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Boiler > Boiler Final > Flashcards

Boiler Final Flashcards

1
Q

How does a Firetube Boiler operate?

A

hot gases of combustion travel through the tubes with water surrounding the tubes. Max pressure approx. 350 psi, BHP approx. 750 (HRT, Scotch Marine, Vertical Firetube).

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2
Q

Define Thermal Efficiency

A

ratio of heat absorbed by boiler water (boiler output) to heat available in the fuel (boiler input)

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3
Q

How does an Electrode Boiler operate?

A

Heat generated by current through boiler water because of conductivity

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4
Q

Why are Superheaters used?

A

creates Dry Steam superheated without water which reduces moisture to protect process equipment and adds heat energy for more work

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5
Q

What fuel oil type must be heated?

A

Fuel Oil 6

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6
Q

Define Pulverized Coal

A

fine powder (talcum-like) blown into the combustion chamber and burned in suspension

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7
Q

Define Natural Draft

A

flow of gases caused by temperature difference between column of air inside the chimney as opposed to column outside the chimney

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8
Q

When must Two Main Steam Stop Valves be used on a boiler?

A

ASME code: high pressure boilers in battery to common header with manhole openings and ample free-blowing drain between the stop valves

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9
Q

What type of valve is the Main Stop?

A

OS and Y Gate, may use Automatic Nonreturn Valve for one closest to the boiler

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10
Q

Why are OS and Y Gate Valves used for Stop Valves

A

Offer no restriction to steam flow and can easily determine position by looking at the stem

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11
Q

When are two Bottom Blowdowns required?

A

Boiler at or above 100 psi (2 valves mounted on same line: both slow-opening, or one quick-opening and furthest slow-opening)

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12
Q

Define Steam Quality

A

ratio of dry steam to total amount of water evaporated. Ex. 98% (98% steam, 2% water)

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13
Q

What is necessary to protect Superheater tubes from overheating?

A

during boiler warm up, open superheater Drain and leave open to allow steam to constantly flow to reduce heat. When boiler 25% or higher of boiler capacity, then close drain

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14
Q

How does a Steam Separator work?

A

Internal drum in steam drum increases steam quality by changing flow direction, causing heavier water droplets to separate from steam

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15
Q

What is the purpose of the Water Column?

A

to reduce turbulence in the water for a more accurate water level in the Gauge Glass

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16
Q

When are two or more Safety Valves needed?

A

Automatic, fully-open, pop-action valve. When boilers have more than 500 sq ft of heating surface or exceed 500 kW of input

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17
Q

What is the amount a Safety can exceed the MAWP?

A

Never more than 6% above the MAWP

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18
Q

What is a Fusible Plug?

A

A device with a core that melts and causes an audible alarm when exposed to a temp above its max temp. Fire side or water side of boiler shell. Last warning before highest heating surface overheats

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19
Q

What is the purpose of a Vent?

A

Valve connected to top of a boiler that allows air to ve removed from the boiler when filling and heating. Allows air to be drawn in when cooling or draining boiler

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20
Q

What is the arrangement of the Blowdown Valves?

A

When two valves are used both maybe slow opening, screw-type or one quick one slow. Quick opening must be closest to boiler shell

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21
Q

What is the purpose of Steam Traps?

A

Accessory that removes air and noncondensible gases and condensate from steam lines and heat exchangers without a loss of steam

22
Q

What is the purpose of the Low Water Fuel Cutoff and when is it designed to operate?

A

Deenergizes the burner limit circuit and shuts down the burner if water level drops below safe level.

23
Q

Define Try cocks.

A

Secondary means of water level indicator located on water column and used instead of gauge glass

24
Q

Define Swell in a boiler.

A

When steam demand increases, steam is removed faster than it can be generated. Water in boiler momentarily rises with an increase in steam demand, which causes a sudden decrease in pressure. Lower pressure causes water to flash into large steam bubbles taking up more room.

25
Q

What is Caustic Embrittlement?

A

Type of corrosion in which boiler metal becomes brittle due to alkaline materials accumulating in cracks and crevises. Carbonates, bicarbonates, and hydroxides affect alkalinity. Riveted and rolled tubes are more susceptible than welded boilers

26
Q

What type of pump is a Reciprocating Feedwater Pump?

