Gate valve

Last updated
An electric multi-turn actuator on a gate valve Drehantrieb auf schieber.jpg
An electric multi-turn actuator on a gate valve

A gate valve, also known as a sluice valve, is a valve that opens by lifting a barrier (gate) out of the path of the fluid. Gate valves require very little space along the pipe axis and hardly restrict the flow of fluid when the gate is fully opened. The gate faces can be parallel but are most commonly wedge-shaped (in order to be able to apply pressure on the sealing surface).

Contents

Typical use

Gate valves are used to shut off the flow of liquids rather than for flow regulation. 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 (e.g. handwheel or motor) to the gate. They are characterised as having either a rising or a nonrising 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. Nonrising 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. Nonrising stems are used where vertical space is limited.

Gate valves may have flanged ends drilled according to pipeline-compatible flange dimensional standards.

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 leakproof 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 2250 psi (15 MPa). 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.

Knife gate valve

For plastic solids and high-viscosity slurries such as paper pulp, a specialty valve known as a knife gate valve is used to cut through the material to stop the flow. A knife gate valve is usually not wedge shaped and has a tapered knife-like edge on its lower surface. [3]

Images

See also

Related Research Articles

Valve Device that controls the flow of a fluid

A valve is a device or natural object that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically fittings, but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure. The word is derived from the Latin valva, the moving part of a door, in turn from volvere, to turn, roll.

Flange External or internal ridge, or rim which provides strength

A flange is a protruded ridge, lip or rim, either external or internal, that serves to increase strength ; for easy attachment/transfer of contact force with another object ; or for stabilizing and guiding the movements of a machine or its parts. The term "flange" is also used for a kind of tool used to form flanges.

Gasket Type of mechanical seal

A gasket is a mechanical seal which fills the space between two or more mating surfaces, generally to prevent leakage from or into the joined objects while under compression.

Check valve Type of valve

A check valve, non-return valve, reflux valve, retention valve, foot valve, or one-way valve is a valve that normally allows fluid to flow through it in only one direction.

Standard diving dress Copper helmet with rubberised canvas diving suit and weighted boots

Standard diving dress is a type of diving suit that was formerly used for all relatively deep underwater work that required more than breath-hold duration, which included marine salvage, civil engineering, pearl shell diving and other commercial diving work, and similar naval diving applications. Standard diving dress has largely been superseded by lighter and more comfortable equipment.

Ball valve

A ball valve is a form of quarter-turn valve which uses a hollow, perforated and pivoting ball to control flow through it. It is open when the ball's hole is in line with the flow and closed when it is pivoted 90-degrees by the valve handle. The handle lies flat in alignment with the flow when open, and is perpendicular to it when closed, making for easy visual confirmation of the valve's status. The shut position 1/4 turn could be in either CW or CCW direction.

A flow control valve regulates the flow or pressure of a fluid. Control valves normally respond to signals generated by independent devices such as flow meters or temperature gauges.

Butterfly valve

A butterfly valve is a valve that isolates or regulates the flow of a fluid. The closing mechanism is a disk that rotates.

Ultra-high vacuum (UHV) is the vacuum regime characterised by pressures lower than about 100 nanopascals. UHV conditions are created by pumping the gas out of a UHV chamber. At these low pressures the mean free path of a gas molecule is greater than approximately 40 km, so the gas is in free molecular flow, and gas molecules will collide with the chamber walls many times before colliding with each other. Almost all molecular interactions therefore take place on various surfaces in the chamber.

Hydraulic machinery

Hydraulic machines use liquid fluid power to perform work. Heavy construction vehicles are a common example. In this type of machine, hydraulic fluid is pumped to various hydraulic motors and hydraulic cylinders throughout the machine and becomes pressurized according to the resistance present. The fluid is controlled directly or automatically by control valves and distributed through hoses, tubes, and/or pipes.

Globe valve Type of device for blocking or regulating the flow of fluids

A globe valve, different from ball valve, is a type of valve used for regulating flow in a pipeline, consisting of a movable plug or disc element and a stationary ring seat in a generally spherical body.

Solenoid valve

A solenoid valve is an electromechanically-operated valve.

Hydraulic cylinder Mechanical tool for applying force

A hydraulic cylinder is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in construction equipment, manufacturing machinery, and civil engineering.

Blowout preventer

A blowout preventer (BOP) is a specialized valve or similar mechanical device, used to seal, control and monitor oil and gas wells to prevent blowouts, the uncontrolled release of crude oil or natural gas from a well. They are usually installed in stacks of other valves.

Diaphragm valve

Diaphragm valves consists of a valve body with two or more ports, an elastomeric diaphragm, and a "weir or saddle" or seat upon which the diaphragm closes the valve. The valve body may be constructed from plastic, metal, wood or other materials depending on the intended use.

Piping and plumbing fitting

A fitting or adapter is used in pipe systems to connect straight sections of pipe or tube, adapt to different sizes or shapes, and for other purposes such as regulating fluid flow. These fittings are used in plumbing to manipulate the conveyance of water, gas, or liquid waste in domestic or commercial environments, within a system of pipes or tubes.

A pinch valve is a full bore or fully ported type of control valve which uses a pinching effect to obstruct fluid flow.

Valve actuator Mechanism for opening and closing a valve

A valve actuator is the mechanism for opening and closing a valve. Manually operated valves require someone in attendance to adjust them using a direct or geared mechanism attached to the valve stem. Power-operated actuators, using gas pressure, hydraulic pressure or electricity, allow a valve to be adjusted remotely, or allow rapid operation of large valves. Power-operated valve actuators may be the final elements of an automatic control loop which automatically regulates some flow, level or other process. Actuators may be only to open and close the valve, or may allow intermediate positioning; some valve actuators include switches or other ways to remotely indicate the position of the valve.

An isolation valve is a valve in a fluid handling system that stops the flow of process media to a given location, usually for maintenance or safety purposes. They can also be used to provide flow logic, and to connect external equipment to a system. A valve is classified as an isolation valve because of its intended function in a system, not because of the type of the valve itself. Therefore, many different types of valves can be classified as isolation valves.

ASME is a non-profit organization that continues to develop and maintains nearly 600 codes and standards in a wide range of disciplines. Some of which includes the Boiler and Pressure Vessel Code (BPVC), Elevators and Escalators, Piping and Pipelines, Bioprocessing Equipment (BPE), Nuclear Facility Applications (NQA), Process Performance Test Codes (PTC), and Valves, Flanges, Fittings and Gaskets (B16).

References

  1. 1 2 Beasley, Albert Jr. (July 1990), Fluid Power (PDF), United States Navy, p. 6-3, NAVEDTRA 14105, retrieved 2016-06-19
  2. "Valves". www.pfeiffer-vacuum.com. Retrieved 2019-08-23.
  3. "Knife Valves, All Types of Valves". www.stoneleigh-eng.com. Retrieved 2019-08-23.