My Compressor Woes Continue

My previous post about owning your own scuba compressor was written for a reason. A little over a month ago, I fired up the compressor to start filling tanks for an Advanced Nitrox & Decompression Procedures class that I was teaching. As it started, it sounded funny. After a couple minutes, the compressor stopped running, but the motor was still on. After I turned it off and removed the compressor shroud, I saw the first stage piston and rod were almost completely out of the bore. The bolt that held the rod to the main bearing had come loose (at 3600 RPM I might add) and pulled the whole assembly out.

My “Oh Shit” Moment

As I starred at now a 100 pound paper weight in utter disbelief, the $$$ were starting to add up in my head. I removed the piston/rod assembly (shown above) and inspected the damage. The threads on the rod end bolt were completely stripped out. Afraid to look, I got an inspection light and magnifying mirror to check the threads on the main bearing. To my complete surprise, they were fine. I was able to go to sleep that night thinking all I needed to do was replace the rod end bolt and I’d be back up running (with minimal expense). Man, I wish I had a nickel for every time I have been naive!

I call up the manufacturer and order a new bolt. They also gave me some tips on how to get the thing installed and wished me luck. A few days later, the new bolt arrived. As I started to dry fit everything, I noticed that the piston was binding on the first stage head (i.e. hitting it). So I adjusted the rod length and got it to work. As I was adjusting it, I noticed that a nut that locks the piston on the rod was not tight against the piston. I was able to turn it by hand. This didn’t seem right. So I call the manufacturer again.

They recommend that I remove the piston from the rod, apply some Loctite and put the piston back on the rod. As I was removing the rod from the piston, I saw that the threads coming out of the piston were very shiny. This can’t be good. Once I got the rod removed, I could see that the threads were fine, but there was metal inside the threads. Anyone want to guess where that metal came from? You guessed it, the hole on the piston where the rod screws into was completely stripped out!!!

Another call to the manufacturer was in order. I asked if I could tap out the hole and they recommend that I didn’t as it may weaken the material (since it was already screwed up). They told me that I would need a totally new piston/rod assembly. So my next question was, “How much does that cost?”. Answer, $210 plus shipping. Oh, and I needed new piston rings. At an additional $60 expense.

So now, I’m into this fix for over $350 (including the new bolt I had to buy). I had dreams of getting an O2 analyzer to finish off the Nitrox stick and some additional money for a backup dry suit. Looks like that plan will change. Did I mention that this winter I’ll need to replace the third stage piston as part of it’s general maintenance schedule? I need a job, just to afford owning the compressor.

Sorry for the rant.
Duane Johnson
Precision Diving