BCIT 5th class boiler engineer quiz 1 Flashcards
Large pipes which collect or supply fluid from a series of smaller pipes or tubes are called
a) headers.
b) collectors.
c) siphons.
d) boiler tubes.
e) waterlegs.
a) headers.
CH001 Q14
A header is a larger pipe which supplies to or collects from a series of smaller pipes or tubes. Also called a manifold.
Large steam generating units used to produce electricity common consume fuel at rates in excess of 100 tonnes per hour.
True
False
True
CH001 Q31
Large Steam Generating units may burn 100 to 1000 tonnes of coal per hour.
The combustion zone of a straight tube watertube boiler is surrounded by

a) widely spaced horizontal water filled tubes.
b) finned tube heat exchange surface.
c) refractory.
d) closely spaced vertical water filled tubes.
e) layers of loosely wound tubes.
a) widely spaced horizontal water filled tubes.
CH001 Q28
As shown in the figure below, the straight tube longitudinal drum boiler is made up of a steam drum and a large number of straight tubes. The tubes are connected to headers at each end and the header, in turn, are connected to the steam drum. The entire unit is supported on a brick setting which contains the furnace area and flue gas passages. The tubes and bottom half of the drum are filled with water. Hot gases from combustion circulated around the tubes and are directed by baffles through the heating zone and out to the stack. The tubes are sloped and as the water is heated and steam bubbles form, the water and steam rise upward through the tubes and are collected in the upper headers and returned to the steam drum. The heavier water flows down the headers at the back end of the boiler to replace the water rising to the drum and circulation is maintained.
The term “condensate” refers to
a) water supplied to the boiler to make up for losses in the system.
b) the water formed when steam gives up heat and returns to a liquid.
c) water supplied to a boiler from the deaerator.
d) water drained from a boiler to remove sludge.
e) water formed by the combustion of hydrogen in the fuel.
b) the water formed when steam gives up heat and returns to a liquid.
CH001 Q22
In a steam heating system the boiler supplies steam to the heating system. In this system various pieces of equipment are connected by supply and return piping. The steam gives up its heat in the equipment and condenses back into water forming what is commonly called steam condensate. This condensate is returned to the boiler to be converted to steam again.
The brick or concrete like material used in a boiler to withstand high temperatures and erosion is called
a) insulation.
b) cladding.
c) foundation.
d) refractory.
e) cement.
d) refractory.
CH001 Q04
Refractory is the protective layer of material that is applied to various parts of the boiler to withstand high temperature and abrasion. It usually has an appearance similar to concrete or brick. Refractory is also added to keep the combustion zone temperature high enough to ensure complete combustion because it absorbs and stores heat from the flame.
The term “uptake” refers to the
a) opening allowing access to the furnace.
b) top of a straight tube boiler furnace.
c) duct that conveys flue gases to the stack.
d) shield that protects the gauge glass.
e) duct that supplies combustion air to the burners.
c) duct that conveys flue gases to the stack.
CH001 Q13
Uptake, the duct used to convey the spent combustion gases from the boiler to the stack or chimney. Also known as the flue vent or breeching.
The actual level of water in a boiler is called the
a) steam line.
b) water line.
c) interface.
d) steam space.
e) water space.
b) water line.
CH001 Q12
Water line is the actual level of water in a boiler. It is the point at which water and steam separate.
The travel of combustion gases once along the length of a boiler is called
a) a travel.
b) an uptake.
c) a combustion gas pass.
d) a furnace tube.
e) a fire tube.
c) a combustion gas pass.
CH001 Q17
Combustion gas pass, one pass is the travel of the combustion gases once along the length of the boiler. If the gases are reversed and passed through additional tubes of the boiler, this is a second pass. For example, in a two pass boiler, combustion gases make two sweeps or passes through the boiler.
A boiler that is only operated when a qualified operator is present to monitor its operation is called
a) an industrial boiler.
b) an HRT boiler.
c) a supervised boiler.
d) an attended boiler.
e) a controlled boiler.
d) an attended boiler.
