Parallel Gate Valve

Parallel gate valves are an alternative to double disc valves, having two discs but only one wedge instead of two. The discs are in permanent contact with the seat rings, getting a tight seal due to the horizontal inconel spring located in between and without the wedging system help.

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.

Actuator: The actuator generates the torque needed to rotate the stem and operate the valve. It can be a handwheel, electric motor, pneumatic actuator, or hydraulic actuator.

Valve body: The valve body houses the internal components of the valve and provides strength to withstand high-pressure fluids. It is often made of stainless steel or other durable materials.

Bonnet: The bonnet is placed on top of the valve body to prevent fluid leakage at the valve stem. It is securely attached to the valve body using bolts and nuts or welding.

Stem: The stem connects the actuator to the gate and is responsible for raising and lowering the gates to control the flow of fluid.

Gate: The gate is the main component that allows or blocks the flow of fluid. It moves parallel to the pipeline to adjust the flow.

Seats: The parallel slide gate valve has two valve seats that provide a seal with the gate. There is a floating seat, which is used for automatic pressure relief when the trade section is under pressure. · When the cavity pressure is greater than the pressure in the channel, the cavity pressure is released to the channel. These seats can be made of soft materials such as plastics and rubber or metallic materials like stainless steel or carbon steel.

Gland packing: The gland packing is a gasket used to provide a seal between the bonnet and the stem, preventing fluid leakage.

Spring: The spring provides initial sealing force, although it does not maintain the sealing force. It is mounted between the gate discs.

Power Generation
Parallel slide gate valves find extensive applications in power plants, particularly in steam and water systems.
They play a crucial role in regulating and isolating fluid flow within power generation processes, ensuring efficient and controlled operation.

Oil and Gas Industry
In the oil and gas sector, parallel slide gate valves are employed for various purposes, including flow control and isolation in pipelines.
Their robust design and reliable performance make them suitable for handling the challenging conditions often encountered in oil and gas operations.

Refining and Petrochemicals
In refining and petrochemical facilities, parallel slide gate valves are utilized for controlling the flow of different fluids in refining processes.
Their ability to handle high temperatures and pressures makes them well-suited for applications where precise control and tight shut-off are essential.

Water Treatment Plants
Parallel slide gate valves are integral components in water treatment plants.
They are employed for regulating the flow of water in different stages of the treatment process, ensuring effective treatment and distribution of clean water to various points in the system.

Chemical Processing
Chemical plants often use parallel slide gate valves for managing the flow of various chemicals and fluids in different stages of the production process.
The valves' design allows for reliable and precise control, contributing to the efficiency and safety of chemical processing operations.

HVAC Systems
Heating, ventilation, and air conditioning (HVAC) systems incorporate parallel slide gate valves for controlling the flow of air, water, or other fluids.
These valves help in maintaining optimal conditions within HVAC systems, contributing to energy efficiency and temperature control.

Marine and Shipbuilding
In marine and shipbuilding applications, parallel slide gate valves are utilized for controlling fluid flow in different systems onboard vessels.
Their durable construction and ability to withstand harsh marine environments make them suitable for marine engineering.

General Industrial Applications
Parallel slide gate valves find widespread use in various industrial settings where precise flow control, reliable shut-off, and durability are paramount.
Their versatility makes them valuable in diverse applications across different industries, contributing to efficient and safe fluid-handling processes.

Gate valves are important components in piping systems, and they are used to regulate fluid flow in various industries. Gate valves are known for their ability to provide a tight seal and are designed to withstand high pressures and temperatures. However, like other components in a piping system, gate valves require regular maintenance to ensure they function optimally.

Valve lapping involves using a lapping machine to smooth out the valve seat and disc, thus enhancing a tight seal when the valve closes. This process is critical to the optimal functioning of the gate valve.

Lubrication is another important maintenance procedure that should be carried out regularly. Gate valve stem threads and stem nut should be lubricated to reduce friction, wear, and make it easy to open and close the valve. A grease gun can be used for lubrication.

The valve packing is responsible for preventing fluid leakage between the valve stem and bonnet. It is essential to adjust the valve packing regularly, at least once a month, or as recommended by the manufacturer, to ensure that it is not too tight or too loose.

Gate valves can become clogged with debris and other foreign materials, leading to blockages and reduced fluid pressure. It is necessary to clean the valve seat, disc, entry and exit ports regularly to prevent fluid blockage.

The bonnet-body connection is an essential part of the gate valve, and it must be secure to prevent fluid leakage. Bolts and nuts should be tightened to the torque recommended by the gate valve manufacturer.

If the gate valve disc does not stop the fluid flow effectively, it may be necessary to replace the disc. To replace the disc, it would be necessary to open the valve bonnet in order to gain access to the interior of the valve.