Term
| What are the three endpoints for a boiler? Which is the most serious? |
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Definition
Endpoint of Combustion
Endpoint of Moisture Carryover
Endpoint of Water Circulation |
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Term
| What are the several types of superheater orientation? Describe? |
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Definition
Radiant: line of sight of burner
Convection: shielded by screen tubes
???
Separately Fired: separate set of burners for the superheater |
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Term
| If pressure in the steam drum gets too high, which safety valve should open first? Why? |
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Definition
| The safety valve on the superheater. If there was no steam flowing through it, the tubes would melt. |
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Term
| Name three desuperheat methods. Desceribe each briefly. |
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Definition
Control Desuperheater:???
Attemperator: add small amounts of water to superheated steam to cool it
Auxiliary Desuperheater: ??? |
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Term
| How does efficiency change with boiler pressure? |
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Definition
| More pressure = more efficient |
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Term
| How much should the increase in feedwater temperature be as it is heated by the exhaust gas (in the economizer)? |
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Definition
| Feedwater up by 40% of exhaust gas heat loss |
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Term
Name several advantages of an economizer.
Name several disadvantages. |
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Definition
Advantages:
Increased efficiency
Lower risk of thermal shock
Disadvantages:
Increased fire hazard
Increased corrosion/leak hazard
Increased maintenance |
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Term
| Name the several types of fuel delivery systems for a furnace. Describe each briefly. |
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Definition
Straight Mechanical: single pipe
Return Flow: recircs back to the day tank
Steam Atomization: duh
Rotary Cup: low pressure applications; spinning bowl spreads fuel |
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Term
| What is the chemical reaction for COMPLETE combustion? |
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Definition
CH3 + O2 --> CO2 + H20
What's important is that you yield CO2 |
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Term
| What is the chemical reaction for INCOMPLETE combustion? |
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Definition
CH3 + O2 --> CO + H20
What's important is that you yield CO (so you can make acids) |
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Term
| List four fuel characteristics. Explain why each is important. |
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Definition
Viscosity: how much the fuel must be heated
Specific Gravity: How dense the fuel is (for ballasting)
Cat-Fine content: too much plastic catalysts gum up machinery
Energy Density: how far can the ship go on the amount of fuel on hand? |
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Term
| What is Dulong's Formula for High Heating Value? |
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Definition
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Term
| Are all rotary pumps positive displacement pumps? |
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Definition
| Yes. Centrifugal pumps don't count; they're their own category |
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Term
| What does the slide valve on a reciprocating pump do? |
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Definition
| Directs the steam/air to the correct side of the drive piston. |
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Term
What does a diffuser ring do?
How is it different from a volute? |
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Definition
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Term
What are the three types of impellers?
Which type has the greatest throughput? |
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Definition
Axial Flow
Mixed Flow
Radial Flow (greatest) |
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Term
| Explain the three numbers used to describe reciprocating pumps. |
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Definition
1st: Power cyl. O.D.
2nd: Driven cyl. O.D.
3rd: Length of stroke |
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Term
| What sends water to the waterwall tubes? |
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Definition
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Term
| What do you call the flat-ish end of the steam drum? |
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Definition
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Term
| What slows down the circulation of water in a naturally-circulated boiler? |
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Definition
| Friction between water and tubes/drums |
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Term
| Describe water's saturated condition? |
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Definition
| When water vapor is in contact with boiling water and is at the same temperature. |
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Term
| Why is superheated steam used in propulsion engines instead of saturated steam? |
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Definition
| It can facilitate higher pressures (thus expand more as it crosses the turbine)than saturated steam. |
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Term
What is latent heat?
What is sensible heat? |
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Definition
Latent: heat that changes a substance's phase without changing its temperature.
Sensible: changes the substances' temperature; not phase. |
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Term
| How does an Accelerated Natural Circulation boiler make water circulate faster? |
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Definition
| Angle the generating tubes more. |
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Term
| What do the screen tubes protect? |
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Definition
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Term
| What factors dictate the generating capacity of a boiler? |
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Definition
Number of burners
Relative size of tubes and downcomers
Heat-absorbing surface area |
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Term
| Which endpoint should come first in a properly-designed boiler? |
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Definition
| Endpoint of Combustion (anything else means that there's damage occurring) |
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Term
| What two purposes do downcomers serve? |
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Definition
1. Distribute water within the water/mud drum
2. Increase the end-point of carryover |
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Term
| Which of the endpoints is most damaging to the boiler? |
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Definition
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Term
| What two purposes do the waterwall tubes serve? |
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Definition
1. Decrease the amount of refractory brick needed on the walls.
2. Allow increases in the combustion rate |
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Term
| Why are downcomers installed between the two casing walls of the boiler? |
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Definition
1. Increase circulation rates (by increasing the temperature differential)
2. Decrease the amount of heat they absorb |
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Term
| How is refractory brick secured to the casing? |
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Definition
| Slots in the brick engage anchor bolts in the wall. |
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Term
| What does a cyclone separator do? |
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Definition
| Causes the rising, wet steam to spin and start the release of moisture. |
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Term
| The main function of a desuperheater is what? |
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Definition
| "to maintain uniform steam flow through the superheater while providing auxiliary steam as required". |
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Term
| What is the operational difference between huddling chamber and nozzle-type safety valves? |
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Definition
| manner in which the steam pressure causes the initial valve opening. |
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Term
| What regulates the arc that a sootblower sprays through? |
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Definition
| The cam on the face of the blower |
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Term
| What indicates excessive soot accumulation? |
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Definition
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Term
| Which type of superheater has the flattest superheat temperature curve? |
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Definition
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Term
| At steady state, what regulates the temperature of the superheater? |
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Definition
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|
Term
What is the top of the steam drum called?
The bottom? |
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Definition
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Term
| If MAWP = 1000 psia, what should the hydro test pressure be? |
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Definition
| 1500 psia (as the safety factor is 1.5) |
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Term
| If a centrifugal pump is run with the discharge valve shut for a long period of time, what will happen? |
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Definition
| The liquid inside will overheat |
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Term
| What controls the admission of steam to the driven cylinder of a reciprocating pump? |
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Definition
| Pilot valve and operating rod |
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Term
| What allows the water-side of a piston pump to be double-acting? |
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Definition
| Each end of the cylinder has a suction and discharge valve. |
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Term
| Which pump type uses a liquid ring to pump air? |
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Definition
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Term
| What does a dirty stack indicate? |
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Definition
1. Too little excess air
2. Dirty burners
3. Soot must be blown |
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Term
| What does the presence of chlorides in boiler water indicate? |
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Definition
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Term
| What minerals cause scaling? |
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Definition
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Term
| What do you do if a mechanical seal leaks? |
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Definition
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