Thread: Oxygen pressure for brazing

Hi All,

Santa brought me a Cigweld Cutskill blowpipe, mixer and #8 brazing tip for Christmas to replace the old one in my oxy-LPG setup. I tried it out today, but I'm getting a pulsating flame. The regulator needle flickers in sync with the pulsing of the flame. I posted here about this a couple of years ago and the consensus was the reg was stuffed. However the problem went away if I used a cutting tip, which I often do to braze heavy pieces, so I didn't replace the reg at the time. I figured the reg didn't like working at low flow rates.

I've done a bit of research today and BOC recommend 50kPa fuel and oxy pressure for all their welding tips. On my oxy reg 50kPa is barely off the stop (see pic). Obviously this reg isn't optimal for my setup, so I went searching for a new oxy reg. However all oxy regs BOC sells allow very high oxygen pressures. For example: Cutskill Oxygen Regulator VI 800kPa – Cigweld
I don't use my oxy-LPG set for cutting. Do I need a regulator with a lower output pressure?

Cheers,
Chris

50 kPa is the textbook pressure to run for welding and brazing tips but higher pressures can be used, albeit at the expense of more touchy adjustments at the blowpipe valves. Your regulator definitely has issues, but you may find that increasing pressures to say 100 kPa for both oxy and lpg may alleviate your issues enough to get you out of trouble.
There may be special low pressure regs out there, but most just use the standard run of the mill ones like the cutskill one you found. Tesuco make reasonably priced regs and gas equipment too, so give them a look as well.
One final thought. You are using an Oxy LPG tip I assume?

Hi Karl,
Thanks for the reply.

Originally Posted by Karl Robbers

50 kPa is the textbook pressure to run for welding and brazing tips but higher pressures can be used, albeit at the expense of more touchy adjustments at the blowpipe valves.

This is what I'm finding. If I crank the reg pressure up, setting the oxy becomes very touchy. I have to very gingerly open the oxy valve at the blowpipe to prevent to LPG flame blowing out. It's always been a pain for me to light an oxy-LPG brazing tip, but higher pressure definitely makes it worse.

Originally Posted by Karl Robbers

There may be special low pressure regs out there, but most just use the standard run of the mill ones like the cutskill one you found. Tesuco make reasonably priced regs and gas equipment too, so give them a look as well.

I found a BOC 8000 reg that only goes to 600kPa. That should be an improvement. I'll check out Tesuco.

https://www.boc.com.au/shop/en/au/bo...r-105105-p-112

Originally Posted by Karl Robbers

One final thought. You are using an Oxy LPG tip I assume?

Yes I am.

I found this on another website. If it's true it would explain the problem I'm having:

"Most regulators are notoriously inaccurate for pressure setting in the first 10-15% of their working range, and will pulsate or have pressure loss. The reason is that the spring that holds the diaphraphm in place doesn't have enough tension in the lower pressure settings. Most regulators won't become totally accurate until they are set at least at 25% of their working range."


Edit: I found this Tesuco reg. 150kPA out. Might do the trick. At $53 it's a lot cheaper than the BOC.
https://www.nationalwelding.com.au/r...n-type-10-in-2

Some progress. The reg stopped pulsing when I tried it today. Perhaps the diaphragm gets sticky if not used for a while?

I bought a size 15 tip today. The higher flow rate makes setting the oxy valve on the blowpipe a lot easier.

I've solved the difficult lighting issue. If I crack open the oxy tap I get a good light up. I'd always thought this was a no-no, but I saw a video by Harris which recommends this technique.

A lower pressure reg would still make setting the oxygen easier with the smaller tips.

This might sound condescending but you are using a LPG regulator

Yes I am. It's a Cigweld adjustable gauge-less reg. I just crack it open, which gives plenty of gas. I should probably upgrade it to a reg with a gauge.

You can adjust the flow with how far open you have the taps on the hand piece.
I always crack a little oxy then then put fuel gas on, after a while you get use to how far to have both open and you can light it first go.

Simon

Originally Posted by jack620

Some progress. The reg stopped pulsing when I tried it today. Perhaps the diaphragm gets sticky if not used for a while?

I bought a size 15 tip today. The higher flow rate makes setting the oxy valve on the blowpipe a lot easier.

I've solved the difficult lighting issue. If I crack open the oxy tap I get a good light up. I'd always thought this was a no-no, but I saw a video by Harris which recommends this technique.

A lower pressure reg would still make setting the oxygen easier with the smaller tips.