Power Engineering 4th Class B2
d
A bimetal thermostat's operating range is between: Choose one answer. a. 5 and 40°C b. 0 and 50°C c. 0 and 40°C d. 10 and 32°C e. 50 and 90°C
b
A condensate receiver low level cutoff switch will: Choose one answer. a. Open a make-up solenoid b. Stop the feed pump thereby preventing damage to it c. Shut off the boiler d. Sound an alarm e. Cause the make-up valve to close
d
A device used to position dampers and control valves is called: Choose one answer. a. A controller b. A relay c. A transformer d. An actuator e. A temperature controller
a
A direct acting controller: Choose one answer. a. Increases its output signal on an increased input signal b. Increases its output signal on a decreased input signal c. Only handles direct acting inputs d. Only handles reverse acting inputs e. Decreases its output signal on an increased input signal
c
A feedwater make-up system should a) utilize demineralizers b) utilize a deaerator c) be able to satisfy normal firing needs d) always be softened water e) be able to satisfy the needs of at least one boiler in a multiboiler plant
a
A flame control switch: Choose one answer. a. Varies electrical current to a modutrol motor b. Will start and stop a boiler c. Cannot have its settings adjusted d. Will not result in simultaneous adjustment of air and fuel e. Eliminates the need for a high limit control
d
A flame failure device a) must be installed on every high pressure boiler b) will shut off the steam leaving the boiler c) will control the pressure of the boiler d) will shut off the fuel to the burner e) will shut down the flame in the boiler
d
A flame failure device is unresponsive to: Choose one answer. a. Ultraviolet light b. Infra-red light c. Visible light d. Fuel flow e. Heat
c
A flame rod: Choose one answer. a. Is used in combination with a photocell b. Is used only for oil fired burners c. Forms an electric circuit with the rod, flame and burner d. Senses the temperature of the flame e. Develops a high resistance in the presence of a flame.
d
A flame scanner (1) requires a photoelectric cell (2) responds to temperature changes (3) requires a clear line of sight to the flame (4) produces a steady voltage signal a) all of the above are correct b) 1 & 2 are correct c) 1, 2, & 4 are correct d) 1 & 3 are correct e) none of the above
d
A flame scanner: Choose one answer. a. uses a pilot-stat b. Responds to temperature changes c. conducts current through the flame d. Requires a clear line of sight to the flame e. Produces a steady voltage signal
d
A float operated mechanical feeder valve in a secondary feedwater supply should: Choose one answer. a. Be a normally closed valve. b. Open just after the low-water cutoff switch opens. c. Be located above the water column. d. Not open until the level is well below the feed pump cut-in level. e. Not be deemed a stand-by device
e
A high gas pressure fuel cut-off switch: Choose one answer. a. Closes when gas pressure is too high b. Automatically resets itself when the gas pressure is restored c. Is located upstream of the automatic fuel valve d. Is a normally open switch e. Prevents excessive fuel pressure from creating an unstable flame condition
e
A high limit control switch a) is necessary on all boilers b) activates after the safety valve opens c) is a normally open switch d) usually does not require manual resetting e) must be used when a boiler is not under continuous supervision
c
A hot water boiler operating control can be a pressure switch: Choose one answer. a. That is normally open b. That is sensitive to the expansion and contraction of boiler water c. Utilizing a closed liquid filled system d. That is sensitive to system steam pressure e. That is sensitive to boiler steam pressure
e
A levelling indicator is found on a) the casing of a heating boiler b) a low-water fuel cutoff switch c) a boiler feedwater pump d) a modutrol motor e) an ON-OFF operating control switch
e
A low fire switch a) is a type of manual over-ride b) takes no part in the start-up of an automatic boiler c) is a normally closed switch d) utilizes a thermal element for its operation e) acts as an interlock to ensure minimum damper setting
d
A manual "high-low" switch should be switched to "high" or "auto": Choose one answer. a. As soon as the main flame has stabilized b. Prior to ignition of the main flame c. When pressure is too low d. When the boiler has been properly warmed up e. During boiler pre-purge
c
A modulating control steam heating boiler: Choose one answer. a. Is always fully automatic b. Will have a narrow operating pressure range c. Maintains a steady boiler pressure d. Will have a constant combustion air, flow rate e. Cannot be adjusted
e
A non-bleed controller bleeds control air: Choose one answer. 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
A pneumatic control system a) uses a sensing device to change pressures in the control line b) requires an intermittent air supply c) always uses pressure actuated final controlled devices d) is not used to control air flow for ventilation e) is seldom used to control humidity
d
