Valves can be used to completely block, fully admit, or partially restrict the flow of a process fluid. One of the earliest valve designs, gate valves are best utilized in liquid-only on/off service. A gate valve lifts a rectangular or circular gate out of the way to allow fluid flow. Since the gate and the pipeline diameter are the same when the valve is fully open, there is nothing to block the flow. The size of the valve is also dependent on the bore diameter. This full-bore design’s low friction loss contributes to significant energy savings and a lower cost of ownership.
What is Gate Valve?
When controlling the linear flow of a fluid, industrial settings often employ gate valves. Gases can be allowed to flow in either direction through these valves. This disk-like device, used to pour slurry or other thick media, is formed like a wedge. Even though it happens infrequently due to low pressure, the gate’s orientation can parallel the opening.
The cutting-through mechanism described above gives rise to the alternative name “sluice valve” for a gate valve. The name of this valve comes from the fact that it allows fluid to flow through a gate. The on/off functionality this form provides also helps automate the flow. Although they can be used for throttling to a certain extent, many gate valve supplier businesses and industry experts discourage this practice. The reason is the gate’s destructive potential.
Learning how a gate valve works is the next step.
Gate Valve Working Principle
To assemble a gate valve, you’ll need the following: a handle (A), a flange (F), a gasket (C), a spindle (B), a bonnet (D), a valve body (E), and a gate (G). The fundamental mode of action is quite elementary. Turning the handwheel rotates the stem, which raises or lowers the gate through the threads. More than one complete valve turn is required to open or close it fully. When the gate is lifted out of the way of the flow, the valve opens. After closing the gate, the bore seals, and the valve closes.
A gate valve’s flow rate varies nonlinearly with its vertical position, with the largest changes occurring near shutdown. Valve service life is shortened when used to regulate flow because the relatively high velocity of the flow during partial opening wears the gate and seat and may produce gate vibrations.
Method Of Controlling A Gate Valve
Gate valves can be operated in three distinct ways:
Manual gate valve:
The operator must crank a handwheel to open or close a gate valve manually. A user must be physically present to turn the wheel. Due to their limited frequency of use once installed, gate valves are most cost-effective when operated manually.
Pneumatic gate valve:
Pneumatic gate valves, as opposed to manual ones, are operated by means of a pneumatic actuator. The actuator utilizes pressurized air to rotate the stem, allowing the gate to be raised or lowered. This enables hands-free, remote-control operation, but a pneumatic system must be installed beforehand.
Electric gate valve:
The electric gate valve does away with the traditional handwheel in favor of an electric motor. The gate can be raised or lowered by electrically powering the actuator, which then spins the stem. This enables hands-free, off-site operation, and it must be wired into the premises. One other name for these is electric gate valves.
Types of Gate Valves
A wide range of gate designs and technologies are available, each capable of producing reliable sealing in specific contexts.
1. Knife gate valve
A knife gate valve can handle both dry bulk solids and viscous fluids. A conventional metal gate is made from a single, sharpened piece of metal. When these valves open and close, they cycle past the seat rings, cleaning themselves.
2. Wedge gate valve
The gate of a wedge gate valve rests between two slanted seats. Fluid pressure is the principal force that helps with sealing, although a strong wedging force on the seats from the tightening of the stem also contributes. The wedge-shaped gate has a longer service life because there is less “rubbing” between the gate and the seats, which occurs only at extreme fluid differential pressure. Wedge-shaped gate valves may be disadvantaged because of the higher compression stress on the seats when it comes to heat binding and restricted valve opening owing to expansion.
3. Parallel slide gate valve
When it comes to the gate and seats, a parallel slide gate valve is your best bet. Seals in parallel slide gate valves are made using line pressure and location. A flat gate’s spring is located between its two halves. A tighter seal is created as the spring pulls the parts toward the seats. Parallel gate valves offer an inherent design benefit in higher temperature situations, making them safer. Since parallel gates don’t have a wedging action, the closing torques are lower, requiring smaller and cheaper actuators or less human effort. Parallel gates slide into place to block dirt and protect seats from wear and tear.
4. Slab gate valves
One-piece gates, known as slab gates, often feature a bore-sized aperture and are sometimes called through-conduit gate valves. When fully opened, the bore aligns with the two seating rings. With this arrangement, the flow is streamlined with little to no turbulence. Transporting crude oil and natural gas liquids (NGLs) is ideal for this innovative design because of the low-pressure loss it incurs. Valve seats have not been contaminated. However, debris might become stuck in the disc cavity. Therefore, the cavity is often equipped with a plug to drain the amassed foreign material for maintenance.
5. Parallel Gate Expanders
Expanding gate valves work because of the mechanical expansion of a gate comprising two fitted slabs. Both cavities open when the slab gate is raised, and the medium can flow through. When the slab gates are closed, they stop the media flow and create a seal by mechanically expanding outward in response to a downward push (the stem on one slab) and an upward force (the step in the valve body).
Both the upstream and downstream seats can be sealed securely using these valves. Power plant isolation valves, process system block valves, and refinery high-temperature valves can all benefit from these valves because of the seal they provide.
When Should You Use A Gate Valve?
The top supplier of pneumatic gate valves will be able to provide valves with a wide range of applications. The following are some common applications for gate valves:
- The Food Market
- Medical and pharmaceutical production
- Oil and gas production
- Uses of Steam
- Functions of Sludge
- Generating Energy
- Chemical and Petroleum Refining
Advantages and Disadvantages of Using Gate Valves
Advantages of Using Gate Valves
- During operation, it loses hardly any pressure at all.
- Its primary function is that of a two-way valve.
- It thrives in environments with extreme heat and pressure.
- When compared to other valve types, gate valves tend to be less expensive.
- Fluids including chemicals, gas, steam, oil, and water, are just a few of the many that can be managed with their help.
- Their construction and use are both rather elementary.
- They experience almost no loss in pressure.
Disadvantages of Using Gate Valves
- It lacks the speed of a globe valve’s closure and opening mechanisms.
- Space is needed for servicing, operating, and installing these valves.
- They can develop leaks due to silt buildup in the valve bottom, which prevents the gate from closing securely.
- These valves move at a snail’s pace.
- When the sluice valve is just partially open, it makes a lot of noise and vibrates a lot.
- Throttling is not recommended with these valves.
- Repairing these valves by grinding and lapping is difficult.
Simple machinery like gate valves has many applications. They are among the best industrial valves because of how flexible they are. All fluids, whether liquids or gases are expected to move unpredictably. Most manufacturing facilities cannot function without industrial gate valves. Valves allow for unidirectional regulation of fluid flows. It does not require a large installation space compared to similar industrial valves. Pressure on the sealing surface is crucial to the valve’s operation, and this is best attained in a wedge design. you can find the reliable and durable valves from ICS Pakistan.