I am writing to you from Maldives and I am a high pressure breathing air compressor technician (Bauer & Coltri sub). I carry out overhaul and servicing on a day to day basis. But, there are some issues I come across which are beyond my scope of knowledge. And I am keen to learn from you.
1. In a 3 stage compressor, sometimes the interstage pressure from 2nd stage rises (back pressure) beyond it’s normal limit which is 45 to 49 bar upon switching off the unit at final pressure of 200 bar.
2. What can be the root cause for this to happen and why does this happen usually?
3. How to correct this issue?
Kindly, suggest me something and I shall be grateful to you.
I don’t have much experience with these compressors, although I love scuba diving and it sounds absolutely amazing to be a diving compressor technician on a tropical island 🙂
I think you need to investigate the inlet and outlet valves of the compressor stages, most importantly:
the outlet valve of the 2nd stage
the inlet valve of the 3rd stage.
I think air is flowing back from the 3rd stage back into the second stage.
Probably just a little, so it becomes only a problem when the compressor (almost) reaches it’s end pressure.
Another problem could be that the outlet valve of the 2nd stage doesn’t open completely of has a lot of resistance (are these closed by a spring on these compressors? Or the intercooler between the 2nd and the 3rd stage is clogged on the inside.
But I don’t think it’s the last two things, most probably the problem is backflow if 3rd stage into the 2nd stage.
Hope this helps 🙂
Thank you so much for taking time to respond my query. I have done all the checks prior to our discussion but, I will still do the needful once I am back to my workshop.
The after coolers can’t be clogged as I have overhauled the entire unit very recently.
Need to check the outlet valve on 2nd stage.
For 3rd stage the inlet and outlet valves are Incorporated as a single unit for this model.
Will keep you posted on this and thanks once again.