G16 Smoke Density Monitor
Ver.2.4 – Revision March 2022 19
Figure 5-4: Mounting of Air Module and Reflector
5.2.5 Purge Air System
Purge air is connected via the non-return valve, air distributor, and hoses to both air mod-
ules. A sealing air kit (part no. 00031) includes the necessary parts.
The purge air consumption is approximately 10-20 NLPM for each set of transceiver/re-
flector. The purge air quality must meet ISO 8573-1 Class 3. Appropriate air cleaning
and/or drying systems can be fitted to meet ISO 8573-1 Class3. When using instrument air,
the optional air supply filter regulator (part no. 31021) must be always used to even out
variations in pressure.
As an alternative to instrument air an optional sealing air compressor can be provided (part
no. 01259).
For stacks and ducts with a negative pressure at all loads, it is possible to use the passive
air purge principle. This means that the purge air connection is simply connected to an air
filter which allows the negative pressure inside the stack/duct to draw in a constant flow
of ambient air and thus, providing a purging effect. However, make sure that the air still
meets ISO 8573-1 Class 3. Otherwise, the lenses will be quickly fouled.
We recommend the use of an optional flow meter (part no. 31022) to adjust the flow control
screw at the purge air connection of the air modules. Flow adjustment is essential since too
much air flow will affect the effective light path length as it blows the flue gas out of the
detection area. Too little air flow will lead to increased fouling of the lenses and could lead
to intolerable temperature rises.
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