12
Detecting Gas Saving Lives
English
3. Operation
WARNING
Prior to carrying out any work ensure local regulations and site procedures are
followed. Never attempt to open the IRmax or auxiliary junction box when
flammable gas is present. Ensure that the associated control panel is inhibited so
as to prevent false alarms.
3.1 Commissioning procedure
1. Check that:
a. The cable connections are correct
b. The supply voltage is set at the control card as 18 to 30 V. The voltage measured
at the
IRmax
terminals (within the Exe auxiliary junction box if used, or at the
IRmax
terminal PCB) and must be set between 12 and 30 V.
c. The links are set for 4-20 mA sink or source as appropriate to control card.
2. Once powered up leave
IRmax
for 30 minutes before attempting zero/cal. This delay is
to ensure thermal stability. (
Note: IRmax will be fully operational from 30 seconds
after power is applied.
)
3. Ensure clean air (i.e. no hydrocarbon gas) before zeroing. Zero reading at control card
(refer to control card instructions).
4. Fit a calibration cap over weatherproof cover to isolate measurement chamber from
ambient air. Such a cap is available from
Crowcon
(M041007). Connect calibration gas
(50% LEL nom) and apply at 1 litre-per-minute flow.
5. After 30 seconds adjust cal/span on control card so that display reads 50% LEL, or
matches concentration of calibration gas applied. The
IRmax
itself should not require
calibration.
6. Remove gas and calibration cap. Re-check zero.
7. At installation, or after the mirror has been changed, the
IRmax
can be zeroed
and calibrated either using an
IR Display
accessory (see page 1) or via a PC
communications kit (see the
IRmax Accessories manual
).
Note
:
ATEX Certified
IRmax
will be supplied calibrated for compliance with
EN61779 (where, for example 100% LEL Methane = 4.4% volume).
Note
:
It is recommended that the calibration cap is used for initial commissioning.
Subsequent calibrations may be conducted by applying gas to the weatherproof
cap remotely via the pipe spigot (thus avoiding the need to directly access the
IRmax
). Calibration without the calibration cap (i.e. directly via the weatherproof
cap) can be performed provided local windspeed is below 2 metres/second. The
flow rate of the gas must be greater than 2.0 litre/minute.
