A valve is a pipeline attachment used to open and close pipelines, control the flow direction, regulate and control the parameters (temperature, pressure and flow rate) of the conveyed medium. According to its function, it can be divided into shut-off valves, check valves, regulating valves, etc.
Valves are control components in fluid transportation systems, which have the functions of shut-off, regulation, diversion, prevention of backflow, pressure stabilization, diversion or overflow pressure relief. Valves for fluid control systems range from the simplest shut-off valves to the most complex valves used in automated control systems.
Valves can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, slurries, oils, liquid metals and radioactive media. According to the material, the valves are also divided into cast iron valves, cast steel valves, stainless steel valves (201, 304, 316, etc.), chrome-molybdenum steel valves, chromium-molybdenum vanadium steel valves, duplex steel valves, plastic valves, non-standard customized valves, etc.
Classify
By function and use
(1) Shutdown valve
This type of valve is used for opening and closing. It is permanently installed in the inlet and outlet of cold and heat sources, the inlet and outlet of equipment, and the branch line of pipelines (including risers), and can also be used as a water drain valve and air release valve. Common shut-off valves include gate valves, globe valves, ball valves and butterfly valves.
Gate valves can be divided into open rod and dark rod, single ram and double ram, wedge ram and parallel ram, etc. The tightness of the gate valve is not good, and it is difficult to open the large-diameter gate valve; The size of the valve body is small along the direction of water flow, the flow resistance is small, and the nominal diameter span of the gate valve is large.
According to the flow direction of the medium, the globe valve is divided into three types: straight-through type, right-angle type and direct flow type, and there are open rods and dark rods. The closing tightness of the globe valve is better than that of the gate valve, the valve body is long, the flow resistance is large, and the maximum nominal diameter is DN200.
The spool of a ball valve is an open-bore ball. The plate-operated valve stem makes the ball open when it is facing the pipeline axis, and it is fully closed when it turns 90°. The ball valve has a certain adjustment performance and closes tightly.
The spool of the butterfly valve is a round disc that rotates along the vertical shaft of the vertical pipe axis. When the plane of the valve plate is consistent with the axis of the pipe, it is fully open; When the ram plane is perpendicular to the axis of the pipe, it is fully closed. The butterfly valve body length is small, the flow resistance is small, and the price is higher than that of gate valves and globe valves.
(2) Check valve
This type of valve is used to prevent the backflow of the medium, and uses the fluid’s own kinetic energy to open itself and close automatically when it flows in the opposite direction. Standing at the outlet of the pump, the outlet of the trap, and other places where the reverse flow of fluid is not allowed. There are three types of check valves: rotary opening type, lifting type and clamp type. In the case of swing check valves, the fluid can only flow from left to right and automatically closes when it flows in the opposite direction. For lift check valves, the spool lifts up to create a path as the fluid flows from left to right, and the spool is closed when it is pressed onto the seat when the flow is reversed. For the clamp-on check valve, when the fluid flows from left to right, the valve core is opened to form a path, and the valve core is pressed to the valve seat and closed when the reverse flow is reversed.
(3) Regulating valves
The pressure difference between the front and rear of the valve is certain, and when the opening of the ordinary valve changes in a large range, the flow rate changes little, and when it reaches a certain opening, the flow rate changes sharply, that is, the adjustment performance is poor. The control valve can change the spool stroke to change the resistance of the valve according to the direction and size of the signal, so as to achieve the purpose of regulating the flow valve. Control valves are divided into manual control valves and automatic control valves, and there are many types of manual or automatic control valves, and their adjustment performance is also different. Automatic control valves include self-operated flow control valves and self-operated differential pressure control valves.
(4) Vacuum
Vacuum includes vacuum ball valves, vacuum baffle valves, vacuum inflation valves, pneumatic vacuum valves, etc. Its function is in the vacuum system, the vacuum system element used to change the direction of the air flow, adjust the air flow volume, cut off or connect the pipeline is called the vacuum valve.
(5) Special-purpose categories
Special purpose categories include pig valves, vent valves, blowdown valves, exhaust valves, filters, etc.
Exhaust valve is an indispensable auxiliary component in the pipeline system, which is widely used in boilers, air conditioners, oil and gas, water supply and drainage pipelines. It is often installed at the commanding height or elbow to remove excess gas in the pipeline, improve the efficiency of pipeline use and reduce energy consumption.
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Post time: Oct-24-2024
