Selection and Application of Pneumatic Control Valve in Automatic Control Process of Chemical Industry

In the chemical automatic control system, the control valve is an important actuator. Its model and installation quality have an important impact on the control quality of the control loop. If the selection and application of the control valve are improper, it will seriously threaten the control valve service life, when the situation is serious, it may even cause system accidents. In the process of chemical automatic control, how should the selection and application of pneumatic control valves be carried out?

 

 

 

Selection of Pneumatic Control Valve in Automatic Control Process of Chemical Industry

1. Selection of control valve type and structure

According to the different strokes, pneumatic control valves can be divided into two different types, namely straight stroke and angular stroke. According to the structure, pneumatic control valves can be divided into butterfly valves, angle valves, sleeve valves, ball valves, diaphragm valves, straight through single seat valve and other types.

 

Among them, the straight-through single-seat regulating valve is the regulating valve with the smallest leakage during use. It has ideal flow performance and simple structure. It can be used in areas with strict leakage requirements, but its flow path is relatively complicated, which is also limited to a certain extent. The scope of its use.

 

The straight-through double-seat control valve is the opposite of the straight-through single-seat control valve. It has no strict requirements for leakage and is suitable for use in areas with large working pressure differences. At present, the straight-through double-seat control is the most widely used in my country A kind of regulating valve.

 

Sleeve valves can be divided into two types, namely double-sealed sleeve valves and single-sealed sleeve valves. Sleeve valves have good stability, low noise and easy disassembly and assembly, but their prices are relatively high and maintenance requirements are high. Therefore, the scope of use is also subject to some restrictions.

 

The flow path of the diaphragm valve is simple, and its production uses high corrosion resistance PT-FE and PFA, which are very suitable for application in strong alkali or strong acid environment, but the regulation performance is relatively poor.

 

 

2. Selection of the material of the regulating valve

The use of control valves has almost harsh requirements for corrosion resistance, pressure rating and temperature. Therefore, the current control valves mostly use cast iron materials, which can effectively improve the corrosion resistance and compressive strength of the control valve; The internal components of the valve are mostly made of stainless steel. If the system has low requirements for leakage, soft seals can be selected. If the system has high requirements for leakage, hastelloy should be used.

 

 

In the selection of corrosion-resistant materials, it is necessary to comprehensively consider the liquid concentration, temperature and pressure, and combine the selection with mechanical shock.

 

 

All in all, the regulating valve is an important part of the chemical automatic control loop. The selection, installation and maintenance of the regulating valve will affect the operation of the chemical system. Therefore, the staff must strictly follow the relevant installation system and comprehensively analyze various factors to select the regulating valve.