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PWEN- Controls & Instrumemtation > Controls & Instrumentation > Flashcards

Controls & Instrumentation Flashcards

1
Q

In nearly all LP steam heating systems the feedwater:

a) Is usually condensate
b) Requires daily close scrutiny of chemical values
c) Is a high make-up percentage
d) Must be deaerated
e) Requires preheating in an economizer

A

a) Is usually condensate

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2
Q

When a boiler equipped with a combination feedwater control and low water cut-off device shuts down due to a low water condition:

a) The feedwater flow will also stop
b) The level must be restored to above the cut-off line before the unit can be restarted
c) It can be restarted by simply resetting
d) A manual reset switch must be used
e) A pre-purged will not be necessary

A

b) The level must be restored to above the cut-off line before the unit can be restarted

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3
Q

An electric feeder valve will:

a) Eliminate the need for low-water fuel cutoff
b) Prevent a low-water trip
c) Open before the low-water cutoff line is reached
d) Require manual action to open
e) Open after the nit trips on low swater

A

c) Open before the low-water cutoff line is reached

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4
Q

The result of a condensate receiver that is too small could be

a) High boiler water level(s)
b) Loss of condensate to the sewer
c) Loss of make-up water
d) Unacceptable high steam pressures
e) Low make-up water flow rates

A

b) Loss of condensate to the sewer

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5
Q

The feedwater supply to most heating boiler is controlled by a ____________ switch

a) Solenoid
b) Float
c) Differential pressure
d) Drum level
e) Pressure

A

b) Float

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6
Q

As a general rule the size of the condensate receiver should be large enough to hold a volume of condensate equal to the water evaporated by the boiler in a/an ______ hour period

a) Two
b) One and one half
c) One
d) three quarters
e) One half

A

e) One half

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7
Q

Prior to a boiler safety valve popping during routine boiler operation:

a) A try lever test should be performed
b) The pressure gage should be checked
c) The high limit switch should be open
d) The feedwater pump should stop
e) The high level alarm should sound

A

c) The high limit switch should be open

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8
Q

A test lead or “jumper wire” is required when testing:

a) High steam pressure or water temperature limiting controls
b) A high gas pressure fuel cutoff switch
c) A safety valve with the test lever
d) the low water fuel cut-off switch
e) A low gas pressure fuel cut-off

A

a) High steam pressure or water temperature limiting controls

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9
Q

Modulating burner controls operate by regulating:

a) Steam flow and fuel flow
b) Fuel temperature and air flow
c) Fuel flow, air flow, and feedwater pressure
d) Fuel flow and air flow
e) Fuel flow and atomizing steam flow

A

d) Fuel flow and air flow

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10
Q

A low fire switch:

a) Is a type manual override
b) Takes no part in the start-up of an automatic boiler
c) Acts as an interlock to ensure minimum damper setting
d) Utilizes a thermal element for its operation
e) Is a normally closed switch

A

c) Acts as an interlock to ensure minimum damper setting

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11
Q

High limit temperature controls:

a) Increase air flow to the boiler if temperature limits are exceeded
b) Open a 3-way mixing valve to add cold water to the hot water to reduce the water temperature
c) Shut off the fuel if the water temperature is too high
d) Are required under section II of the ASME codes
e) are required on steam boilers

A

c) Shut off the fuel if the water temperature is too high

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12
Q

A thermal element is:

a) Used to measure pressure
b) Capable of sensing temperature and converting it to a pressure signal
c) A type of open system
d) Used to measure heat content
e) Commonly termed as “Aquastat”

A

b) Capable of sensing temperature and converting it to a pressure signal

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13
Q

Combustion air safety switches are commonly found:

a) On a natural draft boiler
b) On hot water boilers only
c) On boilers utilizing a forced draft fan
d) As non-interlocking devices and take no part in a start up
e) On gas fired boilers only

