Export butterfly valve common faults and treatment methods

First, some common faults in the use of butterfly valves:

1, the butterfly valve can not be automatically closed, electronic control circuit failure.

2. Common defects in the maintenance of butterfly valve hydraulic system are oil leakage, including internal and external oil leakage.

3, the size of the piston swing cylinder piston collapse.

Second, the export butterfly valve common fault handling method:

(a) First, we must understand the working principle of the outlet butterfly valve:

The circulating pump outlet valve of the 200MW and 300MW generating units of Sha A Power Plant adopts the heavy hammer type hydraulic control non-return butterfly valve, which can be controlled in conjunction with the circulating water pump. After the butterfly valve is pre-opened by 15°, the circulating pump can be started. After opening, the hydraulic drive system automatically maintains the pressure so that the weight does not fall. Even if there is a slight oil leakage in the hydraulic system, which causes the weight to drop more than 15°, the electronic control system can also link up the oil pump motor to make up the oil and maintain the oil pressure. When the circulating water pump is closed, the butterfly valve is linked and closed, and the fast closing and slow closing are closed in two stages. The function is to prevent the impact of water hammer pressure rising in the pipeline when the valve closes, buffering the protection pipeline and preventing the circulation pump from inverting. Because such butterfly valves can function as both stop and stop, they can effectively prevent water hammer, and have many advantages such as pump-valve linkage, safety and reliability, and have been used in water, thermal power plants, public water supply and drainage, chemical metallurgy, etc. since they were put into production. Widely used in the industry. In recent years, there have been gradually developed types and structures such as anti-seawater type, muddy sand type, locking type, no weight type, and disc three-dimensional eccentric structure. But the basic control method is to use electro-hydraulic control. Its hydraulic system is characterized by simple, reliable and easy maintenance. Butterfly Valve Flange Butterfly Valve Clutch Butterfly Valve Stainless Steel Butterfly Valve Hard Seal Butterfly Valve Working Principle 1. Take KD741X-6V butterfly valve as an example. Hydraulic Principle: 1) Open the valve to start the oil pump motor, the oil pump runs, the hydraulic oil passes the filter, oil pump, speed Valves, one-way valves and high-pressure hoses enter the oscillating oil cylinders to force the small and medium pistons in the cylinders to move. The excess hydraulic oil that has not passed the speed control valve flows back to the tank through the relief valve. The piston connected with the cylinder piston causes the weight to rise, and simultaneously drives the valve shaft to rotate the butterfly plate to achieve opening. Adjust the speed control valve to obtain a predetermined opening speed. During this exercise process, the manual valve is in the open state, the solenoid valve is in the closed position, and the bypass manual valve is in the closed position.

2). The valve solenoid valve is energized and the solenoid valve is opened. Under the action of the weight hammer, the pressure oil in the cylinder quickly and slowly closes the angle adjustment valve, closes the regulating valve, slowly closes the regulating valve and the high pressure hose, and is normally opened. Manual valve and solenoid valve flow into the tank, using the potential energy of the hammer to drive the butterfly plate closed to close the valve. The fast closing, slow closing time and fast and slow closing angles of the valve closing procedure are set by the quick closing regulating valve, the slow closing regulating valve and the fast and slow closing angle adjusting valve of the oil cylinder.

3) Manually opening and closing the valve Close the manual valve before the solenoid valve. Swing the hand pump to slowly open the butterfly valve. The bypass (manual) valve is opened and the oil in the oil cylinder flows through the bypass valve back to the tank so that the butterfly plate is closed under the potential energy of the weight. 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) Automatic pressure maintenance after full opening To ensure long-term working of the fuel tank, the pressure is not lower than the required oil pressure, so that Heavy hammers do not drop due to low oil pressure, so a spring-loaded accumulator is connected in parallel in the hydraulic system oil circuit. Under normal circumstances, the accumulator pressure pressure is rated, when the system is a small amount of internal leakage, the accumulator can add oil to the system. When the leakage of the hydraulic system causes the butterfly valve to close and the butterfly plate is closed to 75°, the electronic control system automatically turns on the power and the oil pump restarts to open the butterfly plate to 90°. When there is a serious leakage in the system, the oil pump output oil cannot maintain the butterfly valve open, and when the butterfly plate is closed to 15°, the stop circulation pump power is linked. Avoid damaging the pump and piping.