CH001 Q01
An attended boiler is a boiler that is only operated when a qualified operator is present to watch over and control the various boiler functions.
The boiler shown below is
a) an “A” Type.
b) a “Q” Type.
c) a “D” Type.
d) a “C” Type.
e) an “O” Type.
e) an “O” Type.
CH001 Q26
The boiler shown in this figure is an “O” Type.
The term “heating surface” refers the parts of the boiler
a) that heat is transferred from the hot gases to water or steam.
b) where combustion of the fuel takes place.
c) that keep the high temperature from escaping the furnace.
d) where steam is superheated.
e) where the flame impinges on the walls.
a) that heat is transferred from the hot gases to water or steam.
CH001 Q08
The heating surface of a boiler consists of all parts of the boiler through which heat from the burning fuel is transferred to the water side of the boiler. It includes all parts of the boiler plates and tubes which have water or steam on one side and are swept by fire or hot combustion gases on the other side.
The purpose of multiple drums in a three drum bent tube boiler was to
a) reduce the cost of manufacture.

b) improve heat transfer from the hot gases to the water.

c) reduce required height for low ceiling installations.
d) improve water circulation.
e) provide two mud drum for sediment to settle out.
c) reduce required height for low ceiling installations.
CH001 Q33
The 3 drum design was created to reduce the height requirement of a water tube boiler to allow for installation in low ceiling facilities.
A machined and slightly tapered short pipe found in sectional cast iron heating boilers is referred to as
a) a push nipple.
b) a tapered bushing.
c) a water leg.
d) a tie rod.
e) a cleanout plug.
a) a push nipple.
CH002 Q11
The short tapered pipe between the sections of a cast iron sectional heating boiler is referred to as a push nipple.
Cast-Iron boiler sections maximize heat transfer by
a) exposing as large a surface as possible to the hot gases.
b) using an external furnace.
c) using four push nipples per section.
d) vertical firing.
e) using as few passes as possible.
a) exposing as large a surface as possible to the hot gases.
CH002 Q15
The heat transfer is maximized by ensure that the flue gases are as low temperature as possible when exiting the stack. This requires extended heat transfer surface to extract the heat from the flue gases and transfer them to the water. This is done by using a number of gas passages.
The water filled component that extends from the main section and surrounds the furnace in some cast iron boilers is referred to as
a) a refractory wall.
b) a water tube furnace.
c) an internal extension.
d) a water leg.
e) a convection bank.
d) a water leg.
CH002 Q01
The term waterleg refers to a water- filled section extending from the shell, which surrounds the firebox of some types of boilers. Most locomotive boilers are equipped with waterlegs around the firebox.
A cast iron boiler disadvantage is
a) they are limited to relatively low pressures.
b) they are difficult to assemble.
c) they are subject to corrosion.
d) they have high ductility.
e) they are extremely high cost.
a) they are limited to relatively low pressures.
CH002 Q17
One disadvantage of cast iron boilers is that the pressure they can withstand is low compared to steel boilers.
The term “condensing boiler” refers to a boiler where
a) some of the steam produced in the boiler is condensed before entering the heating system.
b) the flue gases are cooled to the point where moisture is condensed in the boiler heat exchanger.
c) condensate from a gas processing plant is used as fuel.
d) condensate is used as feedwater for the boiler.
e) condensate from the heating system is not returned to the boiler.
b) the flue gases are cooled to the point where moisture is condensed in the boiler heat exchanger.
CH002 Q21
Most fuels contain some hydrogen which is converted to water when burned. In addition, some boilers have water in the fuel that evaporates during combustion. In order to maximize boiler efficiency the flue gases must be cooled as much as possible by transferring heat to the water. However if the temperature is lowered too much, the water vapor in the flue gas begins to condense. This condensation tends to cause corrosion in the heat exchangers and stack. When building these high efficiency boilers, the materials used must be chosen to ensure that they can withstand this corrosion.
The sections of a cast iron sectional boiler are held together by
a) push nipples.
b) gaskets.
c) flaring of tube ends.
d) gravity.
e) tie rods.
e) tie rods.
