On Jan 24, 8:52*pm, Ignoramus11135 ignoramus11...@NOSPAM.
11135.invalid wrote:
reposting to sci.engr.joining.welding

I am sure glad that I chose not to sell this 80 gallon Speedaire
compressor.

Based upon first impressions, the motor and pump run fine. However,
when bringing the tank up to pressure, I heard a hissing noise at
about 140 PSI, and realized that there is a hairline crack in the
tank, near a 2" long weld attaching the engine/pump mounting platform
to the tank.

The crack does NOT track the heat affected zone of the original weld,
in fact it is perpendicular to it.

.

===========

!

Here the "=" signs denote the weld, and "|" signs denote the crack.

In any case, when I saw this happen, I was quite scared and
immediately relieved the compressor of pressure.

I am not yet sure what was the cause of this crack in the first
place. I will try to find what I can.

My question, obviously, concerns my repair options. I can hardly think
of any welding where more is at stake than here, due to pressure. So,
I see the following options:

1) Take off motor and pump, cut holes in the tank and throw it away,
look for another tank.

2) Repair the tank by welding and hydrotest.

Considering option 2, the first question concerns welding. How would
you weld? How do you identify where the crack ends? Would you drill
relief holes at ends of the crack?

The second question is about hydrotesting. I was thinking about
something simple, such as replace tha gauge with a 400 PSI gauge,
close off all openings besides one, fill tank with water, connect to a
hydraulic pump or grease gun, and bring pressure to 400 PSI (the tank
supports 200 PSI) and look for leaks.

This is very time consuming and I would like to know how likely would
it be that I would make some very bad mistake.

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Ig...replace the tank.

I repeat...replace the tank.

The replacement is cheap...make sure you get a ASME rated tank.

Not worth the time, hassle or liability messing with it as a pressure
vessel.

And yes air compressor tanks do go *BOOM*.

Use the old tank for your favorite HSM project.

Be aware that where the water sits it will likely be rusting through.

Let us know what you build with it.

Good luck.

TMT