Gate Valves – The Most Common & Essential Valve
Despite serving very different functions, gate valves, globe valves, and check valves are often spoken about concurrently, due to the many similarities in: construction material grades, trims, and other technical specifications. A Gate Valve, also known as a sluice valve, is the most common type of valve used and are a cost-effective way to provide a quality sealing valve with a high-temperature tolerance.
- Gate valves are obligatory in applications that require minimum pressure loss in areas where bi-directional flow is desirable.
- Once again, because a gate valve is designed to be completely open or completely closed, it will not have the impact on the overall pressure of the system.Gate valves should be designed using the same size opening on either end. Any narrowing or widening will change the flow of fluid and limit the efficiency of a system.
Gate Valve Operation
As the name suggests, gate valves work by a simple “gate” mechanism that executes the important function of regulating fluid flow through the system. The “gate” itself is usually a round or rectangular gate/wedge. However, it’s essential to note that a gate valve only delivers a no-flow or full-flow condition and can only be functioned in one position. It will not work in an application where partial flow is required.
A distinct feature of a gate valve is that the sealing surfaces between the gate and seats are planar, so gate valves are often used when a straight-line flow of fluid and minimum restriction is desired. Gate faces can be parallel, but are most commonly wedge-shaped. Because of their ability to cut through liquids, gate valves are often used in the petroleum industry.
Gate valves are characterized as having either a rising or a non-rising 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.
Gate valves are actuated by a threaded stem which connects the actuator (e.g. handwheel or motor) to the gate. The actuator takes the form of a nut which 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 upper end of the stem to indicate valve position, since the gate's motion is concealed inside the valve. Nonrising stems are used underground or where vertical space is limited.
Gate Valve Types
- WEDGE GATE VALVES: This is your standard gate valve. Also known as a sluice valve, this gate valve opens by lifting a round or rectangular gate valve/wedge out of the path of the fluid that is running through it.
- KNIFE GATE VALVE: This is like your typical gate valve, except this gate valve has a wedge that utilizes a sharp, beveled edge to cut through thicker fluid/material.
The two most common specs for carbon steel valves are A105 and A216 WCB. It is important to note the different sizes ranges that are available in forged (A105) and cast steel (WCB). While cast steel gate valves, globe valves, and check valves can be made to meet virtually any size requirement for your application, forged steel gate valves, globe valves, and check valves are only available up through 4”. Forging is prohibitively expensive at larger diameters, where casting is a much more cost effective for this size range.
About MSI Supply
MSI is a full-line valve distributor, located in Houston, TX, that offers gate valves, globe valves, and check valves in a wide array of materials, including A105, WCB, LF2, bronze, aluminum-bronze, 316SS, 347SS, cast iron, ductile iron, alloy 20, Hastelloy, Monel/Inconel, F5, F9, F11, F22, and more!