The recommended procedures for securing boil
are as follows:
1. Reduce the load on the boiler slowly, cutting
the fuel supply by proper operation of the
2. Maintain normal water level.
3. When the boiler load is reduced to about 20% of
rating, change the combustion control and the
feedwater control to manual operation.
4. Before securing the final fuel burner, open the
drain valves at the steam and nonreturn valve
and the drain valve on the superheater outlet
header. Be sure the bypass valve around the
nonreturn valve is closed.
5. Secure the final fuel burner when the load has
been reduced sufficiently.
6. Continue operating the draft fans until the boiler
and the furnace have been completely purged.
7. Shut down the draft fans.
8. Close the dampers, including the air heater and
superheater bypass dampers, when provided.
9. Follow the manufacturers instructions for the
rate of cooling the boiler. A thermal strain may
occur if the change is too fast.
10. When the boiler pressure has started to drop,
close the steam stop and nonreturn valve.
11. When the boiler no longer requires any feed and
the nonreturn valve is closed, open the valve in
the recirculating connection of the economizer,
12. Let the boiler pressure drop by relieving steam
through the superheater drain valve and the
drain valve at the nonreturn valve. If the boiler is
losing pressure at a rate faster than specified by
the manufacturer, throttle the drain valves as
necessary to get the proper rate. Do not close the
13. When the drum pressure drops to 25 psig, open
the drum vent valves.
14. If a regenerative type of air heater is used, the
rotor may be stopped when the boiler exit gas
temperature is reduced to 200°F.
15. The boiler can be emptied when the temperature
of the boiler is below 200°F. Before sending
someone into any part of the boiler, close and
properly tag all controls, valves, and drains or
blowdown valves connected with similar parts
of other units under pressure at the time. This
move prevents any steam or hot water from
entering the unit. The tags are to be removed
only by the authorized person who tagged out
the boiler and must remain in place until the
work is completed. Ventilate the boiler
thoroughly and station a person outside. Inside,
use only low voltage portable lamps provided
with suitable insulation and guards. Even 110
volts can kill under the conduction conditions
inside a boiler. All portable electrical equipment
should be grounded; and electric extension
cords should be well insulated, designed to
withstand rough usage, and maintained in good
Typical emergency situations encountered with
the operation of boilers are (1) low water, (2) high
water, (3) serious tube failure making it impossible to
maintain water level, (4) flarebacks caused by an
explosion in the combustion chamber, (5) minor tube
failure indicated by trouble in maintaining water level
under normal steam demand, and (6) broken gauge
glass on the water column. Table F, appendix II, lists
the safe procedures to follow when these boiler
BOILER OPERATING LOGS
The main purpose of boiler operating logs is to
record continuous data on boiler plant performance.
Logs become a source of information for analyzing the
operation of the boiler for maintenance and repair. The
daily operating log sheets provide the basic
information around which maintenance programs are
developed. The log is arranged for use over a 24-hour
period divided into three 8-hour shifts. Log sheets vary
among different activities, but you should have no
difficulty in making log entries once you understand
what information is required. The types of information
to be entered in the appropriate column of the log are as
Steam pressure. Based on steam gauge readings
and indicates the performance of the boiler.
Steam flow. Actual output of the plant, in pounds
per hour, to obtain steam flow. The data from these
entries are used to determine the number of boilers to
operate for greatest efficiency.