Gate valve: An on-off valve that works by inserting a rectangular gate or wedge into the flow of the fluid. The fugitive emission standard for gate valves is covered by API 624 and ISO 15848-1. It should be noted that the stem motion in a gate valve is typically linear, which creates a lot of friction between the valve stem and packing. This friction can cause packing wear and tear as well as leakage. Gate valves are available in different types, such as slab, expanding and wedge. Wedge gate valves have a sealing element in the shape of a wedge. A wedge gate valve is a torque seated valve, meaning that the wedge is expanded from both sides due to the stem force and provides sealing. The expansion of the valve closure member due to the stem axial force is called “wedging effect.” Expanding gate valves are also torque seated valves with a closure member in two sections, one male and the other female. Slab gate valves have a flat disk or closure member that provides sealing due to the fluid pressure. Slab gate valves, unlike expanding and wedge gate valves, are not torque seated.Gate valves have more height than ball valves due to their high body and upward stem and gate movement for rising stem design. The height of a gate valve could be considered a disadvantage, since it can impose a manifold structure with higher height. Usage of a linear actuator on top of a valve could make the height differential even greater compared to an actuated ball valve. One should bear in mind that rack and pinion or scotch and yoke actuators, which are used for ball valve automation, stand horizontally when the valve is connected to a horizontal pipe, whereas linear actuators stand vertically when the valve is connected to horizontally installed piping. Fig. 4.33 illustrates the height of an actuated slab gate valve.
Gate valves have more height than ball valves due to their high body and upward stem and gate movement for rising stem design. The height of a gate valve could be considered a disadvantage, since it can impose a manifold structure with higher height. Usage of a linear actuator on top of a valve could make the height differential even greater compared to an actuated ball valve. One should bear in mind that rack and pinion or scotch and yoke actuators, which are used for ball valve automation, stand horizontally when the valve is connected to a horizontal pipe, whereas linear actuators stand vertically when the valve is connected to horizontally installed piping. Fig. 4.33 illustrates the height of an actuated slab gate valve.
Gate valves or ball valves are two typical valves used in the manifolds. Gate valves have a long history of use in blowout (BOP) stacks, trees, and manifolds and are considered relatively reliable devices because both the valve and the valve actuators have been through extensive development with proven field use and design improvements. Figure 19-6 illustrates two types of gate valves. Figure 19-6A shows a (Worldwide Oilfield Machine, Inc.) gate valve with actuator,, and bucket. The hydraulic actuator is designed with a fail-safe model and spring returns with the . The mechanical is for backup. Figure 19-6B shows a gate valve with only an bucket. Both valves are designed, built, and tested based on API 6A [6] and 17D [7], which can be used up to a water depth of
Gate Valves
Gate valves work by inserting a rectangular gate or wedge into the path of a flowing fluid. They are operated by a threaded stem which connects the actuator (generally a hand wheel or motor) to the stem of the gate. If the valve has a rising stem its position can be seen just by looking at the position of the stem. Fig. 5.2 shows the internals of a Gate Valve that is half open.
Gate valves are used when a straight-line flow of fluid and minimum flow restriction are needed. Gate valves use a sliding plate within the valve body to stop, limit, or permit full flow of fluids through the valve. The gate is usually wedge-shaped. When the valve is wide open, the gate is fully drawn into the valve bonnet. This leaves the flow passage through the valve fully open with no flow restrictions. Therefore, there is little or no pressure drop or flow restriction through the valve.
Gate valves are not suitable for throttling volume. The control of flow is difficult because of the valve’s design and the flow of fluid slapping against a partially open gate can cause extensive damage to the valve. Except as specifically authorized by the manufacturer, gate valves should not be used for throttling.
