The gate valve is the most common shut-off valve. Unlike ball valves, they are not quarter-turn devices; instead, they close and open through revolutions of the hand wheel.
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Used in wastewater plants, power plants and process systems, the threaded system of the gate valves give them an advantage over the quarter turn system of the ball and butterfly valve in large applications.
Fluid through gate valves experiences only minimal pressure drop as gate valves allow total flow through its passage when fully open.
This post discusses the functions, symbols, advantages and disadvantages, types, and other essential things you need to know about the gate valve.
Gate valves can also be called sluice valves or knife valves. They are control valves that allow or restrict the flow of media completely. Gate valves use a flat gate to close off flow between pipe flanges.
A gate valve, being a full port valve, has an equal diameter to the pipe through which the fluid passes. Hence, unlike butterfly valves, gate valves minimise pressure losses in the fluid when fully open. Also, because of the equal pipe and valve diameters, gate valves allow for the movement of pigs within the pipe for cleaning and inspection operations.
While butterfly valves can be used in flow regulation and on-off services, gate valves should only be used in on-off services as blocking valves and also to allow fluid flow. They should not be used in throttling.
Because of their uncomplicated construction and capability to be used in different low-pressure applications, gate valves are one of the most common valves in the industry.
The gate valve symbol is composed of two triangles meeting at a point. A vertical line is inserted between the triangles, and solid horizontal lines extend from the opposite sides of the triangle.
The vertical line indicates the blocking operation of the gate valve, and the horizontal lines show that the valve has a two-way function in on-off applications.
The gate valve symbol used in piping and instrumentation diagrams (P&ID) is a modification of the valve symbol, which is the gate valve symbol without the vertical line between the triangles.
The three isometric symbols in the diagram indicate symbols for butt-welding end connections, flanged ends, and socket ends connections.
Gate valves can be classified in three different ways:
Gate valves are mostly differentiated into parallel and wedge-shaped valves. The parallel gate valves shut off flow using a flat gate between two parallel seats. The gate is shut when the pressure from the pipe is allowed to seal the disc to prevent any flow. These gate valves usually function in conditions with minimal pressures or pressure drops.
The gate in the metal seated gate valve is shaped like a cone and enters into a hole in the bottom of the valve when it closes, supported by inclined seats. Impurities are a constant feature of the metal seated valve because of its closure design, leading to wearing out of the gate.
The metal seated gate valve was used before producing resilient seated gate valves.
Resilient seated gate valves, because of the valve's flat base, allow impurities to pass through without being stored in a hole as in the metal seated gate valve.
The rubber element in the gate sucks in the impurities as it closes, and the impurities are cleaned off when it opens again, allowing the gate to return to its normal form.
Rising stem-designed gate valves have stems outside the valve body and move with the gate. As the gate moves upward, so does the stem and vice versa. This movement allows the stem to be monitored for maintenance. This design is best used for surface installations.
Source: AlibabaIn non-rising stem designs, the stem rotates with the gate movement from inside the valve body. An indicator on top of the stem shows the position of the valve. This design can be used in industrial gate valves for surface and underground installations.
These valves seal by the combination of two slab gate valves. The mechanically expanding gates are sealed effectively at the gate seats. They find application mostly in electric systems and petroleum industries.
When used as a control valve, the gate valve can effectively function in several industrial operations. Like other industrial control valves, the gate valve has advantages and disadvantages. Some of its advantages are:
The gate valve is a full port valve. Hence it allows easy passage of fluid with minimal resistance. Unlike other valves, when fully open, the gate valve body does not affect the flow motion or direction.
Gate valves perform better sealing operations than the shutoff valve, which is also a control valve. Even though slower than some other valves, the gate valve offers faster opening and closing operations than the shutoff valve.
Gate valves can function effectively with fluids such as oil, steam, slurries, and suspended fluids. Also, they can function as low vacuum system valves or venting valves.
Gate valves are not restricted to one direction of flow. They are two-way directional valves, and they do not depend on the direction of the medium. Gate valves are good for operations where the fluid direction may switch.
Other advantages of the gate valves include:
Gate valves can be severely damaged if they are open or closed halfway. Hence the gate has to be withdrawn fully into the upper valve area when open and must be allowed to rest on the valve seat when closed before fluid flow.
The movement from the upper valve area to the bottom takes a lot of time, leading to the slow operation of gate valves. Due to its slow operation, gate valves can not be used for fast processes.
The valve gate makes contact frequently with the valve seat; this may lead to scrapings on the gate surface. Surface scrapings cause damage to the gate with time resulting in the shorter life span of gate valves. Damages on the gate surface are not easily repaired.
