Trident DRYSPELL PLUS 10, Manual

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Principle
Pressure swing adsorption dryers purge 15% compressed air at 100 PSI pressure and 1000F inlet compressed air tempera-
ture. This is required to regenerate the bed of adsorbent. The requirement of purge is from basic physical laws and cannot
be altered substantially. Purge loss is a function of Dew point required, Inlet air temperature, Operating pressure and rated
flow. These parameters are have certain values as per standards and Dryers are designed for same. The common standards
are ISO 7183 or CAGI which specifies the standard inlet conditions for the dryer as air temperature 38 deg (1000F) C and
pressure of 7 bar (g) (100 PSI). In practice this is very different. Further a dryer will never be used at its rated flow. When
a dryer is not used at its rated capacity the purge still happens at 15% of the rated capacity. For e.g a Dryspell Plus 100
would purge 15 scfm at 7 bar irrespective of the flow through the dryer. Hence the above dryer with a 80% flow ie 60
scfm would still be purging 15 scfm making the actual purge loss to 25%. This is a common problem with all dyers. Dryspell
plus series dryers come with a front panel purge economizer. Select the Purge economiser switch and the purge flow is
correspondingly reduced. This is done changing the purge time. The purge flow requirement is governed by the Flow rate,
Inlet air temperature, Air pressure and dew point.
Purge optimizer setting = Percentage of rated flow/ (Pressure correction factor * temperature correction factor * Dew point
correction factor) e.g In a given system the Pressure is 120 PSI, Temperature is 1000F, Dew point requirement is -400F
and flow is 80% of rated flow.
Purge optimizer setting = 80/(1.18 x 1 x 1.15) = 58.9 =60%. This saves 40% of purge air. When conditions are not known
or stable set purge optimizer at 100% to ensure dew point.
Through Dewpoint controller - Dynamic Conditions The second method of saving purge is to interface the Dryspell controller
with a dew point switch. A potential free contact of the dew point switch is connected to the controller terminals. The
controller purges correct quantity of air and stops purging. It remains at this state till the dew point at the outlet of the
dryer falls below the set value. At this point the controller changes over to the fresh desiccant tower and starts purge to
regenerate the saturated tower. With this interface highly fluctuating load, varying temperature and pressure can also
factored to save purge air. Please refer user manual for terminal details. This interface also guarantees dew point.
INSTRUCTION MANUAL -
Dryspell Plus
Reference : Manual Version
10