Pneumatic valve selection methods

security pneumatic valve equipment, equipment and piping as a safe protection device. In order to prevent the equipment, equipment and piping within the medium pressure in excess of the prescribed value. When the equipment pressure exceeds allowable values. Pneumatic valve opens, then the whole amount of emissions. In order to prevent the equipment pressure continued to rise; When pressure is reduced to the specified value, the pneumatic valve shall be closed in time. To protect the safe operation of the equipment.
security pneumatic valve is used in the correct involves two aspects of the problem. On the one hand, working condition of equipment or system is to be protected, such as work stress, allowing the overpressure limits, necessary to prevent overpressure of emissions, the characteristics of working medium, operating temperature and so on; On the other hand is a safe action character of the pneumatic valve and parameters. Mainly from the Angle of safety pneumatic valve below to illustrate the key points of selection.
（ ） Safety
the pneumatic valve terms for security pneumatic valve is a kind of automatic pneumatic valve, in terms of structure and performance parameters with general pneumatic valves have many differences, especially some special terms is easy to confuse. Arrangements to make people more clearly understand the use safety of pneumatic valves, and can choose correctly, will some of the main terms.
security pneumatic valve: an automatic pneumatic valve, it is not by any external force, but it was the use of force to discharge a nominal amount of fluid. In order to prevent the system pressure exceeds a predetermined TVC. After the pressure back to normal, pneumatic valve shut down and prevent any media continue to flow out.
directly load type pneumatic valve: a direct mechanical loads such as weight, leverage is aggravating hammer or spring to overcome by pneumatic disc under medium pressure generated by the security forces pneumatic valve.
motivating auxiliary device security pneumatic valve: the security of pneumatic valve using a power aided device, can be in below the normal open under pressure. Even if the assist device failure, this kind of pneumatic valves should still can meet the standard requirements.
with the safety of the supplementary load pneumatic valve: this security pneumatic valve in the inlet pressure to always maintain a rising seal before opening pressure of the additional force, the additional force ( Supplementary load) Can be provided by the external energy, pneumatic valve to open in the safety pressure should be released in a reliable way. Its size should be set like this: the additional force is not released, security pneumatic valve can still in the opening pressure of inlet pressure shall not exceed the national rules and regulations under the premise of achieve the rated capacity of a percentage.
the guide type safety pneumatic valve: a rely on from a pneumatic valve guide medium to drive or control the safety of the pneumatic valve. The pneumatic valve guide itself should be meet the requirements of the standard load type pneumatic valve safety directly.
opening pressure ( Setting pressure) : safety pneumatic valve pneumatic valve under the condition of the running start rising when the inlet pressure, under pressure from the beginning was to be the amount of lateral opening height, medium can be continuous discharge state by visual or auditory perception.
discharge pressure: pneumatic disc reach regulation when you start the height of inlet pressure and discharge pressure of the cap should be obey the demands of the relevant national standards or regulations.
over pressure, discharge pressure and opening pressure difference, usually expressed in the percentage of opening pressure.
back pressure: emissions pneumatic disc to contact with the pneumatic valve seat, after the opening into the inlet pressure to the zero.
opening and closing pressure difference: the difference between the open pressure and back pressure, often use percentage of opening pressure, only when the opening pressure is very low with 'MPa' said.
back pressure: safety pneumatic valve outlet pressure.
the rated discharge pressure: the upper limit of discharge pressure prescribed standards.
seal test pressure: the inlet pressure to the sealing experiment was carried out. Under the pressure measured by closing a sealing surface leakage rate.
open height: pneumatic disc leave the actual lift in the closed position.
port area: refers to the inlet pneumatic valve is to shut down the smallest cross-sectional area of flow channel between a sealing surface, used to calculate without the theoretical displacement of impact resistance.
port diameter: corresponds to the diameter of the port area.
shade area: when the air valve in the pneumatic seat rises above, in the form of formed between the sealing surface of a cylinder or cone surface shape channel area.
discharge area: pneumatic valve discharge fluid channel, the minimum cross-sectional area. For all pneumatic valve type safety. Discharge area is equal to the port area; For safety mini rev type pneumatic valve, discharge area is equal to the shade area.
the theory of displacement, flow and safety section of pneumatic valve port area is equal to the ideal of the nozzle calculation of displacement.
displacement coefficient, the ratio of the actual displacement and displacement theory,
the rated discharge coefficient, displacement coefficient and reduction coefficient ( Taking. ） The product.
the rated capacity, the actual displacement of allowed as a security that part of the pneumatic valve using benchmark.
equivalent calculation of displacement: refers to the condition such as pressure, temperature, dielectric properties and the application of the rated discharge conditions at the same time, the security in the calculation of the pneumatic valve discharge.
frequency jump: safety pneumatic valve pneumatic disc unusually movement back and forth rapidly, pneumatic disc contact pneumatic seat in the movement.
flutter: safety pneumatic valve pneumatic disc unusually movement back and forth rapidly, pneumatic disc out of touch with pneumatic seat in the movement.