Other disadvantages of gate valves include:
Gate valves are usually used in on/off services where they function in allowing or restricting flow. For better efficiency, gate valves should not be used regularly, as frequent friction would lead to the shorter service life of the valve.
Because of its ability to allow flow through the pipeline with minimal pressure losses and permit easy operation of pigs for inspection and cleaning, the gate valve is a commonly used valve for blocking and isolation.
However, gate valves should not be used for flow regulation. Constant fluid contact with the gate causes damage to the disc and seat and invariably shortens the valve's service life.
They have a wide application in the industry which includes operations in petroleum refineries, power plants, manufacturing factories, and chemical production companies. The gate valves function effectively in high temperature and pressure conditions.
The gate valve includes the body, hand wheel, yoke, bonnet, packing gland, stew, and gate. Each part will be explained below.
The valve body is responsible for housing the valve trim and allowing fluid to pass from one pipe end to another. Valve bodies are made from metals, an alloy of metals, or nonmetals of varying kinds.
Also called shells, the gate valve body can be joined to the pipe flanges by butt, sockets, wafers, or threaded ends.
The gate valve body is of three different designs, which depend on the purpose of the gate valve. The designs are Reduced Bore, Full Bore, and Cross Flow.
The bonnet of gate valves primarily functions as valve covers and support for other parts of the valve, such as the disc, stem, and actuators. Also, in the gate valve, the bonnet allows an opening for the stem.
The gate valve bonnet is joined to the body using threads, bolts, or welding. Some valve bonnets are designed to be merged with the body (bonnetless valves), and bonnets are usually made in the same material as the valve body.
The gate valve trim comprises the valve disc, gland sleeve, gland packings, back seat, valve stem, and valve seat. These are parts that have contact with the flow medium. The valve trim parts control the operation of the valve.
The stem is responsible for the control of the disc. When the stem is rotated, it relays this motion to the disc by lifting or dropping it. The gate valve stem is joined to the actuator (sometimes through the yoke) or manual handling machine on the top end and the valve disc on the other end to facilitate control.
The gate valve seat is a resting point for the valve disc to which it is sealed. While some valves have one seat, the gate valve has two seats, one on each end of the pipe flanges. If the disc and valve seat are not sealed properly, it may cause leakages in the valve.
The gate valve backseat holds the stem in the valve open position. It also restricts fluid from going up to the packing chamber and the surface.
The gate valve disc is the part of the valve which performs the function of allowing or restricting flow through the pipeline. It blocks the fluid pressure from moving from one end to another. The disc rests on the valve seat to which it is sealed.
The gland packings prevent leakages from the stem and are usually in a stuffing box. The gland sleeves keep the gland packings in the box.
The yoke connects the actuator to the stem. They are sometimes merged with the bonnet to manufacture several valve designs. The yoke is also called arms.
The gate valve operation is in many ways similar to the operation of most valves. The hand wheel or actuator is controlled to rotate the stem, which controls the gate. For the handwheel, the wheel is turned in several revolutions before the gate valve can be fully open from a closed position or fully closed from an open position.
Control using the actuator is easier as it requires no user at the location, only an actuator system (pneumatic or electric) must be on site. By raising the gate to a fully open position, the valve allows the media to flow through the pipeline without obstruction.
Closing and sealing the pipe to the valve seat retains the flow pressure and restricts the flow of the media beyond the gate. The flow rate of the media experiences erratic change as the gate valve is closed, resulting in an unpredictable relationship between the valve and fluid flow rate.
Fluid pressure and flow against the gate wear out the seat and gate. Gate valves should not be used for flow regulation as the constant flow hastens the damage to the gate and seat.
Installing gate valves should be done properly to increase the service life of the gate valves and to ensure their proper operation. Here are some installation practices to be followed while installing gate valves:
Below are some essential practices to ensure the valve works effectively and lasts longer.
In selecting a gate valve suitable for operation in specific conditions, factors such as suitable material, size and design must be considered. Here are some factors to consider in buying a gate valve:
Materials used for the production of gate valves vary with specific conditions. Common materials are cast iron, cast carbon steel, stainless steel, ductile iron, gun metal, bronze, steel alloys, stainless steel, and forged steel.
Key selection criteria of material to use are fluid service and design temperature. Below are some materials used in the creation of the gate valve:
Material Grades
Below are some common trim material grades used in the production of gate valves
Trim materials are grouped and assigned a trim number or combination number. In the chart below, material for a gate valve seat, disc, stem and backseat are specified against a trim number.
