Not logged inAmerican Welding Society Forum
Forum AWS Website Help Search Login
Up Topic Welding Industry / General Welding Discussion / Gas for plasma?
- - By Robert48 (**) Date 01-12-2011 17:26
I have a Miller Spectrum that I run on compressed air in the shop, and need to use it in the field some. I have a compressor on my truck but as you all know most engine driven compressors with small tanks produce alot of moisture. Especialy on humid days. I just wanted to know if anyone runs a plasma using bottled gas. If so what type, and if it is econimical to use one this way.
Parent - - By Northweldor (***) Date 01-12-2011 17:46 Edited 01-12-2011 17:49
375, 675,  875...?? Can't answer your question without knowing the size, and what you mean by "some" (thickness, amount, frequency??
Parent - - By Robert48 (**) Date 01-12-2011 17:56
It's a 2050. I use it for mainly 3/8 or less mild steel, any thing over that I find I can cut better with a torch. It's hard to say how much it will be used in minutes but probablt less than an hour each time I need it.
Parent - - By weldwade (***) Date 01-12-2011 18:25
You can use nitrogen. I have an air dryer/regulator both on my shop and truck compressors. They are not really that expensive and may be cheaper in the long run than renting/purchasing a nytrogen cylinder? I bake my desicant beeds on a cookie sheet at my ovens lowest setting when they become wet. I have only had to replace the beeds once since I purchased the systems and I have been using them both for the past 6 years.
Parent - By 99205 (***) Date 01-12-2011 18:32
You may want to look at a Hospital grade compressed air bottle.  I've used them quite a bit on HyDef plasma machines.  They aren't  that expensive and will give pretty consistent results between bottles due to the certified gas/moisture mix.
Parent - By rcwelding (***) Date 01-12-2011 19:29
I have a 5hp gas air compressor that I run my Hypertherm 1000 off of... I bought 3 in-line air dryers from Home Dpot... They are about $30 each for a good ones... One would probably do the trick but I still get a tiny bit of moisture in the 3rd one every now and then..

   I live in South East Texas and we have plenty of humidity and condensation in our compressors here...  My machine runs just as smooth as can be...

  Mite be something to look into..!!

  RC
Parent - - By Northweldor (***) Date 01-12-2011 19:39
You asked about economy, and if you get a larger nitrogen cylinder from your lws  (120+) it will likely supply your 2050 for about 17 hrs at 6.75 CFH, and you will have the cost of regulator, hose, and connector, as well as refills. This will likely run you $300-400 initially if you purchase the cylinder and $15-30 per refill depending on your supplier. As weldwade and rc pointed out, it might be better to spend the money upgrading your compressor and dryer.
Parent - - By Robert48 (**) Date 01-13-2011 01:18
How is the cut quality using Nitrogen? I have a water seperator on my compressor and it works ok. I just wanted to see if there is any economical way to loose that big ass compressor off my truck.
Parent - - By Northweldor (***) Date 01-13-2011 01:53
As I understand the plasma process (correct me if I'm wrong), it is the nitrogen in air that is used for the plasma.
If anything, cut quality would be improved by using pure nitrogen, but only by a small amount, since air is 80% nitrogen anyway.
I think, short of buying a smaller plasma with 3/8 quality, and 90psi/ 4.5cfh (Hypertherm 38) you are stuck with your larger air compressor to provide the necessary air for your machine (6.75 cfh).
Parent - By 99205 (***) Date 01-13-2011 05:46
Nitrogen is the main element in  the cutting process. Hospital Air is a 80%(nitrogen) 20%(Oxygen) mix and it's the oxygen that really helps produce very clean cuts.  I have used just Nitrogen when I've run out of Oxygen and the cuts were some what rougher with more dross on thicker metal.
Parent - By empire welding (**) Date 01-13-2011 04:46
i run a spectrum 1000 w/ 400 vantage and a IR 30 gal compressor all the time and use a air dryer/filter.  cuts 1/2-3/4" fine and I go through about the same amount of tips and electrodes as i do off shop air

