Safe pressure testing with gauge manifold

[alexdouglas1969]

I met a guy from Javac at the RAC show who has told me not to use a standard gauge manifold for pressure testing with Nitrogen since the sight glass can 'erupt like a bullet' at the higher test pressures.

Apparantly this is much wose with N2 than refrigerant and we should all be using an N2 rig with its own gauge for testing which goes straight from the manifold onto the system.

But - surely if the MOP is given for 410a at, say 40 bar, then why is it any more dangerous to test with Nitrogen than to have the gauges on at a high system pressure?

No doubt its safer, but I just dont get the theory....

[NoNickName]

If you don't have a pressure reducer, the N2 will reach a pressure of 200 bar when expanded.

[monkey spanners]

This is something i wondered about. Surely the sight glass should be rated for the highest discharge pressure of the system that they are designed to be connected to (plus a safety margin).
What i also heard was that when you open the ofn bottle, if the regulator was set to a high pressure the sudden pressure rise can cause damage to the gauges.

Cheers Jon

[Brian_UK]

What i also heard was that when you open the ofn bottle, if the regulator was set to a high pressure the sudden pressure rise can cause damage to the gauges.The regulator should always be set to zero pressure when being disconnected and should be checked again before opening the main bottle valve.

Teaching to suck eggs I'm sure but......;)


Surely the sight glass should be rated for the highest discharge pressure of the system that they are designed to be connected to (plus a safety margin).I wonder, would you normally be putting that kind of pressure on the sightglass? The high pressure valve would normally be closed so the SG should be isolated.

If you are venting your HP back to the LP side before disconnection then I would expect the LP valve to be open and the HP valve to be 'slowly' opened thereby dropping the pressure.

I suppose we are still back to making things 'idiot proof' though aren't we?

[Pooh]

Brian
it is back to teaching GRANDMA to suck them there eggs again, it surprises me how many people do not know how to pressure test

Ian

[US Iceman]

I missed this thread today, but am going to comment anyway. Better late than never, especially if it keeps someone from getting hurt.

Refrigeration systems and their components are designed for some maximum pressure based on the principle of containing refrigerants. They are not designed to contain nitrogen at the bottle pressure!

Never, ever use nitrogen to pressurize a system for leak-checking without a 2-stage regulator.

A 2-stage regulator is the only SAFE way to do this. The first regulator takes the pressure from the bottle pressure down to you test pressure. The second regulator takes the pressure from the test pressure setting down to zero.

As you begin to start the pressure test, open the service valve on the system to the second regulator (which should be at zero). Slowly raise the second stage regulator pressure to allow the system to pressurize. Continue increasing the pressure until you reach your test pressure.

But never set the first stage regulator to a higher pressure.

I'm beginning to think all of this refrigerant handling certificate stuff needs to be amended to include nitrogen use. If you can't utilize nitrogen properly, the refrigerants should be off limits.:(

[Tycho]

A 2-stage regulator is the only way to do this.

Corrected that one for ya :)

[US Iceman]

Hey Tycho, where have you been hiding? Out at sea drinking beer?

You are correct about the change you made and I concur.

I capitolized the word "safe" to make this point. As you mentioned, this IS the only way to do it. Any other way is NOT safe.;)

[alexdouglas1969]

Yes yes I know about 2 stage regulators and safe pressure testing - my question is this - why is N2 any more dangerous in a gauge manifold at 40 bar than refrigerant at 40 Bar?

[Brian_UK]

I'm beginning to think all of this refrigerant handling certificate stuff needs to be amended to include nitrogen use. If you can't utilize nitrogen properly, the refrigerants should be off limits.:(When I took my CITB ticket part of the practical test was to perform a pressure test using OFN.

It was surprising how many guys were nervous about doing it.


Yes yes I know about 2 stage regulators and safe pressure testing - my question is this - why is N2 any more dangerous in a gauge manifold at 40 bar than refrigerant at 40 Bar?Perhaps the man from Javac was trying to tell you not to use their equipment on modern high pressure systems any more; rather a poor sales pitch I think.