From this chart, an order can be made by the trim number. There will be no need to specify any materials for an order of the gate valve trim. This chart is in line with the API 600 specification.
Source: HardHat EngineeringBelow are codes and standards that are used in the design and selection of gate valves:
API 598
API B16.34
ANSI B16.10
ANSI B16.25 and B16.11
ANSI B 1.20.1 (BSP/NPT)
This post discussed all you need to know about the gate valve, including its function, parts, installation and maintenance requirements, and what you need to consider before buying an industrial gate valve.
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We all must have used or seen a valve or two in our lives; be it shower valves or sink taps, we have come across valves in our daily lives, but they are not control valves because they do not allow you to set or control the amount of flow. An industrial valve allows you to set and control the flow of media manually or automatically. This article will give you a detailed understanding of this device and its applications.
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A control valve is a type of valve that is used to control the flow of a media by varying the size of the passage of flow as directed by the controller. Control valves find use in several industries because they enable the direct control of flow rate. The valve industry has progressed a lot in terms of innovating control valves for different applications.
A control valve is used to control the operating conditions such as pressure, temperature, gas levels, and liquid levels. It accomplishes this function by opening and closing the valves partially or completely after receiving signals from the controller. In industries, valves perform the same function as a shower tap. However, control valves are designed with high precision and are operated by a control system.
Control valves are widely used in controlling the fluid flow in various industries such as oil & gas, food & beverages, pharmaceutical, marine, and pipelines.
Control valves form a vital part of the piping system in the oil and gas industry. They are used to control the flow rate, guide the refining process, and isolate the equipment of crude oil. The industrial gas valves help in providing process control over the temperature and pressure in the Oil & Gas industry.
The control valves operate by varying the size of the passage flow as controlled by a hydraulic or pneumatic signal sent by the system. The automation process of these valves enables them to be operated remotely as compared to having an operator constantly monitor the process.
There are a lot of challenges faced by the food and beverages industry in controlling the fluid flow and temperature, most of which can be solved using China industrial valves. Control valves are popularly used in the food & beverage industry by controlling the incoming feed and moving finished products to warehouses.
The most important task performed by control valves is controlling the temperature to determine the product quality. It is important to carefully select a valve (Valve Selection Guide: Things You Must Know) and tune it for process conditions that are needed to accomplish peak performance. Control valves help get the set point of the manufacturing process and maintain the temperature during the batch cycle.
It is important to choose a reliable industrial valves company that provides a wide range of products that help control the temperature. A control valve solution that has a highly accurate response will help solve all the flow control challenges faced by the food & beverage industry.
There are various types of valves used in the pharmaceutical industry for the sterile processes that are required to be maintained. The most common issue in the pharmaceutical industry is containment because it is important to keep the product and the quality of the product safe. Control valves are perfect for containment in the pharmaceutical industry.
The most significant property of valves used in the pharmaceutical industry is their capability to clean and sterilize equipment. The chemical processing industry involves processes that involve high heat and high pressure and control valves that help in the flow control of the chemicals without cross-contamination.
Asian industrial valves & instruments play an important role in the marine industry. The larger the ships, the higher the requirement of generating power, treating wastewater, and performing operational tasks, all of which require valves. The size of the ship will help you determine the number of and different types of valves that will be required on board.
Industrial control valves are used in the marine industry to load and store a ship's power supply and to provide water for various applications. It helps handle the wastewater process and store liquid cargo onboard. The valves that are used in the marine industry should be durable and reliable because they should not rust or react when they come in contact with seawater.
There are thousands of crucial pipelines that transport liquid and gases from their source to where it is required and that needs different types of industrial valves. Control valves are used to optimize the operating conditions of the pipelines.
The most important aspect to consider while selecting a control valve for the pipeline application is to check whether it is cleanable from the inside.
We have learned till now that control valves are used to control and change the flow path of a media and that they are characterized by their flow coefficient. However, valves are also typed according to their motion and their design. Some of the control valve types by design are discussed in detail below.
An industrial ball valve is a shut-off valve that helps control the flow of media by the means of a rotary ball that rotates 90 degrees around its axis to control or block the media flow. Ball valves are characterized by a long service life and they contribute to reliable sealing throughout their lifespan even when they are not being used.
The advantages of using a ball valve include:
Some of the common ball valve types include:
Application of Ball Valves:
Ball valves are widely used for controlling the flow and pressure of corrosive liquids and gases in the oil and gas industry. They are commonly used in manufacturing sectors, pharmaceutical containment, and residential uses are well. Generally, any liquid or gas application that requires a bubble-tight service uses ball valves.
