Blowdown the boiler completely (see Section 6.5.1 - Main Boiler Blowdown) and examine all
inspection holes in the boiler. If any leakage is evident, proceed as follows:
1.
Disassemble the crab and cover plate and remove the inspection hole assembly.
Remove the old gasket and thoroughly clean the mating faces of the cover plate and boiler
rin
g.
2.
Place the new Topog-E gasket on the cover plate, ensure the gasket is the correct size and is
seating flat against the plate. Do not use any grease, lubricant or adhesive. If the new gasket
is not seated properly before the plate is tightened, the gasket may be pinched causing a
failure when the pressure builds up.
3.
Position the cover plate in the boiler ring, ensuring that the plate is correctly centred.
An off centre cover plate can concentrate forces on the gasket and cut it in two. The cove
r
plate may also drag on the boiler hole ring and fail to seal as the pressure rises.
Set the crab and hand tighten the securing nut(s) sufficiently to provide a snug fit.
Tighten the nuts a further quarter of a turn using a spanner. DO NOT OVER TIGHTEN.
Note: Ens
ure the gasket is aligned correctly so that only the extreme edges are exposed to water treatment or
oxygen attack. If the gasket is misaligned, over tightening to seal a leak will not prevent subsequent leakage at a
later date.
4.
Gradually warm up the boiler, allowing steam pressure to make the seal. If the gasket leaks
dur
ing pressure build-up, tighten the securing nut(s) sufficiently only to stop the leakage. It i
s
im
portant to keep the nuts correctly tightened thereafter, this prevents the vacuum
developed by cooling on shut-down from feeding and draining the boiler.
Note: Ne
w gaskets fitted to inspection holes located along the bottom of the boiler are more difficult to install
without leaking. Small particles of scale or sand tend to run down on the mating surfaces after cleaning but prior
to assembling. This condition is likely to have occurred if excess tightening is required to stop a leak before
warming the boiler. In this event, the best course of action is to drain the boiler and repeat the gasket fitting
procedure. Failure to do so will severely reduce the life of the gasket.
5.
Clean and inspect each water level gauge (sight glass). If any water leakage is evident, renew
the water level gauge gasket.
COVER PLATE AND
GASKET
IN PLACE
CORRECT
PL
ACEMENT
DO NOT
OV
ER-COMPRESS
GASKET
COVER PLATE
NO
T IN CENTRE
Figure. 22 - Fitting a New Topog-E Gasket
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