Circulating water pump outlet valve sand A power plant 200MW and 300MW generating unit adopts weight type hydraulic butterfly check valve, it can control the linked with a circulation water pump, valve - open 15 degrees can start the circulating pump. After the opening of hydraulic driving system of automatic pressure, so that the weight is not decreased. Even a slight leakage in the hydraulic system, so that the hammer fell by more than 15 °, electronic control system can also linkage pump motor oil supplement, keep the oil pressure. When the pump is closed when the valve is closed, the linkage, fast closing and slow closing divided two stages to close, role is to prevent the pipeline water hammer pressure rise close the valve impact, a buffer to protect the pipeline, to prevent the circulation pump reverse. Because of this kind of butterfly valve can be to check and stop function, can effectively prevent water hammer, and a valve linkage, safe and reliable advantages, since since put into production, has been widely used in water, thermal power plant, the public water supply and drainage, chemical and metallurgical industries. In recent years, gradually developed to prevent seawater mud, sand, locking, no hammer type, the butterfly plate three-dimensional eccentric structure form and structure. But the basic control mode is adopted by the electro-hydraulic control, characteristics of the hydraulic system is simple, reliable, easy maintenance.
Working principle
KD741X-6V type butterfly valve as an example
Hydraulic principle
Open valve
Start the oil pump motor, oil pump, hydraulic oil into the swing cylinder through the filter, pump, control valve, check valve and high-pressure hose, said drive cylinder piston in the size, not by excess hydraulic oil control valve through the relief valve to tank. Cylinder driven piston is connected with the connecting head to hammer raised, and also drives the valve shaft so that the disc rotation, to achieve open. Available to adjust the control valve opening set speed. This movement, manual valve open state, the electromagnetic valve closed position, the bypass valve is manually closed position.
Off valve
Solenoid valve, solenoid valve is opened, the weight function, the oil pressure inside the cylinder by the fast and slow off the angle valve, quick closing valves, slow closing valve and hose, normally open manual valve and solenoid valve into the tank, the valve closes the disc drive using hammer potential energy. Shut off valve procedures in the fast, slow closing time and fast, slow off the angle from the fuel tank quick closing valves, slow closing valve and the fast, slow off the angle valve to adjust.
The manual switch valve
Manually close the valve before the solenoid valve, swing hand pump, can slowly open the valve. But will bypass (manual) valve open, oil flows through the bypass valve cylinder back to tank, so that the butterfly plate closed in the potential weight down.
Automatic packing after full
In order to ensure the long-term work cylinder, the pressure is not less than the required oil pressure, so that hammer do not drop because of oil pressure is too low, so the parallel circuit in the hydraulic system of a spring-loaded accumulator. Under normal circumstances, the pressure accumulator oil pressure for ratings, when the system trace the leak, can fill oil to the system storage. When the valve is closed by the hydraulic system leakage, the butterfly plate close to 75 °, automatically switch on the power of electric control system of the oil pump restart open butterfly plate to 90 °. When the system has serious leakage, pump output oil can not maintain the butterfly valve opening, the butterfly plate close to 15 °, the linkage stop circulating pump power. To avoid damage to pumps and piping.
This paper discusses some common problems in the use of
Bypass (unloading) shape and structure of valve and two valves manual valve is the same. When the valve is in normal operation bypass oil discharge valve should be in the normally closed state, before the manual valve solenoid valve should be normally open state. If the mistake before the manual valve solenoid valve closed, when the butterfly valve to be closed, the hydraulic oil can not be through the electromagnetic valve unloading, the valve will not automatically shut down.
Especially to be noted that the solenoid valve has a positive role type and reaction type two types, positive action type solenoid valve is opened in the butterfly case, the electromagnetic valve is always charged, when the solenoid valve is energized, the valve is closed. Reaction-type solenoid valve is the valve is open, the solenoid valve is not charged, when the solenoid valve is energized, the valve is closed. The latter is more suitable for power plant use, because a stable control of the power plant, the electromagnetic valve can be opened at any time to ensure that electricity, can also avoid the butterfly valve close linkage jump caused by the pump errors due to power outages.
And the treatment method of common defects in the maintenance
Butterfly valve's hydraulic system maintenance of common defects of oil spill, including internal and external leakage. The reason is mainly caused by leakage of sealing components, in recent years due to the replacement of oil resistant rubber sealing material, and to strengthen the maintenance, repair, operation and leakage phenomenon Basic stamp.
Resulting in leakage is the main cause of the hydraulic control valve to seal the mouth (sealing) was scratched by sealing the mouth, caused by scratching is mainly because of the impurity, accumulate in the sealing mouth is extruded to make their mark, damage to the sealing line, thus affecting the sealing.
The inner leakage caused by fault phenomena are various, but caused the fault phenomena and not only the internal leakage, there may be the electronic control circuit, which often need to check the electrical repair personnel with discriminant. Analysis of inner leakage fault discrimination method is mainly based on the diagram, use one by one analysis discriminant exclusion method. We summed up the "fault tree analysis" approach, the defect phenomenon from easy to difficult investigation, determine the whole process causes until the last troubleshooting tree diagram in the form of one one lists, clear, convenient to determine the point of failure.
Avoid inner leakage is an effective method is to regularly clean the oil tank, filter oil pressure, oiling strict filtering, the use of the head with a cotton rags to avoid maintenance, cleanliness of these measures can ensure the oil. The butterfly valve oil system maintenance cycle is one year, can basically meet the healthy operation of equipment.
The size of the swing cylinder piston plating chipping is another major defects in recent years during overhaul, estimation is used for a long time not solid coating fatigue loss. Piston wall body hard chromium plating layer peeling after rough, will aggravate the wear of the sealing ring, causing serious leakage. Approach is to retreat chrome layer, to hard chromium plating, re-coating thickness can be between 0.10~0.15mm. New electroplating processing chromium stripping, welding, the school center, coarse, fine Kai technology.
Butterfly valve hydraulic system repair after the valve opening not defects, the majority is due to oil spill control valve or the valve stroke caused by dislocation. In fact control valve (regulation of oil flow), oil spill valve (maximum pressure control system), the hydraulic control valve in a setting does not need to be adjusted.
Leakage of the hydraulic system also is a major point of failure. The main feature is the swing cylinder and the control valve leakage, serious leak explosion, the oil pressure of the system will be unable to sustain jump caused by the pump. By carrying out QC activities, the statistics of circulating water pump outlet valve failure times, using the Platon 80~20% principle analysis of main faults in the hydraulic system leakage, and the main reason for fishbone analysis leakage in the hydraulic system seal material selection improper maintenance of aging and the lack of two factors. Easy to aging in the maintenance of the polyurethane material of seal oil resistant nitrile rubber material to replace, and to strengthen the maintenance, adhere to each overhaul replace all seals, oil change oil filter and check the debugging each minor repairs. Through the PDCA cycle activities, mechanical failure of our factory 12 circulating pump outlet valve rate from 1.25 times / year reduced to 0.2 times / year, greatly improve the reliability of operation of circulating water pump outlet valve and health level.
Conclusion
Only familiar with every detail of equipment, timely and thorough maintenance and strict testing, to ensure the safety and reliability of equipment operation, to improve the health level of the equipment.
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