Perma Pure MDSS (LLC Integrator Series) - Manual (Page 9)

Section C: Principle of Operation
9
C: P
RINCIPLE OF
O
PERATION
The AG-412/193U system is a passive system in the sense that it will not move the sample
gas from point A to point B. It will only dry sample gas that is pushed or pulled through it by
an external pump or pressure/vacuum source. The pump in the system is present only to
provide a vacuum source on the purged side of the membrane dryer.
As sample gas is drawn or pushed through the system by the external pump or
pressure/vacuum source, it is dried to a low moisture condition. A precision orifice serves to
meter a portion of the dried sample gas into the purged portion of the dryer. After passing
through this orifice, the
pressure of the gas drops to about 15”hg. This change in total
pressure of the sample gas also lowers the partial pressure of the water vapor contained in
the gas effectively making it dry enough to be used as purge gas for the membrane dryer.
This purge gas sweeps away the moisture that is being removed from the sample gas flow
by the membrane tube in the dryer.
A silica gel filled tube on the front panel is used in the purge stream to indicate proper
operation. Initially, the silica gel indicator may be blue or pink depending upon the storage
conditions of the system. Once the system is put into operation and within a short period of
time, the silica gel will turn to a mostly light purple color, indicating the sample gas is dry and
ready for analysis. The silica gel material is blue when very dry and pink when not dry.
A vacuum gauge on the front panel shows the level of vacuum as an indication that the
purge pump is functioning.