Air dryer question

[md21722]

I have read a bunch of threads but none seemed to answer my question.

One reason I'm looking for the air dryer is because I have air tools that use a lot of air, like angle grinders. There is usually some condensation coming out the grinder's exhaust. I don't think any amount of air compressor after coolers, or coalescing filters is going to help.

I think I need to lower the dew point of the air to cooler than the tool runs so eliminate the condensate I get at the tool.

Here's why. Say I start the day with filled air tanks. The compressors haven't run at all, so all the stored air is at ambient temperature. I have enough stored air I can run the grinders for about a minute before the compressor kicks on. Even during this minute the tool gets cold enough that I get some condensate. When the compressors run, I get more condensate.

So

1. Am I on the right thinking that the air dryer is the only way to eliminate the issue? Do they make coalescing filters for high volume demands? Something like the Devilbiss DAD-500 says it lowers the dew point to -40F, but also says medium production and is only rated for 25 CFM. Sounds better for something like painting.

2. What happens if the air demand exceeds the rating of the air dryer? Does the air dryer act as a restriction and only flow what its rated? Or does it basically allow undryed air to pass though?

3. I am thinking of getting a 60-85 CFM high temp air dryer and forgoing individual compressor after coolers. The air dryer is rated for up to 200F input air. Anyone see a problem with this? Is there a reason to install compressor after coolers when using the high temp air dryer? So far the highest measured tank temperatures has been about 115 F and I plan on putting the drier after about 25 feet of black pipe. I would think the only reason to use the after coolers is to be able to use a normal temperature air dryer rather than a high temp one.

4. I was looking at the high temp IR models. I know Hankinson is a big name in air drying. Anything wrong with the IR ones? I believe Speedaire's are rebranded Hankinsons.

Thanks!

 

[pcmeiners]

"I am thinking of getting a 60-85 CFM high temp air dryer and forgoing individual compressor after coolers."
A properly sized aftercooler basically cools the compressor output to almost ambient at little to no cost, removing a great deal of heat. So leave out an aftercooler and pay the extra electric cost to cool the air for as long as you run a compressor, it up to you to waste money. Hi or low temp air dryer, makes no difference to the electric bill, the amount of BTU of heat removed is the cost, higher the temp of air going in the dryer per given CF, the higher your bill.

"What happens if the air demand exceeds the rating of the air dryer? Does the air dryer act as a restriction and only flow what its rated?"
If you exceed the rating, the air does not go down to the rated dew point, so you end up with more moisture in the air; the more you exceed the rating, the more moisture.
Dryer does not act as a restriction to control the output, though small units have small tubing which does restrict air flow.

 

[md21722]

"I am thinking of getting a 60-85 CFM high temp air dryer and forgoing individual compressor after coolers."
A properly sized aftercooler basically cools the compressor output to almost ambient at little to no cost, removing a great deal of heat. So leave out an aftercooler and pay the extra electric cost to cool the air for as long as you run a compressor, it up to you to waste money. Hi or low temp air dryer, makes no difference to the electric bill, the amount of BTU of heat removed is the cost, higher the temp of air going in the dryer per given CF, the higher your bill.

IR product literature says nominal power consumption is basically the same on units above 32 CFM.

"What happens if the air demand exceeds the rating of the air dryer? Does the air dryer act as a restriction and only flow what its rated?"
If you exceed the rating, the air does not go down to the rated dew point, so you end up with more moisture in the air; the more you exceed the rating, the more moisture.
Dryer does not act as a restriction to control the output, though small units have small tubing which does restrict air flow.

Thanks.

 

[engineer2]

m I on the right thinking that the air dryer is the only way to eliminate the issue?

Yes, a refrigerated air dryer is the way to go.

Do they make coalescing filters for high volume demands?

Don't know much about them, but you can't defy the laws of thermodynamics. My understanding is they capture droplets of moisture. Not sure how they handle vapor.

What happens if the air demand exceeds the rating of the air dryer? Does the air dryer act as a restriction and only flow what its rated? Or does it basically allow undried air to pass though?

The previous answer summed it up.

