Back purging stainless - CO2/flux/tape/etc?

[kev888]

Thanks to advice and info on here I'm taking my first steps with the TIG welder - its far from neat yet but I'm making a lot of progress and joining metal successfully. Really very satisfying! However I've been shocked by how fast I'm getting through the Argon; my 9kg cylinder is down to half pressure and I've only used about a dozen filler rods running beads and making practice joints - thats probably £45 worth of gas used

Soon i want to progress to welding stainless steel sheet, for food/homebrew use, and I'd intended to back-purge with argon - but I'm a bit worried about the cost even just for torch gas. I'll ask around local gas suppliers in case they're cheaper but I think I'll have to stay non-rental as this'll be a sporadic hobby rather than a regular thing.

Are there acceptable alternatives - could I use cheaper CO2 (not for the torch/tungsten, just to back purge). Or would some kind of flux or heat-resistant tape on the back be enough?

Many Thanks,
Kev

 

[Piero]

Hi

I am new to tig as well, so what I say might not be 100% right, but look up gas saver on google, a know a few people use these to save on argon

 

[FranV8]

Piero is right - it's also known as a flowmeter. Get one! Better are teh type that have a pointed bullet shape indicator in them, I've found my ball one to be quite inaccurate compared to the type I mentioned. Has saved me a fortune.

Also - have a good look at the gas spreadsheet - with TIG you really want to be getting 200-220 bar filled 10-20l bottles as a minimum, expecially when practicing.

 

[Piero]

have a look at this link

http://www.mig-welding.co.uk/forum/showthread.php?t=10101

 

[kev888]

Thanks chaps - very helpful!

A bit more searching has convinced me that CO2 is no good to back purge so it'll have to be argon unless other methods (flux/tape etc) are suitable?

Piero - thanks for the link; i'd found something else the americans use on the torch so was getting confused! Looks good; my regulator definately jumps up a couple of PSI when it stops flowing, so i can well believe there'd be a wasteful surge at each start.

FranV8 - I can find an Argon/CO2 gas spreadsheet, is there one for plain argon anywhere or are argon prices similar? Sorry if its obvious, I'm just a bit new to all this. I hope so, on my current gas price it was starting to get a bit £scary..

The prices in the spreadsheet seem 'much' better than i paid for my 9L rent free 137bar cylinder, though. Unless I almost stop welding, the savings on refills will more than make up for rental, I think - and I have an energas close by, too.

Thanks again,
Kev

 

[Piero]

I have a question to ask the others, might help you as well, who knows

But do you run a gas cooled torch at any grater flow rate than a water cooled torch.

I know the gas is not consumded by the cooling affect but just asking if people run higher flow rates (gas cooled V,s Water cooled)

 

[hotrodder]

Flux or tape aren't really suitable for hygienic work. Solar B flux leaves a hard glassy residue which is a PITA to remove assuming there's even access to get to it. Backing tape isn't cheap and of course you need to able to get the back of the joint afterwoods to remove it and clean off adhesive residue

Nitrogen is sometimes used as a lower cost alternative to argon for purging austenitic stainless. Nitrogen isn't inert so it's less versatile than argon and not as good when corrosion resistance is critical. Obviously would need a rent free cylinder with a fully returnable deposit to even consider it unless talking a huge amount of purging and/or huge purge volumes

i'd found something else the americans use on the torch so was getting confused!

That sounds like what's usually called a 'gas lens'... http://www.mig-welding.co.uk/forum/showthread.php?t=12673&highlight=gas+lens It's a different type of collet body that makes for less turbulent gas flow out of the torch. They often let you get away with slightly lower flow rates unless you're taking advantage of the laminar flow by say having lots of tungsten stick out for access reasons

Doesn't make a difference when welding but air/gas cooled torches typically need longer post flow times to stop the tungsten oxidising while it cools. With a water cooled torch 5 or 6 secs is enough for the tungsten when welding ally at 150 odd amps

Gas use will drop some as you get to grips with the process... making less stop/starts, welding hotter and faster, when 'less is more' in terms of flow rates, getting to grips with purging techniques etc

 

[kev888]

Excellent - many thanks indeed! I think I have what I need now; I should really be using argon to back purge stuff for food use, not tape or flux and definately notCO2.

Nitrogen sounds possible but I see what you mean about versatility and needing rent free. Looking at the prices on that spreadsheet it'd probably be better for me to just go for a bigger argon cylinder - they seem to cost only slightly more than smaller ones and I can use it for the torch too.

I suppose I'll need another regulator for a back-purging setup, and some way of splitting the gas line to it. The spending is almost as steep as the learning curve! All really interesting stuff, though.

Cheers
Kev

 

[hotrodder]

To purge from a single cylinder all you need is a 'valved Y-splitter' (which you fit to the regulator to give you 2 outlets) and ideally a second flowmeter. Pic of one here... http://www.weldequip.com/twin-outlet-valve.htm, pretty much every welding store carries 'em. Search the tig forum for 'purge' and you'll get loads of threads with tips and techniques

 

[kev888]

Ah thanks, that sounds cheaper.

Unfortunately things are suddenly on hold; just switched on my shiny new tig welder to have another practice, but got no arc and very smelly smoke billowing out of the machine

 

[StickNtig]

I have a question to ask the others, might help you as well, who knows

But do you run a gas cooled torch at any grater flow rate than a water cooled torch.

