What is stainless steel gate valve?

A stainless steel gate valve is a type of gate valve which is made entirely of stainless steel material. A stainless steel gate valve is known for its high strength. With that high strength, these valves are suitable for high pressure and high-temperature applications. Stainless steel gate valves are also known to be made of tough bodies, more durable relative to other valves like ductile iron and cast iron valves. Stainless steel gate valves are also known for their corrosion resistance. A combination of corrosion resistance, high strength, and high toughness makes stainless steel gate valves very useful in all high-pressure applications. However, stainless steel gate valves are expensive because the machining of stainless steel is difficult to shape and takes a lot of energy. 

As the name suggests, stainless steel gate valves have a gate to control fluid flow. Stainless steel gate valves are used to control fluid flow by either closing or opening a gate. The process of opening or closing the gate is linear and the gate travels vertically upwards or downwards to open or close the valve respectively. Stainless steel gate valves are not used to regulate fluid flow because this causes its gate to get damaged easily. They are only used to close or open fluid flow. Stainless steel gate valve manufacturers design the valve such that the gate is perpendicular to the fluid flow. This design helps to reduce pressure loss. Stainless steel gate valves are bi-directional which makes them be installed in almost any direction. 

Components of a stainless steel gate valve

Handwheel/actuator 

The handwheel is a component used in manual stainless steel gate valves so that the valve operator can apply torque to open/close the valve. If the stainless steel gate valve is not manual, then it is operated by an actuator. An actuator is a device used in stainless steel gate valve to provide torque to open/close the valve. When the handwheel/actuator rotates, it helps to rotate the stem which is connected to the gate. Thus handwheel works with a stem to open/close the stainless steel gate valve. 

Valve body 

The valve body in a stainless steel gate valve is the main component used to house internal parts of the valve. This component of a stainless steel gate valve is made of stainless steel material. Stainless steel is known to be strong and tough and thus it helps to protect the valve against damage in times of very high pressure and high temperature since these valves are mostly used in high pressure and high-temperature applications. 

Bonnet 

This is a component used to cover the top of the stainless steel gate valve. The bonnet is placed on the top of the valve body and the two are connected using screws or bolts. The screws and bolts help to enhance a tight seal free from fluid leakage. Between screw and bolted connection, the bolted connection is mostly used since it can provide a tighter seal at very high pressure. Another method of connecting the bonnet and the valve body is by welding. The welded bonnet is superb as it provides zero leakage seal. The bonnet is also made of stainless steel material like the valve body which enhances valve strength.

Stem 

This is the component of a stainless steel gate valve which is connected to the handwheel and the gate/disc. The stem is meant to transmit torque from the handwheel through its threads to the gate. This torque is then converted to linear force which is used to raise or lower the gate to open or shut off fluid flow. The stem needs to be strong to enhance its ability to transmit torque to the gate. As such, the stem in a stainless steel gate valve is made of stainless steel to enhance its strength. 

Gate 

A gate in a stainless steel gate valve is an internal component that is tasked with blocking or opening fluid flow. The gate used in stainless steel gate valves can be either wedge or parallel-shaped. 

Seat 

The seat is an interior component of a stainless steel gate valve. Stainless steel gate valves are designed with two seats to ensure a tight seal with the gate. Seats used in stainless steel gate valves are integrated with the body or they are in terms of a seat ring. For seat rings in stainless steel gate valves, they are pressed or threaded into position and seal welded to the body. Integrated seats are valves made of the same material (stainless steel) as the body. Threaded in or pressed in seats allow for variations such as the seat can be made of different materials like PTFE instead of stainless steel. 

Backseat 

The backseat in a stainless steel gate valve is mounted in the bonnet. The backseat helps when the valve is opened fully so that the valve stem can “back seat” against the bonnet to help close off fluid pressure to the stuffing box. This helps to support the main seal on a stainless steel gate valve which is often a stuffing box. 

Trim 

Trim is a name given to the internal components of a stainless steel gate valve. The components under trim include gaskets, seat, seating surface, gate, gate surfaces, seals, stuffing box, and bushing. 