A pneumatic relay can also be called a/an: Choose one answer. a. Selector switch b. Air reservoir c. Bleed type controller d. Cumulator e. Pneumatic-electric switch
a
A potentiometer control a) varies electrical current to a modutrol motor b) will start and stop a boiler c) cannot have its settings adjusted d) eliminates the need for a high limit control e) will not result in simultaneous adjustment of air and fuel
c
A pressure sensor converts pressure changes into a) an electrical signal b) a change in electrical resistance c) variables such as voltage, current, or resistance d) air pressure e) a temperature change
c
A pressure sensor converts pressure changes into: Choose one answer. a. An electrical signal b. A change in electrical resistance c. Variables such as voltage, current, or resistance d. Air pressure e. A temperature change
a
A resistance control or "potentiometer" for modulating control a) works in conjunction with a modutrol motor b) utilizes a mercury switch c) senses steam temperature d) can only be used on a fully automatic boiler e) can operate only in the vertical position
e
A room thermostat should be mounted on an inside wall about _____ above the floor. Choose one answer. a. 0.5 m b. 0.75 m c. 1.0 m d. 1.25 m e. 1.5 m
a
A test lead or "jumper wire" is required when testing: Choose one answer. a. High steam pressure or high water temperature limit controls b. A high gas pressure fuel cut-off 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
b
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 an "aquastat"
b
A thermocouple: Choose one answer. a. Consists of two similar wires b. Produces an electric signal c. Senses infrared light from the flame d. Is made of several thermopiles connected in series e. Is also called a "pilot-stat"
d
A transducer is a device that is used to: Choose one answer. a. Generate a set point b. Produce an off or on signal c. Convert direct acting to reverse acting d. Amplify an electronic signal, or convert it to another energy form e. Filter an electronic signal
b
A transformer is a device that is used to change: Choose one answer. a. AC amperage to DC amperage b. AC voltage from one value to another c. DC amperage from one value to another d. DC voltage to AC voltage e. low power to high power
a
All flame safeguard devices have the following in common: Choose one answer. a. Close the main fuel valve in case of pilot flame failure or main burner failure. b. Require a visible light source. c. Are limited to temperatures comfortable to the hand. d. Monitor the pilot flame and main burner simultaneously. e. Activate an alarm system if flame failure is detected
b
An ON-OFF steam boiler: Choose one answer. a. Will maintain a fairly constant steam pressure b. Operates most efficiently at continuous firing c. Will cycle on and off based on temperature d. Must have a low capacity e. Cannot operate in a multi-boiler system
a
An advantage of an electronic control system is that a) the controllers can accept a wide variety of inputs b) they are inexpensive to operate c) they are inexpensive to install d) the controllers can be used outdoors e) it is very compact
a
An advantage of an electronic control system is that: Choose one answer. a. The controllers can accept a wide variety of inputs b. They are inexpensive to operate c. They are inexpensive to install d. The controllers can be used outdoors e. It is very compact
b
An aquastat a) senses water level b) is like a thermal element without a capillary tube c) can be located away from its point of measurement d) measures water flow e) is a modulating device
c
An electric boiler feedwater valve will: Choose one answer. a. Eliminate the need for a second low-water fuel cutoff b. Prevent low-water conditions c. Open before the low-water cutoff operates d. Require manual action to open e. Open if the boiler trips due to low water
b
An electronic control system is comprised of a a) meter, sensor, and valve b) sensor, controller, and final control element c) sensor, transmitter, and thermostat d) controller, thermostat, and sensor e) thermostat, electronic controls, and furnace
b
An electronic control system is comprised of a: Choose one answer. a. Meter, sensor, and valve b. Sensor, controller, and final control element c. Sensor, transmitter, and thermostat d. Controller, thermostat, and sensor e. Thermostat, electronic controls, and furnace
b
An electronic controller is a) not part of the electronic control system b) used to position an actuator c) used to generate a set point d) a type of sensor e) used only in pneumatic systems
b
An electronic controller is: Choose one answer. a. Operated on variable current signals b. Used to position an actuator c. Cannot interpret variable voltage inputs d. Operate only as on-off controls e. Convert 2-poition inputs to proportional outputs
a
An example of a controlled device would be a) a damper motor operating air louvers b) a hot water boiler c) a radiator d) a steam boiler e) a thermostat
c
An example of an auxiliary device for a pneumatic control system would be a: Choose one answer. a. Reducing valve b. Three way air valve c. Damper d. Pump e. Bellows
a
