Boilers Flashcards
Steam is produced as water is heated at its boiling point at ___ F
212F at atm
Thermal efficiency
Ratio of heat absorbed by the water to the heat provided by the fuel.
I.e. - 100% thermal efficiency occurs when all heat supplied by the fuel is absorbed by water in the boiler
Feedwater
Combination of condensate and make-up water. Is also treated.
Fahrenheit conversion
F = (1.8 x C) + 32
Complete combustion
Combustion that occurs when all fuel is burned using the minimum amount of air above the theoretical amount of air required to burn the fuel
Approximately how many lbs of air is required to burn a lb of fuel?
14-15lb
MATT
M - mixture of fuel and air
A - atomization to break up fuel into small particles to max contact of fuel with air
T - temperature
T - time required to achieve complete combustion
Fire tube boiler
A boiler in which heat and gases of combustion pass through tubes surrounded by water
Water tube boiler
Water passes through tubes surrounded by gases of combustion
A low pressure steam heating boiler is a boiler operated at pressures of not more than ___
15 psi
A low pressure hot water heating boiler is a boiler in which water is heated for the purpose of supplying hot water at pressures of not more than ____ and temperatures of not more than ____
160psi
250F
Which section in the ASME code applies to steam boilers up to 15psi?
Section IV
Which section of the ASME code capture the requirements for power boilers for industrial processes?
Section I
The safety valve capacity must equal or exceed the boiler______
Pounds per hour rating
The ASME Boiler and Pressure Vessel Code states that all boilers with more than 500sqft of heating surface shall have ?
Two or more safety valves
The capacity of the safety valve must be large enough that what for low and high pressure boilers?
LP - cannot rise more than 5 psi above the MAWP
HP - cannot rise more than 6% above the highest pressure at which any valve is set, but not 6% above the MAWP.
Hydrostatic Pressure
Weight of water (.433 psi per vertical foot)
At what temperature do minerals and salt form scale?
150F approximately
Continuous blowdown
A blowdown that discharges boiler at a controlled rate to regulate proper chemical concentration in the boiler water.
Operating Control
Pressure control that senses steam pressure and automatically signals the burner to initiate the start-up sequence when steam pressure is needed and initiate the burner shutdown sequence when steam demand is met.
High Limit Control
Pressure control that senses steam pressure automatically shutdown the burner if the operating control fails.
ASME Controls and Safety Devices for Automatically Fired Boilers (CSD-1) requires a high limit control to have?
A manual reset that requires the operator to reset the control before operation can be restarted
Modulating Control
A pressure control that works with the operating control to vary the burner firing rate
Water expanding into steam has an expansion rate of approximately ______ times its original volume at atmospheric pressure.
1600