How does a stainless steel gate valve work? 

Stainless steel gate valves work by turning a handwheel to either open or close fully. When the handwheel is rotated, it rotates the stem. The stem is connected to the gate/disc. As the stem rotates through its threads it helps in raising or lowering the gate/disc. When this gate raises upwards it opens the valve allowing fluid to flow. When the gate is lowered it closes the fluid flow. Opening of stainless steel gate valve occurs when the handwheel is rotated anti-clockwise while closing occurs when you rotate the handwheel in a clockwise direction. 

Types of stainless steel gate valves 

Rising stem stainless steel gate valve 

This is a stainless steel gate valve in which the stem can move upwards when the valve is opening. Using this type of stainless steel valve, the valve operator can monitor the closing of the valve and thus easily know when the valve is fully closed/opened. This is because when the stainless steel gate valve is fully opened the stem will be exposed above the handwheel. 

Non-rising stem stainless steel gate valve 

This is a stainless steel gate valve that has a blind stem. The stem in this type of gate valve turns to close and open the valve but it does not move down or up as it turns. When the stem in a stainless steel gate valve rotates, it moves in or out of the valve. As such, the gate moves proportionately to close or open the valve. This type of stainless steel gate valve is used in several applications such as water supply, HVAC, gas, steam, and other utility applications. Non-rising stem stainless steel gate valves operate in small spaces relative to rising stem counterparts. 

Stainless steel knife gate valve 

This is a stainless steel gate valve design that reduces contact between various valve components. As such, this stainless steel knife gate valve helps to reduce the wear and tear of its parts in contact. Stainless steel knife gate valves are used for closing/opening services in applications with high levels of suspended solids. These valves are suitable for handling corrosive, slurry, viscous, and abrasive fluids. Stainless steel knife gate valve is easy to operate and it has low weight.

Stainless steel flexible wedge gate valve 

This is a stainless steel gate valve with a solid gate and a cut around the perimeter. The cut is of different sizes, shapes, and depths. When the cut is narrow and shallow it offers high strength but low flexibility. When the cut is wide and deep it reduces strength but enhances flexibility. Stainless steel flexible wedge gate valve design has enhanced seat alignment and better leakage tightness. These valves are used in different applications such as steam systems. Stainless steel flexible wedge gate valves allow the gate to bend when the seat is compressed during the thermal expansion in steam application. This helps to prevent thermal blindness. 

Stainless steel wedge gate valve 

This is a stainless steel gate valve that uses a wedge-shaped gate/disc. When a stainless steel wedge gate valve closes, it does so by pushing the gate to a taper machined on the valve body. The seal becomes better by combining the gate wedge shape of the body with a seat ring. When a stainless steel wedge gate valve opens fully, the back seat enters into a bonnet bush. For actuated valves, the stem does not keep wholly on the back seat to prevent damage. 

Stainless steel slab gate valve

This is a stainless steel gate valve that is unitary with a bore-size hole. When a stainless steel slab gate valve is opened, the holes are coincident with two seat rings. Such orientation in a stainless steel gate valve helps to produce even media flow with minimal turbulence which helps to reduce system pressure loss. Stainless steel slab gate valves need their seats clean. However, the gate cavity can at times be clogged with debris. As such, stainless steel slab gate valves are designed with a plug used for expelling the debris during maintenance. Stainless steel slab gate valves are suitable for transporting crude oil and natural gas liquids. 

Stainless steel parallel slide gate valve 

This is stainless steel gate valve that does not require a wedging action for proper seating. The stainless steel parallel slide gate valve closes using two individual gates connected via a disc holder. Springs in parallel move down to close the valve. When the port seals, the stem plug prevents additional movement. When the valve is open, the gate moves upwards, and the stem sits back. Stainless steel parallel slide gate valve close and open fully with limited movement. 

