Unit 20 - Controls & Instrumentation (Ch. 84-89)
A sump pump will start on high level and stop on low level, this type of control is: A) On/Off. B) proportional. C) proportional plus reset. D) proportional plus rest plus rate. E) mechanical.
A) On/Off.
List two types of electrical signals used in control systems and give examples of where each might be used. 1. ____________________________________________. 2. ____________________________________________.
*1. Voltage signals* - used with switching devices to operate low-water fuel cutoff devices, flame scanners, pump controllers and stepper motors for boiler controls. *2. Current signals* - used for analog instruments where signals must be sent over long distances.
Explain direct acting and reverse acting valve bodies on pneumatic control valves.
*Direct acting* valve closes as the spindle and disk move down and away from the diaphragm. *Reverse acting* valve closes as the disk and spindle more upward and toward the diaphragm.
As used in instrumentation, state the difference between an indicator and a recorder.
*Indicator* - shows only the current value of the process variable. *Recorder* - shows the current value and previous values to allow the operation of the process to be analyzed over time.
Boiler combustion controls are of two types, modulating & ________________. A) feed forward B) proportional C) multi range D) manual E) automatic
*Text book lists modulating combustion control and on/off control but this question showed up in the practice quiz* No other references found
Name three types of sensing elements used to measure flow by creating a differential pressure in the pipe. 1. ____________________________________________. 2. ____________________________________________. 3. ____________________________________________.
1. orifice plate. 2. venturi tube. 3. flow nozzle.
Hydraulic transmission of control signals is done with: 1. oil 2. air 3. steam 4. natural gas A) 1 and 3 B) 1 and 4 C) 2 and 3 D) 2 and 4 E) 1 and 2
A) 1 and 3 oil as used by steam and gas turbines. ch. 69 - pg. 30 steam as used by thermohydraulic regulator ch. 87 - pg. 362
On a gas fired automatic boiler a normal programmed startup takes approximately: A) 105 second B) 65 seconds C) 125 seconds D) 95 seconds E) 75 seconds
A) 105 second
If the boiler pressure increase within the pressure gauge, the: A) Bourdon tube will tend to straighten. B) spring will compress more. C) Bourdon tube will become less circular in cross-section. D) Bourdon tube will become smaller in diameter. E) Bourdon tube will tend to twist.
A) Bourdon tube will tend to straighten.
Normally-closed solenoid operated valves open when A) a coil is electrically energized. B) pressure below the valve disc overcomes the spring pressure above the disc. C) a pneumatic signal exceeds 20 kPa. D) an electric motor opens the valve. E) it is de-energized.
A) a coil is electrically energized.
An automatic boiler On-Off or operating control switch has an adjustment for pressure set-point and another for: A) a differential between the two. B) manual or automatic control. C) for rate of modulation. D) high steam pressure limit. E) rate of feedback.
A) a differential between the two.
A sudden drop in steam pressure causes: A) a sudden increase in drum level. B) a rapid collapse of steam bubbles in the boiler. C) "shrinkage". D) a drop in drum level. E) a single element feedwater control to immediately add water to the drum.
A) a sudden increase in drum level. Also known as "swell".
A modem is a device that: A) allows the computer to communicate over analog lines. B) allows the CPU to perform more than one task at a time. C) boosts signals. D) stores bits of information into groups of eight called bytes. E) provides a type of computer memory.
A) allows the computer to communicate over analog lines.
An analog control loop output must be put through a/an _________________________ before the computer can understand and react to the signal. A) analog to digital converter B) signal inverter C) ROM detector D) modem E) CPU
A) analog to digital converter
A boiler control manual-automatic transfer or selector station: A) can be used to manually override automatic control loops. B) can be changed from manual to automatic without balancing. C) is located upstream of the controller in a control loop. D) output is directed to the primary element of a loop. E) must be operated in manual mode for only short periods.
A) can be used to manually override automatic control loops.
When an operator uses CRT or LCD displays, the computer control display: A) can stretch or compress time periods. B) will be equipped with graph limiters. C) will not have printout capabilities. D) has only single trend display. E) will not be connected to the transmitter signal.
A) can stretch or compress time periods.
Modulating combustion control will: A) change air and fuel flow proportionally to steam pressure change. B) always be at set point when demand is at 50%. C) alter only the air flow if a selector station is on manual. D) respond to changes in atmospheric pressure. E) always be a cascading control system.
A) change air and fuel flow proportionally to steam pressure change.
Modulating combustion control will: A) change air and fuel flow proportionally to steam pressure changes. B) always be at set point when demand is at 50% C) alter only the air flow if a transfer station is in manual. D) respond to changes in atmospheric pressure. E) always be a cascading control system.
A) change air and fuel flow proportionally to steam pressure changes.
Some of the components of an automatic control loop are a sensing element, a transmitter, a _______________ and a control valve. A) controller B) transformer C) transducer D) piping system E) converter
A) controller
A sensing element sends its signal to the: A) controller B) transducer C) control valve D) recorder E) transmitter
A) controller ch. 84 - pg. 300 * However a sensing element may send its signal to a transmitter as an intermediary between controller and sensing element.
A pneumatically actuated control valve which opens on air failure has a: A) direct acting actuator and direct acting valve. B) direct acting actuator and reverse acting valve. C) reverse acting actuator and direct acting valve. D) is typically used for a burner firing rate control valve. E) is typically used for a feedwater control valve.
A) direct acting actuator and direct acting valve.
The output pressure signal of a transmitter relay is usually: A) direct and proportional to nozzle pressure. B) a function of supply pressure. C) inversely proportional to nozzle pressure. D) fed to a final element of a loop. E) the same as the primary element output signal.
A) direct and proportional to nozzle pressure.
Overheating of boiler heating surfaces due to low water: A) is a major cause of boiler failure. B) will cause a furnace explosion. C) can be eliminated with a low-water fuel cutoff. D) cannot occur in a hot water boiler. E) can be prevented with proper water treatment.
A) is a major cause of boiler failure.
A lead sulphide cell is sensitive to IR rays and: A) its resistance to current flow varies inversely with ray emissions. B) its resistance to current does not change during operation. C) will not sense steady IR rays, only pulsating ones. D) will not respond to glowing hot refractory. E) must be replaced at least monthly.
