There are many applications for gate valves, which are an economical choice for many industries. Gate valves provide tight shut-off and are used in various fluid processes. In this guide, you will learn what a gate valve is, how it works, what it is used for, and the types of gate valves you can purchase online.
cast iron gate valves
What is a Gate Valve
Gate valves, prevalent in both above-ground and subterranean pipelines, serve as a common linear valve type. Engineered to commence and cease liquid flow within conduits, these valves empower users to isolate specific pipe sections when needed. Often referred to as water gate valves or sluice valves, they play a pivotal role in various applications.
Typically, gate valves comprise the valve body itself, seamlessly integrated into the pipeline, and a connected handwheel actuator responsible for valve manipulation. This multi-turn wheel assembly, extending above or alongside the pipe and valve, links to a bonnet assembly via a stem. Rotating the wheel in one direction facilitates valve opening, while the opposite direction prompts closure.
Gate valves boast advantages such as complete water flow shutdown for troubleshooting, maintenance, and pipe-cleaning endeavors. Noteworthy is their bidirectional functionality, enabling flow obstruction in both upstream and downstream directions without inducing significant pressure loss during operation.
However, in certain scenarios, gate valves exhibit limitations. Their relatively unhurried opening and closing speed might be a drawback, and they aren't designed for flow control through partial opening or closure.
How Does a Gate Valve Work
During operation, gate valves insert a physical barrier (a gate or disk) into the pipeline, seal it when closed, and lift it out of the way when it opens. A handwheel on the valve bonnet acts as the valve actuator, raising or lowering the barrier as required. It rotates clockwise and anticlockwise to control the flow of liquid.
Basically, gate valves are isolation valves or shutoff valves that can be operated by handwheels. They can either have a rising-stem or a non-rising-stem actuation system. As a result of their effectiveness and ease of operation, gate valves made of stainless steel, iron bodies, and brass are widely used in plumbing and pipeline applications. Also, they are very reliable, mechanically simple, and are usually reasonably inexpensive, depending on the model and size.
The ball valve is another type of isolation valve, though it is physically different from the gate valve. When fully closed, both of them will completely block the flow of water through a duct, which is similar in effect. When choosing between a ball valve vs. a gate valve for a particular pipeline application or industrial setting, numerous factors need to be considered. Normally, they will need to consider environmental conditions and properties of the medium in which they are to be used.
Check valves, another common pipeline device used to control directional flow, and butterfly valves should also be distinguished from gate valves. Check valves and gate valves differ mainly in that the former are designed to prevent backflow; they allow flow in one direction while blocking it in the other. A gate valve, on the other hand, is bidirectional, and when closed, will shut off fluid, vapour, or gas flow in both directions completely.
Butterfly valves are variations on gates or isolation valves, usually opening and closing with just a quarter turn of the actuator. Depending on the position of the valve actuation device relative to the valve body, the gate itself sits parallel or perpendicular to the flow direction inside the pipe. Generally, they are less suitable than gate valves for sealing extremely tightly, but some versions can be used to throttle.
There are two main types of gate valves: wedges and parallels. A wedge-shaped gate valve (including solid tapered wedges, flexible wedges, and split wedges) has two inclined seats and an inclined gate or barrier that is slightly misaligned with the seats. When used in certain applications, this tends to provide a tighter seal. In parallel gate valves, also known as parallel disks, double disks, or parallel slide gate valves, there is a flat gate or barrier that is held perpendicular to the flow of liquid between two parallel seats.
What Is a Gate Valve Used For
Gate valves are used in places like wastewater plants, power plants, and process plants to shut off and isolate liquids. They're especially useful in larger applications because of the mechanical advantage provided by a threaded stem, which is better than a quarter-turn lever used in ball valves. Some really big valves need a way to reduce pressure before the gate can be moved. They are a cost-effective solution as the pipe size gets bigger, beyond 2 inches.
For making gate valves, materials like cast iron and steel are common for bigger valves, while stainless steel, forged steel, bronze, and others are widely used in smaller sizes. You can even find non-metallic options like plastic gate valves. Material choices usually cover everything under pressure for the body, while "trim" refers to other components like seats, disc, stem, and sometimes bellows. Bigger sizes are known by an ASME class pressure rating and come with standard bolted or welded flanges. Sizing these valves is easy because their design doesn't cause much pressure drop.
You can find gate valves with non-rising stems, great for tight vertical spaces like on ships. Rising stem designs offer quick visual confirmation but might be prone to corrosion. Non-rising stem valves often have an indicator to check the gate position. These designs don't affect how well the valve works.
Gate valves are often automated using electrical rotary actuators. Hydraulic or pneumatic linear actuators can speed up their operation. For big gate valves, manually opening and closing them can be easier with geared actuators.
Certain building codes say you need on/off valves upstream of some equipment, like water heaters. Ball or gate valves are good for this, but not globe valves. In the past, gate valves were common in homes, but now lever-actuated ball valves are used more because they're less likely to get stuck "open" from not being used. Installing these in existing systems might need some creative adjustments.
A special kind of gate valve called a knife gate valve controls slurries and thick liquids. Sliding gate valves are for dispensing dry and bulk materials from hoppers.
Types of Gate Valves
Solid Wedge Gate Valve
A solid wedge gate valve is a type of gate valve that features a solid, one-piece wedge-shaped disc or gate that moves up and down to control the flow of fluids through the valve. The wedge disc in a solid wedge gate valve is typically a single, unsplit piece, providing a continuous surface across the flow path when the valve is fully open. It is also less likely to leak than other types of gate valves.
Split Wedge gate Valve
Split wedge gate valves are a type of gate valve that employs a wedge-shaped disc or gate, which is split into two separate parts. Unlike solid wedge gate valves, where the wedge is a single, unsplit piece, split wedge gate valves have a design where the wedge is divided into two segments. This split wedge design allows for flexibility and accommodation of any misalignment that may occur during operation.
Parallel Slide Gate Valve
Parallel slide gate valves are designed with disks that slide in a track up and down. Due to their inability to withstand high pressure, parallel slide gate valves are commonly used in low-pressure applications. Because they are not able to withstand high pressures, parallel slide gate valves are often used in low-pressure applications.
Flexible Wedge Gate Valve
A flexible wedge gate valve has a disk connected to the stem by two hinges, which allows it to move up and down side-to-side. Because it is able to withstand higher pressures than other valves, flexible wedge valves are often used in high-pressure applications.
Bellows Seal Gate Valve
Bellows seal gate valves are a specific type of gate valve that incorporates a bellows element as part of the sealing mechanism. The bellows, typically made of flexible metallic material, surrounds the valve stem and is welded to both the stem and the bonnet. This design creates a hermetic seal around the stem, providing additional protection against leakage.. If you’re looking for a more efficient, tougher solution for your business needs, bellows seal gate valves may be the perfect option.
Double-disc Valve
Double-disc valves are rapidly becoming the preferred choice for process flow control across global industries. These valves enable users to manage flow from two points, providing enhanced control from multiple directions. This significantly boosts effectiveness compared to traditional linear valves, offering superior accuracy and efficiency in regulating the flow of liquids and gases. The exceptional performance of double-disc valves is attributed to their high-quality materials, facilitating easy and minimal wear-and-tear operation during opening and closing. These advantages position double-disc valves as an optimal solution for a wide range of industrial applications.
Gate Valve Supplier
Athenavalve is an industrial gate valve manufacturer and supplier offering products in various materials, including carbon steel, stainless steel, and alloy steel. For more information, please click here to contact us.
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