Minimum emergency electric power.
Emergency Electrical Power.
When steam-driven auxiliaries are used, provide emergency electrical power
generation to start up the plant and operate the following essential services
until steam pressure is reestablished:
a) Coal and ash handling, coal firing, emergency lighting,
controls, control valves, control room ventilation and other essential
operation requirements including the auxiliaries for one boiler.
b) Emergency electric power shall be provided for all essential
services including plant auxiliaries. Minimum emergency electrical power
shall be that which is capable of allowing the plant to generate steam
sufficient to serve essential load.
Feedwater Pumping System. The ASME Boiler and Pressure Vessel Code
(Section 1, Paragraph PG-61) requires that boilers having more than 500 square
feet of water heating surface and firing a solid fuel not in suspension be
provided with two means of feeding water. It is recommended that all coal-
stoker fired boilers with a capacity above 100,000 lbs per hour (12.6 kg/s)
should have dual feedwater systems containing separate headers, check valves,
isolating valves, and regulating valves for operation flexibility and
emergency. All coal-stoker fired coal boilers 20,000 lbs per hour (2.52 kg/s)
and above shall have a steam turbine-driven boiler feed pump and a motor-
driven boiler feed pump per boiler. Provide the steam turbine-driven boiler
feed pump (plant size) with emergency treated water connection for coal-stoker
Steam Usage Considerations. Consider uses for secondary steam to
determine ways to operate a plant more effectively. Several possible ways of
using steam for more economical operation are:
Fuel oil tank heating coil
Absorption type of refrigeration machines
Refrigeration Units. Addition of refrigeration units to a plant
design should be considered where heating plant steam can be used during
summer to serve refrigeration machines. Chilled water produced by steam
absorption or steam turbine-driven refrigeration compressors can be
distributed economically to buildings for space cooling. A combined plant
saves considerable building cost. The addition increases annual plant load
and may reduce owning and operating cost.
Turbine driven equipment can be economical if there is use for low
pressure exhaust steam. Absorption refrigeration equipment does not work
efficiently at low loads. If absorption equipment is not a significant load
it is advisable to utilize electric driven centrifugal equipment. This
eliminates need for low pressure summer steam and saves distribution costs,
line losses, fuel and manpower.