Compressed air dew point

I have ordered the CrossFire PRO with the Razorweld 45. I understand plasma cutting it is desired to have a low dew point of compressed air as this will give better cutting performance as well as longevity of consumables.

What is the desired dew point of compressed air for the Razorweld 45?

welcome to the forum…and hope we can answer this for you.

this is the first real time anyone has really asked this type of detailed question that I remember…look up your manual online and see if it says what is recommended.

truthfully, the best thing to do is try to get the best dry air as you can.

all air with a higher moisture content will do is shorten the life of the consumable tips.

the dryer the better…and that all depends on how much you want to spend…how much you want to do yourself…and how important it is based on your climate where you are working…

a lot of guys just try to make it dry by cooling the air coming right off the piston heads of a compressor and condensing the majority of the condensation before it reaches the tank…then they go through some filters before going to the plasma.

I am a little overboard and will soon have this set up…

  • 60 gallon single stage compressor
  • air right from the piston heads will go through a radiator type cooler with a fan
  • at the end of this cooler willbe an automatic drain to dispose of that water as the air cools
  • next it will go into a “Wet” tank of the 60 gallon unit with an auto drain on that.
  • then it will go through a refrigerated electronic dryer and into a second 60 gallon “Dry” tank.
  • from there it will go through a pre filter…just a standard micro filter…
  • then through a desiccant bead system with color changing beads to warn me of changes in moisture content…
  • last it will go through a motorgurad filter and into the plasma…

yes it is a lot…but it follows the same system we use in the hospital I manage.


Schulz air dryer is 41…

Thanks for the reply! I also work in a hospital setting and familiar with air dryers. We have a couple refrigerated for building automation as well as a regenerative desiccant system which brings dew point down to about -50 deg F for medical compressed air. I also have many years in HVAC specifically so I have some other understandings of pressure/temperature…

I’ve read as just general information that a dew point of +50 deg F is adequate for nearly all general usage. That’s that’s a water vapor content of only 1.1%. Using a refrigerated dryer would reduce the dew point to approximately +38 deg F but would only reduce the vapor content to .8%… so not really a substantial advantage in operating a refrigerated dryer if it really isn’t gonna make any difference in operation of the plasma cutter.

I’ve seen people build these elaborate systems from copper that consume half of their garage wall to dissipate heat and condenser out whatever moisture they can and that seems to be quite effective! I just don’t want to do that. So the hvac guy in me thought I could accomplish the same thing just by creating a reduction in air pressure such as refrigerant does in an air conditioning system when it exits the metering device on its way into the evaporator coil. Sure as heck I found a company that makes what I was envisioning. JT Air Options Inc. So there’s no desiccant and it’s not refrigerated… no electricity.

So with this device I should be able to reach a +50 deg F dew point (1.1% vapor content) quite easily! But I just haven’t specifically seen anyone say what dew point is recommended for plasma cutting. I just read “low”… but never know how low… low actually is.

I ordered this system from JT air solutions and thought if I wanted to try and bring the dew point even lower… such as from the 1.1% to something lower I would just get a smaller desiccant system set up near my plasma table. Only if I have reason to add it though.

So any info to clarify this would be great!

@toolboy , I like pictures

Maximum vapor dew point above.

Remember when we’re talking about compressed air we’re talking about pressure dew point.


how many actually achieve that level…we can strive…


This link was pretty helpful too!

So a -40 deg F would be .01% water vapor content. Thats pretty low! lol! But taking all into consideration if many people using this plasma table is using the diy copper tubing on the wall to rid the system of moisture then they likely would never be getting below the 1.1% vapor content and not noticing any issues. Further more if some users are opting for a refrigerated air dryer they are never gonna get below a 38 deg F dew point either (.80% vapor content) and they don’t appear to be having any issues.

So even at that in order to really get down to that .01 % vapor content I would have to incorporate a desiccant system which may or may not be necessary.

Either way this was all very helpful! So thanks for chiming in! I hate just throwing money at stuff not knowing really if its beneficial or if I’m getting the most for the $$$. So thank you all for the insight!

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I agree.


Unless you have a dew point monitoring system nobody knows what they actually have.

They only can assume based on how the cuts going and through how much condensate you’re collecting and where.

Most people will get their best cuts at the beginning of the day because the compressor pump itself and all the infrastructure is ambient temperature.

As you run most people’s ambient Air temperature in their shop goes up they’re air pump heats up, the tank heats up the lines heat up so then the air s ability to condense reduces.

When you’re on your third or fourth blank into the langmuir your dross will start to increase.
Has anyone else noticed this phenomenon happening to them and wondered why?

If you read the data plate on most refrigerated air dryers they have a maximum inlet temperature.
These units have a specific operating range or swing the refrigerants designed to operate in which produces the maximum amount of condensing. I believe my unit is 49 c. pre cooling before the refrigerator Air dryer is must.
Whether this comes in the form of a radiator that has some kind of active air flow(fan) going past it or it’s a copper tube on the wall radiator with passive air flow through convection.
This brings to mind and quick note; if you build the on the wall type assemblies space it out. the whole back part of the pipe is trying to radiate heat as well. get it six eight inches out from the wall so air can actually flow there. you’re missing out on half your cooling ability if you’re not.

The the whole subject is super cool and a bit of a mystery.

Bit of a tangent of a tangent of a post.

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Those are all awesome points! I considered getting a dew point monitor just so I can actually see what I’m getting at the tool point. I’m just doing this as a hobby… my shop in Wisconsin is air conditioned so I’m not to concerned of high ambient temps in the summer. If anything I’m more concerned about it AT TIMES over the winter because I’m bring my trailer in and snow melts off and the water on the floor just has to evaporate… so it has definitely been stuffy in there at times over the winter.

