First, the butterfly valve to use some of the common faults: 1, the butterfly valve can not be automatically shut down, the fault of the electric control circuit. 2, butterfly valve hydraulic system maintenance is a common defect oil spills, including internal and external oil spills. 3, the size of the swing cylinder piston plating collapse. Second, the export of butterfly valve failure to deal with: (A), we must first understand the working principle of export butterfly valve: Sha A power plant 200MW and 300MW generating sets of circulating pump outlet valves are heavy hammer hydraulic control check butterfly valve, it can Circulation pump linkage control, butterfly valve pre-open after 15 ° can start circulating pump. Hydraulic drive system opens automatically when the packing pressure, so that the hammer does not fall. Even if there is a slight oil leakage in the hydraulic system, the hammer will drop more than 15 °. The electronic control system can also charge the oil pump motor to keep the oil pressure. When the circulating pump is turned off, the butterfly valve is closed, the two phases of fast-closing and slow-closing are closed, the effect is to prevent the impact of water hammer pressure rising in the pipeline when the valve is closed, and buffer protection pipeline to prevent the circulating pump from reversing. Because of this type of butterfly valve can play a check and cut-off function, can effectively prevent the water hammer, and a valve linkage, safe and reliable, and many other advantages, since put into operation, water, thermal power plants, public drainage, chemical metallurgy The industry has been widely used. In recent years, a series of forms and structures have been gradually developed, including anti-seawater type, mud-resistant sand type, locked type, non-weight type, disc three-dimensional eccentric structure and the like. However, the basic control methods are used electro-hydraulic control, the hydraulic system is characterized by simple, reliable, easy maintenance. Butterfly valve Flange Butterfly valve Butterfly valve Butterfly valve Stainless steel butterfly valve works 1, KD741X-6V butterfly valve for example hydraulic principle of a brief, 1, open the valve to start the pump motor, pump operation, the hydraulic oil through the filter, pump, speed Valves, check valves and high-pressure hose into the swing cylinder, pushing the piston in the size of the piston that did not pass through the valve excess hydraulic oil flow back to the tank through the overflow valve. Cylinder piston connected with the connector so that the weight lifting, and at the same time bring the valve shaft to rotate the disc, to achieve open. Adjustable speed control valve can be a predetermined opening speed. During this movement, the manual valve is open, the solenoid valve is off, and the bypass manual valve is off. 2), close the valve solenoid valve, the solenoid valve is open, under the action of the hammer, the cylinder pressure oil by the fast, slow off the angle of the regulating valve, close the control valve, slow off the control valve and high pressure hose, normally open Manual valve and solenoid valve into the fuel tank, the use of the potential energy of the hammer to close the valve to achieve closed valve. Close the valve in the process of fast closing, slow closing time and fast, slow off the angle of the cylinder by the fast-closing control valve, slow closing valve and the valve speed control valve to adjust the angle. 3), manual switch valve close the solenoid valve manual valve, swing hand pump, can be opened slowly butterfly valve. The bypass (manual) valve is opened, the oil in the cylinder flows through the bypass valve back to the tank, so that the disc is closed under the action of the potential energy of the hammer. Spring safety valve Zhejiang safety valve Shanghai safety valve Stainless steel safety valve American standard safety valve German standard safety valve Safety valve supermarket 4), after the full automatic packing to ensure long-term work cylinder, the pressure is not lower than the required oil pressure so that Hammer will not be due to low oil pressure and drop, so the hydraulic system in parallel with a spring-type accumulator oil. Under normal circumstances, the accumulator pressure of oil pressure rating, when the system trace leakage, the accumulator can make up the system. When the hydraulic system leaks to cause the butterfly valve to close, when the butterfly plate closes to 75 °, the electric control system automatically turns on the power to restart the pump to open the butterfly plate to 90 °. When the system has a serious leak, the oil pump can not maintain the output of the butterfly valve open, the butterfly plate closed to 15 °, then stop circulating pump power. Avoid damaging pumps and piping. (B), maintenance of common defects in the treatment: 1, the butterfly valve can not be automatically closed approach: Bypass (unloading) valve and manual valve The two valve shape and structure is the same. When the butterfly valve is operating normally, the unloading valve should be in the normally closed state and the manual valve in front of the solenoid valve should be in the normally open state. If you mistakenly put the solenoid valve manual valve closed, when the butterfly valve to be closed, the hydraulic oil can not unloading solenoid valve, and the butterfly valve will not automatically shut down. Special needs to be pointed out that the solenoid valve is a positive type and reaction type of two types, is the role of the solenoid valve is open in the case of the butterfly valve, the solenoid valve is often energized, when the solenoid valve power failure, the butterfly valve closed. Reaction type solenoid valve is the butterfly valve is open, the solenoid valve is not energized, when the solenoid valve is energized, the butterfly valve is closed. The latter is more suitable for power plant, because the power plant has a stable control power supply, solenoid valve can be guaranteed to open at any time, but also to avoid the power failure caused by the butterfly valve off the linkage pump. 2, butterfly valve hydraulic system maintenance is a common defect oil spills, including internal and external oil spills. 