Boiler Draft Equipment

Front 1

Define draft

Back 1

The process of supplying combustion air to the boiler furnace; a differential in pressure that will produce a flow of air.

Front 2

Primary air vs Secondary Air

Back 2

-Air which may be premixed with fuel before entering furnace.

-The remaining air necessary for combustion.

Front 3

Natural Draft

Back 3

Cold air enters the furnace in a continuous process due to the heated air causing a pressure differential.

Front 4

Most popular type of chimney and why

Back 4

Steel; because of the low first cost and may be erected on the structure that supports the boiler. However, high maintenance costs.

Front 5

Induced Draft and advantage

Back 5

Velocity of the gases are increased, creating a partial vacuum in furnace

*created negative pressure in the furnace preventing toxic gases from entering the boiler room

Front 6

Forced Draft and advantage

Back 6

forcing air into the furnace, creating a positive pressure in furnace. Called a pressurized furnace.

*deals with cool air so fan life is longer

Front 7

Balanced Draft

Back 7

Used in larger boilers, combining a forced draft fan and an induced draft fan.

Front 8

Advantages of mechanical draft

Back 8

-Independent of atmospheric air temperatures

-Independent of chimney temperatures, as opposed to natural draft

-Mechanical draft can be regulated more accurately for fluctuating demands

-Better draft regulation = efficient combustion

-Chimney only needs to be tall enough to expel flue gases.

Front 9

Register/Damper pros and cons

Back 9

Register regulates airflow into the boiler furnace

Front 10

Fan Speed control pros and cons

Back 10

Most efficient operation of a fan is to only supply sufficient amount of air necessary.

However, for constant speed electric motors, other means are needed to control air flow.

Front 11

Outlet damper control pros and cons

Back 11

A damper acts as a throttle valve to control air output of a fan.

However, may be a less efficient use of power for lower loads.

Front 12

Inlet damper control pros and cons

Back 12

Less power required to drive the fan at lower loads.

Somewhat more complicated

Front 13

Variable speed coupling pros and cons

Back 13

More control of fan speed and least amount of energy required at varying speeds compared to other damper controls.

Higher initial cost

Front 14

3 types of draft measuring equipment

Back 14

U-tube manometer: U-shaped tube with water filled about half way and pressure differentials used to judge changes.

Inclined U-tube manometer: More movement with smaller pressure changes so allows for more precise readings.

Diaphragm draft gauge: Uses materials such as rubber as a diaphragm to measure pressure changes and used with a push rod to operate a pointer.

Front 15

Size of air openings in buildings, why are they important?

Back 15

Important because lack of air flow in the building can cause the boiler to draw air from within the building and cause inadequate air flow leading to possible boiler explosions. Also, the lack of air entering the building can cause a partial vacuum in the building which may lead to structural failure, the collapse of walls, doors, and windows.

Front 16

Define combustion as it pertains to boilers.

Back 16

Burning of a fuel to produce heat.

Front 17

3 combustible elements

Back 17

Hydrogen, Carbon, Sulphur

Front 18

Non-combustible elements

Back 18

Moisture, Ash, other trace elements.

Front 19

3 T's of combustion

Back 19

enough air + Time, temperature, and turbulence

Front 20

2 reasons for presence of moisture in fuel

Back 20

Moisture absorbed from the atmosphere or from two atoms of hydrogen and one atom of oxygen being combined from the fuel.

Front 21

Of the three combustible elements, which comprises the largest percentage of it?

Back 21

Carbon

Front 22

Which substance indicates an incomplete combustion in the furnace?

Back 22

Carbon monoxide

Front 23

Symbols representing complete combustion

Back 23

Carbon and Oxygen: C + O2 = CO2

Hydrogen and Oxygen: 2H2 + O2 = 2H2 + O2

Sulphur and oxygen: S + O2 = SO2

Front 24

3 reasons why production of carbon monoxide is undesirable

Back 24

Incomplete combustion = waste of fuels and loss of heating value

escaping of this gas is dangerous

contributing factor to pollution

Front 25

what makes up air and how much percentage?

Back 25

21% oxygen and 79% nitrogen

Front 26

Difference between theoretical air and excess air

Back 26

Theoretical air is the amount of air required to supply just enough oxygen for combustion, however, in reality it takes more for the oxygen to actually mix with the fuel.

Front 27

6 components of flue gas, assuming complete combustion

Back 27

H2O, CO2, SO2, O2, N2, and ash in a divided state.

Front 28

indications and possible outcomes of incomplete combustion

Back 28

appearance of CO, and soot in the flue gases, which is a waste of fuel and may lead to furnace explosion

Front 29

Combustible components of coal and heating value

Back 29

Hydrogen, Carbon, Sulphur, 25600kJ/kg

Front 30

Combustible components of fuel oil, heating value, and advantages compared to coal

Back 30

Carbon and hydrogen, 45360kJ/kg

Less storage space required, amount fed to furnace more easily controlled, less handing equipment and labor required, burn with less residuals and are efficient to use.