A) its resistance to current flow varies inversely with ray emissions.
Two element feedwater control: A) measures water level and steam flow. B) compares forced draft to water level. C) compares fuel flow to steam flow. D) has one element in the feed control valve and one element in the deaerator. E) compares water level to the firing rate.
A) measures water level and steam flow.
A CRT trend display: A) mimics a trend chart. B) is dedicated to a single process. C) is limited to displaying a fixed or nonadjustable time period. D) allows a view of only one process variable at a time. E) is normally mounted beside the final control element.
A) mimics a trend chart.
During the start-up of a boiler equipped with an automatic control system and flame scanning device, the main burner safety shut-off valve: A) must be opened before the ignition transformer energizes. 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 pilot ignition
A) must be opened before the ignition transformer energizes.
A CRT or LCD display trend recorder: A) often has a number of dedicated displays. B) is equipped with graph limiters. C) does not have print out capabilities. D) displays only a single trend at a time. E) is independent of the transmitter signal.
A) often has a number of dedicated displays.
A device which will cause a visible light signal to become an instrument analog signal is the: A) photoelectric transducer. B) transmitter. C) controller. D) final element. E) current-to-pneumatic transducer.
A) photoelectric transducer.
What type of sensing element is used with an on/off combustion fuel system: A) pressure B) level C) temperature D) electronic E) pneumatic
A) pressure
The advantage of using a venturi tube, rather than an orifice plate for flow measurement is it: A) produces less permanent pressure drop. B) costs less to install. C) requires only one pressure tap. D) is less bulky. E) is flexible.
A) produces less permanent pressure drop.
The type of controller maintains the process variable within a range around the set point. It is a/an ______________________________ controller. A) proportional B) On/Off C) mechanical D) pneumatic E) proportional plus reset
A) proportional
A control valve that has one plug that moves upward to close the port is called: A) reverse acting single ported. B) double seated direct acting. C) reverse acting diaphragm actuated. D) direct acting single ported. E) a solenoid
A) reverse acting single ported.
The operating pressure control will control the: A) steam pressure in the boiler. B) gas pressure to the burner. C) water pressure to the boiler. D) boiler furnace pressure. E) steam pressure in the steam header.
A) steam pressure in the boiler.
Putting a controller in "manual" control means: A) the operator selects the controller output. B) the controller output responds to a process variable. C) there is no control of the final control element. D) a man must stand beside the value for safety reasons. E) the plant is about to shut down.
A) the operator selects the controller output. *In other words:* The process variable is controlled by the operator.
A sensing element in a remote location could send its signal to a control room via a/an __________________. A) transmitter B) sender C) conveyor D) express E) recorder
A) transmitter
An incline manometer is commonly used: A) when very low pressures or vacuums are being measured. B) to measure high pressure differentials. C) in conjunction with a flexible rubber diaphragm. D) when reading accuracy is not critical. E) for measure level.
A) when very low pressures or vacuums are being measured.
A two position controller compares conditions to a set point and: A) will start or stop a process. B) desired value. C) will modulate the final element. D) can automatically readjust the set point. E) will maintain final element position at 50%.
A) will start or stop a process.
According to the ASME code, explain the requirements for high pressure limit switches.
All automatically fired steam heating boilers must have a high limit pressure activated switch that shuts off the fuel to the burner when the steam pressure exceeds normal operating pressure.
The coefficient of expansion of mercury is nearly linear for temperatures between: A) -35 to 400°C B) -39 to 450°C C) -30 to 425°C D) 75 to 450°C E) -45 to 485°C
B) -39 to 450°C
The nozzle of a pneumatic transmitter receives a constant air supply pressure of approximately: A) 140 psi B) 140 kPA C) 2 bar D) 25 psi E) 200 kPa
B) 140 kPA
A lockout switch will energize after ______________ seconds. A) 5 to 10 B) 15 to 30 C) 10 to 15 D) 20 to 40 E) 15 to 25
B) 15 to 30
Which of the following statements is FALSE of Pneumatic Signals? A) They are simple and provide trouble free operation. B) They can transmit over long distances. C) Less expensive than electronic instruments. D) Safe in operation.
B) They can transmit over long distances.
What type of control valve has a direct acting actuator and fail closed. A) a double ported plug. B) a reverse acting valve. C) a single ported plug. D) a direct acting valve. E) a direct acting valve with fail safe.
B) a reverse acting valve.
A very important requirement for all pneumatic control systems is: A) maximum transmitter output signal pressure must be maintain. B) air supply be clean and dry. C) tubing diameters must be kept large. D) noise attenuation must be used at each bleed device. E) a proper sized compressor which will run continuously.
B) air supply be clean and dry.
When a process variable has no method of sending information to the final control element, the system is known as: A) an automatic system. B) an open loop system. C) a cascading system. D) a feedback system. E) a feed forward system.
B) an open loop system.
The low-water cut-off of a low pressure steam heating boiler should be tested: A) by electrician who specializes in boiler controls. B) by lowering the water level, and ensuring the boiler shuts off before the water reaches the bottom of the visible part of the gauge glass. C) several times per shift. D) for correct operation on an annual basis. E) by first shutting off the burner, to prevent boiler damage if the cut-off should fail during testing.
B) by lowering the water level, and ensuring the boiler shuts off before the water reaches the bottom of the visible part of the gauge glass.
A hot water boiler low-water fuel cutoff: A) should be tested weekly during routine boiler operation. B) cannot be tested during routine boiler operation. C) cannot be tested. D) must be located at the lowest permissible water level. E) must have a normally closed switch.
B) cannot be tested during routine boiler operation.
A proportional only controller: A) cannot maintain maximum value of the final element. B) cannot maintain set point except at 50%. C) can be compared to the cruise control on an automobile. D) will maintain measured variable at set point. E) will respond fully when deviation is high.
B) cannot maintain set point except at 50%.
This temperature sensor has a negative temperature coefficient: A) thermocouple B) bi-metal strip C) RTD D) thermistor E) thermopile
D) thermistor
An orifice plate whose opening is machines in the center of the plate is called a: A) segmented orifice. B) concentric orifice. C) eccentric orifice. D) head plate. E) centralized flow plate.
B) concentric orifice.
The forms commonly used for power-plant equipment control include analog, digital, mechanical, pneumatic and: A) physical. B) electrical. C) manual. D) thermal. E) magnetic.
B) electrical.
The component of a control system that adjusts the value of the manipulated variable is called the: A) process variable B) final control element. C) manipulated variable D) controlled variable E) transmitting variable
B) final control element.
When a float is used for measuring level, and installation with a vessel is impractical, a device often used is the: A) float manometer. B) float cage. C) differential head meter. D) diaphragm level indicator. E) head transmitter.
B) float cage.
A chromatograph uses electronic devices which: A) utilize electrical current as a measure base. B) have decreased resistance as temperature rises. C) increase in resistance as temperature rises. D) work in conjunction with a thermocouple. E) are made of chromel and alumel.
B) have decreased resistance as temperature rises.
A chromatograph uses electronic devices which: A) utilize electrical current as a measurement base. B) have inverse resistance properties relative to temperature. C) increase in resistance as temperature rises. D) work in conjunction with a thermocouple. E) are made of Chromel and Alumel.
B) have inverse resistance properties relative to temperature.
On a packaged boiler a number of electrical switches connected in series can be categorized as _________________. A) controls B) interlocks C) start-up devices D) programmer controls E) detectors
B) interlocks
An advantage of the electric probe type low-water cut-off is: A) it can be incorporated on an size or type of boiler. B) it is simple in design with no moving parts. C) scale or sediment will not hinder its operation. D) all moving parts are easily accessible for cleaning and inspection. E) the probes will indicate a level even if not completely covered by water.
B) it is simple in design with no moving parts.
In a boiler, the air and fuel flow are adjusted to maintain a constant boiler pressure under all loads. The air and fuel flow are called: A) controlled variables. B) manipulated variables. C) processes. D) control elements. E) controller sensors.
B) manipulated variables.
Level, pressure, temperature, flow, composition, and speed are all examples of what? A) transmitters. B) process or control variables. C) sensory elements. D) disturbances. E) manipulated variables.
B) process or control variables.
Level, pressure, flow, temperature, composition, vibration, speed and clearance are all examples of: A) transmitters. B) process variables. C) sensing elements. D) disturbances. E) manipulated variables.
B) process variables.
With single element feedwater control the level transmitter output is: A) received by a final element. B) proportional to drum level. C) sent to a selector station. D) constant regardless of level. E) a function of steam flow.
B) proportional to drum level.
A recorder utilizing a spiral Bourdon tube will have a pen movement: A) on a logarithmic scale. B) proportional to the change in tube pressure. C) that is often imperceptible. D) range of 0 to 24 hours. E) range of 0 to 7 days.
B) proportional to the change in tube pressure.
A recorder initializing a spiral Bourdon tube will have a pen movement: A) linear to the tube travel. B) proportional to the change of tube pressure. C) angular to the tube travel. D) range of 0 to 24 hours. E) range of 0 to 7 days.
B) proportional to the change of tube pressure.
Control valves: A) must fail closed. B) provide variable resistance in a piping system. C) provide tight flow shut-off. D) must modulate from fully open to fully shut. E) are nearly always reverse acting.
B) provide variable resistance in a piping system.
A proportional controller: A) is also called a multi-position controller. B) provides a proportional output based on the error between process variable and set-point. C) does not allow operator input. D) provides on-off control. E) allows the process variable to always be maintained at the set-point.
B) provides a proportional output based on the error between process variable and set-point.
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.
B) shut off the fuel when the burner flame goes out.
A mercury switch bulb is under high vacuum: A) so it will not explode. B) to prevent corrosion of the contacts. C) to decrease electrical resistance. D) so contacts will not overheat. E) because the switch is normally closed.
B) to prevent corrosion of the contacts.
A controller is a device that primarily: A) sends or transmits a positive rather than negative signal. B) tries to maintain a set point. C) records a system's performance. D) notifies operators of errors or faults in a system. E) is a logic device capable of making decisions.
B) tries to maintain a set point.
A thermocouple consists of: A) a filament that is compared to the object being measured. B) two dissimilar wires connected together to form a hot and a reference junction. C) two dissimilar wires connected to a battery. D) a thermally-conductive fluid, held within a fine tube. E) a thermistor, coupled to a wheatstone bridge.
B) two dissimilar wires connected together to form a hot and a reference junction.
Automatically fired boilers will restart: A) when a lockout switch has been activated. B) when water level has been re-established. C) when power fails. D) if a flame failure has been detected. E) when the operator has completed the purge.
B) when water level has been re-established.
Modulating pressure controller output: A) will shut down and start up the burner. B) will vary the fuel and air flow to the boiler. C) will control the temperature of the furnace. D) is used on small boilers only. E) is unresponsive to steam flow.
B) will vary the fuel and air flow to the boiler.
Low-water fuel cut-offs must shut the fuel off before the water level drops to: A) the lowest possible water level. B) the fire line. C) 25 mm above the bottom of the gauge glass. D) the lowest visible water level in the gauge glass. E) the lowest heating surface.
C) 25 mm above the bottom of the gauge glass.
Electric current control transmission is between: A) 0-100 mA B) 10-20 mA C) 4-20 mA D) 10-100 mA E) 0-10 mA
C) 4-20 mA
Which of the following statements is FALSE of Pneumatic Signals? A) Always lag or delay in the signal. B) Friction causes a decrease in the value of the signal. C) More expensive than electronic instruments. D) Cost of tubing is greater than electrical wiring. E) Ensuring a clean, dry air supply may be costly.
C) More expensive than electronic instruments.
A float operated low-water fuel cutoff has its switch separated from boiler pressure by: A) a float cage. B) a seal cage. C) a flexible diaphragm. D) a siphon. E) packing.
C) a flexible diaphragm.
Integral and Derivative functions are: A) additions to all proportional controllers. B) also called right and reset controllers. C) an aid to improving effectiveness of the process controller. D) used in on/off control. E) integral to derivatives.
C) an aid to improving effectiveness of the process controller.
