DURAG D-R 290, Operating Manual

Page: 83 / 202

5 | Installation
D-R 290 83
Switch between middle and NO (bottom) Switch between middle and NC (top)
NO
normally open
NC
normally closed
Table 5.4: Switch settings SW1 and SW2
The default setting of the switch is NO (switch between middle and NO)
Closing the housing
1. Carefully place the housing cover back over the electronics. The handle at the bot­
tom. Insert the screws and tighten them equally in the opposite sequence to re­
moving them (see Fig. on the left).
2. Swing the measuring unit shut and close the four quick-release clamps.
Before commissioning the D‑R 290 measuring system, the measuring heads must be
parameterised (see section 6.2 Parameterisation and operation of the measuring head
[
}
108] ff).
Installation of the D-SK 290 protective device
Where the flue gas duct or stack is at overpressure or at high temperatures, even a
brief failure of the purge air supply can lead to damage to the measuring devices.
Such damage may be irreparable. Installation of the optional D−SK 290 protective de­
vice (fail-safe shutter) is recommended here. This protective device consists essential­
ly of a D‑SK 290 MA motorised fail-safe shutter and D‑SK AE control electronics with
the F3 air flow sensor.
The measuring system is designed optically and mechanically so that a D‑SK 290 MA
fail-safe shutter can be installed between each welded-in pipe and the measuring
head or reflector. In the event of a fault (power supply failure or purge air failure), with­
in 2-3 seconds the fail-safe shutter mechanically closes the path between the measur­
ing device and flue gas. This provides short-term protection to the measuring device in
the event of a fault.
The fail-safe shutter when closed is not however gas-tight. Because of the danger of
overheating, the measuring head must not be allowed to remain in the flue gas duct
for an extended period unprotected by purge air. The fail-safe shutter provides
protection for a short period before a repair is performed or the measuring head/
reflector is removed.
Fig. 5.17: Tightening
5.5