How Does Gate Valve Work?


All valves are created to stop, permit, or throttle the circulation of a process fluid. Gate valves– one of the original valve styles– are ideally fit for on-off, primarily liquid, service. A gate valve functions by raising a rectangular or circular gate out of the path of the fluid. When the valve is fully open, gate valves are a complete bore, implying there is absolutely nothing to obstruct the circulation because eviction and pipeline diameter have the same opening. This bore size likewise determines the valve size. A benefit of this full-bore style is very low friction loss, which saves energy and minimizes the total cost of ownership. China cast steel gate valve manufacturers can create these bores

Gate and segment

There are four main styles for gate valves.

  1. Slab gate valves consist of a single gate system that raises and decreases between 2 seat rings and are mostly used for transporting petroleum and NGLs. The G4N fabricated gate valve in the STV valves portfolio and the piece gate valve are ideal choices for this application.
  2. Broadening gate valves include 2 units– a gate and a sector– on the other hand with piece gate valves, which have one unit. The gate and section systems collapse against each other for travel and different when the valve is totally opened or totally near affect a mechanical seal.
  3. Wedge gate valves are crafted with a tapered gate with metal-to-metal sealing. On the other hand with a slab or broadening gate valve, wedge gate valves are not pingable due to the fact that of the void that is left in the bottom of the valve body when the valve is open. These valves do not have a bore through the gate itself; rather, the gate withdraws into the valve body when open, which saves height area.
  4. Knife gate valves are used to cut through extremely thick fluids and dry bulk solids. The design of this valve makes it inherently self-cleaning due to the fact that the knife is cleared of abrasives with each stroke as it passes the seat rings and skirts. The gate unit of this kind of valve is thin compared with other gate valve types and is guided in place by the water-type body that sandwiches the gate.


Gate valves can have an increasing or non-rising stem design. Rising stems are connected directly to eviction and supply a visual sign of the valve position. Nonrising stems are usually threaded into the upper part of eviction and have a pointer threaded onto the top to suggest position. Nonrising stem designs are preferably fit for applications where the vertical area is restricted, in great applications, and where scraping or pigging is not required.

Gate valves are designed with a sealing system to offer a tight seal around the stem. Single loaded-spring (SLS) stem seal style, used in Saf-T-Seal piece gate valves and WKM Pow-R-Seal double broadening gate valves, provides exceptional leak protection and a self-adjusting seal developed to minimize maintenance.


Gate valves typically have one of four kinds of bonnets, which offer closure to prevent fluids from dripping out of the valve. Screw-in bonnets are easy, long-lasting sealing units that utilize pressure to seal. Union bonnets supply easy access to the valve body for applications that may need regular maintenance or assessment. Bolted bonnets are normally used for bigger valves in higher-pressure applications. Pressure seal bonnets are designed for services with pressure in excess of 2,250 psi [15 MPa]


Because of the variety of building materials, trim offerings, and style mixes offered with gate valves, they are appropriate for a wide range of applications. From high-temperature coking units to food and pharmaceutical services, gate valves can be depended dependably carry out.

The safeguarded seat-face style of double broadening and slab gate valves eliminates degradation of the seat face triggered by particles while doing so fluid, which makes them perfect for liquid service. When additional protection is required at points in pipeline applications where functional integrity is vital and the effects of ecological direct exposure are higher, such as near waterways and towns, double expanding gate valves are an especially sensible choice.

Smaller 2- to 4-in non-rising stem variation of the Pow-R-Seal API 6A expanding gate valve is commonly utilized in wellhead manifold systems since of its reliable mechanical seal and high-pressure capability.

Drilling manifold systems can also be quickly developed to utilize particular gate valves, such as the STV valve DM series, with space-saving and versatile mounting designs.

What is the difference between single expanding and double broadening gate valves? 

A double broadening wedge is broadened in both open and closed positions, and the two seats are sealed in both open and closed conditions. A single expanding wedge is broadened just in the closed position and the 2 seats are sealed. Hence, fluid enters the cavity outdoors position in a single expanding gate valve, however the cavity is not filled in either open or closed positions for a double expanding gate valve. Double expanding gate valves can ensure no leakages to the cavity in both closing and opening conditions. One benefit of a double expanding valve is that this valve includes 2 half wedges with more disk flexibility in heats due to thermal growth. Double expanding is the favored option of valve for very unclean services in high temperature varieties above 200 ° C.

TCG valves are not suggested for fluid control (throttling) because lengthened usage under throttling will result in fast damage to the seats of the valves along with internal valve elements. The main parts of the double broadening and piece gate valves are body, bonnet, wedge (gate) halves, seats, and stem. The body and bonnet are the main pressure-containing parts. The disk(s) are placed by the stem to obstruct the circulation or open the fluid course. The wedge assembly in a double broadening gate valve consists of two halves, one male and the other female, which are paired together, normally with springs.

A slab gate valve, also called a single disk, is designed to provide seclusion of the piping system or an element when it is in a closed position. This type of valve is also not appropriate for fluid control (throttling). Simply as the double expanding gate valves, prolonged usage of a piece gate valve under a throttling operation will result in wearing and damage of the seats and internal elements. The primary parts of a double expanding and piece gate valve are body, bonnet, wedge (gate), seats, and stem. The body and bonnet are the main pressure-containing parts. The seats are usually floating-type seats with the springs at the back to ensure appropriate tightness in between eviction and seats.

A double broadening valve is two wedge gate valves in series with one bleed gate valve in between. A double broadening valve can be as much as 50% more expensive usually than a piece gate valve in little sizes and 25%– 30% more pricey in bigger sizes. Single broadening valves are normally less costly than double expanding. Single expansion is an excellent choice if a more robust choice than a piece gate valve is required, and the valve is frequently in the closed position. Comparing the metal seat ball valve with a TCG valve, both slab and expanding are more costly in plus sizes such as 30 ″ and 36 ″. In some cases, a ball valve in smaller sized or medium sizes might be more costly than a TCG valve. For example, a 12 ″ Class 1500 ball valve with API 6D design might be more pricey than a piece gate valve in the exact same size and pressure class and API 6D design. One way to estimate the relative cost of the valves is to compare their weights. As an example, a 3 ″ piece gate valve in class 300 was compared to a ball valve with the very same size, pressure class, and material. The slab gate valve was practically two times as heavy as the piece gate valve. Naturally, the weight of a valve is different from one provider to another one.

A double expanding gate valve is not always a much better valve than a slab gate type. But double broadening is a more robust valve considering that less friction and wearing occurs between the seat and the disk during disk traveling. In addition, less fluid is collected and pressurized into the cavity so double broadening has a longer loading life compared to the piece gate valve. However, the actuation of a double broadening valve is challenging due to the fact that this valve is a torque-seated type and over-torquing the valve might damage the disk. Therefore, additional attention should be paid to sizing and selecting the actuator for a double expanding gate valve to prevent over-torquing.

The wedge is expanded at the top (open) and bottom (closed) points in a double expanding gate valve. Growth of the wedge toward the seats by the mechanical stem force and sealing pressure between two halves supplies tight sealing with 2 seats in both instructions. Tight contact of the wedge with the seats at open and closed positions increases the breakaway torque in both closed and open situations, which increases the actuator sizes. For this factor, an end user might avoid picking a double expanding valve to avoid having a bigger actuator. As mentioned earlier, over-torquing an activated double broadening gate valve can damage the seat, wedge, and stem. Slab gate valves are not torque-seated so there is no risk of damage to valve parts due to over-torquing.

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