A

c) On boilers utilizing a forced draft fan

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14
Q

During the start-up, a boiler equipped with an automatic control system and a flame, scanning device, the main fuel supply valve:

a) Must be opened before ignition can take place
b) Can be opened before the flame scanner sees a flame
c) Can be opened any time during the start up sequence
d) Should be opened as soon as the pilot valve opens
e) Must be closed before ignition

A

e) Must be closed before ignition

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15
Q

A flame scanner:

1) Requires a photoelectrical cell
2) Responds to temperature changes
3) Requires a clear line of sight to the flame
4) Produces a steady voltage signal

A

2) Responds to temperature changes

3) Requires a clear line of sight to the flame

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16
Q

Flame safeguard devices:

a) Should be tested following the manufacturers instructions
b) Should be kept as far as away form the fire as possible
c) Should not be cleaned except by a qualified serviceman
d) Should be kept cool enough to be touched by hand
e) Are all unaffected by heat

A

a) Should be tested following the manufacturers instructions

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17
Q

Which of the following is a flame, sensing device?

a) Thermopile
b) Heat sensing control
c) Stack relay
d) Cut-off valve
e) Scanner

A

e) Scanner

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18
Q

A thermocouple:

a) Consist of two similar wires
b) Produces a electrical signal
c) Senses infrared light from the flame
d) Senses changes in fuel line pressure
e) Senses changes in air pressure

A

b) Produces a electrical signal

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19
Q

The function of a flame failure device is to:

a) Shut off the fuel supply when the pressure gets too high
b) Shut off the fuel when the burner flame goes out
c) Shut off the fuel when the fuel temperature is high
d) Shut off the feedwater supply to the boiler
e) De-energize the fan and feedwater systems

A

b) Shut off the fuel when the burner flame goes out

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20
Q

A pneumatic control system:

a) Uses a sensing device to change pressures in the control line
b) Requires an internal air supply
c) Always uses pressure actuated final controlled devices
d) Is not used to control air flow for ventilation

A

a) Uses a sensing device to change pressures in the control line

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21
Q

A pneumatic control system consist of which of the following essential parts:

1) an air compressor with storage tnak, filter, and reducing valve
2) Air piping and tubing forming the air distribution system
3) Controllers such as rheostats
4) Controlled devices such as convectors valves, zone valves, and damper operators

A

1) an air compressor with storage tnak, filter, and reducing valve
2) Air piping and tubing forming the air distribution system
4) Controlled devices such as convectors valves, zone valves, and damper operators

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22
Q

Dual temperature thermostats are set at two different temperatures and the transfer from one to the other is made by, changing the supply air pressure from:

a) 3 to 15 KPa
b) to 25 KPa
c) 20 to 90 KPa
d) to 100 KPa
e) 100 to 125 KPa

A

e) 100 to 125 KPa

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23
Q

In the pneumatic control nozzle and vane system the:

a) Vane approaches the nozzle increasing air pressure
b) Vane approaches the nozzle decreasing air pressure
c) Nozzle pressure increases moving the vane further away
d) Nozzle pressure decreases allowing the vane to move closer
e) Vane and nozzle move to maintain equilibrium

A

a) Vane approaches the nozzle increasing air pressure

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24
Q

In a non-bleed type controller the device that senses a change in room temperature is the:

a) Sensing valve
b) Bellows
c) Set point gauge
d) Temperature switch
e) Feedback switch

A

b) Bellows

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25
Q

A non- bleed controller bleeds control air:

a) When the supply pressure is decreased
b) When the supply pressure is increased
c) Non-bleed controllers do not bleed air
d) When the control air pressure is increased
e) When the control air pressure is decreased

A

e) When the control air pressure is decreased

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26
Q

Thermostats may be classified a cording to there:

a) Application
b) Type of temperature sensing element
c) Type of control action provided
d) temperature range
e) All of the above

A

e) All of the above

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27
Q

Controls motors are divided into two classifications:

a) Large and small
b) AC and DC
c) Valve operators and dampers operators
d) High voltage and low voltage
e) Pump and fan controllers

