Welding Tips and Tricks

I recently bought a hypertherm powermax 30 I was just wondering if I should put an air filter on the compressed air I am feeding it with and if so which kind. Any recommendations or preferences? Thanks Steve

You will definately need one for water and other moisture in the line.

We have the Powermax45 unit and I have a filter/moisture separator at the compressor and then another one right at the inlet to the unit. I think the main point here will be how long the consumables last. So far, so good.
Nice little units!

It's not just moisture...

"Air" is 20% oxygen.

I get to use dry nitrogen for plasma cutting. Nice difference on stainless. HUGE difference on aluminum.

Steve S

What pressure settings do you use for nitrogen?

Using nitrogen will help a lot but its quiet expensive if I may say so, But which is cheaper, to have some filter which will do as well or switching to nitrogen ?

For most purposes, dry air is just fine. A good water (& oil, if you don't have an oilless compressor) separator, followed by a dessicant pack, will help your consumables last, and reduce grinder time.

Nitrogen makes no noticible difference on carbon steel. (If anything, a bit of O2 helps the cut.) It produces less dross on stainless, and much less dross on aluminum, particularly on sections you can drag the tip on.

Nitrogen is impractical for the home shop, though, unless you are doing something small, specialized, and well-compensated. We have a 4000 gallon tank of liquid nitrogen, as dry nitrogen gas (and occasionally liquid nitrogen) are required for our work. That makes using nitrogen for stainless and aluminum cuts a no-brainer... When you buy that much, it's almost as cheap as running the 3-phase compressor.

I use nitrogen at the same pressure as air for the same thickness.

Steve S

Thanks for all the info, yesterday I hooked up my plasma cutter from my compressor with a 3/8in 40 micron air filter( at the compressor end) and a inline desiccant dryer/filter (at the plasma cutter end). It ran great smooth cutting. Only have one question I still had some moisture getting through, should I be concerned? Add more filtering. Has anyone had this experience and what else can I do? Thanks Steve

You're already ahead of the game with that setup. The dessicant won't catch everything because of the sheer volume of air a plasma cutter requires. Ways to further reduce the moisture get progressively more complicated/expensive.

Gauge whether your consumables are holding up well enough (not eating you up on replacement costs), and your cuts are clean enough that you're not wasting undue time dressing them, before you consider any further steps. If you need more moisture reduction, I can share some "homebrew" methods, but unless you plan "production-level" usage, you should be good.

Also, don't forget to watch the dessicant, and bake it dry when needed.

Steve S

Thank you Steve that's exactly what I needed to know, I am a hobbyist so spending a lot of money on filtering air is not something I need to do right now. Thanks again

Draining your air compressor tank on a regular basis will help keep moisture out of the line, especially in really humid weather.

delraydella wrote:Draining your air compressor tank on a regular basis will help keep moisture out of the line, especially in really humid weather.

Draining is good, but!

Despite the common logic, it has NO effect on the moisture in the line. You might have a 1/4" in the bottom of the tank. You might have 4" in the bottom of the tank. The key words are, "In the bottom of the tank". It's stuff that's already condensed out. It's the water above the "saturation" of the air in the compressor. The humidity of air leaving the tank is not affected by standing water in the bottom.

Steve S

What about using an intercooler to reduce the moisture?
(Cooled air causes the moisture to form into droplets.)

My air compressor has a finned copper loop directly behind the cooling fan.
I believe the idea is to cool the hot compressed air before it reaches the tank.

PS: I got this idea from a recent engine purchase ($300) for my hovercraft project.
I needed 80hp at less than 300lbs. https://www.youtube.com/watch?v=DvYaRuXBACc
I chose the Suzuki 3 cylinder, 1 liter, fuel injected, turbocharged, intercooled engine.
http://www.raven-rotor.com/html/redrive.html (80hp at 159lbs.)

Sorry Steve, but I gotta disagree with you there. If you have water in the bottom of the tank , it's really easy to tell that if you're using pneumatic tools like a nail gun because you can see the moisture in the air coming out of the exhaust port. It looks like steam. If i drain out the tank from the bottom and get all/most of the water out, and refill it with air, there's an immediate difference in whats coming out. Again, using a nail gun, there's no more moisture coming out of the exhaust.