1). The main cause of leakage is damage to sealing parts. In recent years, due to the replacement of oil-resistant rubber sealing materials and the regular and regular maintenance of large and small repairs, leakage during operation is basically eliminated. 2). The main reason for the internal leakage is that the sealing ports (wire seals) of the hydraulic control valves are scratched. The scratches caused by the sealing ports are mainly caused by the impurities in the system, which are accumulated on the sealing ports and are squeezed It leaves traces and breaks the seal line, thus affecting the seal. 3), internal leakage caused by a variety of symptoms, but the cause of the failure is not only internal leakage, there may be failure of the electronic control circuit. 3, maintenance of common defects in the treatment: 1), the failure of electronic control circuit which often need to check with the repair electric Discipline. Analysis of the method to determine the point of internal leakage is mainly based on the principle diagram, using one by one analysis of discriminant exclusion method. We summarize the "failure analysis tree diagram" method, the defect phenomenon from easy to difficult to investigate, determine the reason until the last troubleshooting the entire process one by one in the form of a tree diagram can be clearly and easily determine the point of failure. 2) One effective way to avoid internal leakage is to clean the tank periodically, filter the pressure oil, filter it strictly when oiling, and avoid the rags with the cotton yarn head during the maintenance. All these measures can ensure the cleanliness of the oil. Currently the butterfly valve oil system maintenance cycle is one year, the basic equipment to meet the healthy operation. 3), the size of the swing cylinder piston plating collapse is found in recent years, the maintenance of another major flaw, it is estimated that the use of long-term coating is not strong fatigue off. Coated hard chrome layer off the rough piston wall, will aggravate the wear and tear of the ring, causing serious internal leakage. Treatment is to retreat chrome layer, re-plated hard chrome, re-coating thickness can be between 0.10 ~ 0.15mm. Replating a chrome, repair welding, school center, rough, Jing Kai and other technology. 4), butterfly valve hydraulic system can not open the valve after the repair defects, most of the reasons is due to governor valve or spill valve stroke caused by misplaced. In fact, the governor valve (regulating oil flow), oil spill valve (regulating system maximum pressure) and other hydraulic control valve in a set no need to adjust again. 5), hydraulic system leakage has also been a major point of failure. The main characterization is swing cylinder and the control valve leakage oil, a serious leak, the system will not be able to maintain hydraulic pressure to jump pump. By carrying out QC activities and counting the number of butterfly valve failures at the outlet of the circulating pump, the main failure reason that the main failure occurred in the hydraulic system by using Plato's 80 ~ 20% principle was analyzed. The main reason for the leakage analysis with the fishbone diagram was improper selection of the material of the hydraulic system sealing ring, Lack of maintenance of the two factors. In the repair will be easy to aging polyurethane seals replaced with oil resistant nitrile rubber material, and strengthen maintenance, insist on each overhaul of all seals, each minor repair oil change oil and inspection and commissioning. After the PDCA cycle activity, the mechanical failure rate of the outlet butterfly valve of 12 circulating pump in a factory was reduced from 1.25 times to 0.2 times per year, greatly improving the operation reliability and health level of the outlet butterfly valve of circulating pump. Third, the summary: Only familiar with the understanding of circulating pump outlet valve and butterfly valve equipment every detail, timely and thorough maintenance and rigorous testing, to ensure the safety and reliability of equipment operation, to ensure the healthy and orderly operation of equipment.
Percussion drilling is employed when auger or wash boring is not possible in very stiff soil or rock. It also can be used in most soil types.
Here the advancement of a hole is achieved by alternatively lifting and dropping a heavy cutting or hammering bit that is attached to a rope or cable that is lowered into an open hole or inside a temporary casing (casings are hollow cylindrical pipes used for borehole stability and to prevent the loss of drilling fluid through the boreholes).
Usually a tripod is used to support the cable. The stroke of bit varies according to the ground condition. The major disadvantage of this method is that it is not possible to get good-quality undisturbed samples. In very hard rock (and especially fractured hard rock), down-the-hole (DTH) drilling can be employed. In this case the hammer, applying repeated percussive pressure, is located just behind the drill bit inside the hole, unlike the open percussion drilling, where the hammer is on top of the drilling string.
The drilling string provides the necessary force and rotation to the hammer and bit, as well as compressed air or fluids to the hammer and for the flushing of cuttings.
This arrangement also allows for much deeper percussion drilling. However, the DTH drills are typically more expensive.
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