Front 31

Combustible components of gaseous fuels, heating value, and advantages compared to coal

Back 31

Hydrocarbons, methane (80-90%) and ethane (10-20%)

No ash produced when gas is burned

Little handling equipment,

Amount fed to the furnace is easily controlled

Easily mixed with air

No storage space required

Front 32

3 types of mechanical stokers

Back 32

Underfeed, crossfeed, overfeed

Front 33

What is pulverized coal? Advantages

Back 33

Pulverized coal is coal ground to a fine dust or powder. Mixes better with combustion air, cheaper grade coal can be burned and more control over combustion.

Front 34

Define atomization

Back 34

Breaking up of oil to a fine vapour or spray. Heavy oils must be heated prior to atomization.

Front 35

Define refractory and 3 reason for deterioration of it

Back 35

Refractory is material that can withstand very high temperatures.

Ash slag forms, corrodes and erodes refractory

Ash in oil causes ash clinkers will cause portions to break away

Impingement of flame on brickwork

Front 36

4 areas of modern boiler refractory is still used in

Back 36

Burners throats

Inspection door openings

combustion chambers

baffles

Front 37

Flow regulation for:

Solid fuel

Fuel Oil

Natural Gas

Back 37

-Adjustment of primary air flow(for pulverized coal), grate or stoker speed.

-Solenoid valve or control valve

-" "

Front 38

Why is knowing the percentage of CO2 important?

Back 38

By finding the percentage of CO2 in the flue gases, since amount of CO2 produced is constant, you can find the amount of excess air.

Front 39

How is a a bed in a fluidized bed boiler fluizided?

Back 39

Forcing high pressure air up through the bed of the fuel

Front 40

2 types of atmospheric fluidized bed furnaces

Back 40

Atmospheric fluidized bed combustion

Pressurized fluidized bed combustion

Front 41

what is used to reduce CO2 emissions in a fluidized bed?

Back 41

limestone

Front 42

Advantages of fluidized bed combustion

Back 42

Flexibility of fuel choices

Less maintenance

smaller plant size

less fuel preparation

simplified fuel feed

pressurized combustion chamber

Front 43

Flexibility of fuel for FBC

Back 43

ow grade fuels with high moisture

high ash fuel

wood

heavy oil tar sands

coal mine tailings

waste gas refuse

shredded scrap tires

Front 44

Disadvantages of FBC

Back 44

high power requirements for combustion air

carryover

poor combustion control at low operating rates

Front 45

Each boiler must have 1 pressure relief valve unless it has more than ____ of heating surface

Back 45

47m^2

Front 46

Safety valves must be large enough to discharge all the steam a boiler can produce without allowing the pressure to exceed the maximum allowable working pressure by more than ___

Back 46

6%

Front 47

each steam heating boiler shall have one or more officially rated safety valves of the spring pop type, adjusted and seasled to discharge at a pressurte not to exceed:

Back 47

100kPa

Front 48

The safety valve capacity of a steam heating boiler shall be such that, with the fuel burning equipment installed and operated at maximum capacity and all steam outlets are closed, the pressure cannot rise above the maximum allowable working pressure by an amount of:

Back 48

35kPa

Front 49

4 ASME code requirement respecting the mounting of safety valves

Back 49

-the safety valve shall be installed with its spndle in the vertical position and located in the highest practicable part of the boiler proper

-connected directly to a tapped or flanged opening in the boiler

-not connected to an ainternal pipe in the boiler

-no shutoff of any description shall be placed between the safety or safety release valve and the boiler

Front 50

Try lever test

Back 50

Pull the try lever and let steam escape for 5-10s

Done to ensure that steam is escaping properly

Will not ensure that it will open at its set pressure

should be done only when the pressure is up to at least 35kPa

if it simmers after closing, try again. if it happens again it needs to be repaired

Front 51

pop test

Back 51

Increasing steam pressure of boiler to a point where the safety valves are set to pop.

If it fails, drop the pressure back and test the try lever. if it fails again it must be repaired or replaced

Front 52

Difference between safety relief valves for hot water boilers and steam heating boilers.

Back 52

The safety relief valve on a hot water boiler is basically the same as a pop safety valve used on steam heating boilers, however it does not have a blowdown adjustment ring and a bottom guide.

Front 53

4 reason for frequent opening or spilling of a pressure relief valve on a hot water heating boiler.

Back 53

-scale accumulation on the valve seat, preventing it from closing tightly

-varying pressure on the supply line and may occasionally exceed the setting of the valve

-relief valve is defective or designed for the wrong pressure range

-the hot water system is water logged

Front 54

Describe temperature relief device

Back 54

Device meant to reduce the temperature of hot water systems from reaching dangerously high temperatures. A combination pressure-temperature relief device alleviates pressure from a hot water system initially, but if the temperature is also too high, a wax filled probe melts and open the valve for cool water to enter the system.