CH002 Q03
The sections of a cast iron boiler are held together by long tie rods extending the length of the boiler or short tie rods as shown below.
Smaller firetube boilers are low cost and
a) reach operating pressures very quickly from a cold start.
b) require very critical water treatment.
c) have simple rugged construction.
d) are not suited to ON/OFF operation.
e) do not cause much damage on waterside rupture.
c) have simple rugged construction.
CH003 Q35
Small firetube boiler are made with a simple rugged construction. While they will heat up faster than large boilers, it is important not to heat them too quickly or stress may occur to the metal. Any boiler operating under pressure will cause extensive damage if a rupture occurs because water in the boiler will flash into steam increasing its volume by about 1600 times.
In a vertical firetube boiler, the steam space is located
a) at the top of the shell.
b) this type of boiler does not require a steam space.
c) in a separate chamber.
d) in a compartment on the side.
e) at the lower part of the shell.
a) at the top of the shell.
CH003 Q27
In a vertical boiler, the top of the shell is the steam space.
One improvement to firetube boilers was adding a furnace tube inside the shell. This is referred to as
a) an internally fired boiler.
b) a water tube boiler.
c) an HRT boiler.
d) a furnace tube boiler.
e) a package boiler.
a) an internally fired boiler.
CH003 Q03
A boiler in which the furnace is surrounded by water by inserting a furnace tube through the shell or surrounding the furnace with water tubes is called an internally fired boiler.
A boiler in which combustion of the fuel takes place outside the boiler and the hot gases pass through the boiler to heat the water is called
a) a remote furnace.
b) a haycock boiler.
c) a locomotive boiler.
d) a firebox Boiler.
e) an externally fired boiler.
e) an externally fired boiler.
CH003 Q01
An externally fired boiler is a boiler with the combustion chamber outside the boiler drum. This type of furnace is not surrounded by water but is surrounded by brickwork or refractory called the setting.
One advantage of electrode type electric boilers over immersion type is that they
a) can be operated at much higher temperatures.
b) are more efficient.
c) have lower power requirements.
d) are less expensive.
e) do not require a low water cutoff.
e) do not require a low water cutoff.
CH004 Q02
Advantages of the electrode type only
* no low water cutoff is required with the electrode type since no heating effect is produced if the water level is below the electrodes.
* Since the water temperature is the same as the electrode temperature in the electrode type, little scaling is produced.
The maximum operating voltage for an electrode type electric boiler is
a) 480 volts.
b) 1 200 volts.
c) 5 000 volts.
d) 12 000 volts.
e) 16 000 volts.
e) 16 000 volts.
CH004 Q08
Electrode type electric boilers may operate at voltages as high as 16 000 volts and have capacities as high as 30 000 kW.
An electrode type electric boiler may have a capacity as high as
a) 500 kW.
b) 1 500 kW.
c) 3 000 kW.
d) 10 000 kW.
e) 30 000 kW.
e) 30 000 kW.
CH004 Q10
Electrode type electric boilers may operate at voltages as high as 16 000 volts and have capacities as high as 30 000 kW.
When a closed expansion tank is used and the system is cold
a) there will be no air in the tank.
b) the auto fill valve will maintain a system minimum pressure.
c) the tank level will be high.
d) the system should be manually filled.
e) the possibility of air in the system will be high.
b) the auto fill valve will maintain a system minimum pressure.
CH005 Q66
The automatic fill valve is simply a pressure reducing valve which keeps the system filled with water and maintains a set pressure in the system. If some water is lost from the system due to leakage, the system pressure will drop and the automatic fill valve will open to feed the water into the system from the city main or another source of water supply.
Heating boiler fittings
a) are not regulated by ASME Codes.
b) must be registered by the chief engineer.
c) must be approved and registered by the regulating agency of the Province in which they are used.
d) may be used at the discretion of the power plant personnel.
e) do not require attachment of the manufacturer’s identity.
c) must be approved and registered by the regulating agency of the Province in which they are used.
