Through Conduit Gate Valve

What is a through conduit gate valve? 

Through conduit gate valve is a type of gate valve which is designed such that fluid flows straight from the inlet to the outlet port. Through conduit gate valve manufacturers design these valves for on and off applications. If the through conduit gate valve is used for throttling applications it does not provide the required tightness. The design of a through conduit gate valve employs a full bore on the inlet and outlet ports which results in a coefficient of fluid flow resistance equal to the one on the piping system. This makes these valves suitable for use in long-distance transportation of fluids. Through conduit gate valves can be operated manually or by using actuators such as hydraulic, electric, or pneumatic actuators. Through conduit gate valve can have expanded gate or slab gate. The closing member is the gate. Through conduit gate valve manufacturers design the gate with a hole at the bottom. The gate is raised so that the hole is aligned with the valve ports to allow fluid flow. To close the valve, the gate is lowered to make the upper solid part of the gate block fluid flow. Through conduit gate valve manufacturers design these valves for use in different applications such as power plants, oil and gas refineries, and petrochemical and mining applications among others. 

Figure: Through conduit gate valve.

Components of through conduit gate valves 

Actuator

This is the component of a through conduit gate valve which provides the force to open or close the valve. The actuators that can be used in a through conduit gate valve are electric, pneumatic, or hydraulic actuators. Automatic through conduit gate valves are operated using actuators. If the through conduit gate valve is manual it is operated using a handwheel. The valve operator applies force on the handwheel to rotate the stem so that the valve gate can open/close the fluid flow. 

Valve body 

This is the component of the through conduit gate valve which acts as the pressure barrier. This is also the part that houses the internal parts of the valve. Through conduit gate valve manufacturers design the valve body using strong metallic materials to ensure the valve has high strength to withstand high pressure and high temperatures. The valve body contains the valve ports where the valve is connected to the piping system. 

Valve bonnet 

Bonnet is the component of a through conduit gate valve which is placed on the valve body to protect the valve stem and internal parts. The bonnet is connected to the valve body using bolts or screws. The bonnet connected using bolts has flanges with holes to house the bolts and nuts. The bolted bonnet is very strong and is mostly used for high-pressure applications. The bonnet is also made of the same metallic materials as the valve body. 

Stem 

The stem is the part of the through conduit gate valve which is used to connect the actuator to the gate. Through conduit gate valve manufacturer design the stem with threads that make the stem move upwards or downwards to open or close fluid flow. 

Gate 

The gate is the main component of a through conduit gate valve as it is responsible for blocking or allowing fluid flow. The gate is connected to the actuator or handwheel through the stem. The gate moves up and down in the conduit gate valve to open or close the fluid flow. 

Seats 

This is the component that used to provide sealing surfaces to the gate. Seats also helps to prevent fluid leakage in the valve. The seats can be made of soft or metallic materials. Soft materials include plastics or rubber. The soft material is used where the through conduit gate valve is meant for use in low-temperature fluid applications and or where there is corrosion. Metallic seats are used if the through conduit gate valve is expected to be used in high temperature and or corrosive applications. 

Gland packing 

This is a gasket seal placed between the bonnet and stem to prevent fluid leakage. Packing can be made of different materials depending on the application of the through conduit gate valve. Such materials include Teflon, fibrous materials, and elastomeric materials. 

Trim 

Trim refers to the internal parts of the through conduit gate valve which include seats, gate, seating surfaces, and O-rings. 

Figure: Components of a through conduit gate valve.

How does a through conduit gate valve work? 

A through conduit gate valve works by lowering or raising the gate to close or open fluid flow. This valve operates using an actuator for the automatic version or using a handwheel for manual version. The working principle for both the automatic and the manual through conduit gate valves is the same. To open a through conduit gate valve, the handwheel is rotated in the anticlockwise direction. This makes the stem rotate in the same direction as it moves linearly upwards. Movement of the stem upwards causes the gate which is connected to the stem to move upwards. As such, the gate bore raises upwards and it becomes collinear with the valve port which makes fluid flow through the valve. This makes fluid flow straight through the valve with low-pressure drop. To close a through conduit gate valve, the handwheel/actuator is rotated in the clockwise direction. This makes the stem rotate in the same direction making the stem and gate move linearly downwards. As such, the top solid part of the gate moves downward to block fluid flow. 

Types of through conduit gate valves

Rising stem through a conduit gate valve 

This is the through conduit gate valve which is made with a rising stem. A rising stem means that the stem raises above the handwheel when the valve is open. Through conduit gate valve manufacturers design these valves so that they can open by rotating the handwheel which makes the stem move upwards so that the gate bore can be raised. As the stem is being rotated it keeps raising which helps the valve operator to easily know that the direction of rotation is the right one. When the through conduit gate valve is being closed, the stem keeps moving downwards which helps to tell the valve operator that he is trying to close the valve. Rising stem through conduit gate valves is easy to use because one can easily know when opening or closing fluid flow. However, these valves occupy a lot of space and thus they are used where space is not limited. 

