Form 2055
17
Revision Date 5/1/2015
3 . 9 . 2 P R E - O P E R A T I O N A L C L E A N I N G A N D L A Y - U P
Proper lay-up techniques must be used on an idle boiler even if it has never been in operation.
Before pre-operational lay-up, the boiler must be chemically cleaned as outlined in Section 3.2
and 3.3 of this manual. This is required, as noted in this section, to remove preservatives, oil
and grease from the inner boiler. Follow the short term or long term lay-up procedure as
appropriate.
3 . 9 . 3 T A K I N G B O I L E R S O F F L I N E
In operation, boiler water contains suspended solids that are held in suspension due to water
circulation and the action of treatment chemicals. Unless care is exercised when draining the
boiler, these suspended solids settle on the interior surfaces and will air dry to an adherent
deposit, sometimes requiring chemical cleaning to remove. In addition, these deposits may be
misleading regarding the effectiveness of the chemical treatment program.
3 . 9 . 4 P R E - S H U T D O W N P R E C A U T I O N S
For a period of three to seven days prior to shutdown, manual blowdown frequency should be
increased. During this period, the lover conductivity limit should be below 3,500 micro-ohms per
centimeters. The feed of internal treatment must be increased to maintain a specific residual
concentration. Continuous blowdown (when used) should be kept to a minimum so the reduction
of solids is achieved by the increased manual blowdown.
3 . 9 . 5 W A S H D O W N
As the boiler cannot be washed immediately, the heat in the boiler may cause baking of residual
sludge. The boiler should not be drained until cooled enough to prevent this. However, never
leave the boiler filled with water for any extended period of time without taking measures to
prevent corrosion.
3 . 9 . 6 L A Y - U P C O N S I D E R A T I O N S
There are two basic methods of steam boiler lay-up: Wet lay-up or Dry lay-up. The choice of
which method should be used depends on:
The possibility that the boiler may need to be placed operation on short notice.
Disposal of lay-up solution
Freezing
potential
Wet Lay-Up is recommended for relatively short outages, such as seasonal lay-up. This method
has the advantage of allowing the boiler to be brought on line with short notice. But it can pose
problems if there is any likelihood of freezing.
Dry Lay-Up is recommended for longer periods of boiler shutdown or storage. But it is practical
only if boiler can be drained hot (120° F to 170° F) or if external drying can be provided.