Gate valves are classified as either rising-stem or non-rising-stem valves. The non-rising-stem valve is shown in Figure 7-2. The stem is threaded into the gate. As the on the stem is rotated, the gate travels up or down the stem on the threads while the stem remains vertically stationary. This type of valve will almost always
A gate valve is generally used to completely shut off fluid flow or, in the fully open position, provide full flow in a pipeline. Thus it is used either in the fully closed or fully open positions. A gate valve consists of a valve body, seat and disc, a spindle, gland, and a wheel for operating the valve. The seat and the gate together perform the function of shutting off the flow of fluid. A typical gate valve is shown in Figure 12.9.
and fire test requirements
Gate and globe valves can have fire test certificates according to API 6FA or ISO 10497 standards. The fire test certificate is not usually required for gate and globe valves with no nonmetallic parts. A fire test guarantees that the valve will function properly during a fire. is the European regulatory framework for manufacturing, installation, and use of equipment in explosive atmospheres. certification indicates that the valve does not have any source of ignition, which is applicable for equipment in potentially explosive atmospheres. Valves with actuators are usually in the scope of work because the directive does not consider the process source of ignition inside . Only external sources of ignition such as actuators with electrical parts make the valve fall inside .
Gate valves are characterized by a “gate” (Figures 4.49 and 4.50) that closes in a plane perpendicular to the flow of fluid. They are used primarily for on/off, service. Shearing of high-velocity flow will cause a partially open disk to vibrate and chatter, which will damage the seating surfaces and prevent a tight seal. They are suitable for most fluids including steam, water, oil, air, and gas. Gate valves may have either a solid or flexible wedge disk. In addition to on/off service, gate valves can be used for regulating flow, usually in sizes 6 in. and larger, but will chatter unless the disk is fully guided throughout travel.
A gate valve is a control valve that either allows media to flow through unobstructed or stops the fluid flow. The main advantage of a gate valve is the straight-through unobstructed passageway, which induces minimal pressure loss over the valve. The unobstructed bore of a gate valve also allows for a pig’s passage in cleaning pipe procedures, unlike butterfly valves. However, gate valves are slower than quarter-turn valves and should only be used in the fully open or closed position, not to regulate the flow. Automated gate valves exist with either an electric or pneumatic actuator, but a manual gate valve is cost-effective since gate valves are typically used infrequently. Gate valves are also commonly referred to as sluice gate valves.
Gate valve diagram & parts
A gate valve has seven main parts, which can be seen in Figure 3, which are: (A), stem (B), gasket (C), bonnet (D), valve body (E), flange (F), and gate (G). A gate valve or threaded gate valve is the most common connection type to connect the valve to an application. In addition, depending on the specific design and application, the hand wheel, stem, bonnet, and gate can have different designs to accommodate different applications. However, the main function of the gate valve parts remains the same. Continue reading to find those sections.
Gate valve operation
A gate valve operates similar to other valves. To open the valve, turn the hand wheel (A), which moves the gate (G) up or down on the stem (B) via the threads. A gate valve requires more than one 360° turn to open or close the valve fully. When the gate is lifted up, it opens the inlet to the outlet allowing an unobstructed passageway for the media to flow. When the gate is lowered, it closes and blocks the media flow.
The relationship between the gate’s vertical travel and the flow rate is nonlinear for a gate valve, with the greatest changes occurring near-complete closure. When used to regulate flow, the relatively high velocity of the flow at partial opening results in gate and seat wear, which along with possible vibrations of the gate, shortens the valve’s service life. Therefore, a gate valve should only be used for on/off control.
Gate valve actuation method
There are three main types of gate valve actuation methods:
Gate valve types
The gate comes in various designs and technologies to produce effective sealing for differing applications.
Knife gate valve
A knife gate valve is used for thick fluids and dry bulk solids. The gate is only one piece of metal, which is typically pointed like a knife. These valves are self-cleaning as they pass the seat rings every time they open and close.
Wedge gate valve
A wedge gate valve has a gate in the shape of a wedge that sits on two inclined seats, as seen in Figure 4 Labeled A. In addition to the primary force created by fluid pressure, a high wedging force on the seats created by the stems tightening assists with the sealing. The wedge-shaped gate does not stick to the seat in case of high fluid differential pressure and has an increased service life due to less “rubbing” on the seats. However, wedge-shaped gate valves have an additional compression load on the seats that may result in thermal binding and restricted valve opening due to expansion.
