Broken Air Compressor

So I was looking through our old air compressors we have had from years past and I noticed something quite shocking. One of the compressors seems to have broken at the threads right before the check valve. The threads are split. The compressor I am talking about is the VIAIR 90C compressor. I don’t know what happened since this was before my time but it seems concerning to me since if it was a mechanical failure during operation, that wouldn’t be safe. I’ll upload photos tomorrow to show a better understanding.

Yeah…our habit of mounting the compressor under the robot has produced a few of those over recent years. It generally happens when there’s a lot of stuff threaded directly into the compressor output (relief valve, NPT to 1/4" od adapter, switch, etc), which makes a nice lever to break stuff. Sometimes all of the threads are gone, other times it’s just a few.
The 90C compressor head is cast aluminum, so not terribly unexpected.

Oh, so it’s just that all the fittings act as a lever to break it. I thought that someone might have done some crazy stuff and that part blew up.

We had one break exactly like this at IRI in 2018. We had an off-robot compressor with all the components (PRV, Pressure gauge, compressor shutoff switch and shutoff valve) all mounted in a long string of brass T fittings. The total length extended past the far end of the compressor by a couple of inches. Because it was an off-robot compressor, the students decided that this also functioned as a great handle and would carry around the compressor by this long brass assembly.

@AllenGregoryIV gave us a great tip which is to use this AM cross fitting. Not only does this significantly reduce the weight of a chain of brass T fittings and straight pipe sections, but it also reduces the over-hung moment significantly. If you put the PRV and the switch on this and then mount the pressure gauge closer to your storage tank, you probably eliminate the risk of fatiguing the cast compressor housing.

By the way, you can buy a replacement housing for the compressor. It is not much cheaper than just buying a replacement compressor, but you can save a few dollars if you repair it yourself. We elected not to because I could not convince myself that it was legal per the FRC rule about unaltered pneumatic components.

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Sometimes they fail from over-tightening of the tapered threads. Driving a fitting in too far will weaken or split the aluminum.