What is a resilient wedge gate valve?
natural gas control valve
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A resilient wedge gate valve is a type of valve that has a disc insert in the shape of a wedge that sits between two inclined seats. This type of gate valve uses a wedge-shaped disc constructed from strong metallic material and lined with elastomer materials such as. Resilient wedge gate valve manufacturers design these valves to operate either manually or automatically using actuators. The wedged disc travels perpendicularly to the direction of fluid flow when the handwheel is rotated. When the handwheel rotates in the anticlockwise direction, the wedge clears the flow path thus opening the fluid flow and when rotated in the clockwise direction the wedge cuts through the fluid flow to stop the stream. Resilient wedge gate valves are used for on/off services in turbulent and high flow applications. Like any other type of gate valve, this kind of valve can only be used while fully open or closed and cannot be used as an adjusting or throttling valve.
Figure: A resilient wedge gate valve.
How does a resilient wedge gate valve work?
The operation mechanism of a resilient wedge gate valve is very simple and it involves manual rotation of a handwheel to open or close the valve for manually operated valves. For automatic resilient gate valves, the force to open or close the valve is provided by an actuator. The direction of opening the valve is usually indicated by an arrow cast on the handwheel or nut of the valve. When the handwheel is turned in the clockwise direction, the wedge gate fits into the space between the seats, cuts through the flow, and stops the stream flow. When the handwheel is turned in the anti-clockwise direction, the wedge gate frees the flow path thus opening the fluid flow. A resilient wedge gate valve is operated in either a fully open or closed position. The operation of the valve in an intermediate position can lead to increased wear of the gate and seat, hence, reducing the service life of the valve. Resilient wedge gate valve manufacturers recommend consideration of several factors during installation and while operating the valve. Before installation, care should be taken to ensure that the valve is suitable for the service conditions in terms of pressure, temperature, and flow media.
Parts of a resilient gate wedge valve
Handwheel/actuator
The handwheel is the component of a manual resilient wedge gate valve that is used to carefully open or close the valve. Resilient wedge gate valve manufacturers also design automatic valves that are operated using actuators. The actuator provides force to open and close the valve when necessary. With automatic wedge gate valves, there is no need for a valve operator.
Body
This is the component of a resilient wedge gate valve used to contain internal parts of the valve. Resilient wedge gate valve manufacturers design the body with a strong metallic material to give it high mechanical strength which helps to withstand high pressure and high temperatures.
Bonnet
The bonnet is the part that covers the stem and its sealing parts. The bonnet of a resilient wedge gate valve is mounted onto the body using bolts or screws to facilitate easier disassembling and repair of the internal components of the valve.
Stem
The stem is a threaded component a resilient wedge gate valve whose function is to raise or lower the disc or gate to open or close the fluid flow. The stem connects the actuator/handwheel to the gate to facilitate the transfer of closing/opening torque to the gate or disc.
Wedge disc/gate
The function of the wedge disc or wedge gate is to open or close the flow when the handwheel is rotated.
Seats
The seats are inclined to accommodate the wedge gate and to create a tight seal when the valve slides into position to cut the flow.
Stuffing box
The stuffing box contains the packing material which creates a tight seal to prevent leakage of fluid between the turning stem and bonnet.
Gasket
The gasket is a mechanical seal that serves to prevent leakage between end connections such as between bonnet and body and body and the piping system.
Figure: Diagram showing parts of a resilient wedge gate valve.
Types of resilient wedge gate valve
Automatic resilient wedge gate valve
This is a resilient wedge gate valve that is automatic. This means that the valve does not need a valve operator to open or close the fluid flow. Automatic resilient wedge gate valves are designed with sensors that determine when to open or close the fluid flow. This helps to reduce the need for a valve operator. Automatic resilient wedge gate valves use actuators such as pneumatic, electric, and hydraulic to provide the torque needed to open and close the fluid flow. Automatic resilient wedge gate valves enhance safety as it does not need a valve operator.
Figure: Automatic resilient wedge gate valve.
Manual resilient wedge gate valve
This is the resilient wedge gate valve which is operated by a valve operator using the handwheel. The valve operator is responsible for providing the force needed to open or close the fluid flow. Manual resilient wedge gate valves tend to be tedious to the valve operator because they need to be turned several times before closing/opening. Also, manual resilient wedge gate valves can cause injury to the valve operator in case of malfunction. However, manual resilient wedge gate valves are cheaper compared to the automatic types. In addition, these valves can be made automatic as the user needs to consult experts or a resilient wedge gate valve manufacturer for the automation system.
Figure: manual resilient wedge gate valve.
