This is my first reciprocating compressor and can’t find any good information on one so I will post had hope. It is a Bitzer compressor of German design, dual stage with two pistons per bank/four cylinders per compressor with reeds at each piston. Compressor shares a common shaft with the motor which has journal bearings. It is a 2 pole 60 Hz (3600 cpm) motor. Services a DX unit (compresses Freon). I have created spectrums for data collection which include one high resolution of 12K Fmax with 3200 LOR 2 Avg., one velocity with time domain of 153K and 3200 LOR (lines of resolution) 4 Avg., one demodulated enveloping spectrum of Fmax 60K and 3200 1Avg. These were taken once per cylinder over each piston. Is this too many points or too few data collection points? How would one determine if reeds are broken? Is there a way to figure reed pass, or is there one? If there is more G force at one piston than others does this constitute a problem or just imbalance of the unit? Is one times turning speed and its harmonics just that, or are you reading each pistons compression cycle. Should you have harmonics for each compression cycle of each piston? I have more question than knowledge look forward to any information. Is there any books on this that can be recommended? Thanks all!

I have 10 6 cylinder Bitzers that I monitor. Overall we have found very few problems with them. I have yet to detect a broken reed, but none have broken either.. We have had some resonances and pipe strain, and some mounting looseness.

I would add some radial points at the jounal bearings, and there might be an oil pump on the inboard on the main shaft.

The vibration signature is highly sensitive to load, particularly on the pistons, so if you can, make the system variable load and record it. You can record amps, or perhaps discharge pressure etc. The G forces on the final stage can get very high under load.

Bitzer usually has very good exploded view drawings, so you can get a real good idea of what is going on inside the compressor.
http://www.bitzer.com.au/products/index.php?PHPSESSID=f...fecf9e02d9bda4e68e55

If these are Hermitic Compressors, the motor does not have an outboard bearing, it is overhung. So there will be two journal bearings, one inboard of the compressor and one inboard of the motor. Take your data as close as you can to those journal bearings.

This is an old one to drag up, but I'm wondering if either of you two are 1.) still on the board, 2.) Have gotten comfortable with the Bitzers.
I too am looking at some Bitzers. Single stage, 3 banks with 2 pistons per bank. My highest freq. is at 2X and 4X. These of course are part of the 1X harmonics.
Any more info?

Dave