AERCO Steam Generator - Manual (Page 15)

INSTRUCTIONS – AERCO HELITHERM STEAM GENERATOR MODEL SS1B-PLUS
SG-101-13
DESCALING BY THERMAL SHOCK METHOD
Where, under certain conditions of continuous
steady usage, the cold water is so hard or
alkaline that normal flexure of the coils (see
ROUTINE MAINTENANCE) and routine blow-
down (draining the Generator shell) will not
remove scale build-up on the coils, the heating
surfaces (coils) may be thermally shocked,
without damage to any part of the Generator, to
dislodge scale solids.
Proceed as follows:
TS1. Drain the Heater per steps RM1 through
RM4 in the ROUTINE MAINTENANCE
Section. However, instead of holding
the relief valve open in step RM4,
remove the relief valve from the
Generator top head.
TS2. Open the Generator drain valve. Leave
the drain valve open until step TS8 in
the following procedure.
TS3. Connect a source of cold water (for
example, a hose) to the open relief
valve connection.
TS4. Open all stop valve(s) in the Primary
Steam inlet line and the Condensate
outlet line to allow steam to the
Generator. After about 30 seconds, or
until steam is blowing out of the
condensate drain line, close the stop
valve in the Condensate outlet line.
Leave the Primary Steam inlet line open
for about 2 minutes longer, then close
all Primary Steam inlet stop valves.
TS5. Inject a flow of cold water through the
relief valve connection for about 2
minutes. Then shut off the water flow
and open the Condensate drain line
stop vaIve to drain off all Condensate.
TS6. Repeat steps TS4 and TS5 several
times until the water coming from the
Generator drain appears to be relatively
free of solids.
TS7. Remove the cold water source from the
relief valve connection. Open the stop
valve in the main Cold Water inlet line
and allow a complete flushing of the
Generator shell.
TS8. After the Generator shell has been
completely drained, close the Generator
drain valve, replace the relief valve, and
place the Generator back into operation
per steps OP1, OP12, and OP 13 in the
OPERATING PROCEDURES section.
TS9. If Cold Water conditions are so severe
that thermal shocking does not remove
scale deposits, contact the nearest
AERCO Representative for advice.