Steam is widely used in industrial production. In many cases, steam must be automatically controlled to meet the requirements of production process. With the further development of energy saving, how to use reliable and inexpensive devices to control steam effectively and accurately has become a common concern.
The automatic control system includes three parts: sensors, controllers and actuators. Actuators are the most frequently encountered problems in practical work. In actuators, solenoid valves are widely used because of their simple structure, low cost and easy maintenance. However, due to the quality problems of steam solenoid valves, coils are often burnt out, internal and external leakage, seizure and stuck, failure of opening and closing, and the whole set of automatic control devices are often ineffective after installation. This seriously affects production.
The causes of solenoid valve quality problems are:
1. The saturated vapor temperature of 6 kgf/cm2 at high temperature is 163 C. When the pressure is 16 kgf/cm2, the temperature will exceed 200 C. Because this high temperature fluid passes through the center of the solenoid coil, and the coil will also produce temperature rise after electrification, if no special measures are taken, the coil will burn out.
2. When rusting high temperature steam at the same time, the rust of parts contacted with it is stronger than that in oil, air and water, which is also the reason why some solenoid valves are stuck in failure soon after they are used.
3. The steam pressure is very low when the pressure fluctuation is large at the peak of steam use, and very high at the low of steam use, which is also the reason for the failure of some solenoid valves. Especially for indirect solenoid valves, the wear of the main valve can not be compensated, and often can not be opened at low pressure after a period of time.
4. The viscosity of the solenoid valve used in the past is very narrow. Solenoid valves for gases can not be used for liquids, nor for solenoid valves of liquids. When the steam is transported in the pipeline, there will be different content of condensate due to the change of external temperature, which often causes the wrong action of solenoid valve.
Only by solving these problems can the steam solenoid valve meet the minimum requirements. I began to study the steam solenoid valve in 1975. We have taken the following measures to solve the above problems.
1. Using special high temperature electrothermal materials and sealing materials, and adopting special processing technology to make the temperature resistance up to 220 C.
2. The valve body is made of aluminium alloy and the other parts in contact with the medium are made of stainless steel, which solves the problem of corrosion.
3. Distributed direct structure is adopted. The pressure range is 0-16kgf/cm2. The operation is reliable and the service life is not shortened by wear.
4. Special design and inspection measures are adopted to expand the application scope of medium viscosity and ensure that condensate water contained in steam pipes will not interfere with the action of solenoid valves in normal use.
5. The traditional reset spring is omitted and the performance of fatigue resistance and wear resistance is improved by using fluid lubrication.
After more than seven years of practice, the feasibility of this scheme has been confirmed. ZQDF-3 series steam solenoid valves. The operation is reliable and the service life is long.
