Pressure testing with oxygen

[Harry Trafford]

A colleague has pressure test 4 units with oxygen( and survived). He then proceeded to vacuum the system and open the lines. I've a few questions
1. What is the procedure to make sure these units are safe to run?
I'm thinking the refrigerant needs to be removed and given a very long evacuation.
2. These units are r32 so does that bring further problems
3. Last question, How lucky is he it didn't explode already.

[RANGER1]

Harry,
To me depends how good his vacuum was after pressure test!

From his track record it was probably no good, so start again, pressure test, new refrigerant as well.
Oxygen present could cause breakdown of oil, as it would oxidise oil with heat of compression.

[NH3LVR]

I would guess that if he did a proper evacuation it should be fine. That being said if he tested it with Oxygen he might not have the knowledge to do a proper evacuation. A better question might be if he has a attractive Partner that will need to be comforted after he blows himself up?:o

[joe-ice]

If it was vacuumed afterwards i dont see any problems , far as i know oxygen only explodes at a certain level of mixture with air . Other than the explosive bit there would be no difference to another pressure testing gas , He was very lucky though .

[al]

I thought it was the fridge oil it reacted with?

Harry, what the feck were they using oxygen for? it's very hard to mix the bottles up?

A good vac will fix it but ask your colleagues if they remember a similar incident involving a nationwide contractor from a few years ago where a fatality occured.

[joe-ice]

Ya think your right Al , something stuck in the back of my mind about air/ oxygen percentage from long ago . Might be mixing it up .

[martinw58]

if he vacuumed correctly should be ok or did he triple vac with oxygen he's very lucky as is any one that was close to him

[Harry Trafford]

The exact details of what and how he done it, I don't know. From what I understand is the very new guy got the bottle out the van and it wasnt noticed until they where loading the van back up. I didn't even know the oxy and nitrogen had the same connection. I've concerns about recovering the refrigerant out of the system as I might still have oxygen in it. And as we know the recovery machine will be compressing the refrigerant.

[Grizzly]

I quote!
"Oxygen under pressure and hydrocarbons (oil and grease) can react violently, resulting in explosions, fire, and injury to personnel and damage to property. Never allow oil or grease to come into contact with oxygen under pressure."

Anyone doing this must have a death wish!
Or not aware of the dangers.
Anyways as the guys all say a good vac and recharge should resolve!
Grizzly

[Glenn Moore]

This is a straight case of criminal negligence on the so called engineers part which could have had very serious consequences to himself and anyone around him . This incident should be correctly reported to the Health & Safety for a thorough investigation to prevent further instances such as this taking place. The engineer should be sent for re training and re assessment before being allowed to work unsupervised.
Failure to report this makes you complicite in any further acts of stupidity by this incompetent person .

[al]

The H&S dept won't want to know, it's a near miss at the most.

Harry, might be no harm for your foreman/supervisor to do a tool box talk on the cylinders, how they look and what'll happen if they're mixed up!

Years ago it was a common problem as the markings on the cylinders were similar and if the bottles were old a mistake could be made, but even with that as the engineer you should check to be sure.

[monkey spanners]

Guessing this was a new AC install, so just the pipework and evaporator had oxygen in them, would very little to no oil in them.

I know of a similar thing being done on a refrigeration system after repair where the compressor exploded.....

One of the problems in our industry is very few people take the dangers seriously, (or are even aware of them) the pay and training does not reflect the levels we should be working to.

[RANGER1]

The H&S dept won't want to know, it's a near miss at the most.

Harry, might be no harm for your foreman/supervisor to do a tool box talk on the cylinders, how they look and what'll happen if they're mixed up!

Years ago it was a common problem as the markings on the cylinders were similar and if the bottles were old a mistake could be made, but even with that as the engineer you should check to be sure.

Al,
Should you not report near misses though?
Seems pretty crazy that cylinders can be mixed up, as connections different in most places in the world to prevent it.

[martinw58]

oxygen and nitrogen cylinders have the same connections but are different colours

[RANGER1]

oxygen and nitrogen cylinders have the same connections but are different colours

We have connections for every day of the year!

http://gascon.com.au/content/products/pdf/Valve_Summary_AS2473.3.pdf

[al]

Al,
Should you not report near misses though?
Seems pretty crazy that cylinders can be mixed up, as connections different in most places in the world to prevent it.

Yes and no :) I'd be very wary of involving a government dept in this as at the least someone will lose their job, i'm basing this on it being a one off, undoubtedly extremely dangerous but if it was a new install then danger is hope fully reduced. I'd take if up with apprenticeship training as well, obviously not enough is being done to high light danger, as an apprentice it was hammered into me how wrong this could go, as Monkey spanners says the danger isn't taken seriously enough.

[seanf]

Seems to be easily mistaken, when your in a rush and the workshops poorly lit. An experience engineer that went out to do a low pressure leak check, grabbing a wee bottle of nitrogen on their way out the door. It was when they were back at the yard with their van door open, there was no acetylene cylinder or hoses to go with the oxygen, and jokingly asked if they'd being pressure testing.

[still learning]

A near miss definately I would of told the new guy to wake up.
but also maybe checked myself .
if he had been on a fgas course would of said ,read your book again .
and tried to find. The. Exploding. Outdoor unit. Video that's online somewhere .
so glad. I've got a good co worker. With me. Worth their weight in gold .

[Grizzly]

Thank You Harry for an interesting Post.
Not many would admit to knowing about such Dangerous mistake being made.
What's the most important thing about this forum as opposed to other site where slagging people off is the name of the game.
We all assume everyone knows.
But we don't so long may we discus as Engineers how to do things without the know it all H&S ( not the ones who have progressed through the tools) trying to tell us how its done.
Once again thank you Harry.
Grizzly