http://weldingdirect.com/subairfilfor.html  this is similar.
- - By Buser (*) Date 01-13-2011 12:25
We are using Nitrogen on four spectrums now to reduse cromium output in a SS room .  It produces a far superior cut on SS.  The smoke plume is nearly eliminated compared to compressed air.  I'm a big fan so far, but it is definetly not the most economic route!!
Parent - - By rlitman (***) Date 01-13-2011 17:14
Interesting.
I have heard that the oxygen in plasma systems fed with air will increase the cutting action of a plasma cutter (reducing the required current), on steel that can be torch cut.
I guess that in other metals, it just causes problems.

BTW, if you're using large quantities of nitrogen, you can make it very cheaply on site.
There are commercially available machines (some standalone, some you feed compressed air into), which remove the oxygen from air.  They'll get you to around 95% nitrogen, but with nearly zero oxygen, that's close enough.  They work on the same principle of an oxygen concentrator (which is used to remove nitrogen from air, to supply 95% oxygen for medical purposes), just reversed.  I've been seeing them in larger tire shops now, so it can't be too expensive.  Just depends on how much nitrogen you need.
Parent - - By Northweldor (***) Date 01-13-2011 22:25
However, the makers of these machines are advertising, to the tire shops,  the claim that nitrogen tire filling will return up to ten times the cost as profit. I doubt that the same could be claimed for plasma cutting gas replacement.
Parent - - By Robert48 (**) Date 01-14-2011 00:28
How many tires can you fill off of a $20 bottle of nitrogen? It looks like you would have to fill alot of tires to pay for a $10k nitrogen machine vs using bottled gas.
Parent - By Northweldor (***) Date 01-14-2011 14:25
Not at $10 per tire, and many unscrupulous dealers charge more.
This website promotes their machines (as cheap as $500) by saying and providing tables that show that this can soon become the most profitable service in the shop.

http://www.nitrogentiremachine.com/

While the nitrogen fill has definite benefits for aircraft and racing tires , and fleet-owners who can't enforce regular tire checking, it is not the panacea that Jay Leno and others suggest. Checking tires regularly and filling with good old compressed 80/20 will do almost the same thing.

Anyone remember telling bystanders they had "racing air" in their performance car tires?
Parent - - By DaveBoyer (*****) Date 01-14-2011 01:43
If I remember right, old plasma systems used oxygen for the plasma gas and nitrogen for the cooling gas. One of My friends had a 2 gas plasma, He fabricated stainless exclusively.

Air plasma torches are not set up to feed 2 different gasses.
Parent - - By rlitman (***) Date 01-14-2011 17:27
I'm pretty sure that it was nitrogen for the plasma gas, and argon for the shielding gas.  I don't even think oxygen would work as the plasma gas.
Early plasma systems didn't have hafnium electrodes we use today with air plasma that could withstand an oxidizing plasma.
Parent - By Superflux (****) Date 01-15-2011 02:10
Some systems used CO2 and argon. Those were the good ol days having to hook up 2 bottles and regulators...which of course never ran out at the same time.
Parent - By DaveBoyer (*****) Date 01-15-2011 03:20 Edited 01-15-2011 04:14
Well I did say IF...

You got Me curious, so I dug out an old book, Welding Handbook Volume 2 seventh eddition (1978):

"Most non ferrous metals are cut by using nitrogen, nitrogen hydrogen mixtures, or argon hydrogen mixtures"
"Titanium and zirconium are cut with pure argon"
"carbon steels are cut using compressed air or nitrogen for plasma gas"
"some systems use nitrogen with oxygen injected into the plasma downstream of the electrode"
"For some nonferrous cuttingwith the dualflow system, nitrogen is used for the plasma gas with carbon dioxide for shielding"
"For better quality cuts, argon-hydrogen plasma gas and nitrogen shielding are used"
Up Topic Welding Industry / General Welding Discussion / Gas for plasma?

Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill