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Air Dryer
- Thread starter Markhor
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Go with something you can find off the shelf locally or anywhere on the road.
AD9 units are most common and around $200
The older purest air that is available surplus their filter and internal parts kits are common stock due to their age.
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Hi Maribor, welcome to the site. Please put your state and/or other information in.
We have several vendors to purchase from and give you information. Of course in the past, the old timers would scold you for not doing research first......, those times mostly gone.
I recently put a new dryer and pressure control in my m929A2 and it solved my air system problems.....hope it does yours. I had to make a new bracket.
We have several vendors to purchase from and give you information. Of course in the past, the old timers would scold you for not doing research first......, those times mostly gone.
I recently put a new dryer and pressure control in my m929A2 and it solved my air system problems.....hope it does yours. I had to make a new bracket.
Thanks. I will look for the AD9.
Ronmar
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Be sure it has the 24V valve heater... you will also need to source the 24v connector/pigtail to adapt it to your truck’s 24v heater supply...
have you pulled apart your old one? They are really simple, and since you can access the media, it can be cleaned in a de-greaser solution and re-assembled.
That is the only real drawback of the AD9, once you go that route you are commited to buying sealed replacement cartridges...
I did a video on rehabilitating an old style...
Thanks. Thats really helpful.
It doesn't have to be 24v heater. You can use an inline step down between the dryer and truck pigtail. They range from 1amp to 10amp in size. For under $15. Most dryers are 5amp heaters.
This gives you a more wide range of options for dryers. Some dryer types are offered only in 12v as as a unit but have options for a seperate 24v thermostat to swap in.
This gives you a more wide range of options for dryers. Some dryer types are offered only in 12v as as a unit but have options for a seperate 24v thermostat to swap in.
Ronmar
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Yep, buck converters are not all that expensive in the lower wattage size. From what I have seen, it looks like you can buy the whole 24v valve/heater module for about $35 anyway, so it is not horrific to get either one to work...
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Niuhi
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So if the stock air dryer is easily serviced, why change and go with a dryer that takes replacement cartridges? Was or is there an issue because I haven't experienced one.
Ronmar
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I have heard people claim they are better/more efficient, but have yet to see any published numbers on the old style to support such a claim. In fact, based on the sizes and design, it may be just the opposite for two properly serviced units. A new one would probably work great compared to an old dirty one
all of these use coalescing media, as there is no provision for drying out absorbing desiccant that would quickly saturate at these airflows.
First off the old style is a double pass. The first pass is an air cooler between the inner casing and outer wall with heat-sync fins. This condenses some water out and more importantly oil out of the airstream which flows down toward the sump. The AD9 sends compressor output right up into the bottom of the cartridge for any oil to foul the filter media...
Based on cartridge size, I think the AD9 has less actual coalescing media as some of the bottom of that cartridge(20-25%? in the diagrams I have seen) is filter media. Old style passes the cooled air thru a standalone filter(that you can inspect) before it reaches the media(which you can also inspect) but most of the oil and contaminants have already been stripped off by the cooler stage as evidenced by the yellow snot you will find when you strip one.
Once the air reaches the coalescing media they function about the same. Air passes upward thru the media and water coalesces in droplets and dry air passes out the top and into a chamber surrounding the media chamber and out the check valve to the wet tank. Air stored in that chamber is used to back-feed and purge the media When the compressor unloads The old style adds to this by the air in the line from the compressor blowing down thru the cooler stage to purge oil collected there as well instead of it being forced thru the filter and media cartridge.
The AD9 or equivalent may be more efficient than our old style but untill someone compares them side by side and measures water collected to CFM of air passed we probably won’t ever know. From what I see of the designs, there are a couple of things to throw some shade on a claim like that though...
just the opinion of an old guy observing shit
if you clean it and grease the orings as often as you would change an AD9 cartridge it should last indefinitely...
all of these use coalescing media, as there is no provision for drying out absorbing desiccant that would quickly saturate at these airflows.
First off the old style is a double pass. The first pass is an air cooler between the inner casing and outer wall with heat-sync fins. This condenses some water out and more importantly oil out of the airstream which flows down toward the sump. The AD9 sends compressor output right up into the bottom of the cartridge for any oil to foul the filter media...
Based on cartridge size, I think the AD9 has less actual coalescing media as some of the bottom of that cartridge(20-25%? in the diagrams I have seen) is filter media. Old style passes the cooled air thru a standalone filter(that you can inspect) before it reaches the media(which you can also inspect) but most of the oil and contaminants have already been stripped off by the cooler stage as evidenced by the yellow snot you will find when you strip one.
Once the air reaches the coalescing media they function about the same. Air passes upward thru the media and water coalesces in droplets and dry air passes out the top and into a chamber surrounding the media chamber and out the check valve to the wet tank. Air stored in that chamber is used to back-feed and purge the media When the compressor unloads The old style adds to this by the air in the line from the compressor blowing down thru the cooler stage to purge oil collected there as well instead of it being forced thru the filter and media cartridge.
The AD9 or equivalent may be more efficient than our old style but untill someone compares them side by side and measures water collected to CFM of air passed we probably won’t ever know. From what I see of the designs, there are a couple of things to throw some shade on a claim like that though...
just the opinion of an old guy observing shit
if you clean it and grease the orings as often as you would change an AD9 cartridge it should last indefinitely...
Niuhi
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Great reply,I have heard people claim they are better/more efficient, but have yet to see any published numbers on the old style to support such a claim. In fact, based on the sizes and design, it may be just the opposite for two properly serviced units. A new one would probably work great compared to an old dirty one
all of these use coalescing media, as there is no provision for drying out absorbing desiccant that would quickly saturate at these airflows.
First off the old style is a double pass. The first pass is an air cooler between the inner casing and outer wall with heat-sync fins. This condenses some water out and more importantly oil out of the airstream which flows down toward the sump. The AD9 sends compressor output right up into the bottom of the cartridge for any oil to foul the filter media...
Based on cartridge size, I think the AD9 has less actual coalescing media as some of the bottom of that cartridge(20-25%? in the diagrams I have seen) is filter media. Old style passes the cooled air thru a standalone filter(that you can inspect) before it reaches the media(which you can also inspect) but most of the oil and contaminants have already been stripped off by the cooler stage as evidenced by the yellow snot you will find when you strip one.
Once the air reaches the coalescing media they function about the same. Air passes upward thru the media and water coalesces in droplets and dry air passes out the top and into a chamber surrounding the media chamber and out the check valve to the wet tank. Air stored in that chamber is used to back-feed and purge the media When the compressor unloads The old style adds to this by the air in the line from the compressor blowing down thru the cooler stage to purge oil collected there as well instead of it being forced thru the filter and media cartridge.
The AD9 or equivalent may be more efficient than our old style but untill someone compares them side by side and measures water collected to CFM of air passed we probably won’t ever know. From what I see of the designs, there are a couple of things to throw some shade on a claim like that though...
just the opinion of an old guy observing shit
if you clean it and grease the orings as often as you would change an AD9 cartridge it should last indefinitely...
I had originally thought about changing it out, but kept coming back to why. I've never heard of, or experienced a problem with the stock one. If the original one is doing the job, I cant see spending the money to have something else do the same job. I'll just pull mine apart and clean it out, spending the money on something more important. Thanks for the info.
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Guess some believe not all air dryers are the same and some do. I did not want my post to be my air dryer is better than yours it is all in what you believe. Do believe good clean are without oil or water is what we want. I did a Google and looks like most up graded air dryers have 5 stage filters cartridge or spin on and not just one stage desiccant bag. Now my air dryer was in bad shape full of crap is why I up graded. Also I have not looked into the bag of desiccant that is in the old canister so I do not know if it is just a desiccant or also coalescing filter too as they are not the same. Reading up on them and they found you want coalescing first in line not after the desiccant filter. Yes Ronmar all air dryers flow the air in one way for cleaning then reverse purge the filter for the blow off. LMTV FMTV replacement or upgrade air dryers | SteelSoldiers
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Ronmar
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no no no, mines better
Wasn't going there at all, The point I was getting at is they ALL work more than well enough when serviced and kept within their flow limits(Fix your leaks!).
But if your old unit isn’t drying properly, it isn’t because of the design(it’s a pretty good design IMO), it is because it requires maintenance. The same issues will plague an AD9 if over flowed and left unserviced...
They use the term desiccant in that it dries air, but it does so thru the principal of coalescing the vapor into droplets. Absorbing media must be dried, and this requires heat typically and airflow and especially time, to drive the moisture back out of the desiccant and carry it away. None of these dryers have this secondary system.
been working with dry-air systems for 35 years in radar and microwave systems and other applications such as this. There are basically 4 types. Condensing, coalescing absorption and osmosis.
Condensing cools the air and water vapor condenses on the heat exchanger surface like dew on windshield in the morning, or the inside of your shop air compressor tank. They need large surface areas or a refrigeration plant to super cool the surfaces like a typical room de-humidifier does. Have made long copper coolers with drains to dry shop air...
Coalescing we know.
Absorption works on the principal of diffusion, wet flows to dry, like heat flows to cold. The greater the difference the greater the flow. But they only work until the media becomes saturated, then they must be re-generated. This is done by flowing dryer air thru it to absorb the moisture out of the media or applying heat and air to force the moisture out. All this also takes quite a bit of time. The recharge system makes self drying ones more complex. Some bright light, bless their soul, thought of indicating desiccant That is blue when dry and pink when saturated(blue is new, pink is poo) which makes recharging cannisters or gauging service needs really easy if the canisters are clear. I typically recharge media in a microwave or toaster oven then re-install it into a sealed canister till the next canister replacement Is needed. They make neat little ones for your gun safe, when they turn pink, you remove it, plug it into a wall outlet, and the built-in heater drives the moisture off and turns it blue again, then you put it back into the safe. But they are only for sealed containers. You unplug it and set it on the shelf, it will pretty quickly change back pink from the amount of moisture in the large volume of room air...
Osmosis is basically a filter that is too small for the water molecules to pass thru, so the moisture is stripped out of the air in this fashion. These also require a purge cycle to remove the stripped water out of the filter.
Both absorption and osmosis make really dry air, but only at very very small volumes for sealed systems.
condensing and coalescing don’t make quite as dry air as absorption and osmosis, but they can operate at much greater volumes and only need to be drained/purged and not re-charged...
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Moorinsky1
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Great video. Putting this on my to-do list!
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No problem here. In truck air dryers we have oil from the compressor that we need to stop before it gets to the desiccant or into the braking system and or air system. Also since our compressors feed engine oil through them that oil also has all the contaminats that is in used engine oil. This can get into our system. That is what a oil coalescing filter does. The desiccant filter does not like oil or is it good for it. The newer design has a oil coalescing filter and desiccant for water plus as said 5 stages of filtering.
I just do not want just good enough for my air system I want the best that the market has to offer right now. Also I much rather spend a little more money on a up graded air dryer now than chase down problems with all the valves and such that is in the air system. I have been in and out of heavy trucking since 1981 and know what bad air can do to the most important part of the truck. That would be the ability to stop so I am not going to cheap out on that part. Just a pic of my new 1981 GMC General triaxle dump that made me lots of money. I have had a CDL since 1981 and not the beginners automatic only restricted license. Run 53's cross country with no less than 80K so yea might be loosing it a bit but also learned a bit. As always your truck your problem at least here on SS someone will help you figure it out when the time comes.
I just do not want just good enough for my air system I want the best that the market has to offer right now. Also I much rather spend a little more money on a up graded air dryer now than chase down problems with all the valves and such that is in the air system. I have been in and out of heavy trucking since 1981 and know what bad air can do to the most important part of the truck. That would be the ability to stop so I am not going to cheap out on that part. Just a pic of my new 1981 GMC General triaxle dump that made me lots of money. I have had a CDL since 1981 and not the beginners automatic only restricted license. Run 53's cross country with no less than 80K so yea might be loosing it a bit but also learned a bit. As always your truck your problem at least here on SS someone will help you figure it out when the time comes.
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If you feel that there is something more important than your braking system you have a lot to learn!
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Most of us knew what Niuhi meant. I like my old filters too.
Green Mountain Boys
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I replaced my stock air dryer with the PURest air dryer. I found the the PURest air dryer purges with much less noise than the stock air dryer. I think the quieter purges are worth something... to me anyway.
Niuhi
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As I drive a Kenworth daily and have been CDL licensed for 32 years, 17 years with FedEx Freight (no accidents) I'm pretty much up on the consequences of no brakes and the function of the dryer system. My point was if they can be serviced and there's nothing the newer dryers do that's beyond the capabilities of the one I already own why change. I can't justify spending money on something I already own when that money could go for something "important" such as new u-joints or brake parts. So the next time you decide to try and school me with some goofball comment when you don't know me, "don't", I've learned enough about driving on my own. If you have bits of wisdom in regards to these particular trucks (I'm still learning) great I'm all ears. And by the way someone on here made mention that their new dryer purged quieter, and that is one of the reasons I was originally thinking about swapping, because I can't stand being startled by it when say I'm driving in downtown Seattle.