Created on:2021-06-30 14:18

Working principle and troubleshooting of hydraulic system of disc heat disperser

Working principle and troubleshooting of hydraulic system of disc heat disperser

(l) Working principle of hydraulic system of disc heat disperser

The hydraulic transmission system of disc heat disperser is shown in Figure v. The hydraulic system is supplied by the hydraulic pump, the pump inlet is equipped with an oil filter, and the outlet is connected with the hydraulic system. The working oil passes through the precision filter 5. The solenoid directional valve 7 supplies oil to the feed hydraulic cylinder 10 and the body maintenance hydraulic cylinder 11. The operator controls the action of electromagnetic directional valve 7 through the circuit on the control panel, and then controls the hydraulic cylinder to drag the moving grinding plate for axial displacement to change the grinding plate clearance, so as to realize the accurate positioning control of the moving grinding plate.

After the hydraulic pump is started, the electromagnets of solenoid directional valve 7 and 12 are in the power-off state, which is the position shown in the figure. The moving plate feeding hydraulic cylinder 10 and the body maintenance hydraulic cylinder 11 are in the original position, and the hydraulic pump 4 is unloaded through the proportional relief valve 6. When the start button is pressed and the electromagnet IDT is powered on (the control voltage of the proportional relief valve is above 2V), the electromagnetic directional valve (7) works in the left position. The pressure oil pumped by the hydraulic pump 4 enters the rod free cavity of the moving disk feed hydraulic cylinder 10 through the electromagnetic directional valve 7 and the one-way throttle valve 9, and the rod cavity returns oil, and the piston rod extends out; When the 2DT is powered on, the solenoid directional valve 7 is in the right position, the oil is fed into the rod cavity of the moving disc feed hydraulic cylinder 10, the oil is returned to the non rod cavity, and the piston rod is returned to complete the working cycle of the feed hydraulic cylinder; When the 3DT is powered on, the electromagnetic directional valve 12 is in the left position, and the oil is fed into the rodless cavity of the body maintenance hydraulic cylinder 11, while the oil is returned from the rodless cavity, and the piston rod is extended; When the 4dt is powered on, the solenoid directional valve 12 is in the right position, the oil is fed into the rod cavity of the body maintenance hydraulic cylinder 11, the oil is returned to the non rod cavity, and the piston rod is returned to complete the working cycle of the body maintenance hydraulic cylinder. In the hydraulic system, the relief valve acts as a safety valve.

(2) Fault analysis and elimination of hydraulic system

① There is no pressure in the system. There is no pressure in the system, which may be related to the following factors: A. electrical circuit failure, such as wrong connection of the circuit and unreliable connector, makes the hydraulic system unable to work; b. The oil in tank 17 is insufficient, and the oil suction pipe can't suck in hydraulic oil or part of hydraulic oil and a lot of air, which makes the system not work normally; c. The oil filter is blocked, which makes the hydraulic pump unable to suck in the hydraulic oil; d. The amplifier "+" and "I" of proportional relief valve 13 are connected reversely; e. Hydraulic pump 4 and relief valve 14 are damaged; f. Leakage of pipelines and connectors;

g. The oil return port of cooler is blocked.

After the inspection, the oil filter was found to be blocked. After the oil filter was dredged and cleaned, the fault was eliminated.

② The hydraulic cylinder for body maintenance doesn't work. The feeding system works normally, and the pressure is 8Mpa, but the hydraulic cylinder for body maintenance doesn't work.

After inspection, it is found that the installation of the hydraulic cylinder 11 is not parallel to the guide rail, and the strength of the fixed end is not enough. The hydraulic cylinder is in the last position, and the guide rail of the body is scratched. This is the problem. Remove the body maintenance hydraulic cylinder 11 and let it run back and forth under no-load condition, then blow all the oil filling holes of the body with high pressure air, and evenly apply grease on the guide rail. Adjust the hydraulic cylinder based on the guide rail to make the parallel parts parallel to each other. The tolerance of parallelism is 0.05-0.1mm/m. After the installation, the hydraulic pump was started, the hydraulic cylinder 11 of the engine body was maintained, and the fault was eliminated.

③ The feed hydraulic cylinder of the moving disc can only feed but not retract the cutter. The hydraulic cylinder 11 works normally and the system works normally. The pressure is 8Mpa. The feed hydraulic cylinder 10 of the moving disc can only feed but not retract the cutter.