[Andy P]

Yes yes I know about 2 stage regulators and safe pressure testing - my question is this - why is N2 any more dangerous in a gauge manifold at 40 bar than refrigerant at 40 Bar?
Very simple - if the regulator is set wrong for a 2-phase fluid like refrigerant you will get the saturation pressure at ambient temperature in the gauge manifold. If the regulator is set wrong for nitrogen you will get what you deserve! Nitrogen is dangerous because the pressure could be potentially so much higher than is safe for the system

cheers

Andy P

[mr cool]

as long as you dont wind the pressure up above 350 psig you should be ok. i would never blow copper above this for fear of it bursting. let ofn in slowly as it can cause thermal shock, and thats never a good thing!

[frank]

as long as you dont wind the pressure up above 350 psig you should be ok. i would never blow copper above this for fear of it bursting. let ofn in slowly as it can cause thermal shock, and thats never a good thing!

This may make interesting reading http://www.copper.org/applications/plumbing/techref/cth/tables/cth_table3a.htm

[Pooh]

Guys
the copper tube is not the problem as it will stretch to a point its the steel and cast iron components that are likely to rupture. I understood most R410a manifolds did not have a sight glass for this specific reason however as certain companies are selling adapters to connect normal gauge lines to R410a systems it allows the untrained or ignorent to use gauge manifolds designed for lower pressure refrigerants and the inclusion of a sight glass on these manifolds gives the potentially dangerous problem.

Ian

[Tycho]

Think everyone needs to rewind a little...

The problem is not the pressure at 40 bar, or what is most dangerous at that pressure.


The problem is that a N2 bottle has compressed gas at 200 bar, and without a pressure regulator to take down the pressure, you are in a world of sh*t when components starts exploding around you as most are only certified at 38-40 bar, depending on the system.

[Tycho]

Hey Tycho, where have you been hiding? Out at sea drinking beer?

You are correct about the change you made and I concur.

I capitolized the word "safe" to make this point. As you mentioned, this IS the only way to do it. Any other way is NOT safe.;)

Howdy, no not at sea, been in south america since 2nd jan, just got home last week :)

At least you got the beer drinking part correct :D

[Karl Hofmann]

So basicaly what the Javac rep is saying is that the risk exists if some numpty winds up his N2 regulator too high or fails to use a regulator at all?

On the subject of R410, does anyone make a decent quick release connector yet? I had a nasty nip from R410 last year because I couldn't unscrew the standard screw connector quickly enough. I bought a couple from RPW but bizarely they only connected to 1/4 inch hoses which means they would only connect to none R410 gauges...Hmm

[Slim R410a]

So basicaly what the Javac rep is saying is that the risk exists if some numpty winds up his N2 regulator too high or fails to use a regulator at all?

On the subject of R410, does anyone make a decent quick release connector yet? I had a nasty nip from R410 last year because I couldn't unscrew the standard screw connector quickly enough. I bought a couple from RPW but bizarely they only connected to 1/4 inch hoses which means they would only connect to none R410 gauges...Hmm

SRW do a set, a straight one and a 90deg one I've had them for nearly two years now and havnt had a cold burn since! Also got a 1/4 inch once for 407c and a spare 410a one!(its nasty stuff) The only bad thing is you get left with the liquid/gas in the hose.

p.s Karl had my T5 since Jan now, can't fault it at all!

[Karl Hofmann]

SRW do a set, a straight one and a 90deg one I've had them for nearly two years now and havnt had a cold burn since! Also got a 1/4 inch once for 407c and a spare 410a one!(its nasty stuff) The only bad thing is you get left with the liquid/gas in the hose.

p.s Karl had my T5 since Jan now, can't fault it at all!


Thanks for that, I managed to fill my T5 with petrol on thursday :eek: the van told me that something was wrong within a mile so thuresday morning was spent draining it down and refilling with diesel. Fortunately there ware no ill effects.:o

[monkey spanners]

Just checked my yellow jacket R410A gauges and yes they do have a sight glass. I'd expect it to take at least what the high side gauge i rated to, 56bar otherwise whats the point of putting it there, surely the manufacturer would blank off the hole with a plug if the glass can't take the pressure as it apears to be the same manifold body as used with other refrigerants.
I did once connected my gauges (refco) to a system (r22 i think) and saw the needle go all the way round, passed 0 and up to 5-6 bar:eek: Previous engineer had overcharged slightly:rolleyes:

Cheers Jon

[The MG Pony]

Hey we had a gen set that was diesel but wouldn't run till some clunkerd filled it with 10 gallons gas to the other gallons of diesel, think spitted and cuffed but dam, it worked and held a load, so we nick named it dieseline.