An industrial check valve is a device that allows the flow of liquids and gases in only one direction. It has two ports, one that lets the media inside the valve and one the works as an outlet for the media. Since the check valves only allow media to flow in one direction, they are also known as 'one-way valves'.
The important function of check valves is to prevent backflow in any system by using pressure differential. For this reason, they are commonly installed in applications that cause problems because of backflow. Since these valves are one-way, they are cheap and offer easy solutions to solve potential backflow issues.
Some of the advantages of using a check valve include:
Some of the common types of check valves include:
Application of Check Valves:
Check valves are commonly used in preventing the backflow of wastewater and potable water. The specific use of check valves depends on the direction and the configuration of the component that it is installed with. Other applications of check valves are found in mining, process industries, pharmaceutical, and power industries.
Butterfly valves are the types of quarter-turn valves and they work similarly to ball valves. It consists of a disk that is connected with a rod and it opens and closes when the rod rotates to control the direction of the flow. These valves are used for modulating services and are widely appreciated for their lightweight, economical costs, low levels of footprint, and availability in different sizes.
Some of the advantages of using a butterfly valve include:
Butterfly valves come in diverse designs, each of which serves different applications. Some of the different types of butterfly valves include:
A gate valve, as the name suggests, works as a gate to enable the proper flow of liquid by lifting and lowering the gate. It offers an unobstructed pathway, which means that there will be minimum pressure loss over the valve. It also allows for pigging when you need to clean the valve from inside.
Some of the advantages of using a gate valve include:
Some of the different types of gate valves include:
Application of Gate Valves:
An industrial gate valve is commonly used to shut off the flow of fluid completely or provide full flow in a pipeline in a completely closed or open position simultaneously. These valves find great use in underground and above-ground applications that are designed to operate at fully open or fully closed capacity.
While gate valves are generally installed on pipelines as isolating valves, they shouldn't be used to regulate or control the flow of a fluid.
Industrial globe valves are linear motion valves that are commonly used to start, stop, and throttle the flow of a media. These valves are designed with a stem that goes up and down to regulate the flow of liquids and gases inside the valve.
Conventional Globe valves are used for isolation services as well as throttling services. Even though these valves present slightly higher pressure drops than the other valves, they are used where the pressure drop is not a factor that affects the operation of the valve.
Some of the different types of globe valves include:
Application of Globe Valves:
Some of the typical applications of globe valves include:
Below are the main valves categories based on their power.
Manual valves are the valves that need a manual operator to operate the valve using a hand lever or a handwheel. These valves are generally used to start and stop the flow of media or for manual throttling. The optimally working manual valves are those that allow the flow to pass straight through the body with minimal or no pressure drop.
Some of the different types of manual valves manufactured by the valve manufacturing industry include:
Application of Manual Valves:
Manual valves that are available in the market today offer two functions of regulating the flow of media and flow measurement of the media. Each manual valve type has its own specification that is suited for a particular application.
Solenoid valves are used in applications that need the flow of media to be controlled automatically. They are widely used in various types of plants and equipment. There are a variety of different designs such as a solenoid ball valve for water that enables its users to control the flow of water supply automatically.
Some of the different types of Solenoid valves include:
Application of Solenoid Valves:
Solenoid valves are commonly used in various industries to control and restrict the flow of liquids and gases. These valves are also used to mix liquids of different volumes. In automatic systems, solenoid valves are used to product movements and control the flow of media.
Valves help isolate, control, and regulate the flow of media in various industries. There are several different types of valves starting from manual to semi-automatic to fully automatic. You must properly select your control valve to operate your system safely and efficiently without needing much maintenance.
The first thing to do is to select a cost-effective valve type that is suitable for your application. Next, select the appropriate temperature and pressure rating that will be compatible with the materials of your operating system.
While choosing automated valves, you should consider the type of valve based on its life cycle. The type of the valve and the type of the actuator should be picked based on the amount and frequency of modulating cycles. Additionally, control valves need the sizing and choosing a trim size to make sure that the accuracy and stability of the valve are proper.
Some of the factors to consider before buying a control valve include:
Control valves seem like a technical term to understand but it is an important part of our daily lives. The type of industrial valve to use depends on a number of factors, but the important thing to remember is to approach a reliable industrial valves manufacturer to ensure that you receive a high-quality and durable valve.
Contact us to discuss your requirements of Tilting Disc Check Valve. Our experienced sales team can help you identify the options that best suit your needs.