A

c) Valve operators and dampers operators

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28
Q

Using electricity for control purposes has the following advantages:

a) It is readily available
b) The wiring is usually simple and easy to install
c) Signals from sensing elements can produce one output
d) Controllers/actuators do not require an air supply

A

a) It is readily available
b) The wiring is usually simple and easy to install
d) Controllers/actuators do not require an air supply

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29
Q

In a basic control system an example of a controlled device is:

a) A fuel valve
b) A damper
c) A diverter valve
d) An electric switch
e) all of the above

A

e) all of the above

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30
Q

ON-OFF thermostats are equipped with:

a) An open contact switch
b) A high temperature switch
c) A low temperature switch
d) A high voltage switch
e) A low voltage switch

A

a) An open contact switch

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31
Q

the electric resistance of a thermistor will:

a) Decrease when cooled
b) Decrease when heated
c) Increase when heated
d) Remain constant with temperature changes
e) None of the above

A

b) Decrease when heated

32
Q

A pressure sensor converts pressure changes into:

a) an electrical signal
b) A change n electrical resistance
c) variables such as voltage, current or resistance
d) Air pressure
e) A temperature change

A

c) variables such as voltage, current or resistance

33
Q

Electronic controllers can be divided into two types:

a) On or Off
b) Modulating and direct acting
c) Indirect and direct acting
d) On or off and modulating
e) Actuators and relays

A

d) On or off and modulating

34
Q

A reverse acting controller:

a) Increases its output signal on a decreased output signal
b) Decreases its output signal on a increased input signal
c) Increases its output signal on a increased output signal
d) Decreases its input signal on a increased output signal
e) Decreases its output signal on a decreased input signal

A

b) Decreases its output signal on a increased input signal

35
Q

Transmitters or transducers can measure:

a) temperature
b) Air flow
c) Air flow velocity
d) Water flow
e) All of the above

A

e) All of the above

36
Q

the device used to maintain a constant pressure throughout a pneumatic control system is called a:

a) Reducing valve
b) Control regulator
c) Pneumatic valve
d) Balancing valve
e) None of the above

A

a) Reducing valve

37
Q

Proportional band or throttling range is the:

A

Control point range through which the controlled variable must pass to drive the final control element through its full range

38
Q

The steam and water spaces of a cast iron sectional boiler are connected by:

a) Tie rods
b) Tie nipples
c) Hydraulic jacks
d) Steel studs
e) Push nipples

A

e) Push nipples

39
Q

Low pressure boilers are made of:

a) Steel
b) Stainless Steel
c) Aluminium
d) Cast iron

A

a) Steel

d) Cast iron

40
Q

The fins cast on the flat surface of the sections of a cast iron sectional boiler are used for the purpose of increasing the:

a) Effectiveness of the heat transfer
b) Steam capacity
c) water capacity
d) water Circulation
e) Steam output

A

a) Effectiveness of the heat transfer

41
Q

The sections of cast iron boilers are mainly designed to obtain maximum:

a) Water space
b) Steam space
c) water Circulation
d) Heat transfer
e) Steam output

A

d) Heat transfer

42
Q

Most low capacity cast iron boilers:

a) Cannot be site assembled
b) Can withstand higher pressures
c) Will pass through standard size doorways
d) Are factory assembled as packaged units
e) Require special foundations

A

c) Will pass through standard size doorways

43
Q

In a cast iron modular heating boiler, the operation of the burner of each module is controlled by a ___________ that starts or stops modules in sequence as load demand increases or decreases

a) Temperature sensor
b) Step controller
c) Thermostat
d) Temperature transmitter
e) Flow controller

A

b) Step controller

44
Q

Oil burners can be divided into 3 classes:

a) Air and steam atomizing burners
b) Mechanical or pressure atomizing burners
c) Centrifugal or rotary cup burners
d) Atmospheric pressure burners
e) Gravitational pressure burners

