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81 Cards in this Set
- Front
- Back
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What device prevents city water from flowing back to the city supply |
Backflow Preventer
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What three elements are needed for the combustion of fuel.
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hydrogen,oxygen, carbon
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The second law of Thermodynamics
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Heat always flows from a material at a higher temperature to a material at a lower temperature.
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Three methods of heat transfer
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conduction
convection radiation |
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Formula Celsius to Fahrenheit
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Fahrenheit=(1.8xC) + 32
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Air contains what level of
Oxygen and Nitrogen |
Oxygen = 20.95 %
Nitrogen = 78.8 % |
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"BTU"
British Thermal Unit |
The amount of heat energy required to raise the temperature of 1lb of water 1 degree Farenheit.
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Perfect Combustion
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Combustion that occurs when fuel is burned using only the theroretical amount of air,
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Complete Combustion
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Combustion occurs when all fuel is burned using the minimum amount above the theoretical air required to burn the fuel.
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How much air is rquired to burn 1lb of fuel?
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14 - 15 lb of air
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Complete Combustion
M A T T |
M= mixture air and fuel
A= atomization of fuel T= Temperature T=time require to achieve complete combustion |
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Low pressure Boiler Limits
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steam boilers not to exceed 15psi
Hot water boilers not exceed 160 psi 250 degree near boiler outlet |
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High Pressure Boiler has MAWP of
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15 PSI and over 6 boiler horsepower
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Boiler Horsepower
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The evaporation into steam 34.5 lb of water at a temperature of 212 degrees.
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One boiler horsepower is equivalent to?
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33,472 Btu/Hr
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Water boils and turns to steam at?
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212 degrees at 14.7 psi at sea level
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This device reduces the movement of boiler water to provide an accurate water level reading
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Water column
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The most important valve on the boiler
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safety valve
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Total Force
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the total amount of force in pounds acting against the safety valve disc.
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The area on a safety valve that increases surface area and total force applied.
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Huddling chamber
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Blowback
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The drop in pressure that occurs after the safety valve is opened
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All boilers with more then 500 sq ft require how many safety valves
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2 or more
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Safety valve should be
Trylever tested |
Every 30 days
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A safety valve "pop tested"
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Anually
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Hydrostatic pressure
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weight of water per vertical foot
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Latent Heat
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Identified by a change in state and no change in temperature
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Conduction
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heat passed from molecule to molecule through the material
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Sensible Heat
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Heat that can measured with a thermometer
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Primary Air
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controls combustion rate, which determines the amount of fuel burned
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Secondary Air
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Controls combustion efficiency and how completely fuel is burned
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Sensible Heat
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Can be measured with a thermometer
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MAWP is measured in
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PSI pounds per square inch
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Cast Iron boilers
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have no tubes
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Internal furnace
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A furnace in a boiler surrrounded by heating surfaced
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Safety valve capacity is rated in
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pounds per hour
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Chattering is caused by the rapid closing and opening of the _____?
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Safety Valve
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MAWP for low pressure steam valves?
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15 PSI
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The most important valve on the boiler is what?
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Safety valve
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Formula for area of a safety valve?
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A= .7854 x D2 (squared)
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What is total force?
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Is the total amount of force in pounds acting against the safety valve disc.
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Formula for Total Force
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TF = P x A
P = Pressure A = area ( in sq in) |
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What is blowback
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The drop in pressure in the boiler that occurs after the safety valve has been opened
2psi to 4 psi. |
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All boilers with more then 500 square feet of heating surface must have how many safety valves?
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2 or more
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Try lever test (safety valve) must be tested every _____ days?
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30 days with the boiler at a minimum of 75% of the safety valve set pressure.
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POP TEST
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Performed to determine if a safety valve opens at the proper pressure within allowable tolerances and should be performed annuallyl.
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Safety valves repairs should on be performed by manufacturer. True or False
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True
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What is hydrostatic pressure?
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The weight of water per vertical foot (.433 psi per vertical foot)
H = V x .433 =____ PSI |
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Safety valve capacity
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The amount of steam per hour that the safety valve is capable of venting.
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What is a Siphon?
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A bent tube between the boiler and boiler fitting that provides a water seal to prevent contact with steam.
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Vacuum is expressed in what?
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inches of mercury (HG)
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A compound gauge measures what?
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Vacuum in inches of Mercury
Pressure in PSI |
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The water gauge glass must be located at the NOWL
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with the lowest visible part of the gauge glass 2" to 3" above the highest heating surface.
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Blowdown should be done how long?
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5 to 10 seconds
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What are trycocks used for?
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they are used to determine the water level in the boiler if the gauge glass is not working
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Which valves are opened first when performing a bottom blowdown?
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The quick opening valve is opened first and closed last
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What is carryover and priming?
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small particles of water are carried into the steam lines.
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What is the purpose of the blowdown tank?
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prevents damage to the sewer system from steam and hot water by holding blowdown water until its cool enough to discharge.
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Scale is formed on heating surfaces at approximately what temperature?
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150 degrees
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what is the purpose of the surface blowdown?
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Release water surface impurities from the boiler
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What is carryover and priming?
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small particles of water are carried into the steam lines.
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What is the purpose of the blowdown tank?
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prevents damage to the sewer system from steam and hot water by holding blowdown water until its cool enough to discharge.
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Scale is formed on heating surfaces at approximately what temperature?
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150 degrees
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what is the purpose of the surface blowdown?
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Release water surface inpurities from the boiler
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Continuous Blow down is what?
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discharges water at a controlled rate to regulate proper chemical concentration in the boiler water.
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Fusible plug melts a what?
Located where? If melted is makes a ___ noise? |
450 degrees
1" to 2" above the highest heating surface in the direct path of the gases of combustion whistiling |
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Fusible plugs should be replaced?
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Annually
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Boiler Vent
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used to remove air from inside the boiler. Should be opened when filling the boiler.
Usually a 1/2" to 3/4" piping |
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Atmospheric pressure
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14. 7 PSI
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Continuous Blow down is what?
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discharges water at a controlled rate to regulate proper chemical concentration in the boiler water.
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Fusible plug melts a what?
Located where? If melted is makes a ___ noise? |
450 degrees
1" to 2" above the highest heating surface in the direct path of the gases of combustion whistling |
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Fusible plugs should be replaced?
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Annually
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Boiler Vent
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used to remove air from inside the boiler. Should be opened when filling the boiler.
Usually a 1/2" to 3/4" piping |
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Atmospheric pressure
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14. 7 PSI
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Pressure Control
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A switch that starts the burner , controls the firing rate , or shuts down the burner based on steam pressure
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Pressure control should be mounted
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90% to the siphon bend
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When setting a pressure control
Cut in pressure is what? |
cut in pressure and differential pressure = cut- out pressure
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How often should the mecury in a pressure control be inspected?
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twice a year |
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A typical standard burner operating package consists of three separate pressure controls?
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operating control |
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Operating control
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signals the burner to initiate start up |
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High limit control
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shutsdown the burner if the operating control fails
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Modulating control
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works the the operating control to control the firing rate |
