Teledyne API Model M701 Zero Air Generator OPERATION
01671H (DCN6051) 5-7
5.6 Pressure Relief Valve The pressure relief valve is a safety device designed to limit the maximum pressure to
which the M701 can be subjected. It is set to open at 90 psig. This can be quite loud
when the valve opens and sounds like steam escaping. This is normal operation and
does not mean there is a problem with the unit.
CAUTION
Do not adjust the relief valve.
The Regenerative Dryer consists primarily of two parallel columns of molecular sieve, in
which alternately one column is scrubbing the air while the other is being regenerated.
The Regenerative Dryer needs no warm-up and operates at full efficiency as soon as
the M701 is turned on. The molecular sieve is not consumed and is good for the life of
the instrument.
When the M701 is turned on, a four-way solenoid-operated valve directs high pressure
air to one of the two columns and vents the other column to atmosphere. Virtually all the
water in the high-pressure air is trapped by the molecular sieve. A portion of the dried
air is expanded to atmospheric pressure in the outlet shuttle valve and passes in
reverse through the second column. By expanding the air, the volume increases and the
relative humidity decreases thus enabling a small amount of dry purge air to evaporate
the entrained water in the second column. The wet purge air leaving the column is
exhausted inside the M701. The rapid air movement inside the M701 chassis ensures
that the small amount of water involved is safely vented to the atmosphere. The majority
of the dry air from the first column is conducted to the storage tank.
The controller toggles the four-way valve every 2 minutes and the columns alternate
their function. This cycling rate has been selected to provide the optimum balance of
scrubbing efficiency and air usage and is not adjustable.
5.8 Check Valve The purpose of the check valve is to isolate the air in the storage tank from the
components upstream. Thus when the compressor turns off, the air in the storage tank
will be retained and not lost through the drier purge air path or back through the
compressor.