Automotive Air Conditioning Information Forum (Archives)

wcmaness on Wed August 24, 2005 4:56 PM

Year: 1991
Make: Jaguar
Model: XJ6
Engine Size: 4.0
Refrigerant Type: R12
Ambient Temp: 100
Pressure Low: 45
Pressure High: 180
Country of Origin: United States

I read in an earlier post that you should pull a deep vacuum & hold it a while to regenerate the Dryer/receiver. I've also read that you should always replace the receiver/dryer when you open the system. Can the receiver be regenerated or "dried out with a long held vacuum?

Chick on Wed August 24, 2005 6:22 PM

They can't be regenerated. Pete from Keep-it-kool used the best analogy when he said it's like removing the water from cement. The reason for the deep vacuum is to remove the air, and the moisture the air holds. Hope this helps.

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

wcmaness on Wed August 24, 2005 6:33 PM

That's what I was thinking. Thanks.

Test Specimen on Wed August 24, 2005 10:25 PM

Quote
Originally posted by: wcmaness
I read in an earlier post that you should pull a deep vacuum & hold it a while to regenerate the Dryer/receiver. I've also read that you should always replace the receiver/dryer when you open the system. Can the receiver be regenerated or "dried out with a long held vacuum?

Driers sure can be regenerated, we regenerate desiccant all the time. You probably don't have the right stuff to do it however. We use 600 degree nitrogen passed through the drier for several hours to remove the water. You will also have to remove the oil with a flush prior to heating the drier, otherwise you may cause carbon buildup in the drier. The paint is not likely to still be on the outside after you are done. See, its simple as can be. Maybe the cost of a new drier isn't so bad after all.

Chick - your analogy of water and concrete is completely wrong when talking about water and desiccant. In concrete the water is chemically bound into the final product to make a new material - with desiccant the water is not chemically bound, it is physically adsorbed, but can be desorbed if you put heat into the material.

brickmason on Thu August 25, 2005 3:28 AM

Test Specimen,

Your right about concrete. The water in concrete does not dry, it cures.

Take for instance 5 gallons of water which weighs 40 pounds, (40 lbs. of cement), (100 lbs. of sand) and 80 lbs. of gravel. Mix it all together and the total weight is 260 lbs.

After it cures it will still weigh the same unless too much water is added for the proper ratio mixture but the excess water will come to the top and evaporate.

But always remember that if way too much water is added to the mixture then the gravel,(which gives concrete it's strength) will settle to the bottom, leaving only the grout mixture on top which tremendously weakens the strength of the concrete, but the excess water will still come to the top and evaporate.
( It just takes longer for it to evaporate from adding too much water) This is very important when a DIYer mixes their own concrete. To save a lot of effort of stirring water into the mix,(but only around fence posts) there is a process called dry packing. Simply pour the dry mix in the hole around the post and the moisture from the ground will cause it to set up. It takes several days but it really works!

PS. I prefer purchasing Portland cement, masonry sand and 57 stone from the concrete yard for making my own concrete for small jobs.
The premixed sacrete brands, (which can be purchased at most building supply stores, Lowes, Home Depot, etc.) are not near as strong as the portland mix, masonry sand and 57 stone as the premixed bags contain too much sand. The same goes for premixed mortar also.

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Just another brick in the wall

Had a little mule I fed him castor oil and every time he jumped the fence he fertilized the soil

Chick on Thu August 25, 2005 7:59 AM

I stand corrected on the rejuvenation of dissicants. But I like "Peters" analogy to explain why people should not be wasting time popping their driers in the oven, and I doubt many DIY'er have the nitrogin, or the means to heat it to 600 degrres, and I certainly don't recommend them flushing driers.. When you tell people that analogy, they usually buy a new drier, and there isn't time wasted in getting the car up and running. But I am sorry that the info posted is false, but for all intent and purpose, the average consumer cannot rejuvenate their driers by sticking them in the oven overnight.., or flush them. I believe in the past the dissicants were made of something other than silicone or silicates, and they used to explode when retrofitted sending a sand like substance thru the system. It just doen't pay to try to save a few bucks with AC work..In time or money..Just my opinion though..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

wcmaness on Thu August 25, 2005 12:15 PM

Wow - that was a lot more information than I expected or even hoped for. You guys are amazing sources of data. I'm with Chick though - I am not equipped to rejuvenate a drier. I'll pay the 50 bucks for a new one. Thanks so much.

TXAB on Thu August 25, 2005 12:20 PM

Quote
Originally posted by: wcmaness
Wow - that was a lot more information than I expected or even hoped for. You guys are amazing sources of data. I'm with Chick though - I am not equipped to rejuvenate a drier. I'll pay the 50 bucks for a new one. Thanks so much.

