Trouble Attaching Reg To Fire Extinguisher

[KGB]

Hey all, my mate has been using a fire extinguisher with a Harris reg with no issues for a while now and got sick of the crappy Harris reg. He has upgraded to a micromatic reg and tried to fit it all together the other day and as soon as he turned the gas on the reg blew straight off the adapter he was using and smacked into the house. Luckily no injuries.
His extinguisher has a female thread on it and he was using a 1/2" male to male adapter with the Harris reg. The threads weren't a super close fit but were obviously enough to engage safely and get the business done. The threads with the micromatic are way too sloppy and you can just about jiggle the first couple of threads straight in - hence the reg blew off under pressure. Nothing seems damaged, they are just different sizes.
Today we went around to a few tool/plumbing/fitting suppliers in search of a suitable adapter but without success. 3/4" is too big and 1/2" is too small - it looks like 5/8" would be perfect but I have no idea if they exist and they certainly aren't too common.


Can anybody offer any solutions/idea/help? I'm happy to use a combination of adapters if necessary but I really need to get a proper fit for the reg.
I'll try and head to Pirtek on monday and see what they've got.

 

[raven19]

Had similar issues with a 'blow off' using an extinguisher and my micromatic regulator.

I has a tapered brass nipple from bunnings, but the tapered resulted in it blowing off the reg side. I have since found a different fitting with a parallel thread on one end (for the reg), and tapered (with thread tape) on the extinguisher side.

I have yet to install it though, as I am still on my hire gas cyclinder.

Will post pics shortly for discussion further.

 

[TidalPete]

I had a similar problem with my first fire extinguisher. Took it & the regulator along with half a dozen of my best to a small machine shop up the road where a brass adapter was machined to a perfect fit.

TP

 

[crundle]

+1 for a custom made brass fitting. Get someone who can identify the threads correctly to make you up a fitting, it is money or a favour well spent.

Compressed CO2 is not something to mess with lightly.

Crundle

 

[KGB]

Yeah, I was already thinking along the same lines as you guys. Can you tell roughly me how much (wallet) damage to expect for a machined adaptor Pete?

 

[raven19]

This is what I have planned as my theoretical fix for my issue...

Old tapered nipple in the background.

Foreground nipple has parallel thread for regulator end with washer to seat at end of thread. Thread tape for extinguisher end.


End of extinguisher.

 

[KGB]

Raven, I think you may have solved my mates problem. I was thinking he may have been trying a tapered male to male adapter which caused the failure. I've been using a parallel threaded adapter on my extinguisher and reg with no problems - including when it toppled over and smashed one of my gauges.

 

[TidalPete]

Yeah, I was already thinking along the same lines as you guys. Can you tell roughly me how much (wallet) damage to expect for a machined adaptor Pete?

I was quoted $25 two years ago but managed to barter. Have just read the above post re tapered threads & agree that you need parallel threads that are a reasonable fit & not so sloppy that Threadseal can't seal the gaps. Best if the washer is silicone.

TP