Created on:2021-07-09 10:04

Case analysis of hydraulic failure of packer

Case analysis of hydraulic failure of packer

① Symptoms of excessive current of hydraulic pump motor: in the process of downward packing of plunger, the hydraulic pump just started to change, the sound of motor suddenly changed, and the current suddenly increased to 85A, which threatened to force the motor to stop and burn down.

Because of the invariance of the hydraulic pump, the machine disassembled the variable mechanism for sand grinding and cleaning, and returned to normal after adjustment. The old "disease" recurred soon after use. After contacting with the manufacturer, the user will repair the pumping plant and check it with the test bench, and all the indexes are qualified. It will be transported back for trial run and ready for production. However, the situation of the test run was not successful, and the work was futile. It can be seen that the fault is not on the hydraulic pump. Moreover, the hydraulic pump that has just been on the calibration table does not have the possibility of this kind of fault for the hydraulic system in use, so the circuit should be checked. The motor of plunger pump is 22KW, which is started by Y / △ mode. If Y-type can not be switched to △ type after starting, the motor power is only 1 / √ 3 (≈ 0.577) of the original rated power, that is 22 × 0.577=12.694(kW)。 In this way, the hydraulic pump motor power is only about 12KW, but it has to take on the task of 22KW.

The results are all expected: press the "hydraulic pump start" button, the AC contactors 2C and 3cy are powered on, the motor has been running in the Y-type wiring state, no matter how long the time is. Further inspection found that the reason was that the coil and electromagnet were installed reversely when replacing the time relay SJ1. Remove it, turn it around and install it. Set the delay about 5S, and the micro switch acts to switch Y / △ mode. So everything went back to normal.

② Symptoms: the plunger can not go up: the plunger can go down (empty box) in place and stop automatically, the pump and valve work normally, but can not go up (work quits). If you press the "plunger up" button, and then use the jack to press the upper threading plate to send one stroke up, the plunger can go up in place and stop automatically.

At first, it was thought that it was a circuit fault, and no abnormality was found after the field detection of the multimeter. Start the plunger pump to observe. First, you can see a row of bubbles in the transparent oil return pipe on the pump body. With the oil running to the oil tank, the hydraulic pump makes the sound of no oil idling. All these have indicated that the oil tank is short of oil. However, there is 2 / 3 oil on the glass oil level indicator of the oil tank. Obviously, this is an illusion, because the lower drain hole is blocked. Remove the air filter and insert a packing iron wire directly into the bottom of the oil tank. After extraction, the oil level is only 150 mm higher than the oil inlet of the hydraulic pump. Some people think that as long as the oil level is higher than the oil pipe orifice, oil can be ejected. As everyone knows, when the hydraulic pump works, there will be a "vortex" above the oil inlet pipe. The less oil in the oil tank, the deeper the vortex will be when the hydraulic pump is running, and the air will take the opportunity to enter. After adding two barrels of machine oil and removing the air in the system, the up and down movement of the plunger returned to normal.

③ Water in the oil caused damage to the hydraulic pump. The 250ycy-14-1b plunger pump of a packer was used for a short time, and it appeared that the pressure was insufficient and the top pressure was not in place. After a hydraulic pump was replaced, the same situation occurred again. It was found that the oil storage tank at the bottom of the slipper was worn flat and there were a lot of copper particles in the pump. Take a little oil and put it in the palm of your hand. If you look carefully, there are many drops in the oil. Due to the cold weather, the oil is too viscous. Although the water is heavier than the oil, after compression by the system, the water will split into water droplets and mix with the oil, which will not separate and destroy the lubrication of the slipper and stop plate. To shorten the slipper is to shorten the plunger stroke. At that time, they were eager to process, so they had to change the oil first and start production. When the water-containing oil is exposed to the sun in summer, the water will be separated automatically and precipitated to the bottom of the oil barrel. The oil on the top of the oil barrel will be extracted and filtered before it can still be used.

④ Running out of control symptoms: plunger down into a package, beyond the set travel, but the plunger does not stop, the door does not open. At that time, the operator found that the current was too high and the pressure exceeded the normal value, so he immediately shut down the machine and reported it to the team leader and the plant leader for several tests. However, he ignored to see where the actual top pressure reached and then shut down the machine.

There should be two possibilities for this phenomenon. a. The bale is too heavy. One is that the cotton box was manually loaded with the compressed "return bag"; the other is that the current relay was improperly adjusted or failed. b. The top pressure exceeds the set stroke (the compression height of cotton bale in the box should be 420-430mm). The reason is that the travel switch 3hc is out of order or the bump does not touch its roller. On the operating platform, the bump has exceeded 3hc, the compression height of the cotton bale in the box is less than 400mm, and IHC has not been touched. The reason is that the 3hc rocker arm can't make the rocker shaft rotate, so the normally closed contact is constant, the normally open contact is not closed, of course, the plunger doesn't stop, the lock doesn't open, and the hydraulic cylinder doesn't retreat when closing the box door.

The solution is to change a travel switch. It is suggested that manufacturers and users should divide the 1hc into two parts, that is, the travel switch 1hc should be installed in two parts, with the upper one next to 3hc and the lower one next to 5hc. Both series connection, regardless of the plunger up, down, or other reasons, as long as more than the set stroke, the plunger pump will stop immediately. It is better to stop the machine to find out the cause, deal with the fault and ensure the safe production than to trace the responsibility and find out the cause after the accident.

⑤ There is no pressure in the low pressure system, which often occurs in the baler.

Once there was no pressure at the outlet of the hydraulic pump. Under normal circumstances, as long as the suction pipe is under the oil level, the pipeline and pump are not leaking, not blocked, and the operation direction is correct, there will be pressure. The inspection shows that the J-type framework oil seal of gear pump is leaking. Take apart the gear pump and replace it with a 20 gauge one × thirty-five × 10 J-Frame oil seal, the fault has been eliminated.

Another fault is that the outlet pressure of gear pump does not decrease, but the system has no pressure. This kind of fault is obviously that the pressure oil flows back to the oil tank through the relief valve (y-25b type). The first reason is that the valve is not adjusted in place; the second reason is that the valve core is blocked by foreign matters, and most of the oil pumped by the gear pump flows back to the oil tank, unable to form pressure in the system. Therefore, as long as the foreign matter in the relief valve is removed, the system will return to normal.

⑥ 34dym-f50h-t Electro-hydraulic Directional Valve Fault a mdy200a hydraulic baler of a company has been running for a period of time. In the process of compressing cotton bales by the plunger, it stops before reaching the set stroke, and the system has a certain pressure. Compared with the troubleshooting methods in the manual, they have tried one by one, but the fault has not been eliminated. When removing the spool of the hydraulic directional valve, it was found that there was a hole with the size of one meter at the retaining ring of the spool, which caused internal leakage. Take it to the processing place of the lathe, clamp the two ends with the lathe, weld the groove at one end with holes by electric welding, and resume normal production after installation.

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