When a diaphragm device is used for boiler water level measurement, the boiler steam pressure is compensated for or off-set by: A) using a bellows on the HP side. B) a spring which balances the differential pressure. C) applying the pressure to both sides of the diaphragm. D) reversing the reference and variable legs. E) joining the reference and variable legs upstream of the device.
C) applying the pressure to both sides of the diaphragm.
In an area flow meter, the flow is measured: A) at the bottom of the float. B) at the top of the float. C) at the edge of the float head. D) at the outlet connection. E) mid range of the float travel.
C) at the edge of the float head.
Modulating combustion control on a heating boiler is accomplished by: A) shutting down or lighting up the burner as pressure or temperature rises or falls. B) regulating the air flow to control combustion. C) changing the amount of fuel and air to the burner. D) opening or closing the forced draft damper. E) regulating the fuel and feedwater flow.
C) changing the amount of fuel and air to the burner.
The unit kg/m³ describes a material's _____________________. A) specific gravity B) pressure C) density D) flexibility E) displacement
C) density
A valve that seals on the down-stroke is: A) reverse-acting. B) single sealed. C) direct-acting. D) double sealed. E) uni-directional.
C) direct-acting.
In a proportional only controller, the controller stops the drift from set points but does not bring the process back to setpoint. The difference is called _________________________. A) differential B) offset C) error D) reset E) rate
C) error/deviation ch. 84 - pg. 300 & ch. 86 - pg. 342
In a glass stem thermometer the space above the liquid is usually: A) carbon dioxide. B) argon. C) evacuated. D) air. E) approximately 50% air.
C) evacuated. (AKA a vacuum)
A strain gauge can be used to measure: A) stresses in pipe walls. B) pressure in boilers. C) forces on a column. D) the densities of materials. E) the tension given by a compressive loads.
C) forces on a column.
Orifice plates, venturi tubes and nozzles belong to the group called: A) temperature meters. B) pressure meters. C) head meters. D) analog meters. E) constant output meters.
C) head meters.
Integral and Derivative functions A) may be combined with multi-position controllers. B) are also called feed-forward and cascade functions. C) help to maintain a process variable on set-point. D) Are used in on-off control. E) Slow down the controller response when the process variable deviates from the set point.
C) help to maintain a process variable on set-point.
A/An ___________________ instantly show the values of different variables to the operators and maintenance personnel. A) transmitter B) controller C) indicator D) recorder E) process variable
C) indicator
To operate the type of flame failure device which incorporates a lead sulphide cell, it must receive: A) heat from flame. B) ultraviolet rays. C) infrared rays. D) heat and radiation. E) a digital signal.
C) infrared rays.
A steam boiler must be equipped with two low-water fuel cut-off devices when the boiler: A) has over 47 m² of heating surface. B) has dual fuels. C) is not continuously attended. D) uses coal as fuel. E) has two burners.
C) is not continuously attended.
A float operated level control: A) will recognize swell and shrinkage and correct the feedwater flow. B) will have the float in the boiler drum. C) is only used on small boilers. D) is used on fire tube boilers only. E) must be used when a boiler is manually operated.
C) is only used on small boilers.
Automatic systems that can make decisions are termed: A) annunciation systems. D) indicating systems. C) logic systems. D) open loop systems. E) Go-NoGo systems.
C) logic systems.
The most reliable method of checking or testing a low-water fuel cutoff is to: A) blow the low-water cutoff down through the water column until the burner cuts out. B) blow the float chamber down to see if the burner will cut out. C) lower the water in the boiler to the level where the burner should cut out. D) blow down the sight glass to see if the burner goes out. E) manually trip the mercury switches to shut off the burner.
C) lower the water in the boiler to the level where the burner should cut out.
An automatic feedwater regulator is used to: A) operate in place of a boiler feed pump. B) activate the low-water fuel cut-off. C) maintain a constant water level in the boiler. D) control the chemical feed treatment to the boiler. E) maintain the water level in a hot water boiler's gauge glass.
C) maintain a constant water level in the boiler.
A packaged steam boiler modulating combustion control system will routinely: A) maintain drum level within a desired range. B) maintain flue gas temperature at some set point. C) maintain boiler steam pressure within a desired range. D) satisfy all load demands regardless of capacity. E) alter flue flow without changing the air flow.
C) maintain boiler steam pressure within a desired range.
A variable adjusted in order to maintain or achieve a desire value of another variable is termed the: A) process variable. B) final variable. C) manipulated variable. D) controlled variable. E) transmitted variable.
C) manipulated variable.
A circular chart recorder: A) provides a different function than a strip chart. B) is newer design than a strip chart. C) may incorporate a Bourdon tube. D) does not provide a permanent record. E) is used on a computer screen.
C) may incorporate a Bourdon tube.
A device used to convert audio tones to computer language is commonly known as a _______________________. A) transmitter B) multiplexer C) modulator/demodulator D) CPU E) microphone
C) modulator/demodulator
The second from last step in an automatic boiler programmed shutdown sequence is: A) timer shutdown. B) main flame trial. C) post purge. D) operating control switch contacts closing. E) flame failure switch contacts opening.
C) post purge.
Automatic boiler programming controls A) must incorporate a modulating control system. B) do not require interlocking devices. C) require an ON-OFF or multi-range control switch. D) cannot make use of high-low fire control. E) are not interconnected with the water level control system.
C) require an ON-OFF or multi-range control switch. ch. 88 - pg. 372
When a boiler shuts down due to an unsafe operating condition, before the boiler will restart, the trip must be: A) reported to the chief engineer. B) logged. C) reset. D) checked by an instrument tech. E) a & c
C) reset. ch. 88 - pg. 381 & 382 & 386
When an automatic unattended boiler starts up, the program timer will first: A) energize the ignition transformer and pilot gas solenoid valve. B) start the post purge period. C) start the air fan. D) energize the main gas valve. E) energize the main feedwater valve.
C) start the air fan.
In an automatic boiler startup program, if any part of the startup sequence is not complete the controller will: A) hold in the position. B) try again after a timed sequence. C) terminate the startup & do a post purge. D) move to the next step. E) shut the air dampener.
C) terminate the startup & do a post purge.
The boiler must be equipped with a second low-water fuel cut-off when: A) the boiler has over 47 m2 of heating surface. B) the boiler has dual fuels. C) the first device is also used to control the feedwater flow. D) the boiler uses coal as a fuel. E) the boiler has two burners.
