Gate Valve
Ranging from the smallest to the largest size Gate Valve name is derived from the operation of the Gate valve. The Valve Acts like a Gate to stop or allow the flow through the valve. The valve can be opened by lifting the wedge out of the path of the flow Gate valves are actually designed for closing & opening full , so they are not suitable for the Throttling purpose. When the Gate valve is fully open, there is no Obstruction in the Flow path, resulting in very low pressure drop, & they are often suitable for the Hot Tapping & Pigging.
Gate Valves are actually designed for use with the flow of liquids and Gases but there are variation to cope with the specific requirements.
For example, one problem with wedge gate valves in steam service is that when the valve is closed and steam is brought into the system, the metal wedge expands and can get stuck, making opening the valve difficult or impossible.
Knife-gate valves are used when deposit may block a normal wedge gate. The gate is a narrow plate with a shaped edge to cut through solids. They are ideal for applications with a high suspension of solids or fibrous content such as powders, slurry, ash and pulp. Care should be taken when specifying knife gate valves to state whether flow is uni- or bi-directional.