The Basis of Valve Selection

Air operated pinch valve  is a control component in the fluid transportation system, the main function is to open and close, regulate, guide, prevent backflow, pressure stabilization, diversion or overflow pressure relief. Valve is also the most complex component in the pipeline, it is generally assembled from multiple parts, high technical content. With the rapid development of the chemical industry, most of the media in the chemical production plant has large toxic, flammable, explosive and corrosive characteristics, the operating conditions are more complex and demanding, the operating temperature and pressure are high, the valve once the failure, the light leads to media leakage, both pollution of the environment and economic losses, the heavy lead to device shutdown, or even cause malignant accidents. Therefore, in the pipeline design, the scientific and reasonable selection of valves can reduce the construction costs of the device, but also ensure the safe operation of production.

The Basis of Valve Selection

1.Physical Properties

①Material Status

a. The material state of gas materials, including relevant physical data, pure or mixed gas, whether there are liquid droplets or solid particles, whether there are easy to condense components.

b. The material state of liquid materials, including relevant physical data, pure components or mixtures, whether there are volatile components or mixtures of dissolved oil gas (pressure can be reduced to form a two-phase flow), whether it contains suspended solids, as well as the viscosity of the liquid, solidification point, etc.

②Other Status

This includes properties such as corrosiveness, toxicity, solubility to valve construction materials, and whether it is flammable and explosive. These properties will not only affect the material, but also cause special requirements on the structure, or the need to improve the piping grade.

The Working Conditions in operation

①Temperature and pressure according to normal operating conditions, also need to be combined with the operating conditions during start-up and shutdown or regeneration.

② Allowable pressure drop of the system

a. The system allows a small pressure drop, or allow the pressure drop is not small but does not require flow adjustment, then the valve should be selected with a small pressure drop, such as gate valves, straight-through ball valves, etc. (various types of valves to adapt to the working conditions will be mentioned below).

b. Need to adjust the flow, then you should choose a better adjustment performance, with a certain pressure drop of the valve.

③ the environment in which the valve is located, outdoor in cold areas, especially for chemical materials, the valve material generally can not use cast iron and should be selected cast steel (or stainless steel)

The Functions of Valve

①Cutting off.

②Changing the flow direction.

③Stop reflux.

④checking.

⑤ Valves with special requirements, such as jacket, valves with purge ports, valves with bypass and valves with blowing ports.

Power to Open And Close Valves

Most of the valves operated in situ with a handwheel, and the operation of a certain distance with the use of sprockets or extension bars. Some large-diameter valves are designed with motors due to the difficulty of manual opening and closing (it should be noted that such valves with motors in explosion-proof areas need to use explosion-proof motors).

Remote control valve using the power type of pneumatic, hydraulic, electric, etc.