Hi:

Anyone familiar with air dryers? I recently acquired a Bendix AD-IP dryer which I would like to add to my 73 Ford 900. In reading the info on this dryer it refers to a heater/thermostat connector which need to be connected to the ignition kill switch. The info does not explain what this heater does. Can anyone elaborate?

Thanks
PaMnd

 

Is this on an air brake system? It is probably a heated regenerative dryer. When in use the dessicant charge absorbs the moisture in the air. When the dessicant becomes saturated with moisture it will not absorb any more water. You can restore the dessicant by heating it and the heat will drive the moisture out to atmosphere. You usually need a small (15% of design capacity) amount of dry compressed air purging through it for a few minutes to regenerate it.
Not all dessicants are able to be regenerated. Some become usless after absorbing water.

 

Hi:

Thanks for the reply. Yes the Ford does have Air Brakes. Currently I empty the air tanks daily. The system only seems to get moisture during cold weather operation.

The manual for the dryer indicate that the AD-IP dryer does a purge of contaminants when the compressor starts. Here is a quote from the manual:

"PURGE CYCLE
As air brake system pressure reaches the cutout setting of
the governor, the governor unloads the compressor (air
compression is stopped) and the purge cycle of the air dryer
begins. When the governor unloads the compressor, it
pressurizes the compressor unloader mechanism and the
line connecting the governor unloader port to the AD-IP ™ air
dryer end cover control port. The purge piston moves in
response to air pressure causing the purge valve to open to
the atmosphere and the turbo cutoff valve to close off the
supply of air from the compressor (this will be further
discussed in the Turbo Cutoff Feature section). Water and
contaminants in the end cover sump are expelled
immediately when the purge valve opens. Also, air which
was flowing through the desiccant cartridge changes direction
and begins to flow toward the open purge valve. Liquid oil
and solid contaminants collected by the oil separator are
removed by air flowing from the purge volume through the
desiccant drying bed to the open purge valve."

As you can see there is no mention of a need for the heater in the above. Later on the manual describes how to test the heater but no mention of why or when to use it.

Thanks for the info.
PaMnd

 

Hi:

I have been reading up at various sites and I think I have an idea of what the heater purpose is.

According to the documentation the IP integral purge will discharge the contaminants when the truck starts.This is automatic to the air dryer. My theory is that in cold weather if the IP is triggered on startup and the IP is frozen then damage to the dryer could occur. The heater then is there to make sure the IP is not frozen when the purge occurs. After the truck reaches normal temperature then the heater is not needed.

PaMnd

 

Make sure the air dryer is mounted lower then you tanks (air)

 

Hi:

I have been doing some reading on mounting the air dryer and can find no mention on mounting lower than air tanks. The one diagram I have shows the tanks lower than the dryer. Other than that there is no specific on mounting position. Also the tanks are mounted at frame level so getting lower would leave the dryer below the frame.

Thanks
PaMnd

 

The main thing is to mount the dryer below the inlet line from the compressor and keep the line as straight as possible to keep water from condensing and freezing in the inlet air line. I am installing one in my C950 as I have had a few too many treadle valve freeze ups and hope this will help along with insulating the valve and heating it with water from the engine. The dryer heater will cycle as needed to keep the discharge valve from also freezing up.

 

Hi:

The outlet from the compressor becomes the inlet to the air dryer. Keeping this line higher and following a slight downward trend would make sense to allow moisture to collect in the air dryer.

Thanks for your thoughts.
PaMnd