[Peter_1]

Teaching to suck eggs I'm sure but......;)
This is one to remember:D

[Peter_1]

I did once connected my gauges (refco) to a system (r22 i think) and saw the needle go all the way round, passed 0 and up to 5-6 bar:eek: Previous engineer had overcharged slightly:rolleyes:

Same happened some weeks ago (+/- 42 bars HP on a R134a hermetic system) Needle turned completely on my manifold. Client thought that his compressor was making another noise then it did before another tech had come to fix something.

[taz24]

Client thought that his compressor was making another noise then it did before another tech had come to fix something.


Did the othe noise sound something like

Heeeeeeeeeeeeeeeeeelp

:D

Cheers taz.

[momo]

Re post #17 check if your hose to valve screw on adaptor allows adjustment of the (Schraeder) depressor, some do; and you can fine tune it not to let out toooooooooo much freeeeeeeze when releasing;).
The insert in the screw fitting twists on another thread, NOT on all models - so don't force it and make sure you still allow sufficient opening of the Schraeder to vacuum etc.
I'm still hunting in Spain for valve terminated hoses - a recent hopeful convert to the life of sun beach etc brought some with him and my teeth have grown long:D:D (note since he arrived he has simply changed colour eg :mad: with over work on AC rooftop condensers ¿¿¿¡¡¡)
Any supplier by PM?

[riverbv]

Yes yes I know about 2 stage regulators and safe pressure testing - my question is this - why is N2 any more dangerous in a gauge manifold at 40 bar than refrigerant at 40 Bar?

Hi to all.
I'm a new member and this is my first message. There's no danger in using a gauge manifold for leak testing using either N2 or refrigerant at 40Bar as long as it's maintained in a pressure that the gauge can withstand however, it's adviseable to always use an N2 regulator to control the sudden pressure surge of the N2 in the cylinder which can go as high as 120bar.
Some years back one of my technician was leak testing a 30ton unit using N2 and gauge manifold when suddenly the 06E recip type compressor exploded shattering the crankcase portion fortunately no one was injured but it took a lot of explaining to management why it happened.
Have a safe day/night to all

[Tycho]

The regulator should always be set to zero pressure when being disconnected and should be checked again before opening the main bottle valve.



Just re-read this thread and noticed this little gem.

I've been trying for years to tell the young'uns that when closing a ofn bottle, you first set the pressure to zero, then you close the bottle, then you disconnect the hose, then you release the pressure from the highside, then you set the regulator to zero...

whenever you walk away from a regulator, the pressure should be set to zero and the small shutoff valve shall be open... infact, the small shut of valve on the regulator shouldnt have been there at all...
---------------------------

If you are pressure testing a large plant and have to change ofn pack halfway and you leave the pressure set to 40 bar, when you connect it to a new pack and open the bottle valve, the pressure on the low side will spike and the safetyvalve on the regulator will blow... or in the cases where the regulator does not have a safetyvalve... bad things happen...

I've had a few scares with high pressure and I now have great respect for the energy that can be released...

-------------------

I was on a russian trawler a few years back and we were to change the fineoilfilters inside a vertical oilseperator, the preassure read 1 bar and the russian engineers from the ship started taking out the bolts. I tried to tell them that we had to wait till the pressure was zero, but they didnt listen "ooh, but 1 bar only... no problem"

when they took out the last two bolts, the 20kg+ lid started jumping around on top of the seperator... I just stood back and watched as they tried to get the bolts back in, thinking "stupid is who stupid does"

[star882]

I did once connected my gauges (refco) to a system (r22 i think) and saw the needle go all the way round, passed 0 and up to 5-6 bar:eek: Previous engineer had overcharged slightly:rolleyes:

Same happened some weeks ago (+/- 42 bars HP on a R134a hermetic system) Needle turned completely on my manifold. Client thought that his Compressor (http://www.refrigeration-engineer.com/forums/glossary.php?do=viewglossary&term=60) was making another noise then it did before another tech had come to fix something.
"Gross Overcharge Makes Peggy Gauges" (GOMPG)