Of course, it won't get rid of every bit of moisture in the line, but it gets rid of a lot of it.

Other Steve

Yes, draining reduces visible moisture in the line. The problem is, when moisture settles in the tank as liquid, the tank air is already saturated. For plasma cutting, it doesn't matter much whether the moisture is visible or not.

I've also noticed when I use my WFO blower, I see moisture in the air regardless whether I've drained the tank or the standpipe (set up as a secondary moisture trap with a low-point drain).

Steve S

If the quality of the air from a compressor matters for it's intended use such as food industry / water industry / paint spraying / plasma cutting / breathing / diving - then the air must be cooled considerably prior to effective multi stage filtration - we all largely ignore this when using cheap air tools on cheap compressors but it does matter for some things - plasma cutters hate water vapour as it greatly reduces the consumables life - the small coil of pipe between the compressor and it's tank help slightly with cooling - but nowhere near enough - so most of the water vapour in the air being compressed stays warm enough that a cheap filter near the compressor cannot catch it - a filter is only effective once the air is cold enough for that vapour to condense out - so a filter some distance from the compressor will work better - commercial compressors often have a refridgerant cooler / heat exchanger either in a seperate cabinet or sometimes built in with the compressor prior to filtration - just look in a spray shop / body shop. The water in the tank that has already condensed is'nt the problem.

I built a rather complicated system for the paint booth at work. There are dual 80-gal tanks downstream from the compressor, with a heat-exchanger and oil separator between, auto-drains on both tanks, and an 8000 btu air-cooler/dehumidifier after to provide dry air for the two-part epoxy paint our shop uses.

I suspect for the OPs home-shop use, though, the seperator and dessicant pack will likely be adequate, and better than most home users have.

Steve S

Now, I understand the NOTE on my desiccant dryer that suggests to mount it at least 25ft from the compressor. That puzzled me for a while and now I understand that they are simply wanting cooled condensed air prior to filtration. I will make my own intercooler instead.

noddybrian wrote:a filter is only effective once the air is cold enough for that vapour to condense out - so a filter some distance from the compressor will work better.

Wow, that's a lot of info, just wondering if I should move my air filters to the plasma cutter end rather than at the compressor end. To remove as much moisture as possible before entering the plasma cutter or leave it the way it is? Thanks again and keep it coming I'm considering all the options here.

At work, we have separater/filters mounted to the carts our cutters are on, so the final filtration is at minimum 100' from the compressor tank (50' overhead pipe to the nearest connection plus 50' of air hose). The separaters stll pick up water, despite an auto-drain on the tank and a stand-pipe with sump and drain.

So, yes, there's a benefit to having the separation occur as far "downstream" as reasonable.

Steve S

Google "Franzinator" if you want to make an expansion air/water seperator. If you want to follow that up with a chemical dissicant, it'd probably be near perfect for anything less than lab or commercial use. S/F.....Ken M

A cooling fan over this radiator would make this setup much more efficient.
A thermostatically controlled, electric fan from from a vehicle would work great.

echosixmike wrote:Google "Franzinator" if you want to make an expansion air/water seperator. If you want to follow that up with a chemical dissicant, it'd probably be near perfect for anything less than lab or commercial use. S/F.....Ken M

Today I tried putting the all the filters on the plasma end of the compressed air and had no issues with water in the line. Worked great, thanks for all the advice and recommendations. Thanks Steve

Glad it's better for you!

As you see from the other posts, and some of my own comments, there are ways to further improve the system, but you've got to weigh the cost in time and/or money against the price of your consumables and the effort to dress your cut pieces.

Only time will tell if a futher investment can be justified.

Steve S

Thank you, Steve . Eventually once I recoup some money I will upgrade to better filters but for now I'm good. I love having a plasma cutter, unfortunately this completes my toy list. Just kidding Learning tig will be next thanks again