Propane pressure diminishing - new cylinder and the problem is still there

[Sulis (Hazel)]

Hi,

I have a Bobcat which I have just got from Di, a new tank of propane, oxycon (working fine at about 3.75 lpm) and the existing propane hose I've had since my old Hothead days with a fitted regulator and flashback arrestor.

So the scenario is this. I light my torch - penty of propane pressure. Adjust the flame to neutral or even slightly reducing with normal looking flame candles tipped very slightly with orange/yellow - looks great. Start working. After 2 or 3 minutes, the candles are diminishing and the flame is growing smaller. The candles are also looking a lot more blue. So I turn up the propane a tad, carry on. Singing away to the radio (very unpleasant for anyone in the vicinity), after another minute or so I notice the flame is diminishing again and the candles are a lot more blue again. Turn up propane. Repeat until fed up and give up for the night 

All connections seem to be tight enough (done the fairy liquid test). Regulator is fully open (turning the regulator the other way kills the flame a hell of a lot quicker, so I am sure about that). Brand new tank of propane, so I know that's fine.

Here is my guilty secret - I often forget to bleed the pipes when I'm done. I tend to finish torching abruptly of an evening, - when I get called in for something - and being a completely daft old bat, I do forget to go and bleed the pipes occasionally.

So could debris in the pipes be affecting the pressure? Or could it be something else? I know it's not the torch.

I am wondering if I need to change my hose and regulator - what do you think?

All advice gratefully received!   xx

[Wishing Wells Glass]

How odd!  The only time this happens to me is when I'm running out of propane so I'm afraid I can't be of much help.  How much do you 'open' the gas at the actual cylinder? 

And slapped wrists for you for not bleeding your lines!!

x

[julieHB]

Actually, it is the torch   but don't worry, there's nothing wrong with it. I assume this is a fairly new torch? It takes 6-8 months of lampworking before the material in the valves has "set". Here's how I found out (I was also wondering where the propane went when I first had my Bobcat ):

http://www.corinabeads.com/pages/torchreview.php

I have had mine for a year now, and rarely have to adjust the flame..

So, just keep turning the propane up a bit

NB: If you come from a Minor, be aware that the neutral flame looks a bit different, I find that there should be hardly any yellow tips on the fingers at all on the Bobcat. If you do get a lot of glowing specks on the face of the torch it means that carbon is building up and you are running a slight reduction flame all the time.  This can clog up the torch, and in worst case scenario, ruin your torch in the long run. If you want to run a reduction flame for some time do that when the "fingers" are 0.9cm or bigger (basically full umph on the oxygen, then increase propane).  You can have a small flame, just make sure you turn down the propane sufficiently. Do NOT run a small reduction flame for a long period.

Good luck!!

[Shirley]

Ditto what Julie has just said. I've had my bobcat a year now and in the last couple of months the flame has stayed pretty constant with just a little adjustment needed in the first few minutes. It's very economical on gas too.

[Sulis (Hazel)]

Thanks all  

Do you think my Oxy is too low? There are some glowy bits, I think maybe there is some carbon building up. Damn and blast - I blummin hope I don't need a second oxycon!!!!!

And Keiara - sowwy!! Slapped wrists duly accepted.  


xx

[julieHB]

No, you don't need a second oxycon, but you have to accept that you will not have as hot a flame as can be achieved on the Bobcat. I believe it was initially not made for oxycons, but for bottled oxygen, and I expect this is why they later designed the cricket.

Just brush those specks off with a wire brush, and next time let it run oxygen rich for a while.

I ran my oxycon on 3.5l/min all winter, and have only started to up it a bit when it got warmer. When I get rich I'll buy a second oxycon 

[Margram]

Are you remembering to clean out the nozzles (a word for another thread
methinks) with the needle tool? Don't know if that would help...

Marg x

[sea-thistle]

Great info, thanks very much it has been really helpful, as I have been having the same problem with my torch, I have a Nortel Minor. I thought it was perhaps the tubing for the propane, well it goes down to floor level then up again and out the shed, thought perhaps that was the problem. I also bleed my hoses, after and before use.I am only at the moment, as I am learning  and a bit nervous of propane in my workshop for 3 hours at a time, once a week. It's only a few months I have been using the torch, so hopefully the more I use the torch, the sooner the problem will stop with the propane ! lol

[Sulis (Hazel)]

Thanks Julie, I don't mind less heat, so long as the atmosphere/mix of the flame is right then I'm happy  I actually work really sloooooowly, because the glass hypnotises me!!!I kind of zone out altogether, which is exactly why my doctor reckons lampworking is perfect for my health!
I have been brushing the specks off, so will continue with that.

Marg, you've reminded me - thanks! I have put that needle tool somewhere in my shed though..hmmmm - got to find that somehow tonight.

Keiara, sorry, meant to say I have the propane fully open.

So the solution is..

1. Bleed pipes after every session (avoiding slap from Keiara  )
2. Clean nozzles & brush off specks
3. Carry on nudging up that propane if needed, but spend more time in an oxy rich flame rather than reducing
4. Torch more  (ooooh the hardship!!)

Thanks all, you are FABULOUS! x x x