Page 86 - Boiler_Operators_Handbook,_Second_Edition

Boiler Plant Operations 71

ture. Confirmation from all those people indicating they visions for handling it should be provided. Lower the
are prepared should be formally documented before operating level of the boiler feed tank or deaerator and
the boiler is fired. One time one of my service techs condensate tank beforehand if possible. If that’s not pos-
started an ignitor in a furnace where the boilermakers sible, close isolating valves for make-up to those tanks
were working. He lived to tell about it, but it took a lot and manually maintain the lowest reasonable level until
of apologizing to those boilermakers to keep them from pressure in the facility is near normal.
lighting him off. For hot water installations the system should be
Normally when we say a plant is dead we mean flooded, the expansion tank level confirmed, and circu-
dead cold. There’s no heat in a boiler or any auxiliary lating pumps started to generate at least minimum flow
equipment associated with normal operation. We’ll also in the system. This may require a walk-through of all
loosely use the term to describe a plant that has a hot, equipment rooms to ensure the systems are ready to cir-
or warm, boiler but isn’t maintaining normal operating culate water. Any equipment still receiving maintenance
pressure. A dead plant start-up is returning a dead plant should be adequately isolated using proper lock-out and
that had been operating to operating condition. It’s not tag-out procedures.
uncommon to return a plant to service that was shut Lock controls in manual at low fire. Starting a dead
down for the summer or a protracted business slump. plant or boiler should provide a very slow increase in
It’s also occasionally necessary to return a plant to ser- temperature until the boiler’s contents are above 220°F.
vice after a loss of electric power or water supply that That minimizes damage to the refractory from pockets
forced it to shut down. The operations mentioned here of absorbed moisture; a sudden increase in volume as
are assumed to occur after a plant was laid-up according liquid changes to steam will build up pressure inside the
to the procedures described later. Some activities also refractory and rupture it. It’s sometimes necessary to re-
apply to simply returning a plant to normal operation. peat an initial dry-out because the refractory got wet or
Remove sorbent from the boiler, deaerator and refractory repairs were performed while the plant was
other closed vessels, install new gaskets and close man- down.
holes. Check all personnel, tools, etc. are out before clos- Performing operational tests of the boiler’s operat-
ing the vessels. Fill fluid systems as described in New ing limits during the initial firing of the boiler will pro-
Plant Start-up. Everything from leaves to birds can find vide frequent interruptions to the heat. That will reduce
their way into air and gas openings to block them while problems with the refractory and provide early reassur-
a plant is shut down. Check to confirm stack clean-outs, ance that the safety and operating limits are functioning
vent openings and air inlets are clean. Confirm the vent properly. A wise operator will not only confirm limit
valve on the boiler and the free-blow drain are open. operations but record it in the log book.
If the burner on the boiler was dismantled or repaired As soon as steam is evident at the boiler vent, oper-
the steps in New Plant Start-up should be followed to ate vents in the facility to remove air from the steam dis-
ensure proper burner operation. As soon as possible tribution system. If the system has automatic air vents
compare initial operating data with current operating it’s a good idea to operate a few manual vents anyway
conditions to ensure there have been no significant to ensure the automatic vents are working.
changes in the boiler’s performance. In high pressure steam plants close the free blow
Record oil tank levels, fuel gas, steam, and water drain valve only after steady steam flow is certain. The
meter readings to establish values at start-up. Leakage, purpose is to prevent any condensate accumulation over
testing, and other activities may have changed the meter the non-return valve that would slug over into the steam
readings from the shutdown or last recorded state. piping when an interrupted flow is re-established.
A cold boiler should be returned to operating con- Close the boiler vent valve when the pressure is
ditions slowly. When starting a boiler in a dead plant it’s up to 10 psig on heating boilers or 25 psig on power
advisable to bring the served facility up with the boiler. boilers. Allowing a loss of steam until those pressures
That increases the time it takes to raise pressure on the are reached helps ensure all the air is removed from the
boiler and the facility to allow for gradual heating. Open boiler.
all valves that lead to the facility only after confirming If the boiler feed tank is fitted with a steam heat-
all drains and vents in the facility have been closed or ing sparge line it should be placed in operation after the
are manned by trained observers. boiler vent valve is closed. If it is a coil heater it may be
In steam plants this process normally creates a allowed to come up with the plant.
flood of returned condensate as pressure builds so pro- Open the vent valves on a deaerator wide before