3. I am thinking of getting a 60-85 CFM high temp air dryer and forgoing individual compressor after coolers. The air dryer is rated for up to 200F input air. Anyone see a problem with this?

It is probably vastly oversized for the average garage and thus will use more power, but will work fine.

Is there a reason to install compressor after coolers when using the high temp air dryer? So far the highest measured tank temperatures has been about 115 F and I plan on putting the drier after about 25 feet of black pipe.

As mentioned in a previous post, an aftercooler will put less load on the dryer. Some dryers run continuously, so the energy savings may be minimal.

4. I was looking at the high temp IR models. I know Hankinson is a big name in air drying. Anything wrong with the IR ones? I believe Speedaire's are rebranded Hankinsons.

All those brands are reputable. I have a 1966 IR air dryer and it still works.

My dad designed air dryers for a living and I worked in the factory building them, so I have a little bit of knowledge about them. I can't claim I'm an expert, but I recommend them for all air systems. You can find used ones cheap on CL and the HF one seems OK.

 

[md21722]

Thanks. I looked at desiccant air dryers but am concerned about the high flow tools loading up the desiccant too fast. That Devilbiss costs something like $500 and claims to reduce dew point something like -40F but is only recommended at moderate load, 25 CFM max. I have air tools that use more than that. I could put money into after coolers, but after I do that, I can just buy a high temp air dryer for the same or a bit less. A local compressor dealer told me they just sell high temp air dryers instead. That may put more money in their pocket, I didn't get in depth with them about it. But if you look at some, Saylor Beall wants something like $450-500 for their after cooler kit. The air dryer seems to be lower maintenance than desiccant, too. 60-85 CFM is more than I'd need but I figured it was better to oversize in part because our high altitude tends to decrease performance of anything that involves air, and to allow more powerful tools.

 

[pcmeiners]

" I looked at desiccant air dryers"
Desiccant dryers can hold pounds of water, on warm days my compressor's after cooler can produce more than a gallon. Not that an aftercooler produces drier air, but desicant driers hold relatively little water before they saturated, technically they are not designed to dry air for an entire system. A refrigerated air drier and a desiccant drier would be a match to get completely dry air for spray painting.
I suggest you spend a day researching compressed air drying before you make an decisions. No offense intended but you have a little knowledge but not enough to make decisions as of yet.

 

[md21722]

" I looked at desiccant air dryers"
Desiccant dryers can hold pounds of water, on warm days my compressor's after cooler can produce more than a gallon. Not that an aftercooler produces drier air, but desicant driers hold relatively little water before they saturated, technically they are not designed to dry air for an entire system. A refrigerated air drier and a desiccant drier would be a match to get completely dry air for spray painting.
I suggest you spend a day researching compressed air drying before you make an decisions. No offense intended but you have a little knowledge but not enough to make decisions as of yet.

I was just explaining why I don't see a desiccant dryer as a good fit for what I'm trying to do...

Thanks for confirming.

 

[metaldad]

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[stonesfan68]

" ...but desicant driers hold relatively little water before they saturated, technically they are not designed to dry air for an entire system. A refrigerated air drier and a desiccant drier would be a match to get completely dry air for spray painting.
I suggest you spend a day researching compressed air drying before you make an decisions. No offense intended but you have a little knowledge but not enough to make decisions as of yet.

Desiccant dryers are used for instrument and process air systems and are indeed rated to dry the complete flow of air out of the compressor. They just waste a lot of air to get to a -40F PDP.

Using a refrigerated dryer prior to a desiccant dryer is not a good idea as the heatless desiccant dryer uses the heat of the compressed air to purge the moisture out of the desiccant. If you use a refrigerated dryer then you are lowering the temperature of the air. I'm not saying it won't work, it just is not a good practice.

You don't need a desiccant dryer unless you need a PDP of -40F. Desiccant dryers use 15-20% of the compressed air to purge the desiccant of water. If you have a 100 CFM dryer then you will waste 15-20 CFM.

Desiccant dryers are very sensitive to the inlet air temperature and pressure. The maximum inlet temperature is typically 120-130F, so an after-cooler is a requirement.

