1.gate valves:
Gate valve is closed (the gate) along the channel direction perpendicular to the axis of the valve, pipeline mainly as a cutting medium, that is full on or full off. In General, valves cannot be used in regulating the flow. It can be widely applied for low temperature pressure can also be used in high temperature and high pressure, and according to the valves of different material. Gate valves are generally not used for transporting slurry pipeline of such medium.
Advantages:
① small resistance for fluid and second less torque required to open, close c can be used in the media to the two way ring road network management, which means that unlimited flow of media about when fully opened, sealed surface erosion than globe valves of medium small;
② structure is relatively simple, good manufacturing process; f structure length is shorter.
Disadvantages:
① dimensions and large opening height, the space needed to install larger.
② in the process of opening and closing, sealing surface friction, wear larger, or even to cause abrasions phenomena at high temperatures c sealing surface of valve has two, adds difficulties to the machining, grinding and repair about opening and closing time.
2.butterfly valves:
Butterfly valve disc discs rotating 90 degrees back and forth to open and close a valve and adjust the fluid channel.
Advantages:
① simple structure, small size, light weight, supplies, used in large diameter valves; second, the open and close rapidly, flow and hinder small c can be used for medium with suspended solid particles, according to the sealing surface of the strength can also be used for powder and granular media. Bidirectional opening and closing and adjustment of suitable for the ventilation and dust removal pipeline, widely used in metallurgy, light industry, electric power, petroleum chemical industry, such as gas pipelines and waterways.
Disadvantages:
① flow adjustment range is small, when 30% is turned on, the flow will go to more than 95%.
② restrictions due to the structure of the butterfly valve and sealing material to be used for high temperature, high pressure in the pipeline system. General working temperature is below 300 ℃, PN40.
③ relative to the ball valve, globe valve sealing performance is poor, use where sealing requirements are not very high.