VALVE

GATE VALVE

The gate valve, additionally referred to as a sluice valve, may be a valve that opens by lifting a spherical or rectangular gate/wedge out as to the path as to the fluid. the distinct feature of the gate valve will be the sealing surfaces connecting gate and seats are planar, thus gate valves are typically used each time a straight-line flow of fluid and minimum restric­tion is desired. the gate faces will type a wedge form or they actually can possibly be parallel. Gate valves are primarily used out to permit or forestall the flow of liquids, other then typical gate valves shouldnt be taken for regulating flow, unless they actually are specifically created for that purpose. as a result of with the ability out to cut through liquids, gate valves are typically used within the whole petroleum trade. for extremely thick fluids, a specialty valve typically referred to as a knife valve is made use of out to cut throughout the liquid. On opening the gate valve, the flow path is enlarged utilizing a highly nonlinear manner with respect out to % of opening. this suggests that that flow rate doesn't modification evenly with stem travel. Additionally, a partially open gate disk tends out to vibrate due to fluid flow. much of the flow modification occurs close to shutoff by having relatively high fluid velocity inflicting disk and seat wear and eventual leakage if used out to regulate flow. Typical gate valves are designed that should be totally opened or closed. when totally open, the typical gate valve has no obstruction within the whole flow path, leading to terribly low friction loss.

Gate valves are characterised as having either a rising or perhaps a nonrising stem. Rising stems give you a visual indication of valve position as a result of the stem is hooked up out to the gate such that the gate and stem rise and lower along like the valve is operated. Nonrising stem valves could possibly have a pointer threaded on a higher finish as to the stem out to indicate valve position, since the gate travels up or through stem upon the threads while not raising or lowering the stem. Nonrising stems are used underground or where vertical area is restricted. 

Bonnets give leakproof closure regarding the valve body. Gate valves could possibly have a screw-in, union, or bolted bonnet. screw-in bonnet will be the simplest, giving a durable, pressure-tight seal. union bonnet is suitable for applications requiring frequent inspection and cleaning. it additionally offers the body added strength. bolted bonnet is made use of for larger valves and higher pressure applications. 

Another sort of bonnet construction utilizing a gate valve is pressure seal bonnet. This construction is adopted for valves for high pressure service, usually in excess of 15 mpa ( 2250 psi ). The unique feature concerning the pressure seal bonnet may be that the body - bonnet joints seals improves like the internal pressure within the whole valve will increase, compared out to alternative constructions in which the increase in internal pressure tends out to produce leaks within the whole body-bonnet joint. 

Gate valves could possibly have flanged ends which you ll find are drilled consistent with pipeline compatible flange dimensional standards. gate valves are usually constructed from forged iron, ductile iron, forged carbon steel, gun metal, stainless steel, alloy steels, and forged steels.