Yes, you can get a pretty good education by visiting this site.

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"Don't get stuck on stupid!"
---- Lt. Gen. Russel Honore

ice-n-tropics on Thu August 25, 2005 4:52 PM

Tim's Band of Brothers,
If the Mason isn't detailed enough, this 2 cents will be:
I can't recommend Receiver Drier (RD) regeneration but it is not impossible. For hard to get Receiver Driers for European cars I have baked at about 400 degrees overnight with vacuum but without flushing out the oil or repainting the can. I doubt if half the moisture was removed from the desiccant, but there was acceptable cooling afterwards without icing.
A danger would be melting of any plastic parts that are inside the RD (or Accumulator).

The most common desiccant for R-134a is XH7 made by UOP. It's OK for R-12 but not as effective as XH5 because R-12 might get into some of the micro pores.

Hard to find for MB, Hansa RDs in Europe often use some other kind of desiccant which is formed into a single brick instead of little round beads like USA driers. Hansa driers which I have opened had no plastic parts. Don't ever drop one or the brick will break.

Molecular sieve (MS) desiccant is structured with molecule sized micro pore openings which allow H2O molecules to enter but R134a molecules can't get in. R134a has a narrow width (diameter) dimension and a long dimension. The MS size is smaller than the narrow R134a size but greater than the H2O.
New driers can still be usable after being left open for a day if no air is forced through, but it's capacity reserve in partially depleted.
The typical car RD has about 50 grams of desiccant which holds approximately 1/4 oz. of H2O.
Heavy trucks have approximately 6 times more desiccant than cars.

Now I've got fence posts that need to be dry packed.
Cordially,
TEX




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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Thu August 25, 2005 at 6:10 PM by ice-n-tropics

BlackholeForever on Thu August 25, 2005 8:38 PM

I think I was browsing the net a week or so ago, and found an article where they were rejuvenating one of these. I think they cut it open, added new dessicant, and then welded it back together again...

Daniel on Thu August 25, 2005 9:59 PM

The proper way is to cut them open, clean and put new dessicant in and weld them back. I think if you baked it or subjected it to heat the dessicant would discintegrate and flow thoughout the system. I have a few old ones that you can shake the stuff out of them. I believe if you ran solvent through them then subjected them to 600 degrees the dessicant would definately come apart and flow throughout the system.

Chevybob on Thu August 25, 2005 11:16 PM

clueless on Fri August 26, 2005 12:39 AM

Used to work in a desicant packaging plant in the QA department. All desicants we used could be rejuvinated. Molecular Sieve was put in a furnace at 600 Degrees farenheight. For 6 hours.

Silica gel was done under 200 degrees ( forget exact temp.) for 24 hours.

Bentonite clay was heated at about 400 degrees farenheight for 12 hours.

All incoming products were tested in this manner to determine the residual moisture. Other times we were testing for other things.

The only thing I ever had happen was packaging melt. The desicants were not harmed.

Edited: Fri August 26, 2005 at 12:40 AM by clueless

dgilchrist on Sat January 02, 2016 11:35 PM

Im new to the forum, so if this question is in the wrong thread, sorry.
Heres my question. If the desiccant in the drier becomes saturated with water after being "open" for 24 hours.... how do they not absorb moisture while in shipment? Do those little rubber plugs really keep out atmosphere? Are they shipped in a slight positive nitrogen purge?

Edited: Sun January 03, 2016 at 12:04 AM by dgilchrist

dgilchrist on Tue January 12, 2016 1:11 PM

Did I really stump the board with my first post?

Edited: Tue January 12, 2016 at 1:12 PM by dgilchrist

Cussboy on Wed January 13, 2016 1:16 PM

Quote
Originally posted by: dgilchrist
Did I really stump the board with my first post?

Let me reply. In our lab we purchase see-through cartridges filled with indicating desiccant. When uncapped, and left in contact with the atmosphere, air ingress (moisture ingress) is pretty slow (static system). However, once gases are set up to flow through the cartridge, even low levels of moisture in the gases quickly turn the indicator color (dynamic system).

So when one replaces the desiccant cartridge on a vehicle, sure - don't take three days to do it !!! But if you're worried that it takes 3 minutes to connect instead of 2 - then you worry about too much.

There are experts on this board (believe GM Tech, and others) who oftentimes does NOT swap out the drier when doing certain repairs, if the system did not lose all its refrigerant, and there was no chance of particulates getting through, etc.