Body in line mainly used to control the process pipe cutting fluid, connected or switch port. Now commonly used pneumatic switch valve body are mainly ball valve, butterfly valve, gate valve, cut-off valve, diaphragm valve and throttle valve, etc. From various body below advantages and disadvantages as well as application scope were about.
(1) ball valve. The cock valve evolution, and open-close part is sphere.
Features are: (1) the low flow resistance, resistance coefficient and the length of the pipeline with same; (2) in high pressure and high temperature can also realize completely seal; (3) quick opening and closing, (4) the full open and close switch should, because the ball and seat sealing surface and the dielectric isolation, are less susceptible to corrosion; (5) structure is simple, remove, maintenance, replacement are more convenient.
Ball valve applications:
Due to the valve has the features of simple structure, force, dc path, less leakage and easy to operation and maintenance advantages, very suitable for chemical production, are used for pressure great, valve surface by the impact, high temperature, the sealing requirements strictly, diameter is not very big occasions, such as: vinyl chloride pipe, air pipes etc. In addition, slurry medium switch can choose V ball valve.
(2) butterfly valve. Butterfly valve opening and closing a disc type is left open.
Advantages are: (1) the simple structure, small volume, convenient installation, (2) the flow resistance coefficient is small, opening and closing fast; (3) can be used in large diameter valve; (4) can transport mud, in apertures stockpile liquid at least.
Defect is: (1) the use of pressure and operating temperature range is small, (2) the poor sealing.
Butterfly valve applications:
Butterfly valves because of the pressure loss is bigger, so is suitable for pressure loss of the pipe system in requirements is lax. In addition, in the large diameter valve, butterfly valve has more advantages, such as pipe diameter larger acetylene gas and hydrogen chloride gas pipeline, all use butterfly valve body pneumatic rapid cut-off valve to complete the abnormal state of valve quickly closed, to ensure the safety of the device.
(3) gate valves. Gate valves is refers to the closing member (ram) along the channel axis vertical movement of the valve.
Has the following advantages: (1) the fluid resistance is small, the sealing surface of scour and erosion by the medium small; (2) the open and close more effort; The flow direction of medium (3) is not restricted, not vortex, not reduce pressure; (4) the simple form, structure length is short, manufacturing technology, wide range.
Faults are: (1) physical size and opening are bigger, the space needed to install also bigger; (2) in the opening and closing process, sealing surface easy to wear, even in high temperature easy cause scratches.
Gate valve applications:
Gate valves are normally applies to don't always need to switch, and keep the gate open or seated working conditions. Many used for steam pipeline and the diameter of the feed water pipe and fluid resistance general requirements of smaller occasion.
(4) cut-off valve. Globe valve is refers to the closing member (disc) along the center line of the valve seat moving valve, valve lever open or shut down stroke is relatively short, has very reliable cutting function.
Advantages are: (1) in the opening and closing process, because disc and body facing the friction between the small, so wear; (2) the opening is small, so smaller; (3) in the valve body and disc usually only a sealing surface, so the manufacturing process is good, facilitate maintenance.
Faults are: (1) the liquid resistance is big, easy to cause the pressure loss; (2) not appropriate for large diameter line applications. (3) opening and closing moment is bigger, structure length is longer.
The closing of the valve application:
Due to the cut-off valve has the features of simple structure, good seal performance, manufacturing maintenance convenient features, for small diameter pipeline, and require a good turn off sealing, the cut-off valve.
(5) the diaphragm valve. The diaphragm valve body and cover are equipped with a flexible diaphragm, rely on the diaphragm of the upper and lower stroke to realize seal.
Its advantages are: (1) the structure is simple, easy to fast disassembly and maintenance; (2) because of its operating mechanism and medium flow passage off, can guarantee the purity of medium; (3) lining material diversity, can be applied to all kinds of medium, has good corrosion resistance characteristics.
Defect is: (1) the lining material limit its use temperature and pressure too much; (2) the diaphragm for wearing parts, will be subject to conditions and dielectric properties and change regularly.
The diaphragm valve applications:
The diaphragm valve applies to the chemical corrosive or suspended particles of the medium, and even difficult to transport of dangerous medium.
To sum up, the choice of the body should be comprehensive consideration of the leakage rate, medium type, medium temperature and flow rate coefficient, etc. Various kinds of parameters and performance. In the production of PVC, because of acetylene, vinyl chloride, PVC resin no corrosive and more gas, liquid and particle state exists, the body much adopt stainless steel material.
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