Steam control valve for high temperature and high pressure of the medium, the selection is quite important, if the selection of inappropriate, it will frequently fails in the use process, seriously affecting the normal operation of equipment and systems. Below we through some problems needing attention in selection and use an example to talk about the steam control valve.
A large chemical enterprises, the need to use steam to control the reactor temperature, steam heat recovery steam from thermal power plant, temperature 200 ℃, the pressure is about 1.2MPa, the constant demands to control steam pressure steam regulating valve, the valve inlet pressure of 0.8 ~ 1.0MPa, the outlet pressure is 0.4 ~ 0.5MPa. Start the selection, because there is no clear field parameters, selection of the electric single-seat control valve, use soon fault frequently, actuator, control module, motor burn damage reduction gear broken things, often occur. After sent to the scene to observation, analysis, to find the cause of the trouble. Originally, valve outlet pressure difference is bigger, the actuator in the work load is too big, can also be said to overload, so there will be a reduction gear overwhelmed, several broken and motor, module damage things, what is more, the user in system design pressure point (in the improper selection of pressure changes quickly place), control parameter setting of PID pressure control module of the system also has a problem, cause the whole system sensitivity is too high, the pressure is a little change, the regulator will output the control signal to drive the pneumatic control valve, causing frequent action, regulating valve that shock, causing the whole system shock, not only controlled variable cannot be stable, the regulating valve overwhelmed, unable to complete tasks.
With the user after consultation, decided to replace the single-seat control valve electric control valve sleeve, sleeve valve spool balance because of structure, can produce more than offset of steam through the unbalanced force, reduce the electric actuator load, is conducive to the long-term stable operation of regulating valve. The reason why not to choose the balanced single-seat regulating valve, is to consider the single-seat valve guide seals not resistant to long-term wear steam conditions, and the system is not high on the valve leakage requirements, sleeve valve completely can be competent this work. At the same time, to determine the pressure point, when the sleeve valve replaced, debugging the system, the PID parameter to set, decreased with increasing integration time, the system response time, tweak, pressure fluctuation of steam to meet the use of the premise. After such an adjustment, basically solved the problem.
In fact, if the best solution to consider, according to the site conditions and requirements, using the pneumatic engine valve more suitable for the user, just laying air supply line is not convenient, not only the adoption.
Thus, the electric control valve, the selection is important, installation, commissioning and maintenance is more important, there are a lot of fault are users not familiar with the performance of control valve and caused maintenance use. You can't control valve isolation from the control system, and it and the entire system together to consider, to adjust, and control valve actuator, is a dynamic, prone to various faults, this is the manual valve is not more than. Moreover, with the increasing use of fieldbus control valve, originally by the system to complete the task, to the valve body, the maintenance of control valve, put forward higher requirements.
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