The main reasons are: a. the electromagnet 2DT is not powered on or the valve core of the solenoid directional valve is stuck; b. The one-way throttle valve 9 on the tool withdrawing side is adjusted too small; c. The amplifier of proportional flow valve is faulty; d. The proportional flow valve 13 itself has a quality problem.

After investigation, it was found that causes a, B and C were quickly eliminated, and the problem mainly focused on the proportional flow valve 13 itself. After further observation, it was found that the vibration of the heat disperser caused the fluctuation of the proportional flow valve spool, which made the spool in a semi closed state and could not be retracted. After replacing the proportional flow valve 13, restart the machine, everything is normal, and the fault is eliminated.

④ The main reasons are as follows: 1; a. The air accumulated in the pipeline or absorbed by the hydraulic pump 4 causes the hydraulic cylinder 10 to crawl during operation; b. The oil seal rings at both ends of hydraulic cylinder 10 are too loose, causing the system to crawl at low speed; C. The system is not cleaned or mixed with dust, yarn head, metal powder, rubber and other foreign objects during oil filling operation, and soaked in the oil tank for a long time, blocking the oil hole or unreasonable design of oil tank 17, resulting in oil return bubbles and untimely oil change, resulting in unclean oil; d. The poor performance of one-way throttle valve 9 or the roughening of hydraulic cylinder 10 caused the failure of hydraulic components.

After inspection, it was found that the oil seal rings at both ends of the feed hydraulic cylinder 10 were too loose. After tightening the lock nuts at both ends of the hydraulic cylinder according to the regulations, the fault was eliminated.

⑤ There are several reasons for system noise and noise.

a. Hydraulic pump 4 sucks air. The main reasons are: air leakage at the oil inlet of the hydraulic pump, long oil suction pipeline; The pipe diameter is too small; The oil suction surface of oil pipe is too low or the oil suction port of hydraulic pump is too high; The oil filter is deformed or the flow area is small; The oil tank is airtight; The oil viscosity is too high.

b. Hydraulic pump 4 is faulty. Gear pump tooth profile accuracy is low, the pump axial clearance wear increases, so that the oil delivery is insufficient or the pump speed is too high, leading to the failure of the hydraulic pump.

c. Relief valve 14 fails to work. The reasons for the action failure of the relief valve are that the damping hole of the relief valve is blocked by oil sediment, the spring is deformed, stuck or damaged, the valve seat is damaged, and the fit clearance is not suitable.

d. Mechanical vibration. Mechanical vibration can be caused by oil pipe collision or support wall collision, oil pipe vibration, hydraulic pump and motor installation is not concentric, relief valve vibration and so on.

It was found that the stiffness of the pressure regulating spring of the relief valve was not enough, which caused resonance and noise under the action of hydraulic force. After replacing the pressure regulating spring, cleaning and oil changing, the fault was eliminated.

⑥ The pressure is not stable. After the hydraulic pump 4 starts, the pressure reaches the set value, but after 30 minutes, the pressure drops to 4.0 MPa and remains stable. The same problem still occurs when the hydraulic pump is restarted. When the oil leakage is eliminated and the relief valve 14 and proportional relief valve 6 work normally, the problem is concentrated on the hydraulic pump 4. After inspection, it was found that the body of hydraulic pump 4 was seriously heated, and the oil absorption filter was completely blocked by pulp fiber, so it could not absorb oil at all. Drain the hydraulic oil in the oil tank completely, clean the oil tank completely, replace the hydraulic pump and oil suction filter, and fill in the filtered new hydraulic oil. After restarting the hydraulic pump, the working pressure of the system is normal and there is no pressure fluctuation.

⑦ Feed hydraulic cylinder self-propelled phenomenon feed hydraulic cylinder 10 self-propelled phenomenon, leading to lower positioning accuracy, the main reasons are: A. one way throttle valve 9 and hydraulic lock 8 are not correctly arranged, resulting in hydraulic lock 8 control cavity back pressure, sealing is not tight, positioning accuracy is reduced; b. The poor quality of the hydraulic lock 8 causes the seal of the hydraulic lock to be not tight and the positioning accuracy to be low; c. The sealing ring of feed hydraulic cylinder 10 has leakage; d. The hydraulic oil is contaminated.

After inspection, the arrangement position of one-way throttle valve 9 and hydraulic lock 8 is correct; Hydraulic lock 8 works normally without abnormal phenomenon; The sealing ring of feed hydraulic cylinder 10 is intact. Therefore, the problem focuses on the pollution of hydraulic oil. After checking that the hydraulic oil was slightly polluted, the problem was solved after filtering the hydraulic oil and cleaning the hydraulic lock.

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