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
To change 1lb of water at 212F to 1lb of steam at 212F requires _____ BTU.
970.3
Every 11 degrees added to the feedwater prior to going into the boiler increases boiler efficiency by?
1%
Thermostatic steam trap
Has a bellows filled with a fluid that boils at steam temperature. The bellows expands or contracts depending on whether it is surrounded by steam or condensate.
Float thermostatic steam trap
Has a ball float that opens and closes a discharge valve depending on the amount of condensate in the chamber
Inverted Bucket Steam Trap
Steam enters the bottom and flows into an inverted bucket.
Distillate Fuel
Fuel oil that has low viscosity and includes No. 1 and No. 2 fuel oil
Therm
The quantity of gas required to produce 100,000 btu
How many lbs of air is needed to burn a pound of fuel.
14 to 15 lbs of air
Air proving switch
An air pressure-actuated switch that closes after proving sufficient pressure of combustion air from the forced draft fan.
Turndown ratio
Is the ratio of the maximum firing rate of the burner to the minimum rate
Draft
The flow of air or gases of combustion caused by a difference in pressure between two points
Breeching
A duct used for the transport of gases of combustion from the boiler to the stack
Induced draft
Mechanical draft from air pulled through the boiler furnace with fans located in the breeching
Manometer
A device that measures draft by comparing pressures at two location and is measured in inches or tenths of an inch
Draft can be converted to pressure by multiplying inches of water column times ______.
0.036
Stack condensation in conventional boilers is most likely to occur?
In heating boiler installations where light loads and intermittent firing cause a cool stack condition.
The feedwater is heated to a maximum of _____ for reducing the amount of dissolved ______ and _______ in the feedwater.
210F; oxygen ; carbon dioxide
Boiler water pH typically should be between ?
10 and 11.5
ASME Symbol Stamps
S A E V M L PP H
S - Power Boiler A - Boiler Assembly E - Electric Boiler V - Safety Valve M - Miniature Boiler L - Locomotive Boiler PP - Pressure Piping H - Heating Boiler
A pressure reducing valve for make-up water on a low pressure boiler system should reduce the pressure to:
12-18psi
The aquastat starts and stops the burner based on different demands depending on boiler type. What is it for hot water? Steam?
Hot water - water temperature demand
Steam - pressure control based on pressure demand
The pressure relief valve on a low pressure hot water boiler cannot exceed _____ or the MAWP designated on the boiler.
160 psi
One-pipe hot water heating system
One pipe to supply heated water from the boiler in a loop to return the water through the same pipe
One-pipe series system
Circulates water through one pipe that loops through each heating unit in order
One-pipe primary-secondary system
Use diverted valves to control water through a secondary loop to the heating unit
Two-pipe hot water heating system
One pipe to supply heated water from the boiler and one pipe to return water to the boiler
Two-pipe direct return system
Circulates supply water in the opposite direction of the circulation of the return water
Two-pipe reverse return system
Circulates supply water in the same direction as return water
Modulation
Accomplished by reducing the fuel and air input to the combustion process. Similar to changing the throttle setting on an internal combustion engine.
Turndown ratio
The ability of a boiler to reduce its heat output rate. Is the reciprocal of the lowest possible decimal percentage of full-heat output rate the boiler can maintain.
I.e. - a boiler can maintain stable operation down to 20% of its maximum heat output rate, it would have a turndown ratio of 5:1.
Unconfined space
Must have a minimum of 50ft^3 volume per 1000 btu/hr. Of gas input rating of all gas-fired appliances in that space.
The NFPA code states that the minimum dimension of any rectangular supply air duct is ____ inches and any screening covering these openings cannot be finer than _____ inch mesh.
3 inches
1/4 inches
The number of blowdowns require is determined by?
Feedwater analysis
A ____ pump is a boiler accessory that draws condensate back from the system by producing a negative pressure on the condensate return lines
Vacuum
Oxygen in the boiler water causes
Pitting
A therm is equivalent to____ BTU
100,000
A ____ draft fan is located before the furnace
forced
Impurities that increase the surface tension of boiler water are removed with a ____ blowdown
Surface
The primary function of the water column on a low pressure boiler is to _____
Reduce water movement
The boiler vent is opened when ____
warming and draining the boiler
A low water condition requires _____ immediately
securing fuel to the burner
CO in the flue gas is an indication of _____ combustion
incomplete
T/F - Oxygen is required for teh combustion of fuel
True
T/F - A siphon is located between the boiler and steam pressure gauge to prevent water from entering the Bourdon Tube.
False
T/F - At the NOWL, the gauge glass is approximately half full.