Front 55

Direct liquid level detection vs indirect liquid level detectionq

Back 55

Direct: Usually through the use of gauge glasses attached to the vessel itself and showing the water level over some vertical distance.

Indirect: Remote detection that can be seen from the operating floor. Common methods are with diaphragms or remote-water-level indicators.

Front 56

What is used to prevent large amounts of water from escaping in the event of a gauge glass breaking?

Back 56

Through many safety shutoff devices and some employing stainless steel balls that block the fluid passages when large amounts of water suddenly rush out of them.

Front 57

3 advantages to mounting gauge glass on a water column instead of directly on the boiler

Back 57

-Traps sludge or sediment

-Dampens any agitation of the water

-Provides a place for installation of high and low level alarms like try cocks.

Front 58

W#hat are try cocks used for?

Back 58

Point level detection when gauge glass is being replaced.

Front 59

Upper operating pressure limit for round tubular gauge glasses.

Back 59

2800kPa

Front 60

3 types of gauge glasses

Back 60

Round tubular gauge glass

Armored-type/Flat gauge glass

Transparent glass gauge

Front 61

Describe transparent gauge glass

Back 61

One piece central chamber with cover plates on each side that hold the two glass windows

Front 62

Reasons for and effect of gauge glass failure

Back 62

Failure due to corrosion from alkalinity and silica depletion at higher temperatures. Misalignment of fittings.

Gauge glass failure means not being able to tell the water level properly without secondary gauge glasses or try cocks.

Front 63

Use of top, middle and lower trycock

Back 63

Upper: If opened and steam comes out, water is at a lower level. If mixture of steam and water appears, level is at or above this point. Reduce flow of water or drain water through blowoff valve.

Middle: If opened and steam appears, water is at lower level, increase flow of water to restore level. If mixture of steam and water appears, no action is necessary.

Lower: If mixture appears, water is above this point. If steam appears, shut off boiler due to low water levels.

Front 64

2 safety precautions when replacing gauge glass.

Back 64

Face or portable shields should be used.

Front 65

Describe warming up newly replaced gauge glass on a steam boiler.

Back 65

Crack open the steam valve with the drain valve open to heat up the glass, then close the drain valve and open the water valve and steam valves fully after the water level stabilizes.

Front 66

Hopkinsons remote boiler water level indicator vs Igema remote indicator. What is the major advantage of the Igema?

Back 66

No moving mechanical parts.

Front 67

Decribe the operation of an "Igema" remote water level indicator.

Back 67

Increasing water level in the boiler forces the indicating liquid up on the indicator glass and displays the water level.

Front 68

6 purposes of a steam drum in a modern steam boiler

Back 68

-Stores steam so that load increases can be accomplished quickly and smoothly.

-Allows for the installation of equipment that will separate water out of the steam before the steam goes to superheaters, turbines or other processes.

-Place for installation of equipment that removes impurities from the steam.

-place from which heavy concentrations of impurities are removed via the blowdown line.

-for the distribution of feedwater into the water circuits of the boiler

-for the introductions of water treatment chemicals.

Front 69

Define drum internals

Back 69

All the devices installed within the boiler steam drum, including various types of steam separators, chemical feed lines, boiler feedwater and continuous blowoff lines

Front 70

Purpose and operating principles of a primary cyclone steam separator.

Back 70

Serves to separate water and steam from high pressure boilers.

Steam and water swirl within the cyclones at high velocities, forcing the water to the periphery of the cyclones.

Front 71

Dry pipe

Back 71

Redirects steam and water in lower pressure boilers. Sends water back into the boiler drum.

Front 72

Turbo separator

Back 72

Utilizes angled baffles called spinner blades that impart a spin to the water/steam mixture. The water is separated and heads down while the steam rises and enters a secondary separator.

Front 73

Secondary Separator

Back 73

Generally, rows of corrugated metal that cause steam to change directions many times while depositing water into the metal panels to be drained.

Front 74

Dryers/steam scrubbers

Back 74

Located at the top of the drum. Final contaminant removal before steam leaves the drum. Usually wire mesh or screen that pick up droplets of water. More complicated one are made from stainless steel wire and wash water that removes the silica from the steam.

Front 75

Internal feed pipe.

Back 75

Internal feed pipes are used to distribute feed water to the boiler without thermal shock and excessive turbulence. Some smaller boilers have short pipes that discharge water into baffles. Larger boilers have pipes that run the entire length of the boiler and are perforated. Water enters directly above the downcomers.

Front 76

Continuous blowdown pipe

Back 76

Located many centimeters below the normal water level. Used to discharge large concentrations of dissolved solids.

Front 77

Chemical feed pipe

Back 77

Used to distribute chemicals that control the amount of scale, corrosion and sludge within the boiler through the use of an internal pipe.