DURRIDGE RAD7, Руководство пользователя

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4 DRYSTIK
4.1 Passive DRYSTIK
A passive DRYSTIK may be installed in the Water
Probe system without modifying any other part of the
system or the operating conditions.
Th e inner
membrane tube goes between the exchanger and the
desiccant while the outer sheath is purged by dry air
from the RAD7 outlet.
Th e two fl ows should be in
opposite directions along the DRYSTIK. A 12”
DRYSTIK will increase the life of the desiccant by a
factor of about
fi ve.
4.2 DRYSTIK ADS-3 and ADS-3R
DURRIDGE’s DRYSTIK ADS-3 and ADS-3R models
include a pump upstream of the inner membrane
tube, and a needle valve downstream of the tube.
Th is
increases the pressure inside the tube, which
increases its e
ffi ciency.
A typical setup has the RAD7 pump set to OFF
(
Setup, Pump, Off [ENTER]
), the DRYSTIK
pump running continuously and the needle valve
adjusted to give a
fl ow rate of about 0.2 L/min.
When using an active DRYSTIK, a Small Drying
Tube or larger Laboratory Drying Unit full of
desiccant can be added to keep the air sample in the
RAD7 below 7% RH. It should be inserted between
the DRYSTIK air outlet and the inlet
fi lter on the
RAD7, as shown in Fig. 4 on the following page. Th e
desiccant will last for a very long time, and the drying
tube will add only a tiny volume to the air loop.
4.3 E ff ect on Response Time
With a fl ow rate of only 0.2 L/min it will take about
20 minutes for the air in the loop to go around once.
Th is will add an extra 10 or 15 minutes to the
response time for radon. For long term studies the
slower response is generally not important, whereas
the frequency of replacing the desiccant may be. So
an active DRYSTIK may be of considerable bene
fi t.
4.4 Custom DRYSTIK Settings
Th e standard 0.2 L/min fl ow rate of the DURRIDGE
DRYSTIK is typically used because it matches the
average
fl ow rate of a RAD7 in AUTO mode, and it
also matches the performance of the installed pump
at a pressure of 44 PSI (3 atmospheres). DURRIDGE’s
Active DRYSTIK models can be set to maintain a 44
PSI pressure inside the inner membrane tubing and a
fl ow rate of 1L/min or even more, to restore the speed
of response of the system while virtually eliminating
the need to periodically replace the desiccant. See the
DRYSTIK user’s manual for details.
Section 4 DRYSTIK 11