(b) Treatment methods for common defects in maintenance:

1, butterfly valve can not automatically close the processing method:

The bypass valve (off-loading) valve and the manual valve have the same shape and structure. When the butterfly valve is running normally, the bypass unloading valve should be normally closed, and the manual valve before the solenoid valve should be in the normally open state. If the manual valve of the solenoid valve is mistakenly closed, when the butterfly valve needs to be closed, the hydraulic oil cannot be unloaded through the solenoid valve, and the butterfly valve cannot be automatically closed.

In particular, it is necessary to point out that the solenoid valve has two types: positive action type and reaction type. The positive action type solenoid valve means that when the butterfly valve is opened, the solenoid valve is often energized. When the solenoid valve loses power, the butterfly valve is closed. Reaction-type solenoid valve means that when the butterfly valve is opened, the solenoid valve is not energized. When the solenoid valve is energized, the butterfly valve is closed. The latter is more suitable for the power plant, because the power plant has a stable control power supply, the solenoid valve can ensure that the power is turned on at any time, but also can prevent the butterfly valve from closing the linkage pump.

2. Common defects in the maintenance of butterfly valve hydraulic system are oil leakage, including internal and external oil leakage.

1) The main cause of external leakage is the damage of the sealing components. In recent years, due to the replacement of oil-resistant rubber sealing materials, and regular maintenance of large and minor repairs, regular and external leaks have been basically eliminated.

2) The main cause of internal leakage is the seal port (line seal) of each hydraulic control valve being scratched. The seal scratch is mainly caused by impurities in the system and accumulating on the seal port. It leaves marks that damage the seal line, thereby affecting the seal.

3) The phenomenon of failure caused by inner leakage is various, but the cause of the failure phenomenon is not only internal leakage, but also the failure of the electronic control loop.

3, the treatment of common defects in maintenance methods:

1) Failure of the electronic control circuit This often requires checking and judgment with the electrician. The method of analyzing and distinguishing the endoleak failure points is mainly based on the principle diagram, and the analysis and discriminant elimination method is adopted. We summed up the "fault analysis tree map" method, the defect phenomenon from easy to difficult to troubleshoot, determine the cause until the final troubleshooting process with the form of a tree list, you can clearly and easily determine the point of failure.

2) An effective method of avoiding internal leakage is to regularly clean the fuel tank, filter the pressure oil, strictly filter the oil when it is injected, and avoid the use of rags with cotton yarns during inspection. These measures can ensure the cleanliness of the oil. At present, the maintenance period of each butterfly valve oil system is one year, which can basically meet the healthy operation of the equipment.

3) The size of the oscillating cylinder The piston plating layer collapse is another major defect found in the overhaul in recent years. It is estimated that the long-term use of the plating is not due to fatigue. The rough piston wall after detachment of the hard chrome plating will exacerbate the wear of the sealing ring and cause internal leakage in severe cases. The treatment method is to remove the chromium plating layer, re-plating hard chrome, and the thickness of the re-plating layer can be between 0.10 and 0.15 mm. The re-plating treatment includes chromium removal, repair welding, school centering, coarse and fine starting and other processes.

4) The defect that the valve cannot be opened after the hydraulic system of the butterfly valve is repaired is mostly caused by misalignment of the timing valve or the oil spill valve. In fact, the hydraulic control valve such as the speed control valve (regulating the oil flow) and the oil spill valve (adjusting the maximum pressure of the system) do not need to be adjusted after a set time.

5) The leakage of the hydraulic system was also a major point of failure. The main characteristic is that the swinging oil cylinder and each regulating valve leak oil. When a serious explosion occurs, the system oil pressure will not be maintained and the jump pump will be caused. Through QC activities, statistics on the number of butterfly valve failures in circulating water pump outlets, and using the principle of 80-20% of Plato to analyze the major faults occurring in the hydraulic system, and the main reason for leakage analysis using fishbone diagrams is the improper selection and aging of hydraulic system seals. Lack of maintenance two major factors. In the overhaul, the easily-aged polyurethane seals were replaced with oil-resistant nitrile rubber, and maintenance was strengthened. Each overhaul period was changed to replace all seals. Each minor repair period was used to change the oil filter and check and debug.

After the PDCA cycle, the mechanical failure rate of the outlet valve of the 12 circulating pumps of a certain factory was reduced from 1.25 times/year to 0.2/year, greatly improving the operational reliability and health level of the butterfly valve of the circulating water pump.

Third, summary:

Only when you are familiar with the details of the circulation pump outlet valve and butterfly valve equipment, and thoroughly maintain and strictly debug it, can you ensure the safety and reliability of the equipment operation and ensure the healthy and orderly operation of the equipment.

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