C) the first device is also used to control the feedwater flow.
Single element feedwater control systems are very efficient in maintaining the boiler water level when: A) the boiler has a large water capacity. B) the boiler is a fire tube boiler. C) the fluctuations in load are slow and small. D) load demands are low. E) the boiler is gas fired.
C) the fluctuations in load are slow and small.
During a programmed startup if an igniter spark is visible but no flame appears, the operator should suspect: A) boiler low water level. B) the main burner manual fuel valve is closed. C) the pilot manual fuel valve is closed. D) the scanner lead sulphide cell is weak. E) the boiler steam pressure operating control switch is open.
C) the pilot manual fuel valve is closed.
Glass thermometers with a mercury fill, are sometimes pressurized with nitrogen so: A) they can be installed in any position. B) they can be used at a very low temperature. C) they can be used at higher temperatures. D) the vaporizing temperature of the mercury is lowered. E) the thermometer can be used at higher pressure.
C) they can be used at higher temperatures.
The function of a programming control is: A) to supervise feedwater supply to the boiler. B) to regulate the fuel supply to the burner. C) to regulate combustion controls during start-up. D) control the boiler blowdown rate. E) to regulate fuel, air, and water supply to the boiler.
C) to regulate combustion controls during start-up.
The function of a programming control is: A) to supervise feedwater supply to the boiler. B) to regulate the fuel supply to the burner. C) to regulate combustion controls during startup. D) control the boiler blowdown rate. E) to regulate fuel, air and water supply to the boiler.
C) to regulate combustion controls during startup.
The major elements needed to construct automatic control loop instrumentation systems includes a sensing element, a ___________________, a controller and a control valve. A) recorder B) resistor C) transmitter D) manometer E) float cage
C) transmitter
A single element thermohydraulic feedwater regulator uses ______________ as operating media. A) oil and nitrogen B) CO2 and water C) water and steam D) mercury and water E) air and water
C) water and steam
The drain of a hot water boiler low-water fuel cutoff should be opened _______________ to flush out any debris. A) annually B) daily C) weekly D) monthly E) each shift
C) weekly
Liquids must be vapourized: A) in order to measure density. B) if purity is to be measured. C) when a chromatograph is being used. D) when conductivity is measured. E) when resistance or reluctance is being measured.
C) when a chromatograph is being used.
The variable area meter consists of: A) a fluid being measured, flowing through the tube from the top to the bottom. B) a float across which the differential pressure varies. C) a tube which is of constant area. D) a tapered tube in which the fluid being measured flows through the tube from the bottom to the top. E) an opening that can be varied are required.
D) a tapered tube in which the fluid being measured flows through the tube from the bottom to the top.
Most solenoid valves operate so that the upstream line pressure will: A) act to open the valve. B) be less than downstream pressure. C) be sensed by a transmitter. D) act to close the valve. E) must pass through a restriction or nozzle.
D) act to close the valve.
A helix strip bimetallic thermometer is wound into a spiral to: A) dampen the motion. B) ease the installation. C) increase range of temperature measurement. D) amplify the motion of the pointer. E) retard the expansion of the strip.
D) amplify the motion of the pointer.
When a recorder receives a signal from a transmitter, the recorder incorporates a/an ____________________________. A) signal reverser B) pneumatic relay C) flapper-nozzle assembly D) capsule or bellows E) transducer
D) capsule or bellows
An open loop control system requires: A) a transducer and a recorder. B) more accurate sensing devices. C) a very small amount of dead time or lag. D) constant operator attention. E) two final control elements.
D) constant operator attention.
In an automatic control system, the controller output signal changes the position of the: A) recorder. B) transmitter. C) sensing element. D) control valve. E) indicator dial.
D) control valve.
A low-water fuel cut-off is fitted to a boiler to prevent: A) damage to the radial stays in the steam dome. B) the fire from shutting off too quickly and damaging the boiler. C) shutting off the water when there is no fuel. D) damage to the boiler from an overheated condition. E) damage to the boiler from over pressure.
D) damage to the boiler from an overheated condition.
The majority of new computer controlled process plants are: A) large mainframe computers. B) stand-alone microcomputers. C) individual digital controllers. D) distributed control systems. E) manually operated processes.
D) distributed control systems.
In a control system, the controller tries to eliminate deviation by sending a signal to the: A) sensing element. B) transmitter. C) transducer. D) final control element. E) relay.
D) final control element. ??????
The mechanism basic to all pneumatic transmitters is the: A) actuator. B) positioner. C) relay. D) flapper, nozzle, and restrictor. E) amplifier.
D) flapper, nozzle, and restrictor.
A thermocouple will produce a signal which: A) will be read on a pressure scale. B) will be fully proportional to a temperature difference. C) increases as temperature decreases. D) is not quite proportional to temperature differences. E) varies inversely with temperature.
D) is not quite proportional to temperature differences.
For an electronic analog control loop, the transmitter generates a signal in: A) ohms B) milliohms C) amps D) milliamps E) volts
D) milliamps
The electrical output from a thermocouple is measured by a/an ____________________________. A) milliampmeter. B) wattmeter. C) milliwattmeter. D) millivoltmeter. E) ohmmeter.
D) millivoltmeter.
A Bourdon tube is often in the shape of a spiral so that A) its final output has less travel. B) gears can be used for final output. C) higher pressures can be sensed. D) more power and travel of the output occurs. E) its sensitivity will be decreased.
D) more power and travel of the output occurs.
An example of a use of hydraulic control is: A) on a boiler feedwater valve. B) for a boiler Maxon. C) for a cooling water valve. D) on a steam turbine governor. E) for air control for boiler combustion.
D) on a steam turbine governor.
In a float type low-water fuel cutoff, the main purpose of the mercury switch is to: A) open the burner circuit when the level is high. B) close the burner circuit when the level is low. C) activate a low water alarm. D) open the burner circuit when the level is low. E) close the burner circuit when the level is high
D) open the burner circuit when the level is low. *the mercury is not touching the contacts when the water level is low and the circuit is broken/open shutting off the fuel.
