Dehydrator

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sallen
Posts: 85
Joined: Sat May 09, 2015 8:39 am

Dehydrator

Post by sallen » Thu Jul 16, 2015 9:46 am

I have an older Cablewave APD-20 that just failed. The compressor still pumps air but the unit is pumping out a white powder with the air which I would guess is the Desiccant. Has anyone recently had to rebuild the APD-20 which is an older unit.

Is this unit still worth repair, I have a second APD-20 that needs to be repaired. Are these units still worth fixing?

I spent a lot of time of the RFS website trying to find any documentation with no luck. IS there any place else that sells parts for these old dehydrators the APD-20? Should I get something mew? Any suggestions on a new replacement dehydrator?

Any thoughts on the white powder it started to pump out, into the transmission line?

rich wood
Posts: 107
Joined: Mon Jan 24, 2011 10:56 am
Location: Madison, WI
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Re: Dehydrator

Post by rich wood » Fri Jul 17, 2015 9:12 am

Howdy,
Dehydrators are sort of worth rebuilding. Once one stage goes the rest are getting reading to go too. You can call RF Specialties, they are an RFS dealer and ask Chris Kreger (800 467-7373) about rebuild kits and the price of a new unit. The size of unit is dependent on the line size and length and how tight the system is for holding pressure.

sallen
Posts: 85
Joined: Sat May 09, 2015 8:39 am

Re: Dehydrator

Post by sallen » Fri Aug 07, 2015 7:02 pm

Thought I would follow up with some dehydrator talk. I have not repaired the dehydrator but replaced it with a new RFS dehydrator. It turns out the dehydrator at a second site around the corner was also in trouble showing pink in the humidity indicator window. Both transmitter sites are owned by the same company so it was decided to get a new RFS unit and a used one off Ebay that I found.

I did originally call RFS for parts they were helpful but did not have the parts in stock for my older unit. I shopped around for an Andrew dehydrator but a New RFS unit, the APD20-D was all I could find that could be shipped to me within 5 days (it was Friday so it took a couple of extra days) and was under $2k. The only place I could find a dehydrator in stock ready to ship was from a company that sells to the 2-way/cell industry called Tally. They had several in stock in Kansas, The new RFS unit is Firmware upgradeable and has LED's to indicate under pressure, and humidity (no blue indicator) and other things. It has a USB port to log stuff, I have not played with that yet. Just plugged it in let it run ten minutes then hooked it to the transmission line manifold that I had to clean out. Basically I had to disassemble the whole manifold, valves and gauges to clean out the white powder the old unit contaminated the lines with. The good news, not much if any of the white powder made it to the transmission lines. It stayed in the distribution system.

The Ebay unit, when it arrived looked like New old stock, It fired up the Humidity indicator turned a nice blue. I also installed a run time indicator for this unit that indicates how long the unit runs. If I get 5-10 years out of the unit I will be happy. I now look at the humidity indicator on both units one a week. I look at the run indicator on the ebay unit to see if it's running too much.

rich wood
Posts: 107
Joined: Mon Jan 24, 2011 10:56 am
Location: Madison, WI
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Re: Dehydrator

Post by rich wood » Sat Aug 08, 2015 9:27 am

Excellent. A run time indicator is an excellent addition. You can also add a pressure sensor to the system and tie it into the remote control so when/if the system looses pressure you will know about it immediately.

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davek
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Location: Sydney, Australia

Re: Dehydrator

Post by davek » Sat Aug 08, 2015 4:57 pm

The problem with those little dehydrators is what happens in the event of a leak developing in a feed line. The compressor is usually not gutsy enough to continue feeding dry air into the line, and will often just burn out after continuous running. At the facility where I work we have sized our units to be able to provide continuous flow to handle up to a 1/8" hole in the feed line.

Also another short-coming of a lot of these units is dealing with the very wet air that comes from the air compressor. I have modified our Puregas units by adding a water separator at the output of the compressor. It will remove 95% of the moisture from the air before passing it into the rest of the system - which no doubt makes the job easier for the desiccant stacks, and should help to keep the internals of the system cleaner as well. I have rebuilt a few dehydrators where the internals have been caked with residue left over from handling wet air.

One final tip; if you are pressurizing more than one feed line, adding a flow meter to each line make it much easier to spot any potential leaks as well as quickly identifying which line is the culprit.

Edit: one other final tip! Some units with electronic humidity sensors will probably need a to have a small flow of air maintained to keep the sensor from "fogging up". With our new Puregas units, a small bleed valve is added to the output, which is set to flow about 1 litre/minute. Otherwise the humidity alarm trips out and shuts the unit down completely!

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