I know the gas is not consumded by the cooling affect but just asking if people run higher flow rates (gas cooled V,s Water cooled)

No.

 

[zx9]

Ah thanks, that sounds cheaper.

Unfortunately things are suddenly on hold; just switched on my shiny new tig welder to have another practice, but got no arc and very smelly smoke billowing out of the machine

That's bad, what is/was it and do you know what happened to it? I assume as it is

shiny new

that it will be guaranteed by the seller, let is know how you get on with any repair or replacement.

 

[langy]

You will save a fortune in gas with a flowmeter, use one on the purge line also.
The cheapest way with argon that i have found is using a W size BOC bottle, the small bottles just havn't got enough in them for cost effective TIG welding.

 

[kev888]

Thanks chaps. Yes I think a flow meter sounds a good investment.

zx9 - yes indeed; it wouldn't even start the arc and I'd changed nothing since it was happily running decent beads so I'm fairly certain something in it has 'gone'. It was an R-tech 200amp tig welder, which I'd believed should be a better brand than the cheap chinese/ebay ones - most dissapointing, and to be frank worrying as its a major investment for me (even before I'd realised how much the gas would be). I'd been in a dilemma between that and the inverter fusion on weldequip.

Still, I realise even the best can have the odd failure, so it'll come down to customer support now. As it failed so quickly i'm hoping they'll replace it with no quibble, but its not a great start so i'm almost wondering if I should ask for a refund and try the weldequip one - the reviews seem to say they're similarly good though, so probably r-tech deserve a chance to put things right.

Cheers
Kev

 

[carl0s]

Thanks chaps. Yes I think a flow meter sounds a good investment.

zx9 - yes indeed; it wouldn't even start the arc and I'd changed nothing since it was happily running decent beads so I'm fairly certain something in it has 'gone'. It was an R-tech 200amp tig welder, which I'd believed should be a better brand than the cheap chinese/ebay ones - most dissapointing, and to be frank worrying as its a major investment for me (even before I'd realised how much the gas would be). I'd been in a dilemma between that and the inverter fusion on weldequip.

Still, I realise even the best can have the odd failure, so it'll come down to customer support now. As it failed so quickly i'm hoping they'll replace it with no quibble, but its not a great start so i'm almost wondering if I should ask for a refund and try the weldequip one - the reviews seem to say they're similarly good though, so probably r-tech deserve a chance to put things right.

Cheers
Kev

I could be wrong, but I thought the R-Tech ones are the cheap/eBay ones, with the difference being that the R-Tech do support the buyer. So, as long as you have a warranty, they should fix it. Not sure what happens if there's a repeat 2 years down the line though.

I went for the Inverter Fusion one. Found a place doing them extra cheap.

 

[kev888]

Having done a bit of trawling, it seem to be thought that r-tech import them (or parts of them) from china but upgrade some bits as necessary and then back them up with UK support and warranty - I hope.

Generally they seemed well regarded at the budget end of things, hence partly why i chose them.. ho hum

Cheers
Kev

 

[Paul G]

Hi Kev,

As I said in the U2U, hope you get the welder sorted.

Here's a pic of my argon reg set up. The big hose goes to the welder and the little one is my purge line.
Just a simple Tee as the flow meters have flow controls on them.

Depending on the job I might purge at 6 l/p/m to start with but as the welding progresses and all the joints
are sealed I can often turn this down a bit.

The aircraft exhaust in my avatar is an example.
It's supposed to make a horizontally opposed 8 cyl appear from the outside to be a V12.

Good luck with the welder.
Cheers,
Paul G

 

[kev888]

Thanks Paul, thats really helpful! I'd not realised the flow meters could also have controls, that makes it a lot easier than I'd imagined :-)

News from R-tech first thing this morning, and i only emailed last night. They say its very unusual which is reassuring; possibly just an oil-filled capacitor having failed, hence the smoke. Anyway, they're sending a new machine out and collecting the old one tomorrow.

Top stuff - I'm really impressed with their customer support, they're almost falling over each other to help me. I guess no-one can avoid the odd failure so its how they deal with it that makes the difference, and in this case it seems to be everything I could wish for. I'd been rather concerned as you hear horror stories from some suppliers, but it seems my worry was needless. Excellent - hopefully the couriers will do their bit too.

Cheers
Kev

 

[zx9]

Good news Kev, fingers crossed for Tuesday.

 

[gerry3]

Thanks Paul, thats really helpful! I'd not realised the flow meters could also have controls, that makes it a lot easier than I'd imagined :-)

News from R-tech first thing this morning, and i only emailed last night. They say its very unusual which is reassuring; possibly just an oil-filled capacitor having failed, hence the smoke. Anyway, they're sending a new machine out and collecting the old one tomorrow.

Top stuff - I'm really impressed with their customer support, they're almost falling over each other to help me. I guess no-one can avoid the odd failure so its how they deal with it that makes the difference, and in this case it seems to be everything I could wish for. I'd been rather concerned as you hear horror stories from some suppliers, but it seems my worry was needless. Excellent - hopefully the couriers will do their bit too.

Cheers
Kev

I am glad to hear that you have had a good result from R-tech., and I am sure you will now have a very reliable machine.It is in such circumstances when service counts most. All I can say is well done R-tec. and keep up this good customer service.
There is an old saying that "you can always sell some thing the first time but not the second ".