A

a) Air and steam atomizing burners
b) Mechanical or pressure atomizing burners
c) Centrifugal or rotary cup burners

45
Q

The compressed air used as atomizing air in the air atomizing oil burner is also called:

a) Secondary air
b) Primary air
c) Pre-mixed air
d) Pre-compressed air
e) Post-compressed air

A

b) Primary air

46
Q

When using mechanical fuel oil atomization:

a) kPa steam pressure is required at the burner
b) Dry saturated steam or superheated steam should be used
c) High pump pressure is required
d) Steam pressure is required to keep the bypass open
e) to KPa oil pressure is required…

A

c) High pump pressure is required

47
Q

The 2 basic varieties of mechanical atomizing oil burners are the:

a) Variable capacity burner
b) Constant capacity burner
c) Modulating burner
d) Stationary burner

A

b) Constant capacity burner

c) Modulating burner

48
Q

The reducing of oil into very small particles is termed:

a) Fluidization
b) Fractionation
c) Turbulence
d) Atomization
e) Distillation

A

d) Atomization

49
Q

Intermediate and high fire burner nozzles have higher capacities than the primary burner nozzle:

a) To give greater firing variations
b) To prevent pressure surges
c) To prevent ignition puff-backs
d) Because of the pump being of the positive displacement type
e) To allow better boiler warm-ups

A

e) To allow better boiler warm-ups

50
Q

An air, atomizing compressor is usually:

a) A variable displacement type
b) A centrifugal type
c) An axial type
d) A positive displacement type
e) A regenerative type

A

d) A positive displacement type

51
Q

A multi-burner cluster has secondary and tertiary nozzles ignited by:

a) An igniter spark
b) An intermittent pilot flame
c) An interrupted pilot
d) The primary burner
e) A continuous pilot

A

d) The primary burner

52
Q

The purpose of the deflector vanes in tej center of a ring (gas) burner is to:

a) Atomize the gas particles
b) Increase the gas velocity
c) decrease the air velocity
d) Promote turbulence of gas and air mixture
e) Increase the temperature of the furnace

A

d) Promote turbulence of gas and air mixture

53
Q

One of the advantages of using natural gas as a fuel in a boiler is:

a) No storage space is required
b) low cost
c) Abundance in supplies
d) Portability
e) No transmission lines required

A

a) No storage space is required

54
Q

The pilot burner for gas fired heating equipment can be:

a) Manual
b) Continous
c) Intermittent
d) Interrupted
e) Automatic

A

b) Continous
c) Intermittent
d) Interrupted

55
Q

An atmospheric premix burner has air entering around the burner that is termed:

a) Primary air
b) Secondary air
c) Atomizing air
d) Combustion air
e) Tertiary air

A

b) Secondary air

56
Q

An intermkittent pilot:

a) Lights the main flame then extinguishes
b) Must be manually ignited
c) Lights the main flame and remains ON with it
d) remains ON when the main flame extinguishes
e) Lights a pilot flame then extinguishes

A

c) Lights the main flame and remains ON with it

57
Q

When a gas fired burner is burning fuel properly:

A

a) It will have a blue flame with short yellow tips

58
Q

An inspector’s test connection:

A

its not mandatory on LP boilers

59
Q

According to the current code, the scale on the dial of the steam gauge for a steam heating boiler shall be graduated to not less than:

A

200 KPa

60
Q

The force of the steam pressure acting on the safety valve disc is a function of:

a) Disc area
b) Hudding chamber volume
c) Seat diameter
d) Percent valve opening
e) Blowdown ring diameter

A

a) Disc area

61
Q

The prime importance of boiler fittings is:

a) Economics
b) Efficiency
c) Safety
d) Convenience
e) Ease of operations

A

c) Safety

62
Q

An essential fitting between the boiler and the steam pressure gauge is to prevent:

a) Air from entering the gauge
b) Water from entering the gauge
c) Hot steam from entering the gauge
d) Air from entering the boiler
e) Hot steam from entering the boiler