A set of conditions that prevents a piece of equipment from starting because of an unsafe condition is a/an: A) interconnected conditions B) protectives C) trips D) permissives E) pre-startup variables
D) permissives
A fire eye or flame scanner keeps the burner circuit energized as long as the burner flame is maintained. This is accomplished using a: A) control valve B) recorder C) thermocouple D) photoelectric transducer E) controller
D) photoelectric transducer
A valve actuator: A) cannot be reverse acting. B) will always have one side of the diaphragm open to atmosphere. C) is a two-position device. D) position is a function of controller output. E) causes a valve to always fail open.
D) position is a function of controller output.
Relative to flow, velocity is kinetic energy and when velocity increases, the: A) pressure and potential energy, will also increase. B) cross-sectional area of the piping will be increased. C) the mass quantity flowing per second will decrease. D) potential energy in the form of pressure will decrease. E) density will decrease.
D) potential energy in the form of pressure will decrease.
A combustion air proving switch: A) senses O2 content of the air. B) senses flue gas pressure. C) detects O2 in flue gas. D) senses windbox pressure. E) senses air temperature.
D) senses windbox pressure.
An increase in steam pressure causes a sudden drop in water volume in the drum, and is known as _______________. A) swell B) growth C) rise D) shrink E) decline
D) shrink
Boiler furnaces are purged: A) so that the programmer has time to verify permissiveness of interlocks. B) in order to ensure combustion gases are not fully removed prior to ignition. C) while the operator is given the opportunity to check fuel and water systems. D) so that combustibles are fully removed prior to ignition. E) to cool any glowing refractory.
D) so that combustibles are fully removed prior to ignition.
During a programmed start, if the forced draft fan starts but shuts down after 5-10 seconds, you should first check: A) the fan motor contacts. B) the motor overload protection. C) the motor windings temperature. D) the low draft pressure switch. E) the dampener position.
D) the low draft pressure switch.
Low-water fuel cut-off should shut the fuel off is the water level drops below: A) the lowest permissible water level. B) the fire line. C) 25 mm above the bottom of the gauge glass. D) the lowest visible water level. E) below the tops of the tubes in the top row of tubes.
D) the lowest visible water level.
The apparatus that converts current signals to pneumatic and pneumatic to current signals is a _____________________. A) diverter. B) inducer. C) inverter. D) transducer. E) transformer.
D) transducer.
Low pressures and vacuums may be measured: A) with a transducer. B) with a controller. C) in tonnes. D) with a manometer. E) in newtons.
D) with a manometer.
The Bourdon tube is often shaped in the form of a "C", having an arc span of about: A) 180 degrees B) 360 degrees C) 200 degrees D) 90 degrees E) 270 degrees
E) 270 degrees (3/4 turn)
The type of combustion fuel control frequently used on small package boilers, is a/an: A) scanner control. B) modulating control. C) high fuel level cut-off. D) constant pressure control. E) On/Off control.
E) On/Off control.
Which of the following is a programming language? A) Pathon B) Word C) Executible D) C+- E) Pascal
E) Pascal
For a filled system thermometer, sensing is due to: A) differential pressure B) light emission C) voltage created by dissimilar metals D) different expansion rate of metals E) change in volume of a liquid.
E) change in volume of a liquid. Needs to be verified text book says fluid (liquid or gas)
A control loop controller: A) operates without a set point. B) sends a signal to a primary element. C) measures the manipulated variable value, eliminating the need of a primary element. D) eliminates all set point deviation. E) constantly compares input signals to the set point.
E) constantly compares input signals to the set point.
A sensing element responds to the value of the ______________. A) controller B) recorder C) control valve D) transducer E) controlled variable
E) controlled variable
If the igniter fails to spark, which of the following is not a possible cause? A) electrodes grounded. B) loose ignition cable. C) ignition cable shorted. D) faulty transformer. E) faulty flame scanner.
E) faulty flame scanner.
On a basic pneumatic transmitter, a movement of the flapper towards nozzle will: A) increase the nozzle bleed. B) change the size of the supply orifice. C) maintain steady transmitter output. D) change transmitter supply pressure. E) increase feedback bellows pressure.
E) increase feedback bellows pressure.
When controller output is proportional to the amount of error/deviation, the controller is: A) derivative only. B) integral. C) two-position. D) proportional plus reset plus rate. E) proportional.
E) proportional.
Control valves: A) consist of a valve body and accommodator. B) are not considered a final control element. C) provide a fixed resistance to flow. D) have one major component. E) require a pressure drop across the valve to maintain flow.
E) require a pressure drop across the valve to maintain flow.
In a natural gas programmed boiler startup, what is the last step before the main fuel valve opens: A) fan starts B) purge times out C) igniter activates D) pilot lights E) scanner detects pilot flame
E) scanner detects pilot flame
The CSA code states that a steam boiler not under continuous attendance must be equipped with a second low-water fuel cutoff which: A) must be a manually reset device. B) can also activate an alarm. C) may be equipped with isolate valves. D) must be a normally open switch. E) serves no other purpose.
E) serves no other purpose. * When the first device is used for boiler feedwater control.
The second element of a two element feedwater control system compensates for, or offsets: A) level variation. B) differential feedwater pressure. C) differential steam flow rate. D) feedwater temperature variation. E) shrink and swell.
E) shrink and swell.
The constant head connection in a remote water level indicator is made to the ____________________________________. A) feedwater pump discharge B) water space C) atmosphere D) feedwater regulating valve E) steam space
E) steam space
The Bourdon tube can be used with a bulb and capillary tube to measure _________________________. A) viscosity B) water head C) flow D) humidity E) temperature
E) temperature
Temperatures are measure by: A) watt meters. B) Bourdon tubes. C) thermowells. D) pressure differential. E) thermocouples.
E) thermocouple.
A device that can change one form of measurement into a signal, is a: A) controller. B) logic device. C) primary element. D) relay switch. E) transmitter.
E) transmitter.
Cascade control utilizes: A) one controller, one transmitter and two valves. B) one controller, two transmitters and two valves. C) two controllers, one transmitter and two valves. D) two controllers, two transmitters and two valves. E) two controllers, two transmitters and one valve.
E) two controllers, two transmitters and one valve.
