DURRIDGE RAD7 Руководство пользователя - Страница 11

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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. The inner

membrane tube goes between the exchanger and the

desiccant while the outer sheath is purged by dry air

from the RAD7 outlet. The two ﬂows should be in

opposite directions along the DRYSTIK. A 12"

DRYSTIK will increase the life of the desiccant by a

factor of about ﬁve.

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. This

increases the pressure inside the tube, which

increases its eﬃciency.

A typical setup has the RAD7 pump set to OFF

Setup, Pump, Off [ENTER]

(

pump running continuously and the needle valve

adjusted to give a ﬂow 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 ﬁlter on the

RAD7, as shown in Fig. 4 on the following page. The

desiccant will last for a very long time, and the drying

tube will add only a tiny volume to the air loop.

Section 4

DRYSTIK

), the DRYSTIK

4.3 Eﬀect on Response Time

With a ﬂow rate of only 0.2 L/min it will take about

20 minutes for the air in the loop to go around once.

This 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 beneﬁt.

4.4 Custom DRYSTIK Settings

The standard 0.2 L/min ﬂow rate of the DURRIDGE

DRYSTIK is typically used because it matches the

average ﬂow 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

ﬂow 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.