An operating control switch for an ON-OFF boiler: Choose one answer. a. Uses a differential spring to reduce cycling b. Can only have its cut-in setting adjusted c. Has an un-adjustable span between cut-in and cut-out d. Utilizes a resistance coil e. Operates in conjunction with a Modutrol motor
e
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 _____ period. Choose one answer. a. Two hour b. One and one half hour c. One hour d. 45 minute e. 20 to 30 minute
d
Authority or Compensation Authority is the: Choose one answer. a. A process of automatically adjusting the setpoint of a controller. b. Point in which the compensation effect is reversed in action. c. System element that senses a variable other than the controlled variable. d. Setting that indicates the effect a compensating sensor has on the main setpoint. e. Entity that awards compensation after a workplace injury
c
Because of variations in flow rate, nearly all large steam heating plants utilize: Choose one answer. a. Fully modulating burners b. A deaerator c. A condensate receiver d. Multiple boilers e. Steam pressure, regulating valves
b
Boiler fuel should be shut off immediately if it fails to ignite, in order to: Choose one answer. a. Save fuel b. Prevent furnace explosions c. Save money d. Save power e. Prevent fireside corrosion
c
Combustion air safety switches are commonly found a) on natural draft boilers b) on hot water boilers only c) on boilers utilizing a forced draft fan d) on gas fired boilers only e) as noninterlocking devices and take no part in a startup
c
Control motors are divided into two classifications: Choose one answer. a. High-torque and low-torque b. AC and DC c. Valve operators and damper operators d. High voltage and low voltage e. Pump and fan controllers
a
Dissolved oxygen in condensate: Choose one answer. a. Will cause pitting in a boiler b. Can cause pitting on the return lines c. Causes grooving of the condensate lines d. Is removed with amines e. Necessitates the installation of a deaerator
e
During start-up of a boiler equipped with an automatic control system and a flame scanning device, the main burner shutoff valve: Choose one answer. a. Must be opened before the pilot will ignite b. Can be opened before the scanner sees a flame c. Should be open during the full start sequence d. Should open as soon as the pilot valve opens e. Must be closed before pilot ignition
a
Equalizing lines on a condensate receiver float chamber a) will dampen level fluctuations b) keep receiver level equal to boiler level c) maintain make-up flow equal to condensate flow d) eliminate the need for a make-up level control valve e) maintains equal flow of condensate to multiple boilers
c
Flame rods: Choose one answer. a. Should be cleaned of carbon deposits monthly. b. Generate a voltage, which is then used to monitor flames. c. Should shut off the fuel within four seconds of flame failure. d. Are unreliable and unsafe. e. Should not be exposed to temperatures above 100°C
a
Heating plants with multiple boilers often have: Choose one answer. a. Independent boiler feedwater controls b. Individual feedwater systems c. Problems controlling water level d. Separate condensate receivers e. A common feedwater control valve
e
In a basic electric control system an example of a controlled device is a) a fuel valve b) a louver c) a diverter valve d) an electric switch e) all of the above
a
In a basic electric control system an example of a controlled device is a: Choose one answer. a. fuel valve b. thermostat c. pressure-stat d. humidistat e. flow switch
d
In a basic electrical control system the device that senses a drop in air temperature is called the: Choose one answer. a. Final controlled device b. Pneumatic temperature sensor c. Humidistat d. Thermostat e. Regulator
b
In a non-bleed type controller the device that senses a change in room temperature is called a: Choose one answer. a. Sensing valve b. Bellows c. Valve chamber d. Temperature switch e. Valve diaphragm
c
In a self-contained control system the energy for operation is provided by: Choose one answer. a. Electricity b. Air pressure c. The reaction of the sensing device d. A bellows e. A bleed type nozzle
a
In electric switch configuration the term "contact arrangement refers to: Choose one answer. a. Normally open or normally closed position b. Switches in series or parallel c. Double or single pole switches d. Switches mounted vertically or horizontally e. Relay contacts
a
In nearly all LP steam heating systems the feedwater: Choose one answer. a. Is condensate b. Requires daily close scrutiny of chemical values c. Contains a high percentage of makeup water d. Is deaerated e. Is softened
a
In the pneumatic control nozzle and vane system the: Choose one answer. 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 both move to maintain equilibrium
a
Maintenance of a flame safeguard device should NOT include which of the following? Choose one answer. a. Using a fine file to clean the contact points b. Removing oxidation from the contacts c. Blowing dust out of the sight tube d. Removing deposits from a flame rod e. Drawing a piece of hard paper between the contacts.
