1st A Flashcards
What is the purpose of nitrogen in a boiler
Nitrogen will control the burn ratio of fuel in the furnace
If you use 3 tons of coal on a 8 hour shift and averaged 150 boiler HP what was the rate of evaporation
One boiler HP=34.5lb steam
34.5x150x8=41,400 of steam
What devices are on a fuel oil train to the boiler
-thermometer
-shut of valve
-vacuum gauge
-duplex strainer
-PRV
-metering valve
What is a motor
coverts electrical energy into mechanical energy
What is power factor
ratio between apparent power and the actual power in an AC circuit
What is torque
mechanical twisting force producing rotation
measured in foot pounds
Define dynamo
machined used to covert mechanical energy into electrical energy and electrical into mechanical
Name the three components of the magnetic circuit of the dynamo
-field coils
-air space
-poles and rotors
What is a generator
converts mechanical energy into electrical energy
Does an AC alternator or generator require DC voltage
Yes, it is required to make the magnetic field
Define cycle
One complete positive and negative alternation of wave form in an AC circuit
Define frequency
The number of occurrences in a unit of time, such as voltage in an AC circuit
How is frequency controlled in an alternator
-Changing the rotation speed of an alternator
-Number of poles
How is voltage controlled in an alternator
By changing the rotating speed of the DC exciter generator
What is the main difference in an AC and DC generator
AC-Magnetic field is produced in the rotor
DC-Magnetic field is produced in the stationary coils
What is a surge tank
storage tank holding a reserve of feedwater for whenever boiler demands are more than the deareators can keep up with
What is a push nipple
A tapered connection used to assemble sectional boilers
List three reasons why you would use a flexible connection
-quiet
-less wear
-easily aligned
What is combustion
-chemical reaction between oxygen and combustibles
-Rapid oxidation by which heat energy stored is the fuel is liberated
How is a HRT boiler supported
-Rollers and saddles
-overhead beams to permit movement of the boiler as it expands and contracts
HRT slope
1”-3” from front to rear for drainage and circulation
Why are HRT boilers dangerous
Drums and joints are exposed to high heat causing stress and unequal expansion and contraction of the tubes and boiler shell which can cause a fire side explosion
What provisions are made on a watertube boiler with curved tubes for tube removal
-Some of the tubes are left out
-Tubes are staggered
-Every other row is omitted
Where is the boiler badge plate located
Front of the boiler vessel
Define factor of safety
Comparison of Tensile strength to the calculation
actual working stress-bursting pressure/working pressure
Six things listed on boiler badge plate
-design steaming rate
-boiler design pressure
-boiler operating pressure
-boiler operating temp
-economizer design pressure
-economizer design inlet temp
3 reasons How or why does corrosion happen in a boiler
-near cracks
-metal near joint
-low or high pH
five advantages of fire tube boilers over water tube boilers
-Less expensive to purchase
-Easy to clean and repair
-Simple construction
-low fire cost
-quick response to load changes
describe a kingsbury thrust bearing
-Uses a thin film of oil
-supports weight up to 220 tons
-tramsmits axial load to the foundation or machine support of the rotating equipment
What is current measured in
amps
what is voltage measured in
volts
how is an ammeter connected
in series
What is a therm
unit of measurement for natural gas over time
-one therm is equal to 100,000 BTU’s
Why are hollow tubes stronger than solid tubes
larger moment of inertia for bending
Name three factors that cause scale
-calcium
-magnesium
-poor water treatment
Give four reasons to treat boiler water
-reduce scale
-prevent foaming and priming
-reduces corrosion
-improves efficiency
When do you blow down the gauge glass? Why do this
-regular scheduled intervals
-remove any blockage within the water or steam pipework that connects the boiler to gauge glass
Describe the operation of a centrifugal pump
spinning impeller draws liquid into the center and discharges it from its outer edge into a spiral casing
how is the discharge pressure of a centrifugal pump stage determined
-calculation of impeller size
-impeller speed
-friction losses
-size of suction and discharges
describe a motor driven rotary pump
-positive displacement pump
-do not use valves
-efficient on both low and high viscosity liquids with a low NPSH requirement
what is a vent condensor
small condenser located on the vent of a larger condenser pulling air and vapor to discard the air to atmosphere. The vapor is condensed and flows to the hot well
What is double flow turbine
steam enters the center of the turbine and flows both directions parallel to the shaft balancing end thrust
What is bleeder turbine
allow for extraction of steam at various pressures from the turbine for other processes
what is mixed turbine
admits steam of various pressures into the turbine
what do you check on the turbine hourly
pressure and temp,
-bearings,
-cooler,
-steam pressure,
-abnormal noise
what do you check on the turbine monthly
check oil for water and sludge,
-oil strainer,
-governor,
-overspeed trip,
-vacuum breakers,
-condenser
what do you check on the turbine yearly
dismantle and check for corrosion
-wear dirt and scale
-oil and steam passages
-erroded blades
-valve seats
-lubrication system
-governor parts
-vacuum pump
-air leaks
When installing a steam header what (8) factors must be taken into consideration
-adequate support
-expansion and contraction
-operating pressure
-velocity and pressure drops
-insulation
-valve location
-trap location
-flow of condensate
name four methods of welding
-stick
-mig
-fcaw
-gtaw
if you have a 200’ steam line carrying 150lbs of steam pressure in a 90 degree room how much room is needed for expansion
(387.9-90) x (12x200) x .00000734
297.9 X 2400 x .00000734=
5.24”
list six qualities of lubrication oil
-filterability
-low viscosity
-hold up under heat
-good cooling properties
-low acid
-good moisture barrier
define relative humidity
percentage of moisture contained in the air as compared to the amount of moisture the air could contain at that temperature
what is a congealing tank
-brine is frozen during off peak hours
-able to handle high peak loads with uniform temp
what is brine holdover in ammonia
stainless steel tank containing an evaporator coil surrounded by liquid. as the compressor runs the liquid freezes. once the compressor is turned off the frozen solution continues to absorb heat extending the off cycle
what is a king valve
located on the outlet of the reciever or branch line used to confine the refrigerant so repair can be made
on an enclosed compressor how is ammonia removed from the crank case
a bypass line is installed from the crank case to the suction line
seven advantages of a rotary pump
-self priming
-low NPSH requirement
-can handle high viscosity liquids at a high efficiency
-wide speed range
-available for low capacity, high head, or high capacity applications
-capable of high suction lifts
-slip is low
what forms of energy losses are in a turbine
-steam leakage between stages
-eddy friction losses
-windage friction
-radiation
-mechanical friction
-steam velocity losses from last stages to condenser
what is seal stripping
sealing stripes between turbine stages to reduce leakage between stages
what is a dummy pistion
-large disk that is part of the rotor
-different pressure on each side creating a thrust action toward the high pressure side balancing end thrust
-located between impulse and low pressure section
which tubes on a stirling boiler are beaded
-ever other tube in the bottom row of the top drums for drainage
-every other tube in the top of the mud drum
why are the tubes on a stirling boiler bent
so they enter the drum radically, this allows the tubes to be properly expanded into the drum and improves circulation
how many pounds of air are required to burn one pound of carbon
air is 23.15% o2
1/.2315=4.319
4.319x2.67=11.53 lbs of air
