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
Valve construction
Bonnet
Pressure seal bonnet
Knife gate valve
Images
See also
References

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] An electric multi-turn
actuator on a gate valve
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

Knife valve is different category also different HS code and structure , and this valve dosent have wedge and
disc is knife , For plastic solids and high-viscosity liquids, a specialty valve often known as a knife gate valve
is used to cut through the material.[3]

Images
 A 2″ stainless steel Inconel gate valve Cryogenic 254 SMO Cryogenic super
gate valve with casting gate valve duplex gate valve
flanged ends. Bolts frozen up during
connect the lower operation
valve body with the
upper “bonnet”.
Visible threads on
the valve stem
protruding above the
handwheel show
that this is a rising-
stem valve.

Play media

Nuts and bolts for Gate valve being

incoloy valves installed on a new Gate valves
water service to a
fire hydrant. The
valve material is
ductile iron.

See also
Ball valve
Blast gate
Butterfly valve
Control valve
Diaphragm valve
Globe valve
Needle valve
Process flow diagram
Piping and instrumentation diagram
References
1. Beasley, Albert Jr. (July 1990), Fluid Power (http://www.cbtricks.com/miscellaneous/tech_public
ations/neets/fluid_power.pdf) (PDF), United States Navy, p. 6-3, NAVEDTRA 14105, retrieved
2016-06-19
2. "Valves" (https://www.pfeiffer-vacuum.com/en/know-how/mechanical-components-in-vacuum/v
alves/). www.pfeiffer-vacuum.com. Retrieved 2019-08-23.
3. "Knife Valves, All Types of Valves" (http://www.stoneleigh-eng.com/knifevalve.html).
www.stoneleigh-eng.com. Retrieved 2019-08-23.

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