Experience|What blocked the oil circuit of the five-color offset press?
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If the lubricant is the blood of the machine, then the pump is the heart of the machine. Once a problem occurs in the heart, it will inevitably bring a series of serious consequences.
The five-color offset printing oil pump suddenly does not produce oil, even if the new oil pump is replaced. After ten days of fighting, the fault was solved smoothly. Here, the author will share the maintenance experience of the fault with everyone.
Fault phenomenon
A Heidelberg five-color offset press suddenly showed a "cardiac arrest" (the oil pump could not supply oil).
According to the oil road maintenance experience, we immediately carry out emergency disassembly, repeatedly clean each filter system, and then re-install and debug, the problem still exists.
Therefore, we doubt whether the oil pump is too large due to excessive wear and tear.
In order to eliminate the fault as soon as possible, the equipment department decided to purchase a new oil pump to solve the production urgency. However, since there is no spot in the country, the imported oil pump has to wait for a week, so the production department decided to use the time of the accessories to carry out annual maintenance of the machine.
During this period, we carried out a serious and thorough inspection of the old oil pump and found that the old oil pump is still good and will continue to be installed and used. After a three-day trial run, everything worked fine.
But one night later, half a month later, the oil pump suddenly went on strike, and the computer showed that the main circulating oil flow was too low. If you continue to run, the control system will automatically lock the main motor.
And once the main motor is locked, the consequences will definitely be more serious!
Replace the new oil pump
The next day, we came to the scene again and suspected that the old oil pump might have been damaged and could not work for a long time.
At this time, the new oil pump has arrived at the factory, so we immediately started to disassemble the outer casing and the rig, and finally replaced the new oil pump.
Unexpectedly, after starting the new oil pump, there is still no oil. After careful observation, we found that there is a pressure relief hole next to the oil separation valve on the inner wall of the wall panel, which indicates that the oil pump is working normally, but the oil that is pressed out cannot enter the oil pipe.
Obviously, the key to the problem now is that the oil circuit is blocked.
Carefully check
In order to solve the problem as soon as possible, we first consulted some experienced engineers, but unfortunately there is no ready answer. If you can't help, you can only rely on yourself.
We are thinking hard, wondering if the two solenoid valves on the oil valve are broken?
The next day I went to work, we carefully removed it again. After disassembling the valve core, it was found that there was no damage to the structural parts inside; after the 24V power supply was turned on, it still worked as usual. This shows that the solenoid valve is good.
We guessed again, is it difficult to make the oil pipe reversed? Impossible!
The solenoid valve upside down position is reversed? Impossible!
The solenoid valve wire is reversed? It is even less likely!
Once again, doubts, verifications, denials, doubts, re-verifications, and denials, the hopes of inner ignited were shattered again and again, and everyone almost lost their way.
Under this scenario, all the people who participated in the repairs were hit hard, but no one was discouraged, and everyone still decided to try again.
After lunch, we drilled into the belly again and installed a solenoid valve.
In order to verify the role of the solenoid valve, we decided to power off the solenoid valve first. The result was a strange thing: the oil circuit was unimpeded, and once it was energized, the oil circuit was blocked.
Based on this phenomenon, we have locked the focus of the problem on the solenoid valve. What is the control of the solenoid valve? Is it a circuit board or a sensor? Faced with such a complicated problem, it cannot be solved for a while.
Since it is definitely a circuit problem, according to the number of the wire on the solenoid valve, check it according to the drawing. When we opened the electric box inside the fifth side operating side shield, we successfully found two relays connecting the two line terminals of 1075 and 1076, respectively, and wiped them out cleanly, then intentionally inserted the position upside down and re-energized. The result is that the oil road is open!
Analyze the reasons
It turns out that the two solenoid valves of this five-color offset press have different functions, one of which is to switch the oil pressure of 1 bar and 12 bar, and the other is to switch to the lubrication side bearing and the delivery chain when switching to 12 bar oil pressure. .
According to the computer setting of the five-color offset printing machine, when the machine runs 15,000 rpm, the oil circuit needs to be switched by the solenoid valve, and the 12 bar pressure lubricating oil is transmitted to the roller bearing, the bushing and the delivery chain on the side of the body. Timing lubrication, after the lubrication is finished, switch to the main machine cycle through the solenoid valve spool.
However, in some cases, the relay is frequently energized and de-energized for many years, and an electric spark is generated when the contacts are switched, so that the two contacts are stuck together like an arc welding.
When the oil circuit is switched over and the relay is required to be powered off, it cannot be disconnected. The solenoid valve is energized by its control and erroneously blocks the circulation of the main oil circuit.
When I think about it, we suddenly understand that it is no wonder that when the solenoid valve was first removed, it was hot, because the relay contacts were stuck, causing it to work incorrectly under power-on conditions.