22
INM MTL 130-0202 Rev 4
6.7 Re-mounting the katharometer and reaction tube
Re-mounting is the reversal of removal. Always make sure that all ferrules are undamaged
and put in place correctly – Figure 3 illustrates this.
Re-make all the electrical connections and then apply power to the analyser.
Check that the voltages on the elements are correct – refer to 7.4.1; if they are not, either the
elements need more drying, or another fault is indicated – refer it to your local MTL Gas sales
office.
If everything is satisfactory, double check all couplings and reconnect to the normal sampling
system. Verify calibration and re-apply the plant sample.
6.8 Checking reactor
If the control thermocouple fails, the controller displays alternately ‘InPt’ and ‘FAIL’. Check
for any loose connections – terminals 7 & 8. If these look satisfactory, then the reactor
assembly will need replacing.
If the controller continues to display a low temperature after power up (typically ambient),
check the reactor power connections. If these look satisfactory, check the voltage on
terminals 9 &10 which should be in the order of 18V ACrms .
If the voltage is correct, disconnect the reactor power wires from terminal 9 &10 and check
the resistance across the ends of the cable. This should be in the order of 4 ohms. If it is
substantially higher then the reactor assembly will need replacing.
If the voltage is at or near zero, check the reactor fuse. If this is intact, then a failure within
the electronic module is indicated - refer it to your local MTL Gas sales office. If the fuse
is open circuit, disconnect the reactor power wires from terminal 9 &10 and check the
resistance across the ends of the cable. This should be in the order of 4 ohms. If it is
substantially lower then a fault in the wiring or the reactor assembly is indicated. If any
intermediate wiring is known to be correct the reactor will need replacing - refer to your local
MTL Gas sales office.
6.9 Changing the electronics control unit
SAFETY NOTES
Changing the electronics unit requires the power to be disconnected from the instrument. This
will cause any alarm contacts to failsafe to the alarm condition and the analogue output to drop to
zero. Ensure that the control of the plant will not be compromised by these signals going to alarm
conditions.
CAUTION
Record all user programmable settings before carrying out this procedure.Settings include alarms,
analogue output span (some instruments), calibration gas concentration, actions under calibration
or faults conditions and the digital filter value.
6.9.1 Tools required
M4 nut spinner recommended.