Parallel slide gate valve
A parallel slide gate valve has a flat gate and seats parallel to it. Parallel slide gate valves use line pressure and positioning to make a tight seal. Flat gates consist of two pieces and have a spring in the middle. The spring pushes the pieces towards the seats for enhanced sealing. Due to their inherent design, parallel gate valves have a safety advantage in higher temperature applications. Furthermore, since there is no wedging action in parallel gates, closing torques are comparatively smaller, resulting in smaller, less expensive actuators or less manual effort. Due to their sliding into position, parallel gates keep dirt away from the seating surfaces.
Slab gate valves
Slab gates, also called through-conduit gate valves, are one-unit gates that include a bore-size hole. The bore is in line with the two-seat rings in the open state. This alignment creates a smooth flow with minimal turbulence. This unique design allows for minimal pressure loss in the system and is perfect for the transportation of crude oil and natural gas liquids The valve seats remain clean. However, the disc cavity can capture foreign material. Therefore, the cavity typically has a built-in plug for maintenance purposes of draining the accumulated foreign material.
Parallel Expanding Gates
Expanding gate valves have two slab gates matched together that provide sealing through the mechanical expansion of the gate, as seen in Figure 5. When lifted, both of the slab gate’s cavities allow the media to flow. The upward force on one slab and the stoppage of the second slab, by a step in the valve body, allows for outward mechanical expansion for a proper seal. When closed, the slab gates block the media flow, and the downward force (stem) on one slab and upward force (step in valve body) allows for outward mechanical expansion for a proper seal.
These valves provide an effective seal simultaneously for both upstream and downstream seats. This seal makes them ideal for applications like isolation valves in power plants, block valves in process systems, and high-temperature valves in refineries.
Bonnets
The bonnet of a gate valve protects the internal parts of the gate valve by creating a leak-proof seal. Therefore, it is removable for repair or maintenance purposes. Gate valves can have screw-in, union, bolted, or pressure seal bonnets depending on the application.
Screw-in bonnets
Screw-in bonnets are the simplest in construction and can be seen in Figure 1. They are common in small size valves and provide a durable leak-proof seal.
Union bonnets
Union bonnets are held in place by a union nut. The union nut sits on the lower edge of the bonnet and screws into the valve body threads. This type of design ensures that the leak-proof seal created by the nut does not deteriorate by frequent removal of the bonnet. Therefore, union bonnets are common for applications that require regular inspection or maintenance.
Bolted bonnets
Bolted bonnets provide sealing in larger valves and higher pressure applications.
Pressure seal bonnets
Pressure seal bonnet gate valves are ideal for high-pressure applications . Pressure seal bonnets have a downward-facing cup inserted into the valve body. When internal fluid pressure increases, the cup is forced outward, improving the seal.
Stem design
The gate is raised and lowered by the spinning of a threaded stem (Figure 2 Labeled B). As discussed, a manual wheel or actuator spins the stem. Depending on the design, it is either considered a rising stem gate valve or a non-rising stem gate valve. So, as you spin the stem, it either raises or stays in place with the spin.
Outside Screw and Yoke (OS&Y), also referred to as rising stems, are fixed to the gate. Therefore, the threads are on the actuation side. So, as the gate is raised or lowered, the stem moves with it up and down. Consequently, they have built-in visual indicators of the state of the valve and are easily lubricated. Since they have moving components, they cannot be used with bevel gears or actuators. Therefore, rising gate valves are suitable for manual actuation.
On the other hand, a non-rising stem is fixed to the actuator and threaded into the gate. An indicator is often threaded onto the stem to show the open or closed state of the valve. Non-rising gate valves are common in underground installations and applications with limited vertical space.
Gate valve applications
Gate valves have numerous industrial and residential applications.
FAQs
What is a gate valve?
A gate valve is a control valve that either allows media to flow through unobstructed or stops the fluid flow.
How does a gate valve work?
A gate valve works by rotating the stem (manually or with an actuator) to raise or lower a gate. The gate either allows unobstructed fluid flow or stops the fluid flow.
What is a gate valve used for?
A gate valve is used to allow for unobstructed fluid flow or to stop the fluid flow.
View our online selection of gate valves!
