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38 Cards in this Set
- Front
- Back
What is the main disadvantage of a fire tube boiler? |
As pressure and temperature increase, the thickness of the shell will also increase. |
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A water tube boiler is considered to be a boiler that has: |
Two drums and tube system used for direct heat transfer |
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Steam generating units used in power generation primarily produce: |
Superheated steam |
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A miniature boiler is built in accordance with which ASME section? |
Section 1 (Power boilers) |
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A heating boiler is built in accordance with what ASME section? |
Section 4 (Heating boilers) |
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What device will a power generation steam plant use between the high pressure and low pressure turbines? |
Reheaters |
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What is the primary function of an internal separator? |
To separate wet saturated steam into dry saturated steam |
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The feedwater distributor pipe is located in the: |
Lower water space of the steam drum |
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Retractable sootblowers are used for cleaning: |
Radiant superheaters |
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The piping system from the steam generator to the turbine would be built in accordance with what ASME code? |
B 31.1 (Power piping) |
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Which agency would rate a steel high pressure boiler? |
SBI (Steel Boiler Institute) |
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How are boilers built to ASME section 1 rated? |
Gross rated |
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Heating boilers are generally net or gross rated? |
Net rated |
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What ASME code are high pressure boilers covered under? |
Section 1 (Power boilers) |
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Why are fire tube boilers limited to a specific capacity? |
Because as the capacity increases, the thickness of the shell increases. |
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What are the advantages of firetube boilers? |
Capable of handling rapid fluctuations in steam demand Efficient operation with minimal water treatment Tubes are easy to clean to maintain fuel efficiency |
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What is the main disadvantage of fire tube boilers? |
They do not respond rapidly to a large change in load because of their large volume of water at saturation temps |
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Why do water tube boilers become.more cost effective in large capacities? |
Because the shell on the steam drum is smaller and can therefore be thinner |
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What are the advantages of a water tube boiler? |
Most of their water in in the tubes which allows them to respond quickly to large changes in load demand |
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What are the disadvantages of water tube boilers? |
The tubes are more difficult to clean and they require more water treatment. |
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Where are the moisture separator devices located? |
Inside at the top of the steam drum, before the steam leaves the nozzles. |
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What type of steam is used in power generating plants? |
Dry steam |
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What is misting? |
Misting is when many small particles of water become entrained in the steam flow. |
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Where is the skimmer installed? |
In the steam drum, just below the NOWL |
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What type of valve is used on the blowdown line? |
A balancing type valve (angle or y pattern) |
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What are 2 types of economizers? |
Integral and separate |
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What are the advantages of an economizer? |
Increased boiler efficiency, heat from flue gases is recovered. Less shock to the boiler drum (economizer preheats cold water entering the drum) |
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What are the disadvantages if economizers? |
Increased fan power is required (economizers increase resistance to combustion/ flue gas flow Increased resistance to feedwater flow Corrosion of internal and external surfaces More maintenance (economizers must be kept clean for efficiency) |
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Superheaters are classed as either: |
Internal ot separately fired |
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A convection superheater has a rising steam temperature characteristic. Describe what this means. |
As steam temp increases, output fuel (firing rate) increases |
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A radiant superheater has a falling steam characteristic. Describe what this means. |
The steam temp will be high at low loads (output) and will drop as the load increases. (More heat at a lower rate of flow) |
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Name 3 benefits of superheat. |
Reduced consumption No condensation losses Less moisture in steam to erode turbine blades and reduce efficiency |
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What are the 2 types of sootblowers? |
Stationary and retractable |
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Why is it important to remove soot and flyash from the boiler firebox and flues? |
Soot and flyash can build up on the boiler tunes and reduce efficiency of heat transfer and contribute to tube corrosion |
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What is the preferred cleaning medium for sootblowers? |
Superheated steam |
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What are the 3 methods of removing ash? |
Hydraulic (slurry/water) pneumatic (air removal) and mechanical (conveyor belts/boxes) |
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How do you calculate BHP from lbs of steam? |
lbs of steam ÷ 34.5 (lbs of water/hr) |
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How do you calculate lbs of steam from BHP? |
BHP × 34.5 (lbs of water/hr) |