Rising step resilient wedge gate valve
In a rising stem resilient wedge valve, the stem nut is positioned on the cover, and the stem rises above the handwheel when the valve is closed. When the handwheel is turned to open or close the resilient wedge gate valve, the stem nut pushes the stem up and down. At the same time, the flaps mounted to the stem are opened or closed by lifting or lowering the thread between the handwheel and the thread. In both closed and open valve positions, the stem of this type of gate valve can be seen from the outside. This design is widely preferred because it offers several benefits such as easy lubrication of stem thread, easy operation, and uninterrupted flow when the valve is in the fully open position. Also, resilient wedge gate valve manufacturers design these valves to help the valve operator easily know when opening or closing the valve by monitoring the movement of the stem. However, rising stem resilient wedge gate valves occupy a lot of space and they are preferred for use where space is not limited.
Figure: Rising stem resilient wedge gate valve.
Non-rising stem resilient wedge gate valve
A non-rising stem resilient wedge gate valve has a rotary stem that turns to open or close the gate when torque is applied on the handwheel, but the lifting screw does not move up above the handwheel during operation. One of the major disadvantages of this type of resilient wedge gate valve is susceptibility to corrosion and damage due to the difficulty of lubricating the stem threads. However, these valves are of great importance where space is limited as they do not take up a lot of space like their rising stem counterparts.
Figure: Non-rising stem resilient wedge gate valve.
Applications of a resilient wedge gate valve
- Resilient wedge gate valves are used in the domestic tap Water supply.
- They are used in sewerage treatment plants.
- These valves are used in industrial and fire protection systems.
- They are used in transporting oil and gas.
- Resilient wedge gate valves are used in food and beverages applications.
- They are used in chemical industries.
Advantages of a resilient wedge gate valve
- A resilient wedge valve has a low-pressure loss.
- It also prevents the water hammer effects due to the slow turning of the handwheel to the right number of turns required to open or close the wedge gate.
- It has excellent performance and high durability due to inherently corrosion resistance and elastomer-lined wedge gate.
- The direction of the medium is not limited because the valve is bidirectional.
- Resilient wedge gate valves are versatile as they can be used in different applications.
- These valves have zero fluid leakage.
Disadvantages of a resilient wedge gate valve
- Opening and closing a resilient wedge gate valve takes a lot of time.
- The resilient wedge gate valve is subject to a lot of friction and abrasion of the sealing surface during closing and opening.
- The resilient wedge gate valve cannot be used for flow regulation or throttling.
- A resilient wedge gate valve may experience a lot of vibration in partly open condition
Troubleshooting a resilient gate valve
The resilient wedge gate valve is hard to operate
- Presence of trapped pressure in the valve. Open the resilient wedge gate valve to relieve any trapped pressure.
- Damage to the operating parts due to the use of excessive torque. Adjust the torque output of portable actuators as recommended by the resilient wedge gate valve manufacturer. Perform the last or first turns of operation by hand.
- Excessive buildup in the valve due to irregular valve operation. Exercise the valve gradually and cycle from open to close to try to remove internal buildup.
Valve leaks during testing
- Foreign material or air in the line. Open the resilient wedge gate valve enough to get high-velocity flow to flush out foreign materials. Repeat several times until leakage stops.
- Trapped of air in the valve. Allow enough time to fill the valve and vent off-air.
Leakage in the stem
- Worn out O-ring-seals. Replace the O-rings.
- Loose packing gland bolts and nuts. Tighten the bolts and nuts.
Leakage in the valve body
- Cracked or damaged body or bonnet. Inspect the damage and contact the resilient wedge gate valve manufacturer for further details.
Leakage in the seating area
- Foreign materials are embedded in the valve wedge. Partially open the valve to obtain a high-velocity flush to clean the valve.
- Severe damage or cut to the elastomer lined wedge. Disassemble the resilient wedge gate valve and check for damage. Replace the wedge gate if necessary.
Leakage in the bolted connections
- Loose bonnet-to-body bolts or stuffing box bolts. Remove bolts and nuts that attach the bonnet to the valve body. Remove bonnet to inspect bonnet gasket and wedge interior of the valve body. Replace any damaged part as necessary.
- Inspect thrust washers and stuffing box gasket (O-ring) and replace if damaged
Summary
A resilient wedge gate valve has a wedge-shaped disc insert that is lined with an elastomer and sits against two inclined seats. These valves are manufactured from strong metallic materials such as ductile iron, stainless steel, carbon steel, and cast iron. When the handwheel is turned in the clockwise direction, the wedge gate fits into the space between the seats, cuts through the flow, and stops the stream flow. When the handwheel is turned in the anti-clockwise direction, the wedge gate frees the flow path thus opening the fluid flow. Resilient wedge gate valve manufacturers recommend these valves for use in either fully open or closed positions to avoid abrasion and erosion of the seats. Resilient wedge gate valves are commonly used for domestic water supply, in wastewater and treatment plants, fire protection systems, foods and beverages, HVAC systems, and irrigation systems that have a backflow control system. Some benefits of a resilient wedge gate valve include minimal reduction of flow pressure, long service life, versatility, easy installation and operation, and zero fluid leakage among others. However, a resilient wedge gate valve is slow to open and close and thus time-consuming. They are also prone to scuffing and erosion of the sealing surfaces, especially during opening and closing, and cannot be used for flow regulation and throttling.