Figure: Rising stem through a conduit gate valve.

Non-rising stem through a conduit gate valve 

Non-rising stem through conduit gate valve is a valve in which the stem does not move up and down as it rotates to open or close the fluid flow. This type of valve operates by turning the stem to move in or out of the valve which moves the gate up or down to open or close the fluid flow respectively. Non-rising stem through conduit gate valve manufacturers designs these valves with opening and closing indicators to help the valve operator to know when closing or when opening the valve. Without these indicators, the valve operator can easily damage the valve without knowing. This type of through conduit gate valve occupies a smaller space relative to the rising stem counterpart. 

Figure: Non-rising stem through conduit gate valve.

Through conduit gate valve with a slab gate 

This is a through conduit gate valve which uses a slab gate. The construction of this type of valve entails use of one seat which moves up and down between two seat rings. This design of a gate sliding between two seats makes a through conduit gate valve suitable for use in media with suspended particles. Through conduit gate valve manufacturers design these valves with self-positioning sealing surfaces which makes them safe from thermal deformation of the valve body. When the through conduit gate valve with slab gate is fully opened, the gate bore is linear and smooth, which reduces the coefficient of fluid flow resistance and thus no pressure loss. 

Through conduit gate valve with wedge gate 

This is a through conduit gate valve which uses a tapered gate. This type of valve closes by pushing the wedge gate to a taper in the body. A perfect seal is created in this through conduit gate valve by a combination of the seat ring and the wedge shape of the body. Through conduit gate valves with wedge gate use metal seats which makes them suitable for use in high pressure and high-temperature applications. 

Applications of through conduit gate valves 

• Used in mining industries. 
• These valves are used in gas and oil refineries. 
• Petrochemical applications.
• Pharmaceutical applications. 
• Food and beverages industries. 
• These valves are used in the water supply. 
• Steam power plants. 
• Paper and pulp industries. 

Advantages of through conduit gate valves 

• Versatile for use in different industrial applications. 
• Durable since they can be repaired for reuse.
• This valve can be cleaned which makes them suitable for applications that demand high levels of hygiene such as foods and pharmaceuticals. 
• They are free from fluid leakage 
• These valves are made of strong metallic materials which makes them strong for high pressure and high-temperature applications. 
• Low-pressure drop which makes them energy efficient. 

Disadvantages of through conduit gate valves 

• They operate slowly unlike ball valve. 
• They are not suitable for use in throttling applications. 

Troubleshooting through conduit gate valves 

Leakage through the stem packing 

• The packing is worn out. Replace the packing. 
• The packing is loose. Tighten the packing. 

Leakage through the seats 

• Worn out seats. Replace the seats.
• The seat is damaged. Replace the seat. 
• The O-ring is worn out. Replace the O-ring. 

Leakage through the bonnet 

• Worn out or damaged gasket. Replace the gasket. 
• Loose bolts connection. Tighten the bolts. 
• Misaligned gasket. Align the gasket properly.

Through conduit gate valve needs a lot of force to open/close 

• The valve is not well lubricated. Check the through conduit gate valve manufacturer’s instructions regarding lubrication. 
• Stem packing is too tight. Loosen the stem packing slightly. If the packing is very loose it will cause leakage. 
• Foreign materials in the valve. Open the valve and clean any foreign materials. 

Summary 

Through conduit gate valve is a type of gate valve which is meant for on and off fluid flow applications. When the valve is used for throttling applications it does not provide effective tightness. Through conduit gate valve manufacturers design the valve with a full bore at the inlet and outlet ports to allow fluid flow straight from the pipeline. This design helps to reduce pressure drop and thus enhances pumping efficiency. As such, through conduit gate valves are suitable for use in long-distance transportation due to very low-pressure loss. These valves are operated manually using a handwheel or they are operated by the use of automatic actuators. The various types of conduit gate valves include rising stem through conduit gate valves, non-rising stem through conduit gate valves, through conduit gate valve with slab gate, and through conduit gate valve with wedge gate among others. These valves are used in different industrial applications such as mining, pharmaceuticals, foods and beverages, water supply, steam power plants, petrochemicals, and paper industries among others. The advantages of using a through conduit gate valves are very durable, useful in different applications, high strength, zero leakage, low-pressure drop, and high levels of hygiene. However, these valves are not suitable for throttling fluid flow, and they operate slowly unlike other valves like ball valves.