A

c) Hot steam from entering the gauge

63
Q

The purpose of the pipe siphon installed between the boiler and the pressure gauge is to prevent:

A

Hot steam from entering the gauge

64
Q

If a heating boiler with an automatic feedwater system requires a large amount of water to be fed manually, this may indicate

a) You are producing a great deal more steam
b) There is probably a leak in the system
c) There has been a drastic change in the water quality
d) Your return lines are no working
e) The flow meter is not working properly

A

b) There is probably a leak in the system

65
Q

Do not open the safety valve with the test lever:

a) If the valve is less than 2.5 cm inlet diameter
b) If the pressure is less than 75% working pressure
c) If there are more than 2 safety valves on the boiler
d) If the valve is not vented to the roof
e) After 9 pm in populated areas

A

b) If the pressure is less than 75% working pressure

66
Q

Which of the following fittings would you expect to find on a hot water heating boiler:

a) Thermometer
b) Safety relief valve
c) Blow off or drain valve
d) Water column

A

a) Thermometer
b) Safety relief valve
c) Blow off or drain valve

67
Q

Your boiler is operated with automatic water feeders. If the boiler suddenly requires an increase in water treatment, what should you look for:

a) Nothing. Simply increase the pump stroke to put more chemicals into the system
b) See if the chemical pump has stopped
c) Check for a loss of feedwater
d) Check to see if the chemical supplier has sent the wrong chemicals
e) Make sure the blow-off valves are open

A

c) Check for a loss of feedwater

68
Q

A hot water boiler is protected from overpressure by means of:

a) A safety pop valve
b) A high limit pressure control
c) An expansion valve
d) An air release valve
e) A safety relief valve

A

e) A safety relief valve

69
Q

In a hot water heating system, the closed type expansion tank should be:

a) kept full of water
b) Open to the atmosphere
c) Partly filled with water
d) Isolated from the system
e) Closed and independently heater

A

c) Partly filled with water

70
Q

Thermal shock to boilers can be reduced by:

a) Warming up boilers slowly
b) Keeping the boiler free of scale build-up
c) Covering the tube sheets with refractory
d) Not allowing full flow of cold water into a warm hot water boiler
e) All of the above

A

e) All of the above

71
Q

Upon starting a cold gas-fired boiler water initially may leak from the reversing chambers due to:

a) The fire tubes not expanding into the tube sheets
b) A fire tube has failed
c) Combustion gasses are condensing on cold boilers surfaces
d) There is boiler water on ten fire side of the fire tubes
e) The fireside was just hydro tested

A

c) Combustion gasses are condensing on cold boilers surfaces

72
Q

A gradual increase in stack temperature is an indication of:

a) Poor burner operation
b) Too much excess air
c) Unclean heating surfaces
d) Poor damper operations
e) All of the above

A

e) All of the above

73
Q

If your low pressure steam boiler was in service and you found that there was not water level showing in the gauge glass, your first action would be to:

a) Leave the easing lever on the safety valve
b) Cut off the fuel and air to the furnace
c) Start the standby feed pump
d) Send fro the boiler inspector
e) Call a reliable plumber

A

b) Cut off the fuel and air to the furnace

74
Q

If the safety relief valve on your hot water boiler was opening u, the cause could be:

a) Steam collecting in the water space
b) Expansion tank completely filled with water
c) Faulty automatic fill valve
d) Circulating pump running too slow

A

b) Expansion tank completely filled with water

c) Faulty automatic fill valve

75
Q

During the warm up period of a heating boiler the main burner goes out. The operator should:

a) Shut down the boiler immediately purge the boiler and restart it
b) Shut down the boiler, close the fuel valves and determine the cause of the problem
c) Try to re-light the burner immediately
d) Check the altitude gauge to ensure there is enough water in the system
e) Clean the burner, purge the boiler and restart it

A

b) Shut down the boiler, close the fuel valves and determine the cause of the problem

PWEN- Controls & Instrumemtation (3 decks)

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