b
Modulating combustion controls Choose one answer. a. Regulate the steam and feedwater flow b. Regulate the fuel and air flow c. Control the atomizing air d. Control the combustion programmer e. Control the draft and feedwater temperature
a
Neutralizing amines: Choose one answer. a. Raise the pH of condensate b. Lower the pH of boiler water c. Eliminate boiler pitting d. Can cause return grooving e. Absorb carbon dioxide
b
On a cluster burner, the high fire nozzle will: Choose one answer. a. Be in operation on start-up. b. Operate continuously when steam demand exceeds boiler capacity. c. Be ignited by a pilot flame. d. Operate regardless of where the manual over-ride switch is set. e. Respond to electrical resistance
a
On-off thermostats are equipped with: Choose one answer. a. An open contact switch b. Humidity compensation c. Two or more switches, operated in sequence d. A potentiometer e. A resistance slidewire
c
Parallel blade dampers are usually used for: Choose one answer. a. Changing the direction of the air flow b. Varying the amount of air flow c. Turning the air flow on or off d. Proportional operation e. Mixed air control (outside and inside air)
d
Pneumatic controllers are divided into two basic classes,: Choose one answer. a. Direct and reverse b. Off/on and proportional c. Positive and negative action d. Bleed and non-bleed e. Reset and gain
b
Pressure controllers can be divided into two classes: Choose one answer. a. High and low temperature b. High and low pressure c. High and low flow d. High and low voltage e. Panel mounted or duct mounted
c
Prior to a boiler safety valve popping during routine boiler operation: Choose one answer. a. A try lever test should be performed b. The pressure gage should be checked c. The high limit switch should open d. The feedwater pump should stop e. The high level alarm should sound
d
Proportional band or throttling range is the: Choose one answer. a. Control method in which the final control element moves proportionally to the deviation of the controlled variable from the setpoint b. Control algorithm that combines the proportional and integral algorithms c. Compensation action where a decrease in the compensation variable has the same effect as an increase in the controlled variable d. Control point range through which the controlled variable must pass to drive the final control element through its full range e. Sustained deviation between the control point and the setpoint of a proportional control system under stable operating conditions
d
Quickly closing the main burner manual cock valve during boiler operation should trip the: Choose one answer. a. Flame scanner b. Combustion air proving switch c. Low gas pressure fuel cut-off d. High gas pressure fuel cut-off e. Low fire interlock switch
b
Resistance temperature devices can provide a relatively linear resistance variation from: Choose one answer. a. -60 to 80°C b. -40 to 120°C c. -40 to 250°C d. 0 to 100°C e. 40 to 100°C
c
Setpoint deviation is also called: Choose one answer. a. Derivative b. Proportional band c. Offset d. Integral e. Gain
d
The Hartford loop will: Choose one answer. a. Only be installed on multiple-boiler systems b. Ensure continuous circulation of a hot water system c. Prevent steam from entering a steam pressure gage d. Prevent boiler water level from going below the lowest safe water level e. Replace the feedwater check valve
b
The bimetal sensing element consists of a strip made up of two thin layers of metal with: Choose one answer. a. Similar rates of thermal expansion b. Widely different rates of thermal expansion c. Different specific heats d. Widely different rates of thermal conductivity e. Different resistances
e
The combustion air proving switch a) should be checked when air flow is minimum b) should not be checked while the boiler is in the purge cycle of start-up c) is a normally closed switch d) must always be a manual reset device e) should be checked when air flow is maximum
a
The device used to maintain a constant pressure throughout a pneumatic control system is called a: Choose one answer. a. Reducing valve b. Gradual switch c. Pneumatic valve d. Balancing valve e. Proportional band controller
