Pneumatic valve plant

to measure quality of pneumatic valve has the following several indicators: seal reliability and responsiveness of action, such as strength, stiffness and longevity, the pneumatic valve as the basic unit in the system, heating equipment and existence of fluid-solid coupling vibration and vibration control requirements. To ensure that these indicators, the following main problems need to be solved in the first place.
control ( Determining the action of pneumatic valve reliability)
pneumatic valve main steam and reheat steam pneumatic valve control system failure is one of the steam turbine five big accident, mainly displays in the pneumatic valve opening does not accord with the design, including the actuator failure, stroke lead, lag, these affect the strength and vibration of pneumatic valve. Pneumatic valve opening control directly affects the working conditions of turbine, it attaches great importance to and has become one of the core issue of research.
in recent years, doing research on the reliability of pneumatic valves, intelligent pneumatic valve is the main attack direction in the research of intelligent pneumatic valve working condition with discretion, and self-regulating function in real time. The key components of intelligent pneumatic valve is digital locator, digital positioning for the microprocessor to pneumatic valve actuator accurate positioning, monitor and record the data of pneumatic valve.
intensity ( Should meet the requirements of life, rigid)
the frequent startup of unit strength of pneumatic valves and especially the influence of the pneumatic valve life, especially in regulating pneumatic valve control of steam turbine, the focus of the previous research on the pneumatic control valve, it now seems strength problem also nots allow to ignore. Deputy editor of the journal of powerengineering carolanngiovando writing articles emphasizes scientific research workers should not put all the attention has focused on the control problem, we should pay attention to strengthen the study of pneumatic valve strength, life, sealing, pneumatic valve work because they are the most basic conditions.
（ ) Because of frequent startup of the unit, the original main steam pneumatic valve may be can not meet the requirement of the new operation. Because the main steam general pneumatic valve is designed according to the basic load, the design process by static pressure, temperature, creep test its strength, there exists no problem of low cycle fatigue life. Condition has changed now, the original design may not necessarily meet the requirements. Pump pneumatic valve network to do this, it is necessary to consider in the design of low cycle fatigue life design, make a design condition is consistent with the operating conditions, in order to achieve the purpose of prolonging life.
（ ) Because of the actuator stroke control accuracy, pneumatic valve core impact load on pneumatic valve seat. Have power plant had been pneumatic seat fracture, crack was rushed into the turbine, causing a sharp drop in output of the steam turbine, the rotor fault heavily damaged.
in addition, for high pressure pneumatic valves, etc. , and cavitation phenomenon of original casting defects, pneumatic valve, pneumatic valve, cracks after the analysis and forecast the life of a topic worthy of further study.

vibration pneumatic valve opening change, poor dynamic performance of the actuator and pneumatic valve is leaking causes of vibration, vibration on pneumatic valve itself damage is very small, but a great influence on the whole unit, performance in the low frequency oscillation.
low frequency oscillation of the unit is divided into two kinds: one kind is the oil film oscillation, this unit is in acc or no-load running, produced by support bearing oil film; Another kind of steam oscillation, it is more complicated than the oil film oscillation, in vibration force under the action of steam, often occurs after the unit load. Pneumatic valve opening change and leakage is one of the important reasons to produce steam oscillation. Data have shown that the United States and Germany have happened steam oscillation destroyed machine accident, our country also had destroyed the mw and mw steam turbine machine accident, due to the lack of real time data record, so cannot be determined the cause of the problem, but suspected to be connected with two kinds of low frequency oscillation. Thus, eliminate and reduce the steam oscillation is very important, it depends on the pneumatic valve opening change and the produced by the leak of exciting force to do system research. Through reasonable design of pneumatic valves open and close schedule, can reduce the risk of steam oscillation.
leakage ( Internal leakage and leakage)
（ ) Leakage is not only the causes of vibration, and it may cause pollution, leakage of leakage will cause energy loss. To a certain extent, can avoid the system vibration, at the same time, it can prolong the service life of equipment, increase efficiency.
（ ) Supercritical unit of high pressure pneumatic valve life sometimes is very short, started a few times will change the packing. Research new packing or design new form of effective sealing, to prolong the life of this kind of high pressure pneumatic valve, improve the operation reliability is a must. -
at present, the pneumatic valve package level enhances unceasingly, only above a few problems, a good solution to ensure the comprehensive performance of pneumatic valves and good overall quality.