Dry Shop Air - Step 4 (Refrigerant Dryer - More Capacity)

[MtnBiker]

The air system has been running pretty well except for those larger plasma cutting jobs where we need the doors open for ventilation. We lost a few large parts due to the desiccant dryer getting saturated (yep, even here in Phoenix). Made the decision to buy a refrigerant dryer to get those dew points down and take the load off of our desiccant.

For those not familiar, a refrigerant dryer will run your compressed air through a set of coils very much like an air conditioner air handler - except under pressure. Will cool incoming air down to below 40 degrees and then separates out any condensed water. We installed a water holding tank under the dryer stand - the dryer has an auto drain line. In our case - a plasma cutter needs dry air for both cut quality and consumables life. Ruined parts are the net result if you have too much humidity in your compressed air. Paint shops will also use these dryers as that too requires dry air.

Talked to a few manufacturers and like the price and capacity of the Atlas Copco lineup. Took forever to get here but we installed our FD-10 today.



This unit will work well up to about 20 CFM (more than enough for our compressor) and cycles the compressor/fan when not in use. We decided to install downstream from the after-cooler and upstream from the pressure tank. That way, the tank will always have very dry air and that should help with longevity (no water, a lot less corrosion).

We have a water separator and a coalescing filter downstream from the after-cooler to remove as much water and oil as possible before the dryer does its magic. Before we feed the air to the plasma torch, we run through another set of filters and then through a 2-quart Desiccant dryer (which can reduce dew points to below freezing - quite the trick).

Here is the full installation:



Now I need to install one of those shower curtain shields that David Best uses to keep my dryer and 3-phase generator from dying a chip-induced early death - being so close to the mill. The things we do in a small shop!

If interested, the dry air saga starts here: https://www.hobby-machinist.com/threads/dry-shop-air-step-1-compressor-after-cooler.94795/

 

[fixit]

When I worked with compressors in my other life I dealt with a vendor that DEHUMIDIFIER the INTAKE AIR. That eliminated the water going into the compressor. Two modes of results by the process was #1 ACTUAL OUTPUT of the compressor was greatly increased by a good percent but the air output was hot due to not needing an aftercooler. Mode #2 the actual HORSEPOWER REQUIRED was reduced due to less water in the air and an aftercooler was used to lower air temperature. It was a very interesting design and we are talking about BIG compressors 800 to 2000 hp in size. Some installations actually split the discharge line to provide hot dry air for part of the process and cooled air for other parts of the process. My company said it was witchcraft and would not even listen. Our competitors did and found it had many benefits.

fixit

 

[projectnut]

When I worked with compressors in my other life I dealt with a vendor that DEHUMIDIFIER the INTAKE AIR. That eliminated the water going into the compressor. Two modes of results by the process was #1 ACTUAL OUTPUT of the compressor was greatly increased by a good percent but the air output was hot due to not needing an aftercooler. Mode #2 the actual HORSEPOWER REQUIRED was reduced due to less water in the air and an aftercooler was used to lower air temperature. It was a very interesting design and we are talking about BIG compressors 800 to 2000 hp in size. Some installations actually split the discharge line to provide hot dry air for part of the process and cooled air for other parts of the process. My company said it was witchcraft and would not even listen. Our competitors did and found it had many benefits.

fixit

The company I worked for had several multi thousand hp compressors, ammonia compressors, generators, and steam turbines in their powerhouses. The air and ammonia compressors were in one building and the turbines and generators, occupied another. When I first started there, they had well over 100 refrigerant dryers in production rooms, mechanical support rooms, and machine shops.

As time went on some of the air compressors and related equipment were upgraded. Part of the upgrade was to remove some of the refrigerant dryers from production rooms. I wasn't paying much attention to the project as I had my own responsibilities. I'll bet they were dehumidifying the intake air prior to compressing it as you speak of. I didn't follow up closely, but I do know they went from only generating what power they needed to hooking up to the local grid so they could sell power to the utility company. When the facility closed in 2016, they took one of the turbine and generator systems to another facility and sold another for over $1.5 million at the auction. At that time the turbine was over 15 years old, and the generator was closer to 50 years old.

 

[MtnBiker]

The company I worked for had several multi thousand hp compressors, ammonia compressors, generators, and steam turbines in their powerhouses. The air and ammonia compressors were in one building and the turbines and generators, occupied another. When I first started there, they had well over 100 refrigerant dryers in production rooms, mechanical support rooms, and machine shops.

As time went on some of the air compressors and related equipment were upgraded. Part of the upgrade was to remove some of the refrigerant dryers from production rooms. I wasn't paying much attention to the project as I had my own responsibilities. I'll bet they were dehumidifying the intake air prior to compressing it as you speak of. I didn't follow up closely, but I do know they went from only generating what power they needed to hooking up to the local grid so they could sell power to the utility company. When the facility closed in 2016, they took one of the turbine and generator systems to another facility and sold another for over $1.5 million at the auction. At that time the turbine was over 15 years old, and the generator was closer to 50 years old.

I'm glad I could spend a lot less than $1.5M for dry air!

 

[MtnBiker]

I'll do one more PSA for "real" industrial compressors (I know they go way up in cost and capacity from here) but a good commercial Baldor or equivalent motor running at about 1,725 rpm on these entry-level commercial units is so so much quieter than the typical big box store versions running 2X speed. These units have the added benefit of easy "hot-rodding" for after-coolers, silencing intakes like Solberg, rebuild kits to keep things running for the long haul. Good value long-term. We picked up this Chicago Pneumatics 5hp/80 gallon/2-stage unit lightly used for about $1K and it has been a beast.

 

[MtnBiker]

When I worked with compressors in my other life I dealt with a vendor that DEHUMIDIFIER the INTAKE AIR. That eliminated the water going into the compressor. Two modes of results by the process was #1 ACTUAL OUTPUT of the compressor was greatly increased by a good percent but the air output was hot due to not needing an aftercooler. Mode #2 the actual HORSEPOWER REQUIRED was reduced due to less water in the air and an aftercooler was used to lower air temperature. It was a very interesting design and we are talking about BIG compressors 800 to 2000 hp in size. Some installations actually split the discharge line to provide hot dry air for part of the process and cooled air for other parts of the process. My company said it was witchcraft and would not even listen. Our competitors did and found it had many benefits.

fixit

Sounds like the big guys know what they're doing. On our setup, the Atlas dryer has a heat exchanger that uses the cold, dehumidified air to cool down the intake air before going to the cooling coils. The spec is 37 degrees dew point. We're down to ambient coming out of the after-cooler with most of the water already separated, then what amounts to a two-stage cooler in the refrigerant dryer. Hoping this gives us some margin on the plasma torch. Having to replace customer provided materials, especially plate, is both expensive and logistically tricky,

 

[Larry$]

We've got a 25hp screw compressor, then an air to air cooler 2" in & out pipes, a refrigerated drier, coalescing filter, pressure regulator, copper loop air piping and desiccant driers on all CNC equipment. All drops from the main line come off the top of the pipe. Main lines are sloped to drains.