a
The effective throttling range of control pressure used in 100 kPa circuits is usually considered to be from: Choose one answer. a. 20 to 90 kPa b. 0 to 100 kPa c. 3 to 15 kPa d. 2 to 25 kPa e. 20 to 103 kPa
b
The electrical 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
b
The electrical resistance of a thermistor will: Choose one answer. a. Decrease when cooled b. Decrease when heated c. Increase when heated d. Remain constant with temperature changes e. Depend upon its application
b
The feedwater supply to most heating boilers is controlled by a _____ switch. Choose one answer. a. Flow b. Float c. Differential pressure d. Drum level e. Cut-off
b
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
The main steam boiler control device used with an on/off combustion fuel control is a _____ sensing element. Choose one answer. a. Pressure b. Level c. Temperature d. Flow e. Pneumatic
d
The most common type of damper operator is a: Choose one answer. a. Relay b. Spring c. Bellows d. Piston e. Pilot positioner
b
The most important fitting installed between the operating switch of a steam boiler and the boiler itself is a Choose one answer. a. Tee with a plug b. Syphon c. Blowdown valve d. Test connection for an inspector e. Pressure gage
b
The result of a condensate receiver that is too small could be: Choose one answer. a. High boiler water level 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
e
The setpoint transfer from a day-time to a night-time setpoint, when a dual-temperature thermostat is used, is made by changing the air pressure from Choose one answer. a. 3 kPa to 15 kPa b. 5 kPa to 25 kPa c. 20 kPa to 90 kPa d. 0 kPa to 100 kPa e. 100 kPa to 125 kPa
d
The term that refers to the normal electric supply voltage is ___________. Choose one answer. a. Operating voltage b. Low voltage c. High voltage d. Line voltage e. Standard voltage
e
The type of combustion control frequently used on a small packaged boiler is Choose one answer. a. a semi-automatic control b. a modulating control c. a proportional control d. a constant pressure control e. an on-off control
c
Thermocouples are connected in series to: Choose one answer. a. Monitor more than one flame source b. Increase the sensitivity of the detection system c. Generate a higher voltage d. Provide redundancy if one should fail e. Create what is called a "flame rod"
e
Thermostats may be classified according to their a) application b) type of temperature sensing element c) type of control action provided d) temperature range e) all of the above
c
What is the purpose of the high limit control on a hot water boiler? Choose one answer. a. To stop the boiler if the water level control fails. b. To act as a emergency stop for the operator c. To shut down the burner if the water temperature exceeds 121 deg C. d. To prevent the pressure in the boiler rising above 210 kPa gage. e. To prevent excessive pressure from developing
b
When a boiler equipped with a combination feedwater control and low water cutoff device shuts down due to a low water condition: Choose one answer. a. The feedwater flow will also stop b. The level must be restored to above the cutoff line before the unit can be restarted c. It can be restarted by pressing the manual reset d. The operator must open the feeder valves to allow water into the boiler e. The condensate pump must be restarted
e
Which of the following is NOT a final control device for a heating system? Choose one answer. a. Control valve b. Damper c. Fan d. Louvre e. Steam flow
c
Which of the following is NOT an advantage of electrical control systems? Choose one answer. a. Electricity is readily available b. The wiring is relatively simple and easy to install c. Certified electricians must install the control system d. Signals from sensing elements can produce more than one output e. Controller/actuators do not require an air supply
e
Which of the following is a flame sensing device? a) thermopile b) heat sensing control c) stack relay d) cut-off valve e) scanner