Who blocked the oil circuit of the five-color offset press?
If lubricating oil is the blood of the machine, then the oil pump is the heart of the machine. Once a heart problem occurs, it will inevitably bring about a series of serious consequences.
The author’s company has encountered a strange thing: the oil pump of the five-color offset printing machine suddenly does not produce oil, even if it is replaced with a new oil pump, it does not produce oil. After more than ten days of hard work, the fault was resolved smoothly. Here, the author will share with you the maintenance experience of the fault.
Failure phenomenon
One afternoon, a Heidelberg five-color offset press of our company suddenly suffered from "cardiac arrest" (the oil pump could not supply oil).
According to the oil circuit maintenance experience, we immediately carried out emergency disassembly, repeatedly cleaned each filter system, and then reinstalled and debugged. The problem still exists.
So, we wonder whether the oil pump is too worn and the oil output is insufficient?
In order to eliminate the fault as soon as possible, the equipment department decided to purchase a new oil pump to solve the production emergency first. However, because there is no stock in China, the imported oil pump has to wait a week, so the production department decided to use the time of waiting for the accessories to carry out the annual maintenance of the machine.
During this period, we conducted a thorough and thorough inspection of the old oil pump, and found that the old oil pump was still in good condition, so we continued to install and use it. After 3 days of trial operation, everything is normal.
But half a month later, late at night, the oil pump suddenly went on strike, and the computer showed that the circulating lubricating oil flow rate of the main engine was too low. If it continues to run, the control system will automatically lock the main motor.
Once the main motor is locked, the consequences will definitely be more serious!
Replace the oil pump with a new one
The next day, we came to the site again to check 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 dismantle the casing and the rig belly, 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 divider valve on the inner wall of the wall panel that is continuously spraying oil, indicating that the oil pump is working normally, but the pressed oil cannot enter the oil pipe.
Obviously, the crux of the problem now is that the oil circuit is blocked.
Check carefully
In order to solve the problem as soon as possible, we consulted some experienced engineers as soon as possible, but unfortunately there is no ready answer. I can't help but rely on myself. You can learn the basics of the offset printing workshop on your own. Click here to enter the study.
We thought hard and wondered if the two solenoid valves on the oil divider valve were broken?
As soon as we went to work the next day, we carefully disassembled it again. After disassembling the spool, it was found that there was no damage to the structural parts inside; after the 24V power supply was turned on, it still worked flexibly as usual. This shows that the solenoid valve is good.
We guessed again, is it possible that the tubing is reversed? Impossible!
The up and down position of the solenoid valve is upside down? Impossible!
The solenoid valve wires are reversed? It's even more impossible!
Doubts, verifications, denials, doubts, verifications, and denials again and again, the hope that ignited in my heart was shattered time and time again, and everyone almost lost their direction.
Under this scenario, all those who participated in the maintenance were shocked, but no one was discouraged, and everyone decided to try again.
After lunch, we drilled into the belly again and installed the solenoid valve.
In order to verify the function of the solenoid valve, we decided to power off the solenoid valve first. As a result, something strange happened: the oil circuit was unblocked, but once it was energized, the oil circuit was blocked.
Based on this phenomenon, we locked the focus of the problem on the solenoid valve. What is it that controls 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, check down according to the drawing according to the number of the wire on the solenoid valve. When we opened the electrical box in the fifth group of operating side shields, we successfully found the two relays connected to the two wire terminals of 1075 and 1076, took them out and wiped them out, and then inserted them upside down intentionally, and re-energized them. As a result, the oil circuit is open!
Analyze the reasons
It turns out that the two solenoid valves of this five-color offset printing machine have different functions. One of the functions is to switch the oil pressure of 1bar and 12bar, and the other is responsible for switching to the lubrication of the side bearing and the delivery chain when the oil pressure is switched to 12bar. .
According to the computer settings of the five-color offset printing machine, when the machine runs at 15,000 revolutions per hour, the oil circuit needs to be switched through the solenoid valve to transfer the 12bar pressure lubricating oil to the roller bearing, shaft sleeve and delivery chain on the side of the body. Timing lubrication, after the lubrication is finished, the solenoid valve spool is operated to switch back to the main engine cycle.
However, in individual cases, the relay will be frequently energized and de-energized for many years. When the contacts are switched, an electric spark will be generated, which makes the two contacts stick together like arc welding.
When the oil circuit switching is over and the relay is required to be de-energized, it cannot be disconnected. The solenoid valve is controlled by it and has been energized, which mistakenly blocked the circulation of the main engine oil circuit.
Thinking of this, we immediately understood that when the solenoid valve was just removed, it was hotter, because the relay contacts were stuck, which caused it to work incorrectly when it was powered on.
Summarize
This troubleshooting gives the author a deep experience: Difficulties are springs, and if you are weak, it is strong. As long as we think of something more, and hold on for a while, we can cross it with one foot!
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http://www.joyful-printing.net
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