General classification of valves
This classification method is divided by principle, function and structure, and is the most commonly used classification method at home and abroad. Generally, there are gate valves, globe valves, throttle valves, instrument valves, plunger valves, diaphragm valves, plug valves, ball valves, butterfly valves, check valves, pressure reducing valves, safety valves, traps, regulating valves, bottom valves, filters, blowdown valves, etc.
Because the valve is widely used, so it plays a great role. For example, in power plants, valves can control the operation of boilers and steam turbines; In petroleum and chemical production, valves also play a role in controlling the normal operation of all production equipment and process flow. The same is true in other departments. However, valves are often overlooked when compared with other products. For example: in the installation of machinery and equipment, people tend to focus on the main machinery and equipment, but ignore the valve. This will reduce the efficiency of the whole production or stop production, or cause a variety of other accidents. Therefore, the selection, installation, use of valves must be serious and responsible work.
Electric drive valve is a commonly used driving mode of the valve, usually called the driving device in the form of the valve electric device, the characteristics of the valve electric device are as follows: 1) fast opening and closing, can greatly shorten the time required to open and close the valve; 2) can greatly reduce the labor intensity of the operator, especially suitable for high pressure, large diameter valve; 3) Suitable for installation in the position that can not be operated manually or is difficult to access, easy to achieve remote control, and the installation height is not limited; 4) Conducive to the automation of the whole system; 5) The power supply is easier to obtain than the air and liquid sources, and the laying and maintenance of the wire is much simpler than the compressed air and hydraulic pipelines.
The disadvantages of valve electric devices are complex construction, more difficult to use in wet places, for explosive media, need to use flameproof measures.
Valve electric device according to the type of valve driven, can be divided into Z type and Q type two categories. The output shaft of Z-type valve electric device can turn out many circles, suitable for driving gate valve, globe valve, diaphragm valve, etc.; The output shaft of the Q-valve electric device can only rotate 90. Applicable to drive plug valve, ball valve and butterfly valve. According to its protection type, there are common type, flameproof type (represented by B), heat resistant type (represented by R) and triad type (i.e. outdoor, anti-corrosion, flameproof, represented by S).
The valve electric device is generally composed of transmission mechanism (reducer), motor, stroke control mechanism, torque limiting mechanism, manual - electric switching mechanism, opening indicator, etc.
Pneumatic and hydraulic valves
Pneumatic valve and hydraulic is a certain pressure of air, water or oil as the power source, the use of cylinder (or hydraulic cylinder) and piston movement to drive the valve, the general pneumatic air pressure is less than 0.8MPa, hydraulic pressure or oil pressure is 2.5MPa~25MPa. Or diaphragm valve; Return transition gas and liquid drive devices for drive devices used to drive ball valves, butterfly valves or plug valves. The driving force of hydraulic device is large, suitable for driving large caliber valves. For example, when used to drive plug valves, ball valves and butterfly valves, the reciprocating motion of the piston must be converted into a rotary motion. In addition to the use of cylinder or hydraulic cylinder piston to drive, there is no use of pneumatic film driven, because of its stroke and driving force is small, so mainly used for regulating valve.
Manual valve is the most basic actuation mode of the valve. It includes two kinds of direct drive by hand wheel, handle or plate hand and drive by transmission mechanism. When the opening torque of the valve is large, it can be driven by gear or worm drive to achieve the purpose of omission. Gear drive is divided into spur gear drive and cone gear drive. Gear drive reduction ratio is small, suitable for gate and globe valves, worm gear drive reduction is larger, suitable for plug valves, ball valves and butterfly valves