HYDRAULIC PRESSURE TESTING + AIR

[Dasboot]

Kids studying to be ME told me they want to test a steel cylinder by filling it 90% to 95% with water and 10% to 5% with compressed air. The idea being that compressed air is readily available in their dad's garage, and that by filling only the 10% ~ 5% volume with air it is less dangerous. I told them that pressurized air at high pressure will be dangerous even in a small volume. Can you second my opinion before they hurt themselves ?

 

[berkshire]

From a practical point of view, I was lifted 10 feet across a room as an apprentice, by a failing seam on an oil tank that was being tested for leaks, at only ten pounds per square inch using air.
So I concur with your evaluation, filling the tank with water, before adding air will make it less dangerous, but it is STILL dangerous.
B.E.

You are judged not by what you know, but by what you can do.

 

[GenB]

fill 100% water and add air with small bore 1/4 air delivery I would buy it.
why not to get a hand pump. I can test to 5,000 psi with a cheap hand pump.
don't kill yourself

 

[LittleInch]

The thing to remind them is that the pressure test will be the first time that their fabrication will have seen pressure. Hence the possibility of failure is ever present. Where that failure could occur is not foreseeable and if that happens in the air filled bit you can still create a projectile or high energy event.

If they want to use air, then create a separate hydro tested vessel which you fill with water and then pressurise with air at the top, making sure that you only use that much water in the test.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way