Author:Site Editor Publish Time: 2018-10-02 Origin:Site
The isolation valve belongs to the on/off type valve, which is only in the open or closed state. Isolation valve is basically has a requirement for the leak level. Relatively speaking, the safety requirements are higher than that of the on/off valve, and some parts have higher requirements for the opening and closing speed.
Isolation valve should be said to be a valve that emphasizes fluid separation on both sides and is safer. Many parts without special requirements use on-off valves instead. Globe valve is use as isolation valve if working condition's requirement is not high.
The main steam isolation valve is used for the secondary steam system of the PWR nuclear power plant. It is arranged on the top of the nuclear safety related plant and electrical plant and is located outside the containment. The main steam isolation valve and drive unit should be designed to prevent steam. The over pressure of the containment during the rupture of a main steam line in the containment between the generator and the main steam isolation valve and limits the cooling of the main system due to the rupture of the steam line.
Gate valve is a kind of on/off valve.The gate valve is a gate of the opening and closing part.The direction of movement of the gate is perpendicular to the direction of the fluid. The gate valve can only be fully open and fully closed, and cannot be adjusted and throttled. The gate valve is sealed by the contact between the valve seat and the gate. Usually, the sealing surface will be welded with metal material to increase wear resistance, such as surfacing 1Cr13, STL6, stainless steel, etc. The gate has a rigid gate and an elastic gate. According to the gate, the gate valve is divided into a rigid gate valve and a flexible gate valve.If divide by material,the gate valve would be as following:such as carbon steel gate valve, alloy steel gate valve, stainless steel gate valve, cast iron gate valve, titanium alloy gate valve, Monel gate valve, copper alloy gate valve, lead alloy gate valve, etc.
Advantage of gate valve:
1. The flow resistance is small. The inner medium passage of the valve body is straight through, the medium flows in a straight line, and the flow resistance is small.
2. It is more labor-saving when opening and closing. Compared with the globe valve, the direction of movement of the shutter is perpendicular to the direction of flow of the medium, whether it is open or closed.
3. High height, long opening and closing time. The opening and closing stroke of the gate is large, and the lifting is performed by the screw.
4. The water hammer phenomenon is not easy to produce. The reason is that the shutdown time is long.
5. The medium can flow in any direction on both sides, which is easy to install. The gate valve channels are symmetrical on both sides.
6. The length of the structure (the distance between the two connecting end faces of the casing) is small.
7. Simple shape, short structure length, good manufacturing process and wide application range.
8. Compact structure, good rigidity of the valve, smooth passage, small flow resistance, stainless steel and hard alloy on the sealing surface, long service life, PTFE packing, reliable sealing, light and flexible operation.