A

Positive Displacement

27
Q

Define pH.

A

Scale of acidic to alkaline 0 - 14, 7 being neutral

28
Q

What do the three numbers on the Reciprocating Pump name plate stand for?

A

Diameter of the steam piston, diameter of the water piston, and length of pump stroke

29
Q

Define TDS.

A

Total Dissolved Solids, measurement of concentration of dissolved impurities in boiler water. Measured with a conductivity meter

30
Q

How does an Economizer work?

A

Heats feedwater by passing it through a finned-tube heat exchanger placed in the path of the gases of combustion, typically between the breeching and the outlet dampter

31
Q

Name the types of Blowdowns.

A

Bottom, Surface, Continuous, Automatic, Timer Controlled Automatic, Concentration Controlled Automatic

32
Q

Define Shrink in a boiler.

A

Process where the water level in a boiler momentarily drops with a decrease in steam demand. Causes sudden increase in steam pressure, where less water turns to steam which takes up less space. Can cause priming or carryover if feedwater is fooled into sending more water to the boiler

33
Q

What is Viscocity?

A

Measurement of internal resistance of a fluid to flow

34
Q

What type of boiler is a Scotch Marine?

A

Firetube with an internal furnace

35
Q

When is a Steam-driven Feedwater Pump required?

A

Boilers fired with solid fuel (coal) may have one

36
Q

What is the concept of a Packaged Boiler?

A

Boiler that arrives completely assembled from the factory. Quality of construction better, but pounds of steam are limited by shippable size of boiler

37
Q

Name the four systems required to operate a boiler?

A

Fuel, draft (combustion air and exhaust), feedwater, steam

38
Q

What gas system is safer?

A

Low Pressure Natural Gas because gas leaks are less likely due to lower pressure

39
Q

When are two or more feedwater pumps needed?

A

ASME requires two means of supplying feedwater if boiler surface area is over 500 sq ft

40
Q

Why do we require Primary Air?

A

Supplied to burner to atomize fuel oil or convey pulverized coal and control the rate of combustion, thus the amount of fuel burned

41
Q

Why do we require Secondary Air?

A

Supplied to furnace by draft fans to control combustion efficiency by how completely fuel is being burned

42
Q

What is a Boiler Heating Surface?

A

Part of the boiler with water on one side and combustion gases on the other. Heat transfer surface

43
Q

What is the purpose of Tube Passes in a boiler?

A

By increasing the passes of combustion gases against the heating surface, more heat can be absorbed by the boiler

44
Q

What allows for manual reset to be reset?

A

The Manual Reset Valve cannot be opened until the Pilot is lit and proved. The Vaporstat is between the manual reset valve and the zero gas governor. It is deenergized when there is insufficient gas pressure.

45
Q

Define Therm.

A

100,000 Btu

46
Q

What is the required range of a Steam Pressure Gauge?

A

1 1/2 to 2 times the safety valve pressure rating. Center part of any gauge is the most accurate, this is why

47
Q

What is a Deaerator?

A

Feedwater heater operating under pressure to separate oxygen and other gases from the water venting to the atmosphere. Can store condensate and removes dissolved gases from feedwater

48
Q

What are the required elements of combustion?

A

Heat, fuel, oxygen

49
Q

Define Dry Layup.

A

Long-term storage of a boiler with all the water drained out. Allow for thorough cleaning and boiler inspection

50
Q

How often must we check the Flame Scanner?

A

At least once a week

51
Q

What is a Hydrostatic Test?

A

Main Steam Stops are secured along with drains between them left open, remove high and low water alarm acturators, remove or gag safety valve, and increase water pressure to 1 1/2 times safety valve by using a hand pump. Applied to boilers after major repair to test integrity of the shell, drums, or tubes

52
Q

Define Watertube Boiler.

A

Boiler with water inside the tubes and combustion gases around the tubes. Designed for higher pressures up to the Critical Pressure (density of water and steam are equal) 3206 psi

Boiler (2 decks)

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