True
T/F - A low water conditon in the boiler can cause overheating of the tubes.
True
T/F - City Water does not require treatment for use in a boiler
False
T/F - Steam traps, prevent the flow of condensate back to the deewater pump
False
T/F - Clogged fuel oil strainers cause high suction readings
True
T/F - Anthracite coal is hard coal
True
T/F - Draft is measrured with a manometer
True
T/F - Sludge is removed from teh boile with a surface blowdown
False
T/F - A dearator is a boiler water treatment accessory that heats feewater to the temperature of saturated steam within the pressure vessel.
True
T/F - All valves are closed when completing a dry lay-up
True
T/F - The boiler room log is used to record boiler operation events.
True
T/F - Forced circulation hot water heating systems are more common in a large building than natural circulation hot water heating systems.
True
T/F - The pressure reducing valve in a hot water heating system regulates the water pressure of water returning from heating units
False
T/F - A boiler is an open vessel in which water is transformed into steam under pressure by the application of heat
False
T/F - An HRT boiler is a watertube boiler
False
In a watertube boiler, the ____ passes through the tubes and the ____ passes across the ourside surface of the tubes.
water; combustion gases
The three most common fuels used in steam production are _____
natural gas, fuel oil, coal
T/F - In a natural draft furnace, the amount of draft, is affected by the height of the stack
True
Fuel oil grades commonly used in boilers are designated by No. ____ for the lightest grade of fueld oil through No.____ for the heavies grade of fuel oil.
2; 6
A boiler has quick - and slow-opening blowdown valves . The sequence used for the blowdown is_____
open quick-opening, open slow-opening, close slow-opening, close quick-opening
The most important boiler fitting is the _____
safety valve
The valve with the least amount of restriction is the _____ valve.
Gate
Steam boiler safety valves must be sized to prevent steam pressure from exceeding the MAWP by ____%
6%
Flame safeguard systems can monitor ______
pilot and main flame
Sensors used for flame detection in boilers include ____
lead sulfide cell, ultraviolet scanneer, thermocouple
A ___ blowdown is performed to remove sludge from the boiler
bottom
a pH level of 7.0 is an indication that the boiler water is _____
neutral, neither basic or acidic
At seal level, atmospheric pressure is approximately ___ psia
14.7
Specific gravity is the ratio of weight of a volume of a substance to the weight of the same volume of _____
water
Heat transfer can occur by ___
conduction, convection, radiation
Water weighs approximately ____ lb/gal
8.3
Boiler safety valves should be repaired by a ____
authorized safety valve repair company
T/F - MSDSs should only be available to supervisors and managers
False
T/F - The EPA does not regulate discharges of waste water from utility and industrial boiles
False
Foaming of boiler water from floating foreign matter causes an increase in ______
surface tension
Blowing down is most effective during a period when the steam output is _____
at a low rate
The water column must be located ___
at the normal operating water level
A boiler that is priming has ____
water carried over with the steam
If the low water alarm sounds ____
secure the fires
A feedwater pump can become steambound from _____
feedwater temperature too high
Infrared or ultraviolet rays are sensed by the _____
flame scanner
As the steam pressure increases in a boiler, there is a corresponding increase in the _____
boiler temperature of the water in the boiler
Complete combustion is _____
burning all the fuel with the theoretical amount of air
When testing a safety valve by hand on a low pressure steam boiler, the boiler must be at a minimum pressure of ____ before the try lever can be lifted without damaging the valve
5 psi
Draft in a boiler is a measured in _____
inches of water
A positive pressure before the furnace indicates ____ draft
forced
Preparation for a boiler inspection requires having the boiler _____
cool, opened and thoroughly cleaned
The firing rate of the burner is controlled by ____
modulating pressuretrol
A fan located between the breeching and the stack is a ___
induced draft fan
Class ____ fires are electrical fires, such as motor or transformer fires
C
A main steam stop valve would most likely be an ____
os&y gate valve
The evaporation of 34.5 pounds of water per hour from and at 212F is defined as ______
one boiler horsepower
A compound gauge is a pressure gauge that indicates _____
vacuum in inches of mercury or pressure in psi on the same gauge
When burning No. 6 fuel oil, a ____ is required.
Fuel oil heater
A ____ prevents the flow of boiler water back to the city water supply.
backflow preventer
The amount of british thermal units (BTU) per pound or gallon of fuel is the _____.
heating value
____ is the accumulation of minerals such as calcium and magnesium on boiler heating surfaces.
Scale
Tubes in a firetube boiler are mounted into the _____ located at the front and rear of the boiler.
tube sheet