 

Applications of stainless steel gate valves 

• Stainless steel gate valves are is used in chemical plants. 
• Stainless steel gate valves are used in transporting crude oil and natural gas liquids. 
• These valves are used in pipeline industries. 
• Stainless steel gate valves are used in slurry applications. 
• They are used in liquids, gas, and steam applications. 
• Stainless steel gate valves are used in the control of hydrocarbons, feedwater, air, and fuel gas applications. 
• Stainless steel gate valves are used in high pressure and high-temperature applications. 
• Stainless steel gate valves are used in food processing and beverages applications. 
• These valves are used in the heating, ventilation, and air conditioning (HVAC) systems of buildings.

 

Advantages of stainless steel gate valves 

• Stainless steel gate valves have low small fluid resistance. 
• It requires a small force to open and close the valve. 
• Stainless steel gate valves are bi-directional. 
• Stainless steel gate valves are very strong for high-temperature and high-pressure applications. 
• Stainless steel gate valves can be manual or operated by an actuator. 
• Stainless steel gate valves get less erosion on the sealing surfaces by the flowing fluid when they are fully open relative to stop valves. 
• Stainless steel gate valves have a relatively simple body design for ease of repair, cleaning, and maintenance. 
• Stainless steel gate valves are of different varieties which makes them serve in many applications. 

 

Disadvantages of stainless steel gate valves 

• Stainless steel gate valves open and close slowly. 
• Stainless steel gate valves need a large area for operation, maintenance, and installation. This is because the stainless steel gate valve’s overall height and dimensions are large.  
• Stainless steel gate valves tend to make a lot of vibrations and noise while in use. 
• Stainless steel gate valves use two sealing surfaces which makes it difficult to process, grind, and do maintenance. 

 

Troubleshooting stainless steel gate valves 

Stainless steel gate valve leakage 

• Leakage past packing after installation. This could be due to the stainless steel gate valve having been subjected to high temperatures during shipment. It could also be due to normal packing wear. Tighten the packing or replaced it as necessary. 
• The stainless steel gate valve is leaking past its seat. Gate or seat is damaged. Replace the gate or seat as necessary. 
• Leakage past the seat. Worn out the seat or worn out O-ring seal. Replace the seat or the O-ring seal as necessary. 
•  Leakage in the seat. Foreign materials stuck in the gate. Remove the materials by flushing dirt through the valve. 
• Leakage through bolted connections. Check loose body to bonnet connections. Tighten the connections (bolts, nuts, screws) as necessary. 

The excess force needed to open/close the stainless steel gate valve 

• The valve needs lubrication. Check recommended lubrication by the stainless steel gate valve manufacturer. 
• Misalignment between gate and stem. Loosen the valve yoke and handwheel/actuator and check the stem and gate alignment. Correct any misalignment and then tighten again. 
• Stainless steel gate valve packing is very tight. Loosen the packing. Follow stainless steel gate valve manufacturer’s instructions in regards to tightening the packing. 

 

Summary 

A stainless steel gate valve is a gate valve that has most of its components made of stainless steel. Stainless steel is a metallic material known for its high strength and toughness. As such, gate valves made using stainless steel are of high strength and more durable. Stainless steel gate valves use a gate that is tasked to block or open fluid flow. These valves work by using a handwheel/actuator which transmits torque to the gate through a component known as a stem. When the actuator/handwheel is rotated anticlockwise it raises the gate and thus opens fluid flow. When the stainless steel gate valve is rotated clockwise, it lowers the gate and thus blocks fluid flow. Stainless steel gate valve manufacturers design the valves in a way that makes the gate and fluid flow perpendicular to each other in a straight flow path. This helps to reduce pressure drop in the valve since fluid flow in a straight line has a low-pressure drop. 

Stainless steel gate valves are used in different industries such as chemical industries, petroleum, water supply, food and beverage processing, HVAC systems, among others. Stainless steel gate valves are mostly preferred due to their superb features and advantages which are very strong, simple design, bi-directional capability, suitable for different actuators, small pressure drop, low fluid resistance, and ability to work at high temperature and high pressure.