Putting space behind that copper tubing and the wall is a great point and very cool to see the success people have had improvising something to get the bulk of moisture condensed out! It clearly works from all the videos I’ve seen.

You touched too on lowering the air temp going into the plasma cutter… that there is a max temp. This further had me thinking that maybe I would add some kind of transmission type cooler to the side of my compressor as well. Seems simple enough and very effective. Would only help lower the air temp even more before in my case going through the pressure drop in the dryer I ordered.

Only thing I had to consider was if I could set the operating pressure of my compressor to turn on around 150 psi and off at 175. Fortunately I was able to dial it up from the 150 it was at from the factory. The pressure will enter the dryer where it will drop dramatically to about 90-100 psi if I recalled. That reduction in pressure allows any moisture down to about 50 deg F dew point to boil off. So doing what a whole wall of tubing would do in just a few feet of space.

But yes this is a pretty interesting topic. And one I just wasn’t seeing any specifics on. So hope others can find this useful as well!

That’s cool stuff I’ve been reading through the website.

This is the real trick here.
Hard to have a pressure drop without a difference in pressure I guess.
Did you find any charts for performance or gallons per hour or any matrixes?
It’s asking for 145 to 175 PSI incoming pressure.
I wonder how that range compared to the outlet pressure effects it’s condensing?

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I think we were both replying at the same time we covered the exact same 175psi thing lol

Love to see some kind of statistics.

Ranges, besides the pressure.

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From their main page go to the “bulletins” tab I think it said. They had tons of info there. I believe the unit I ordered was the smallest one. It was good for up to 20 cfm. And like the images you uploaded you just need to input that 145-175psi to the dryer and they adjust the dryer output to 90-100psi I believe. From there you would/could reduce it again wherever your equipment is. So the output from the dryer the smallest model they had was a 20 cfm. I believe the plasma cutter has a requirement of around 6 cfm. My air compressor is pretty much right there… else I’ll be in the market for a bigger compressor. Hopefully big enough for whatever I’ll be doing just starting off.

Thanks for posting these images. This is the first I’ve really used this forum and for some reason I was able to upload a picture like you were. Lol!

I’ve noticed too that many of yur typical air compressors not really designed for commercial use tend to have a max pressure cut off at like 100 psi or 150 psi. So that wouldn’t really work with this type of dryer because as explained you need that pressure drop to lower the dew point yet still have high enough pressure down stream to be useful. Fortunately my compressor I was able to dial it up to 175. It kicked back on at 150. So hopefully this works for me. Looks like there’s many different ways to accomplish similar outcomes. I just didn’t want a wall full of copper nor did I want something else spinning my electric meter.

So being an engineer I will give you all a lesson to help you understand what this dew point thing is and how to determine what dew point to dry your air to.

So your dew point is dependent upon your air temperature. Now if you have an unheated garage in the winter and your compressed air may get to be -20F then you will need to have a dew point that is just lower than -20F. If you have a heated shop and you will never fall below 50F then you will need to have slightly less than 50F and you will be fine.

The dew point is the temperature at which the water in the air will condense out and start sticking to surfaces and then we have problems like misfires and consumables burning up. So it all depends upon the lowest temperature in your shop.

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Also forgot to mention that refrigerated dryers are limited by the freezing point of water and cannot get the dew point below freezing. They can get close but not below freezing.

Now desiccant and regenerative desiccant dryers can easily get you to -40 dewpoint but it usually comes at a cost of compressed air for the regen cycle so factor that into your CFM when sizing a compressor for your shop. The regen units are the expensive ones with the double tanks. You can use desiccant in a cheaper non-regen unit but they usually work best after a refrigerated dryer as they will load up with moisture quickly. A non-regen unit will need to be refilled or the desiccant will need to have the water heated out of it.

My recommendation is if you have a shop that will never see freezing temperatures then use a refrigerated dryer. If you see freezing temperatures then use a desiccant dryer after a refrigerated dryer.


I understand what your saying about the dew point/point water vapor condenses… but the manual for the plasma cutter is saying a max of -40 deg F for DP.

I was actually thinking too by your own account that if I only needed a dew point slightly lower than my lowest room temp that I would be perfectly fine using a system that brings the dew point of the compressed air to 50 deg F… but then you still recommended a refrigerated unit.

If you can find a refrigerated unit then you are done. They just work. The aftercoolers and copper pipes usually work too but you are at the mercy of environmental conditions. The passive systems like the pipe on the wall just barely get the dewpoint to the ambient temperature. Although they usually work, I personally feel much better about having my dewpoint much lower than ambient temperature.

Although the Harbor Freight refer. dryer comes with its own reliability issues I would personally use that in my shop because I can maintain and repair most things that would fail on it. I have used Ingersoll Rand ones in industry and they have had problems too. If I was lucky enough to find a used one in a better brand I may buy one of those too.

A refer. dryer is good at getting a bulk amount of water out of the air. With warmer temperatures usually comes higher humidity.

I don’t have my table yet but I am sharing experiences to try and help.
I used to work in a Wisconsin factory with indoor compressors and dryers that sent air to outdoor equipment. Having -40 weather meant checking the dryers were in tip top shape or there were frozen lines outside and a 80ft manlift was usually needed to fix the situation. Glad I don’t have those issues anymore.

I hope this was helpful.

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this is why I stick to what I am doing…if you have the space and tanks…

  • compress air
  • cool air before primary tank, dump condensate
  • primary tank have condensate dump also
  • then go through refrigerated dryer to secondary dry tank
  • then through desiccant beads
  • then through super fine filter

Who is the George selling consumables? I’d like to make an order. :+1:
George’s plasma shop.