5
2 Description
2.1 Areas of application
Refrigerating plants (such as indoor ice rinks, cold stores, etc.),
frequently use ammonia as the refrigerant. Ammonia (NH
3
) is a
toxic
, pungent-smelling and colorless gas. These refrigerating
plants are monitored for escaping ammonia (leakage).
To do this, tubes and system parts filled with water are monitored to
determine whether ammonia (NH
3
) has penetrated (dissolved in the
water). The ammonia-sensitive sensor type 201040 described here
is suitable for this purpose.
2.2 Function
A gas-permeable, hydrophobic PTFE film makes the connection
between the process medium and the sensor electrolyte. A
hydrogen ion-selective electrode is immersed in the electrolyte.
Ammonia escaping through the PTFE film changes the pH value of
the electrolyte. The NH
3
concentration in the process medium can
be measured in this manner. The electrolyte contains ammonium
(NH
4
+
) ions, with which the sample gas is in chemical equilibrium.
2.3 Operating conditions
The concept of an ammonia leakage monitoring system must
ensure that the escaping coolant reaches the ammonia-sensitive
sensor type 201040 quickly.
The sensor must be installed in a quick-change fitting part no.
00379538. The porous PTFE washer in this quick-change fitting
must not be clogged! If it is, ammonia leakage will be detected too
late or not at all. If necessary the customer should install a filter
upstream from the sensor.
The flow rate of the monitoring circuit must be checked at regular
intervals! A few drops over several hours is sufficient. If the flow rate
Attention:
The ammonia-sensitive sensor type 201040
described here is
not
suitable for detecting ammonia
in ambient air!