Gate valves come in various designs and categories, depending on their internal framework. Parallel slide gate valves are designed to control the flow by either shutting off or letting through the fluid by the linear movement of the internal discs of the valve. The parallel slide gate valve provides superior sealing and operational performance when compared with a conventional wedge gate valve particularly in high pressure and temperature applications. This makes them ideal for use on steam and high temperature water services.
The parallel slide gate valve comprises two discs that maintain contact with the parallel body seats. The discs are designed to remain flexible to accommodate temperature changes within the line, thereby causing no effect on the valve’s operation. They use line pressure to assist in sealing, thus offering and maintaining tight closure. During opening and closing, the discs ‘slide’ across the seat faces, helping to clear any direct and foreign matter from the seating faces.
Benefits of Parallel Slide Gate Valves
Does Not Require High Torque Force to Shut Off
The valve operation does not require a high torque or operating force to shut off since it uses position seating. The valve uses line pressure to hold the downstream disc against the downstream seat of the body, thus providing a positive shut off without leakage. Compared to how a double-disc wedge is designed to work, this is a big win. A double-disc wedge relies entirely on torque to force the wedge shaped disc into the body seats, and in no time, the seat face is permanently damaged, forming a leak path.
Less Torque Requirement
Due to being a position seating type valve and its ability to use the line pressure to seal, the parallel slide gate valve requires less torque, or operating force, to open and close. This allows for smaller actuators to be used to operate the valve, which provides cost advantages.
Wider Seating Surface
The wide flat seating surface of a parallel slide gate valve serves as an advantage by preventing seat deformation, which might later lead to leaks, saving you on regular repair and maintenance. The wide seating surface area also helps prolong the lifespan of the seat by reducing the wear.
Wedge gate valves have a comparatively thinner seating surface making its seating surface vulnerable to deformations.
Reduction In Seat Wear
The wide seating surface in the parallel gate valves also contributes to reducing seat wear by providing a uniform bearing stress over a larger area.
No Reseating of Disc
A significant advantage of the parallel slide gate valve is that the seating design and wide flat seat helps the discs of the valve remain in their original position even after the valve has reached its operating temperature. This is also the case for when the valve cools down from operating at a high temperature.
Wedge gate valves however are very different. Due to their design, the valve may require you to reseat it after it has reached operating temperature to achieve a tight seal due to the thermal expansion of the body.
Wedge gate valves are also subject to ‘thermal locking’ where a closed valve has been operating at high temperature and then allowed to cool down. As the body of the valve cools and contracts, the wedge can become jammed between the body seats, making it extremely difficult or virtually impossible to open the valve.
Low Fluid Resistance
The parallel slide gate valve has a low flow resistance. Lower pressure rating valves have full bore opening while higher pressure valves generally have a venturi design bore to keep pressure loss to a minimum. It also has a long-life span compared to other gate valves since it gets little to no damage due to the low fluid pressure loss.
Superior Sealing Performance
The parallel valve provides a tight seal against any flow, making them ideal for pipelines carrying critical fluids. Here are some of the reasons for making parallel slide gate valves superior in sealing:
- Perfect for applications with varying operating temperatures
- Easy to operate due to being position seated
- Eliminates possibility of thermal locking
Bidirectional
The parallel slide gate valve can operate with flow from any direction. If your pipeline has a two-way flow, you do not have to install additional valves to use in the opposite direction.
Benefits of Parallel Slide Gate Valves: Final Thoughts
At this point, you do not need any convincing as to why you should consider purchasing or replacing your wedge gate valves with a parallel slide gate valve. There isn’t any valve that would serve as a bidirectional with a superior sealing performance on critical temperature applications than the parallel slide gate valve. Connect with our experts to discuss your needs and find lasting solutions.