The low-water fuel cut-off, shuts off the ___________________ if the water level is too low.
Fuel
Explain why double seated control valves are better-suited to throttling action than single seated.
Less force is required to position the control valve because the pressure of the fluid acts on the top of one seat and the bottom of the other. This nearly cancels of the force due to the pressure that tends to hold a single seated valve open or closed.
Describe modulating combustion control as it applies to a steam boiler.
Modulating control occurs when the burner remains lit at all times but the flame size is increased and reduced by controlling fuel and air flow to the burner according to steam pressure. As the steam pressure drops, the fuel and air flow are increased and vise verse.
Explain the operation of a diaphragm level indicator used as a remote level indicator for a boiler.
The diaphragm chamber is located below the steam drum of the boiler. One side is attached below the water level and the other side above the water level on the steam side. The leg attached above the water level has a lefg As the water level changes the mass of water also changes which changes the pressure of the fluid at the bottom of the drum (1 vertical meter of water exerts a pressure of approximately 9.81 kPa on earth). The change in pressure of the leg below the water level causes the diaphragm to flex. The diaphragm is connected through linkage to an indicating pointer that rises and falls on a scale to indicate the level in the boiler.
Describe a single element drum level control loop employing electronic or pneumatic instrumentation with a remotely mounted controller. **This question needs to be re-written because it is a little confusing.*
The differential pressure cell of a level transmitter is attached to the boiler steam drum above and below the water level. This cell senses the level in the boiler and the transmitter generates an instrument signal that is sent to the controller on the control panel. The level is displayed on the controller indication and the level signal
State the purpose of a low-water fuel cutoff device.
The low-water cutoff (LWCO) device shuts the fuel off to the boiler if the water level in the boiler falls below the lowest safe water level.
A boiler control transfer or selector station A) can be used to manually override automatic control loops B) can be changed from manual to automatic without balancing C) is located upstream of the controller in a control loop D) output is directed to the primary element of a loop E) must be operated in manual mode for only short periods
a
A computer normally displays information to the operator via A) a CRT or LCD B) an icon C) a CAD D) a Modem E) a CPU
a
A typical use of a mainframe computer system in a process would be A) the operation of a modulating control valve B) acting as a "host" computer C) producing hard copies of a plant system D) producing graphics of a plant system E) storing information onto a floppy disk
a
A valve which gives good throttling action, takes less actuator force, but does not seal well is a: A) Double seated valve B) Reverse acting valve C) Multiple-disc valve D) Single seated valve E) Direct acting valve
a
An analog control loop output must be put through a _____ before the computer can react to the signal. A) Digital converter B) Signal inverter C) ROM detector D) Modem E) CPU
a
If a shutdown occurs during normal firing of a boiler and the steam pressure is below the normal cutout value, the problem could be: A) An interlock, such as the combustion air proving switch, has failed B) Main flame trial failure C) Pilot flame trial failure D) Igniter transformer failure E) High steam pressure limit switch tripped
a
If during the pilot trial for ignition period, the pilot does not ignite, a lockout will occur A) If the trial for ignition period has lasted approximately 15 to 30 seconds B) Immediately C) Within 4 or 5 seconds D) After the flame relay de-energizes E) After the main burner flame ignites
a
If pilot or low-fire flame occurs in a boiler which one would NOT be the possible cause? A) Low fire switch open. B) Insufficient pilot or low fire flame. C) Supply to main nozzles restricted or cut off. D) Inoperative programmer.
a
In a two element feedwater control the following items are measured: A) boiler water level and steam flow B) feedwater flow and steam flow C) boiler water level and feedwater flow D) boiler water level and fuel flow E) temperature and volume of feedwater
a
Inputs for logic and supervisory computer functions are mainly: A) By switch contacts B) Actions of an operator using the keyboard C) Stored on a disk which is required for operation D) Controlled by relays E) Non-decision making
a
On a boiler with high-low fire control, if the damper positioning switch is in the wrong position A) the damper motor may not operate B) a pre-purge will not occur C) a high fire main flame ignition could occur D) nothing will happen when the manual start switch is closed E) the pre-purge period will last indefinitely unless the problem is corrected
a
On a gas fired automatic boiler a normal programmed start-up takes approximately: A) 105 seconds B) 55 seconds C) 27 - 40 seconds D) 120 seconds E) 70 seconds
a
The manual fuel shut-off valves of an automatic oil-fired boiler must be opened A) Prior to pre-purging B) After pre-purging and just prior to pilot ignition C) Immediately after completion of the pilot flame trial D) After the automatic main burner fuel valve opens E) At the same time as the automatic main burner fuel valve
a
If no ignition occurs when starting a boiler which one would NOT be the possible cause? A) Lack of spark. B) Insufficient pilot or low fire flame. C) Spark but no flame. D) Low fire switch open. E) Timer switch in test position and timer stopped in prepurge.
b
Soft keying is: A) Done only with laptop computers B) Done to make the computer quicker and easier to use C) A method of pressing a key twice before a result is obtained D) The same as using a mouse or joystick E) Also called "double-clicking."
b
At the end of the pre-purge period, the combustion programmer: A) Shuts down B) Opens the main fuel valve C) Closes the pilot valve D) Ends the ignition trial E) Energizes the ignition transformer
e
The main function of a mainframe computer system is to: A) Evaluate systems by comparison B) Rapidly process large amounts of data C) Perform only a specific dedicated task D) Produce hypothetical solutions to problems E) Act as a networking switch
b
Transmitters that transmit digital codes directly to a computer are known as: A) Digital transmitters B) Smart transmitters C) Analog transmitters D) Pneumatic transmitters E) Modems
b
When personal computers are linked together and information flows between them, it is called: A) Telecommunicating B) Networking C) Teleconferencing D) Linking E) Hardware sharing
b
Boiler modulating feedwater control flow rate depends on A) level set point B) control valve position C) actual level D) feedwater pressure E) set point, level, and valve position
e
With single element feedwater control the level transmitter output is A) received by a final element B) proportional to drum level C) sent to a selector station D) constant regardless of level E) a function of steam flow
b
A device use to measure variations in atmospheric pressure is called a _____________________________.
barometer.