Gate valves are used to shut off the flow of liquids rather than for flow regulation, which is frequently done with a globe valve. When fully open, the typical gate valve has no obstruction in the flow path, resulting in very low flow resistance.[1] The size of the open flow path generally varies in a nonlinear manner as the gate is moved. This means that the flow rate does not change evenly with stem travel. Depending on the construction, a partially open gate can vibrate from the fluid flow.[1]
Gate valves are mostly used with larger pipe diameters (from 2″ to the largest pipelines) since they are less complex to construct than other types of valves in large sizes.
At high pressures, friction can become a problem. As the gate is pushed against its guiding rail by the pressure of the medium, it becomes harder to operate the valve. Large gate valves are sometimes fitted with a bypass controlled by a smaller valve to be able to reduce the pressure before operating the gate valve itself.
Gate valves without an extra sealing ring on the gate or the seat are used in applications where minor leaking of the valve is not an issue, such as heating circuits or sewer pipes.
Valve construction
Common gate valves are actuated by a threaded stem that connects the actuator or motor) to the gate. They are as having either a rising or a stem, depending on which end of the stem is threaded. Rising stems are fixed to the gate and rise and lower together as the valve is operated, providing a visual indication of valve position. The actuator is attached to a nut that is rotated around the threaded stem to move it. stem valves are fixed to, and rotate with, the actuator, and are threaded into the gate. They may have a pointer threaded onto the stem to indicate valve position, since the gate’s motion is concealed inside the valve. stems are used where vertical space is limited.
Gate valves may have ends drilled according to pipeline-compatible flange dimensional standards.
Gate valves are used to shut off the flow of fluid by inserting a rectangular gate or wedge into the path of a flowing fluid. Gate valves require very little space along the pipe axis and hardly restrict the flow of fluid when the gate is fully opened enabling gate valves to offer straightway flow with very little pressure drop. Gate valves are mostly used with larger pipe diameters (from 2″ to the largest pipelines) since they are less complex to construct than other types of valves in large sizes. More recently, however, the larger sizes have been supplemented by butterfly valves due to space limitations under which they are installed.
The gate valve, as illustrated in on the right, generally consists of a gate-like disc, actuated by a screwed stem and hand-wheel which moves up and down at right angles to the flow. In the closed position, the disc seats against two faces to shut off flow. To retain the fluid in the pipeline, a gland is provided which is supplied with some type of packing to resist leakage.
Gate Valve Working Principle
Gate valves consist of three major components: body, bonnet, and trim. The body is generally connected to the piping by means of flanged, screwed, or welded connections. The bonnet, containing the moving parts, is joined to the body, generally with bolts, to permit cleaning and maintenance. The valve trim consists of the stem, the gate, the wedge, or disc, and the seat rings.
The main operation mechanism is very simple. When the hand-wheel is turned, it rotates the stem, which is translated into the vertical movement of a gate via threads. They are considered multi-turn valves as it takes more than one 360° turn to fully open/close the valve. When the gate is lifted from the path of the flow, the valve opens and when it returns to its closed position, it seals the bore resulting in a full closure of the valve.
Gate Valve Closing Member Design
The closing member, sometimes referred as gate also, comes in a variety of designs and technologies to produce effective sealing for differing applications. There are usually two types of gate valve closing members which are having further varieties.
Gate valves are typically constructed from cast iron, cast carbon steel, ductile iron, gunmetal, stainless steel, alloy steels, and forged steels.
All-metal gate valves are used in ultra-high vacuum chambers to isolate regions of the chamber.[2]
Bonnet
Bonnets provide closure for the valve body. Gate valves may have a screw-in, union, or bolted bonnet. A screw-in bonnet is the simplest, offering a durable, pressure-tight seal. A union bonnet is suitable for applications requiring frequent inspection and cleaning. It also gives the body added strength. A bolted bonnet is used for larger valves and higher pressure applications.
Pressure seal bonnet
Another type of bonnet construction in a gate valve is pressure seal bonnet. This construction is adopted for valves for high pressure service, typically in excess of . The unique feature of the pressure seal bonnet is that the bonnet ends in a downward-facing cup that fits inside the body of the valve. As the internal pressure in the valve increases, the sides of the cup are forced outward. improving the body-bonnet seal. Other constructions where the seal is provided by external clamping pressure tend to create leaks in the body-bonnet joint.