Materials that must be transported in high temperature usually need steam regulation. So, we must be careful to choose the type of control valves, otherwise, failure may happen in service, which will affect the operation of machine badly. The followings are some examples to illustrate the problems need to be considered.

 

In a chemical product company, control valves are needed in temperature regulation of retort. And its driving force is steam, its source is residual heat from thermal power plants, its temperature is 200 centigrade and its pressure is 1.2mp, above all, control valve must regulate steam pressure in average. The temperature of control valve's inlet is from 0.8 to 1.0 and outlet is from 0.4 to 0.5. The parameter is not precise because the surrounding environment is not taken into consideration when installation in the beginning. The electric single seated valve breaks down from time to time not long before operation. Then it is fixed and lots of analysis is made before finding out the cause, that is, the pressure difference between inlet and outlet is much too large. Because load of actuator is too high while working, say, overload, the reduction gear   will be overwhelmed, and as a result it will damage motor and module. What’s worse, if users choose the pressure measuring point improperly (choose somewhere pressure changes promptly) in system design, there will be problems in PID parameter setting of pressure control module in operating system.

 

After communicating with technicians of consumers, we decide to substitute the old valve with ZAZM. Since then, the machine runs fine and nothing wrong happens. We can sense the importance of choosing the right type from this case. Thus, we must be careful with the choice of types in the early stage, or it’ll be troublesome in later stage.