State the most common signal range for pneumatic instrument signals.
between 20 and 100 kPa
Pneumatic controllers are divided into two basic classes __________________________ & ______________________________.
bleed and non-bleed
A process computer connected to digital inputs is protected from harmful voltages by means of: A) Splitter bars B) Fuses C) Isolating circuits D) Circuit breakers E) Stand-alone devices
c
After extinguishing the main flame, the next step in a programmed burner shutdown is A) The timer motor stops B) The main flame trial ends C) A post-purge begins. D) Operation control switch contacts close E) Flame failure switch contacts open
c
The margin by which an automatic controller misses the desired value is called ______________________.
error
If a blower does not start which one would NOT be the possible cause? A) Main disconnect switch open. B) Blown fuses, tripped overloads, loose electrical connections. C) Damper positioning switch in wrong D) Combustion control safety lock-out switch tripped. E) Limit control circuit not completed.
c
If the damper motor does not operate on a boiler which one would NOT be the possible cause? A) Damper positioning switch in wrong position. B) Linkage loose or jammed. C) The lock-out switch has tripped. D) Motor does not drive to "open" or "close" during prepurge or close on burner shutdown. E) Motor does not operate on demand.
c
If the pilot flame is adequate but the main burner fails to ignite, the programmer must: A) Hold the program in its present state B) Recycle the start-up sequence C) Proceed to post purge and lockout while sounding an alarm. D) Go directly to a lockout condition E) Sound an alarm
c
On a steam boiler with single element feedwater control, the following item is measured: A) steam flow B) feedwater flow C) boiler water level D) fuel flow E) feedwater pressure
c
On-off controls are common on? A) firetube boilers B) watertube boilers C) small package boilers D) large package boilers E) all of the above
c
The timer of a programmed combustion control consists of a motor and a: A) Bellows B) A nozzle and vane assembly C) Number of cams and switches D) Transmitter E) Drive shaft
c
The type of circuit used to store (write) and retrieve (read) information from a computer is known as its: A) Bytes B) Motherboard C) RAM D) CPU E) ROM
c
When an automatic unattended boiler starts up, the program timer will first: A) Energize the ignition transformer and pilot gas solenoid valve B) Start the post purge period C) Start the forced draft fan D) Energize the main gas valve E) Energize the main feedwater valve
c
Which of the following would be the best choice for a powerhouse control-room installation? A) A minicomputer B) A mainframe computer C) A microcomputer D) A netbook computer E) A laptop computer
c
With an automatic oil-fired boiler programmed control, a typical firing period begins approximately: A) 44 seconds after FD fan starts B) 75 seconds after FD fan starts C) 60 seconds after FD fan starts D) 10 seconds after pilot extinguishes E) 47 seconds after pre-purge
c
A device used to convert audio tones to computer language is a: A) Transmitter B) Multiplexer C) Plotter D) Modulator/demodulator E) CPU
d
A multiplexing sequence may be repeated as frequently as A) Once per hour B) Twice per minute C) Twice per second D) Four times or more per second E) Fifty times per second
d
A proportional-only controller: A) Are mostly used for on/off control. B) Compare actual conditions to controller outputs. C) Must provide reset action. D) Cannot always maintain the process variable exactly at the set-point. E) Are sometimes called Multi-position controllers.
d
An interrupted pilot of an automatic boiler: A) Burns continuously, like that in a home furnace B) Ignites before the main burner ignites, and is extinguished when the main burner is extinguished C) Is one that has been extinguished by an inadequate flame signal D) Ignites, is proven stable and extinguishes after the main flame is established E) Must be manually ignited
d
Boiler furnaces are purged: A) So that the programmer has time to verify permissiveness B) So that combustion gases are fully removed prior to ignition C) So that the operator has time to check the fuel and water systems D) So that combustibles are fully removed prior to ignition E) To cool the hot refractory
d
Data cannot be permanently stored on a A) CD-ROM B) Hard disk C) PSU D) Monitor E) DVD-ROM
d
Digital output signals are processed by _____ before an analog controls can react to them. A) Digital receivers B) Logic controllers C) Modems D) Analog converters E) Integrated circuits
d
One common example of a photoelectric transducer used on boilers is the _______________________________ scanner.
flame
If the burner stays on low fire on a boiler which one would NOT be the possible cause? A) Boiler pressure above high-low fire control setting. B) Damper positioning switch in wrong C) Inoperative damper motor. D) Flame detector weak or defective. E) Defective high-low fire or modulating control.
d
Run time totals, recorded by a computer, are commonly used: A) In graphic displays B) For inventory control C) For logic supervisory systems D) For maintenance management E) With a modem
d
The programmer will go through a post purge: A) Only if pilot fails to ignite B) Only on flame failure C) By manually advancing the timer D) On any type shutdown except, power outage E) On routine shutdown only
d
One of the most widely used process variables in a system is ______________________.
flow
A flapper-nozzle assembly is basic to all A) controllers B) transmitters C) recorders D) pneumatic devices E) actuators
d) pneumatic devices/transmitters.
An upset in a plant process is called a/an _______________________.
disturbance
If shutdown occurs during firing a boiler which one would NOT be the possible cause? A) Loss or stoppage of fuel B) Defective fuel valve, loose electrical connections C) Flame detector weak or defective D) Lens dirty or sight tube obstructed E) Boiler pressure above high-low fire control setting.
e
Sharing and transferring information between computers is termed: A) Central processing B) Multiplexing C) Plotting D) Number crunching E) Networking
e
The common standard control modes for a plant control system are A) integral and derivative B) proportional and reset C) proportional, reset, and integral D) reset, integral, and rate E) derivative, proportional, and integral
e
The main component of any computer is the: A) Keyboard B) Screen C) Modem D) Printer E) Central processing unit
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
e
Modulating combustion control on a heating boiler is accomplished by changing the amount of ________________ & ________________ to the burner.
fuel & air
To increase the movement of a Bourdon tube without use of linkage, that may cause additional error, the tube can be formed into the shape of a ___________________ or a __________________ and as a result become more accurate.
helix or spiral
The five main components of a two element feedwater control system are the ________________________, ________________________, ________________________, ________________________, and ________________________.
the drum level transmitter the flow transmitter the feedwater control valve the controller the manual/auto station
