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Regenerating HWH desiccant

August 13, 2012, 07:22:53 pm

I've been trying to regenerate my desiccant for the last hour or so by using the microwave 
At 300 degrees for 3 minutes as per someone's post  and I still can't get them to turn blue!!
 Does this mean that they are so old they can't regenerate or that they might be a different type of desiccant and will never turn blue?
 Has anyone else had this same problem and if so, what was done about it?
 Thanks in advance. R Bark

 

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Re: Regenerating HWH desiccant

Reply #1 – August 13, 2012, 07:35:18 pm

                               Some options.......Desiccant option for the HWH system

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Re: Regenerating HWH desiccant

Reply #2 – August 13, 2012, 10:47:24 pm

Richard....  was the silica gel light purple before you started?  If not, it might not have an indicator in it.  If that is the case, I'd get some from FT or elsewhere with the indicator.

I just regenerated some silica gel (it is very humid here in Asheville, NC).  I put it in a shallow dish (like a glass pie plate) and used the microwave only for 1 minute at full power.  Then I stirred it with a spoon and repeated this process for a total of 3 minutes.  It went from light purple to deep blue.  The indicator is cobalt chloride which is purple when it combines with water and blue when it does not have a water molecule attached.  Being an inorganic salt, I would think it would be very stable.

One word of caution though.  The last time I changed the desiccant  I noticed that the third trap (the one nearest the pump on my setup and after the desiccant) had some fine powder in it.  I have not seen this before.  Could it be that repeated regeneration using the microwave has damaged some of the silica gel beads?  I cleaned out the trap and will keep an eye on it. 

Also, make sure you check the cover on the silica gel containing trap.  If it is not locked, the pressure in the system will push off the trap and you will have silica gel everywhere.  Don't ask how I know this!

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Re: Regenerating HWH desiccant

Reply #3 – August 14, 2012, 10:15:28 am

We have one of those OLD HWH compressors that were installed before slides were introduced. The pump has a sediment bowl and does not use desiccant. A couple of times in the two years we have had the coach, I have pulled the bowl and the purge valve at the base of it. A white powder accumulates and causes the purge valve to leak when it should seal. I assume the powder is material that drops out with the moisture from the compressed air. You may be seeing the same kind of powder accumulating in the desiccant.

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Re: Regenerating HWH desiccant

Reply #4 – August 14, 2012, 10:58:16 am

The indicator fades with age.  Mine is old enough that the blue tint is barely noticable when regenerated.

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Re: Regenerating HWH desiccant

Reply #5 – August 14, 2012, 11:54:32 am

George, mine is a pinkish/ whitish color that didn't change at all except for about 10 to 15 pellets that did turn blue. Think I'll bake them in the oven and see what happens. If no change, I'll order some new desiccant. I kinda like the orange stuff.

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Re: Regenerating HWH desiccant

Reply #6 – August 14, 2012, 11:59:14 am

Tom, that might be the case with mine. I'll know after I try the oven. Are you still using the original stuff or have you bought new desiccant? If so, where did you get it?

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Re: Regenerating HWH desiccant

Reply #7 – August 14, 2012, 12:02:26 pm

Richard....  another possibility is that your gel only has a small amount of indicator in it.  That is, it is mostly white with a few blue granules.  I bought some recently and I would say about 1 particle in 100 is colored.  If that is the case for yours, you might be OK.

Interesting on the stability.  There is a good monograph on Wiki about CoCl2, but I cannot get the forum software to cite it correctly.  Since it boils at over 1000 degrees, it certainly is not evaporating.  Maybe it forms some form of cobalt silicate, but that is blue also.  Go figure.  I suspect this stuff does not last "forever."  Just the rigors of heating it up repeatedly can damage the silica gel particles and decrease their water adsorbing properties.  I'm going to switch mine out at least every year. 

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Re: Regenerating HWH desiccant

Reply #8 – August 14, 2012, 12:43:44 pm

Timely topic.  I'll pass along what I've learned so far, using a lot of good information from this current topic and from archives.

Aux Compressor recently had been going on and staying on more often and longer than I liked, sometimes in the middle of the night while in camp.  Found dessicant to be pink.  Removed metal sleeve around the bowl, then removed bowl (bowl is pressed in and held with an o-ring - need a strong hand grip, twist back and forth while pulling down to remove it), but center post which is pressed into the head of the dryer unit and passes through dessicant bowl didn't come with it, perhaps because I had already removed the nut from the threads at the bottom of it (duh!) but probably because it was frozen in place.  Particals scattered all over.  All over.

Microwaving removed pink, but did not return all particals to blue.  Mostly white, with a very few blue.  Took several 1-minute trials to achieve.

Center post is very tender.  Thin walled, soft metal.  Removing it required a light grip with a vise-grip tapped with a hammer.  Very corroded, and the end which is pressed into the head of the unit needed cleaning with a wire brush.

Reassembly requred passing center post through the bowl, attaching bottom nut, and spooning dessicant into the bowl from the top, past a wire mesh screen attached to the post.

Here's where my problem started.  Metal sleeve surrounding the desicant bowl needs to twist-lock into the head of the unit.  Sleeve's function is to control the mess if bowl should ever explode, and more importantly, helps lock bowl in place so air pressure can not blow it out of place.  I could not make this happen, and didn't have unlimited time to redo. 

Now what.  Wire and duct tape.  Fashioned a wire harness over top of unit, passed through holes in sleeve, and twisted together at the bottom.  Then liberally wrapped the whole unit north and south, as best I could with the best duct tape I had.  Had my own mummy on board.

Mummy is good.  Not elegant, but works for now.  Passed the test this morning.  Slide came in and locked in place.  Compressor came on for bladder control:) and turned inself back off in short amount of time when the job was done.  Dessicant is still white with blue.  Good enough, I think, to let me finish my trip and do a better fix when I get home.

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Re: Regenerating HWH desiccant

Reply #9 – August 14, 2012, 02:31:16 pm

Bob,I have the same issues with corrosion on the center shaft except there are pin holes in the shaft! Called Wilkerson and they have a complete unit with the silica for $97.20 with 5 days to ship. Grangers has the same unit for $116.65 also with the silica. I ordered from Graingers and will pick it up tomorrow. The part number is x-06-02-000 ( regulator dryer)
 Thanks for all the input everyone!
 Richard Bark

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