I could put money into after coolers, but after I do that, I can just buy a high temp air dryer for the same or a bit less. A local compressor dealer told me they just sell high temp air dryers instead. That may put more money in their pocket, I didn't get in depth with them about it.

The price difference between adding an after-cooler followed by a standard refrigerated dryer versus buying a hi-temperature inlet dryer is typically minimal. In addition, installing an aftercooler takes some extra labor. I work a an industrial compressor distributor and when someone calls in with a reciprocating compressor and complaining of moisture in their air lines then I go straight to the hi-temp dryer.

The hi-temp refrigerated air dryers made by Ingersoll-Rand include the coalescing pre-filter, so no other filtration is required.

 

[pcmeiners]

"Desiccant dryers are used for instrument and process air systems and are indeed rated to dry the complete flow of air out of the compressor. They just waste a lot of air to get to a -40F PDP."

For approx $500, the OP is not talking about a regenerative system, nor does it appear he wants to spend what it would cost for a regenerative dryer. For $500 you get a few pound of desiccant in an air filter type canister, not suitable for an entire air system, unless your willing to change the desiccant after a few hours of high CFM use ( in humid areas).

"The price difference between adding an after-cooler followed by a standard refrigerated dryer versus buying a hi-temperature inlet dryer is typically minimal."

True, but you missed the point I made in my posts which you did not read, the OP does not need to pay the extra cost of running high temp air into a dryer. An aftercooler removes a tremendous amount of heat at very low to no cost, then a dryer removes more at a rather high energy cost.

 

[JoeFin]

I have read a bunch of threads but none seemed to answer my question.

One reason I'm looking for the air dryer is because I have air tools that use a lot of air, like angle grinders. There is usually some condensation coming out the grinder's exhaust. I don't think any amount of air compressor after coolers, or coalescing filters is going to help.

Ok - you don't need an air dryer for an angle grinder nor any of the go to air tools. An automatic oiler would best serve this purpose.

YES you do need VERY dry air for automotive painting, plasma cutters, CNCs equipped with pneumatic controls, ect ect. In that case drop the money for one

Other wise just fab up some thing to coalesce the moister out of the air and remember to oil your air tools daily

 

[edl]

i went a little different

i live in an extremely humid climate and like the OP get lots of water out the exhuast of air tools that consume a lot of air (in my case a die grinder taking off paint) - when the compressor runs for long stretches the filters fill with water and there are several inches at the bottom of the tank

the compressor has an after cooler between the pump and the tank, yes - but makes no appreciable difference that i can see

I have a small garage and not a lot of space and so i thought i would fabricate a radiator type design out of copper tube to get the feet needed for a long run without a lot of space

but in the end, i made a portable base for a small air dryer that i use when i am consuming a lot of air or painting - it is a Zeks unit that retails for $1400 but i found second hand for $400

here are a few pictures

this particular unit is a heatsink so there is a resovoir of coolant that is cooled and as the temp on that heats up it kicks the unit on - extremely quiet - and only use it when i want and where i want

the outbound filter is to lower pressure for hvlp and remove any final contaminants (only an issue for painting) - i have two hoses just for the unit to try to keep the air clean for the spray gun

hope this helps

 

[MacMcMacmac]

A high temp dryer is just a regular dryer with a fan cooled aftercooler built into it.

You can run a refrigerated dryer before a dessicant dryer no problem. Most heatless dryers use purge air to drive off the moisture from the offline bed. A refrigerated dryer is an excellent way to eliminate the first easy 80% of the moisture load. If the desiccant dryer uses the heat of compression to regenerate, then it won't work. Most large dryers do not use purge air, as it is too wasteful at higher flow rates. The last dryer system I worked with flowed over 32000cfm and would have used about 750hp worth of air for purge. It was also a silica gel based system with 8000lbs per vessel, that dried air for 14hrs per tower, and went to -80F dewpoint.

If that DeVilbiss system is just a set of filters with a can of desiccant in it, you will have to change it out every so often for fresh stuff. You probably will be able to regenerate it in an oven though.

Searching the classifieds for a used refrigerated dryer might turn up a bargain.

 

[sberry]

I don't use any. I have another tank in series before it goes to manifold.