andrews R18 Series, Technical Documentation Manual

Page: 61 / 71

18IP22B
53
8.6 Component Electrodes
replacement Remove the burner trolley as described earlier. The ignition and
sensing electrodes can now be replaced as follows:
Disconnect the aluminium wire from the base of the electrodes.
Remove central bolt securing the electrodes to the pilot burner
bar and lift off the electrodes.
When re-assembling ensure that the electrodes are correctly
replaced (refer to fig. 32) with the pilot burner bar in position.
Check operation of electrodes by carrying out the relevant
parts of section 6, commissioning.
Burner bars
Remove the burner trolley as described earlier. Remove the
insulation covered stainless steel channels.
With the exception of the pilot burner bar, the burner bars are
removed by first lifting the end of the burner out of its locating
notch and then withdrawing the burner from its injector.
To remove the pilot burner assembly, disconnect the wiring to
the sensing electrode and the ignition electrode. Avoid damag-
ing the electrodes. Replacement of the burner bars is described
in section Servicing. Ensure that the burners are not damaged
or warped.
Injectors
Remove the burner trolley and burner bars as described before.
With the burner bars removed the injectors can be unscrewed
from the gas manifold.
Ensure that injectors are unblocked and are the correct size -
1.85 mm diameter (natural gas).
Use an approved pipe sealant on the injector thread to ensure
a gas sound seal.
Replace components in the reverse order of removal.
Gas train
(including gas train components).
Ensure that the gas service cock is closed, release the gas
union, disconnect the plugs from the front electrical tray and
release the bolts at all 4 sides of the burner trolley and withdraw
the burner trolley. Solenoid valve heads can be replaced with
valve in situ by releasing the appropriate fixing on the valve
head. Ensure that the new valve head is wired in accordance
with the separate supplied wiring diagrams.
The main gas train is removed as follows:
Remove first the cover plate from the servo-motor coupling.
Loosen the grub screw securing the keyed shaft of the modula-
ting valve servomotor to its coupling and remove the motor by
unscrewing fixing screws. It is not necessary to remove the gas
train if only replacing this component.