drop. This is because this Y-pattern globe valve has a low-pressure drop.

Figure: Y-pattern stainless steel globe valve.

Angle pattern stainless globe valve

This is a type of stainless steel globe valve in which the inlet and outlet ports are positioned at 90^o degrees. As such, the fluid flow occurs at 90^o degrees. Angle pattern stainless steel globe valves have a lower coefficient of fluid flow relative to the Y pattern stainless steel globe valves. These valves are used in applications that have pulsating flow since they can handle the slugging effect of that flow. When an angle pattern stainless steel globe valve is mounted near a pipe bend it helps to reduce fluid flow resistance, unlike the T-pattern valve. Also, when the angle globe valve is mounted near a pipe bend it helps to reduce the number of pipe joints.

Figure: Angle pattern stainless steel globe valve.

Threaded bonnet stainless steel globe valve

This is a stainless steel globe valve in which the bonnet and the body are connected using threads. Stainless steel globe valve manufacturers design the body with male threads and the bonnet with female threads or vice versa. This type of stainless steel globe valve is the least expensive and it employs a simple design. The threaded bonnet stainless steel globe valve is suitable for use in low pressure and low-cost applications.

Figure: Threaded bonnet stainless steel globe valve.

Flanged bonnet stainless steel globe valve

This is a stainless steel globe valve in which the bonnet and the body have flanged ends. Stainless steel globe valve manufacturers design these valves with flanged ends so that the bonnet and body can be connected using several bolts to guarantee a very tight seal. Flanged bonnet stainless steel globe valves are easier to assemble and install. These flange globe valves are suitable for use in high pressure and high-temperature applications such as steam power generation plants. The flanged ends and bolts result in zero leakage connection. However, the use of the bolts and flanges end up making these valves heavier relative to other valves.

Figure: Flanged bonnet stainless steel globe valve.

Welded bonnet stainless steel globe valve

This is the type of stainless steel globe valve in which the bonnet and the body are connected using welding. This type of stainless steel globe valve is used where the fluid to be conveyed is very hazardous and or where the valve repair and maintenance is not desired. Such applications include the transfer of petroleum products and hazardous fluids like acids. The welding method of connection ensures that there is zero leakage of such hazardous fluids. The welded bonnet stainless steel globe valve undergoes a non-destructive test on the weld perimeter to ensure that there are no defects emanating from the weld which may cause fluid leakage. Welded stainless steel globe valves are suitable for use in high-pressure and high-temperature applications.

Figure: Welded stainless steel globe valve.

Applications of stainless steel globe valves

Stainless steel globe valves are used in oil and gas refinery systems.
These valves are used in steam power generation plants.
They are used in chemical industries.
Stainless steel globe valves are used in heating ventilation and air conditioning systems.
These valves are used in water supply systems.
They are used in water cooling systems and heater drains.
They are used in lubrication systems.

Advantages of stainless steel globe valves

Stainless globe valves have good shut-off capabilities.
These valves are durable because they can be serviced whenever they break and then be reused again and again.
Stainless steel globe valves are versatile because they can serve in different industrial applications.
These valves work well even where there are frequent operations.
They operate fast relative to other valves like gate valves.
Stainless steel globe valves can be operated either manually or they can be automatic.
They can be used in high temperatures and high-pressure applications.
They are resistant to corrosion.

Disadvantages of stainless steel globe valves

Stainless steel globe valves have a high-pressure drop.
They tend to make more noise, unlike other valves like ball valve and plug valve.
They are heavy relative to other valves.

Troubleshooting stainless steel globe valves

Leakage through stem packing

Loose packing nut. Tighten packing nut with torque level recommended by the stainless steel globe valve manufacturer.
Insufficient packing rings. Add more pieces of packing rings.
Worn out or damaged packing. Replace the packing.

Leakage through seating surfaces

Damaged seats. Replace the seats.
Foreign materials on the seats. Disassemble the valve according to the stainless steel globe valve manufacturer’s instructions and remove any foreign materials.

Leakage through the body-bonnet connection

Loose connection. Tighten the body-bonnet connecting elements like bolts and screws to have sufficient torque as recommended by the stainless steel globe valve manufacturer. Remember excessive torque on the connection can cause damage to the gasket and thus more leakage.
Worn out or damaged gasket. Replace the gasket.

The stainless steel globe valve is hard to open or close

The valve stem is bent. Replace or rectify the bend.
Valve packing is over tightened. Loosen the packing nut slightly. Remember loose packing will cause fluid leakage.
Dirt on the stem. Clean dirt.
Worn stem nut threads. Replace the stem nut.

Summary

Stainless steel globe valve is a type of globe valve in which the body, bonnet, and stem made of stainless steel material. This type of valve is used for throttling, opening and closing fluid flow. This type of valve is suitable for use in applications that have high pressure and high temperature. This is because the stainless steel material has a high melting point of around 1400 ^oC which makes it withstand high temperatures in most industrial applications. Stainless steel globe valve manufacturers design these valves with either soft seats or metallic seats. Soft seats are used where the valve is meant for use in low-temperature applications of less than 60 ^oC while the metallic seats are used where the valve is to be used in high-temperature applications of above 60 ^oC. Stainless steel globe valves are operated either manually or are actuated using actuators like hydraulic, pneumatic, or electric. There are various types of stainless steel globe valves which include threaded bonnet stainless steel globe valve, flanged bonnet stainless steel globe valve, welded bonnet stainless steel globe valve, T-pattern stainless steel globe valve, Y-pattern stainless steel globe valve, and angle pattern stainless steel globe valve. These valves are used in different applications such as steam power generation, oil and gas refineries, water treatment, chemical industries, lubrication systems, and HVAC systems among others. The advantages of using stainless steel globe valves are corrosion resistant, durable, versatile, and free from leakage, good shut-off capabilities, and they operate fast.