What could be the possible reasons for minor cylinder collision in a reciprocating compressor?
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This post was last edited by lovestory on 2011-2-14 at 16:13. One of the two 40M3 reciprocating air compressors in my workshop has been under repair for almost a year now, yet the underlying problem hasn’t been resolved; there is still a noticeable noise of the second cylinder hitting the other cylinder. 1. The initial coking has been removed; the cause has been ruled out ； 2. Later, it was said that the coolant in the machine room cooler was leaking, but after shutting down the machine and applying pressure, the machine room cooler continued to function normally. The day before yesterday it was transferred to a smaller machine; after it was repaired, it was brought back today. Within two hours, the abnormal noise appeared again. The mechanics are utterly stuck and still haven’t found the real cause. If it’s about rich gas carrying liquid, then why don’t similar-sized rich gas compressors operating under the same conditions experience similar issues? I’m a process engineer; I’m seeking help from everyone.
Are the compression ratios of large and small machines different? The rich gas contains some liquid components, which are compressed when the large machine is in operation. For reference only.
I’m not aware of your manufacturing process, nor do I understand what you mean by “rich gas” – what is the water content? Generally speaking, when designing such systems, designers take the water content into account. Check relevant information and compare the designed water content with the actual value. It is recommended that the original poster adjust the stroke clearance.
Thank you for the reply from above. I forgot to mention that it’s a catalytic cracking unit; the exhaust volume is around 80 M3 of rich gas, which has already been separated using an oil-gas separator to isolate gasoline and water； Additionally, this compressor is one of two compressors of the same size; it is the only one that has undergone repeated inspections and repairs without the root cause being identified. The air valve and the piston have both been checked; no problems were found when it was turned on. But it just doesn’t run well. The gap has been adjusted; the maintenance staff reported that if it is adjusted further, the other stage, that is, the first-stage cylinder, will no longer function properly. It seems the required gap is no more than 3.5 millimeters.
Reply to 1# yiransunny: The main reason for the cylinder failure is: liquid in cylinder 1. Insufficient clearance in 2 cylinders. 3 The piston rod nut is loose. There are foreign objects in the 4-cylinder engine. 5 The oil-water separator is not functioning properly. Personal opinion: The insufficient clearance in the cylinder leading to cylinder collision was caused by the assembly work done by the maintenance staff, but the possibilities I mentioned above cannot be ruled out.
Reply to 4# yiransunny: Compare the operating parameters of these two machines to see if there are any abnormal values among them. (It can be determined through abnormal parameters)
If there are indeed no issues with repairing and assembling this machine, then the most likely cause is liquid in the cylinder. Incomplete separation in the oil-gas separator, excessively high intake temperature, or a damaged intake air filter can cause liquid to enter the cylinders, leading to minor cylinder scoring.
Reply to 7# xxp3232: But another machine of the same size has no problems. Personally, I think separation should be ruled out if it’s not good. The current solution is to increase the temperature at the secondary inlet to 45–60 degrees, but the results are not satisfactory.
Could it be that the direction was wrong from the start? A knocking sound in the cylinder doesn’t necessarily mean there’s a cylinder collision! According to the information provided by the poster, the clearance between the front and rear dead centers of this machine is around 3.5 MM, which is fine. As the other machine is working properly in the case of liquid slugging, this also proves that such a problem does not exist. It is recommended that the poster check the bolts connecting the cylinder to the middle block, as well as the connection between the piston rod and the crosshead. If everything is fine, then check the fit between the flywheel and the shaft, as well as the condition of the keys. If there is a problem with these components, they will all produce a sound similar to that of cylinder collision.
Based on your description, the possible reasons for the knocking sound coming from the cylinder are: 1. The crankshaft connecting rod mechanism is not aligned with the center of the cylinder. 2. If it is a live cylinder liner, there may be poor positioning or looseness. 3. The piston rod is bent or the connection nut is loose. 4. There may be slight water hammer. Also, is that sound actually the sound of something hitting the cylinder?
Reply to 9# lovestory: The maintenance staff always claim that it’s due to liquid shock, but this isn’t very convincing, as another unit of the same type has no problems at all. If there are problems with other components, the repair technicians should be able to detect them. (It has been repaired many times, yet the root cause has not been identified, nor has the problem been truly resolved; this has become an issue for the repair shop.) ). However, thanks to the reminders from the teachers above; I will discuss the above matters with the maintenance staff again. Thank you again!