Among the various types of gate valves, parallel slide gate and wedge gate valves are frequently compared to each other due to their unique features and suitability for different applications. Isolating the flow of liquids or gases is a critical function in many industrial applications, and gate valves are a popular choice for this purpose.
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While both types of valves offer a tight seal when fully closed, they differ in their design and operation. For services that require a binary on/off flow control, where the valve should be either fully open or fully closed, a gate valve is ideal. In the following paragraphs, we’ll explore the key differences between parallel slide gate valves and wedge gate valves to help you choose the best valve type for your specific requirements.
A parallel slide gate valve features two independent discs which are held against the parallel body seats by a light spring located between them. This design ensures that the disc maintains parallel alignment with the flow path and relies on pressure within the line to achieve tight closure. As the discs are always in contact with the seats in the valve body, the risk of damage or wear is greatly reduced.
Utilising a parallel slide gate valve in a piping system offers numerous advantages. First and foremost, its streamlined design contributes to minimal fluid resistance and pressure drop, enhancing efficiency in high-flow applications. The valve’s independent two-piece disc assembly and parallel seating alignment ensure superior sealing performance, reducing leakage and improving overall safety.
Being bi-directional allows for installation in either direction without compromising performance or operation. Additionally, the valve’s unique design reduces the torque requirement for opening or closing, enabling more miniature actuators and lowering operating costs and energy consumption. With a broader seating surface compared to other gate valve types, the parallel slide gate valve provides a tighter seal and mitigates the risk of seat wear.
Furthermore, the design and parallel alignment of the valve contribute significantly to reducing seat wear, leading to a prolonged valve lifespan and diminished maintenance requirements. An additional notable advantage is that the seating design prevents the need for reseating the discs, even after the valve has experienced operating temperatures or subsequent cooldowns.
Despite their advantages, parallel slide gate valves have certain limitations. One notable drawback is their limited suitability for precise flow regulation, as these valves are primarily designed for on/off flow control. The linear movement of the two-piece disc assembly in parallel slide gate valves can lead to slower operation when compared to alternative valve types. Additionally, the higher cost associated with the valve’s two-piece disc assembly and precision manufacturing sets it apart as a more expensive option than other gate valve types.
Wedge gate valves are designed with the closing element or gate having a wedge-shaped configuration, allowing for the gate to ‘wedge’ into the valve body for a secure and tight seal when in the closed position. These valves are commonly utilised in water distribution systems due to their exceptional sealing performance. Wedge gate valves are available in two variations: single-disc and double-disc. The double-disc wedge gate valve offers an enhanced level of sealing by incorporating two gates that have some flexibility in movement, resulting in an even tighter closure.
Despite the benefits they offer, parallel slide gate valves come with certain limitations. One significant drawback is their limited applicability for precise flow regulation, as their primary design focuses on on/off flow control. The linear movement of the two-piece disc assembly in parallel slide gate valves may result in slower operation when compared to alternative valve types. Moreover, the increased cost associated with the valve’s two-piece disc assembly and precision manufacturing distinguishes it as a more expensive choice compared to other gate valve types.
When considering wedge gate valves in your applications, it’s crucial to consider several key disadvantages. One significant drawback is the higher operating torque often required by wedge gate valves compared to other valve types, potentially impacting ease of operation and necessitating more robust actuation systems.
These valves are primarily designed for on/off applications and are not recommended for situations requiring precise flow control with fine adjustments or throttling. Another concern is the potential for gate sticking or jamming, especially under certain operating conditions or when dealing with debris or sediments in the liquid or gas. This issue can significantly affect the valves’ operational efficiency.
Additionally, due to their wedge-shaped gate design and the potential for gate sticking, wedge gate valves may demand more frequent maintenance to ensure proper functioning and prevent performance issues.
When contemplating using wedge gate valves in your applications, it’s essential to consider several notable disadvantages. A significant drawback is the typically higher operating torque required by wedge gate valves compared to other valve types, which may impact ease of operation and necessitate implementing more robust actuation systems.
Primarily designed for on/off applications, these valves are not recommended for situations that demand precise flow control with fine adjustments or throttling. Another concern is the potential for gate sticking or jamming, particularly under specific operating conditions or when dealing with debris or sediments in the liquid or gas. This issue can markedly impede the operational efficiency of the valves.
Additionally, owing to their wedge-shaped gate design and the associated risk of gate sticking, wedge gate valves may require more frequent maintenance to ensure proper functioning and prevent performance issues.
It is essential to consider factors such as flow control requirements, pressure/temperature conditions, maintenance needs, and budget constraints to ensure the chosen valve aligns with your operational objectives for the long-term success of your fluid control systems.
With our extensive industry knowledge and wide range of valve solutions, John Valves is committed to providing high-quality products that meet the latest industry standards and deliver reliable performance. Whether you require precise flow control, high-pressure capabilities, or minimal maintenance requirements, we have the expertise to guide you in selecting the optimal valve for your application.
Contact us today to learn more about our comprehensive valve offerings and let us be your trusted partner in finding the right valves for your needs.
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Pararel Slide & Wedge gate valve
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(Mechanical)
(OP)
3 Jul 03 05:36What diference between Pararel Slide & Wedge gate valve .How they are different in their application?
How to select between two type of valve?
(Industrial)
6 Jul 03 11:29The parallel slide gate valve has a parallel disc sealing against seats by means of spring force, whereas a wedge gate valve has a wedge shaped disc which gets locked on to the seats by means of the mechanical seating load applied. Where a very tight shut off is required generally wedge gate valve is preferred. But in this valve the body cavity may trap pressure and hence particularly in steam applications can result in locked-up condition of wedge. Hence, in such applications a parallel slide gate valve is preferred.
(Electrical)
6 Jul 03 13:42I believe that some of the parallel slide gates generally port off the high (as I recall) pressure side to the area between the gates to provide a tight pressure seal (equalizes the high side and allowing the springs to work)of the gates... this type of valve can lock up particularly in steam applications IF this center area is not connected (and allowed to vent through the ported connection) -- these type valves will usually have a small pipe on the outside of the valve connecting the center portion to the high side...
(Mechanical)
7 Jul 03 22:46The relieved "bonnet" area is fast becoming the standard for PSVs. It is my belief that while wedge gates still have their place in industrial applications, steam is not one of them. As expansion and contraction occur a forced fit wedge tends to bind. This is particularly a concern in Combined Cycle plants where temps are going up to 1100F.
Another concern for this is training of the users. Operators are brainwashed that to get tight shut off a valve must be wrenched into the seat. While this is true of a wedge gate due to a forced or "torque" seat, a parallell disc gate is position seated. With a Parallel gate if the handwheel is hit with a cheater bar the position bar will bend. You should look for a valve that has immovable stops cast in the body to prevent this.
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