Looking for recommendations for a reliable refrigerated dryer mfg. We have a couple of customers who cannot go with desiccant at this time. Both are small, aprox 35 CFM units.

If you have had good luck with a particular manufacturer/model, can you PM me?

Thanks,

Bob W

Bob,

I've had good luck with Powerex, or Hankison, and Wilkerson as manufacturers of refrigerated dryers. The problem that Al addresses is that a cycling (utilizing a thermal expansion valve or hot gas bypass valve) or non-cycling (thermal mass) are limited to a minimum of around 34-40 F pressure dew point at all levels of demand. About 30 years ago we came up with an easy fix for a client that didn't want the headaches that desiccant dryers offer. We simply put a membrane dryer in series behind a refrigerated. You only need about 10F dewpoint suppression, so it can be downsized. It's bullet proof, and actually gave us decades of trouble-free service.

Be careful on the membrane filter manufacturer, some options will deplete O2 molecules.

Scott Jussel

God willing, I'll be there. I'll keep an eye out for you!

Thanks for the help from everyone. A few comments if I may...

Scott, thanks so much for the idea on the membrane dryer. I am looking into it...

As for the MFG's mentioned, I ran into the following:

Powerex was mentioned but they now sell Hankison for this size dryer. I do not know if they private-labeled them in the past.

The information I have seen for Wilkerson (website) shows a Parker dryer (victim of another merger, probably).

I have not been a fan of refrigerated dryers for some time now. Way too finicky lately. Desiccant is the best way to go IMO.

As for the comments from Al and Scott regarding "5.1.3.6.3.7  Medical Air Dryers.

They shall be designed to provide air at a maximum dew point that is below the frost point [0°C (32°F)] at 345 kPa to 380 kPa (50 psi to 55 psi) at any level of demand", I am familiar with this, and if I am not mistaken refrigerated dryers can achieve this. I believe Mark spoke of this maybe 10 years ago at a meeting. 

Al mentioned:  "Its the requirement for the performance of the dryer to be below 32 at all times." I (respectfully) disagree with this interpretation. The code states that the dryer is to be "designed" to provide dew point below 32 degrees. I believe the word "performance" is different somehow, and would involve monitoring it as such (below 32). 

Getting back to "designed", a refrigerated dryer can do this taking into account the pressure drop (80+ psi dryer inlet air pressure vs 50 psi line pressure where dew sensor is located).  If my dewpoint calculator is correct, if a dryer can get down to 40F pressure dew point (Scott's higher number) at 80 PSI (compressor cut-in) dew point downstream of regulator (50 PSI) would be registered at 30.6 F. Just below the code limit, but it can be improved upon slightly if the compressors cut in at a higher pressure or if the dryer was able to achieve a lower pressure dew point. 

Anyway my post is getting too long, especially considering the prevalence of desiccant dryers now. I do welcome any feedback.

Bob

I remember it being a while ago, but am hoping it wasn't 20 years...

If I recall he was speaking of how liquid sitting in the separator bowl (with a float drain) would cause moisture to re-enter the airstream. (Re-entrainment?), and how electric auto drains would minimize that effect.

Thanks Scott,

Bob