Gate Valve is designed for fully open or fully close of fluid, it means gate valve must be completely closed or completely open and semi-open can not be used.
This valve has a gate or door vertically, a round shape or square, that is going up and down in the fluid path and in cases of necessity to connect or disconnect the flow.
Gate valve in different shapes and different sizes are available. All components are identical with respect to various models have minor differences in terms of the company's overall sliding mechanism are the same for all valves that differ is only in terms of construction.
Gate Valve has 3 main parts: the Body, usually connects by flanges and bolts to the pipe and to prevent of leakage between valve and pipe flange sealing gasket (Gasket) uses. the Bonnet that is Part of the gate valve on top of the body and connected by flanges and bolts, for the purpose of tightening and prevent of leakage between the body and bonnet there is a gasket set and Finally, Trim which includes the stem or shaft, wedge and the Seat Ring.
Classification of the Gate Valve as per mechanism:
(A) Gate Valve with a movable shaft (Rising Stem)
By turning the hand wheel, shaft and gate move together and go up and down.
(B) Gate Valve with fixed shaft (Non Rising Stem)
By turning the hand wheel, gate move up and down.
Gate Valves has different type as per sealing:
1. Resilient / Soft Seat Gate Valve
2. Metal Seat Gate Valve
3. Parallel Slide Gate Valve
4. Knife Gate Valve
items 1 and 2 have the highest consumption in networks and water distribution lines, item 3 uses more in the case of suspended sand is high or high fluid flow rate, item 4 are mainly use in sewage systems
advantage and disadvantages of gate valves:
• Ability to complete cessation of fluid and use as full bore
• installation in horizontal and vertical position (Bidirectional)
• the lowest pressure drop
• opening and closing flow is not fast
• in case of half opening , valve will be shaken