CH005 Q01
Boiler fittings must comply with the requirements as set out in the ASME Code. In Canada, they must also comply with the rules in the CSA Standard B51 and the Provincial Boilers Acts. They must be approved and registered by the regulating agency of the province in which they are to be used. In order that valves and fittings are of the proper strength and material for the particular service for which they are used, it is necessary that they be clearly marked or identified.
Blowdown of a safety valve is defined as
a) an increase in pressure that the valve opens.
b) the difference between opening and closing pressures.
c) lifting the test lever to blow steam out.
d) draining water from the safety valve.
e) the adjustment of the pressure setting of the valve.
b) the difference between opening and closing pressures.
CH005 Q26
The difference between the pressure at which the valve opens and the pressure at which the valve closes is called the blowdown of the safety valve. A threaded adjustable angular ring “G” (Figure) may be screwed up or down to vary the amount of port opening “F.”
The lowest water level at which a boiler can be operated without damage or overheating is referred to as the
a) lowest operating level.
b) lowest working water level.
c) lowest visible water level.
d) lowest permissible water level.
e) lowest safe water level.
d) lowest permissible water level.
CH005 Q30
The lowest visible part of the water gauge glass shall be at least 25 mm (1 in.) above the lowest permissible water level recommended by the boiler manufacturer. With the boiler operating at this lowest permissible water level, there shall be no danger of overheating any part of the boiler.
The purpose of the small vent valve or cock located on top of the shell or on top of the water column on most boilers is to allow
a) air into the boiler when the boiler is being filled with water.
b) water into the boiler when the boiler is being drained or cooled preventing the formation of a vacuum.
c) water to escape from the boiler when the boiler is being filled with air.
d) air to escape from the boiler when the boiler is being filled with water.
e) water to escape before the steam stop valve is opened during the warm-up period.
d) air to escape from the boiler when the boiler is being filled with water.
CH005 Q40
The vent valve is used for the following purposes:
- It allows air to escape from the boiler when the boiler is being filled with water.
- It allows air into the boiler when the boiler is being drained or cooled preventing the formation of a vacuum.
- During the warm-up period of the boiler the air freed from the water by heating as well as the air that filled the steam space can be allowed to escape before the steam stop valve is opened.
- The vent valve can also be used to check that the boiler is filling before the level rises to the gauge glass (air will be blowing out). In a similar manner the vent can be used to determine when the boiler has finished draining because air will no longer be drawn in.
When an electric probe type low-water fuel cutoff is employed on a heating boiler, it is important to
a) vent off any hydrogen caused by electrolysis of the water.
b) check and clean the probes at regular intervals.
c) ensure the probe housing is properly insulated to prevent electrocution.
d) ensure the boiler is frequently blown down.
e) add salt to the boiler water to ensure good conductivity.
b) check and clean the probes at regular intervals.
CH006 Q03
It is necessary to check and clean the probes at regular intervals. Scale or sediment on the probes reduces or completely stops the current flow, resulting in a boiler shutdown. Note that these probes use alternating current and therefore electrolysis of the water does not occur and no hydrogen is formed.
A low-water fuel cutoff 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) damage to the boiler from over pressure.
d) shutting off the water when there is no fuel.
e) damage to the boiler from an overheated condition.
e) damage to the boiler from an overheated condition.
CH006 Q11
The main cause of heating boiler failure is overheating of the heating surfaces due to low water conditions. Normally, the water covering these surfaces will keep the temperature of the metal at a safe value. A low water level, however, allows the boiler metal temperature to increase to a point where it weakens and is not able to withstand the internal boiler pressure. This may result in the boiler metal rupturing and a massive release of pressurized steam and hot water. The ASME Code and CSA B51 require that every automatically fired boiler which is not under continuous attendance by a certified operator shall be equipped with an automatic low-water fuel cutoff device that automatically shuts off the fuel supply when the water level drops to about 25.4 mm (1 in) in the gauge glass.
The low-water cutoff can be tested by
a) closing the steam discharge valve.
b) shutting off the fire.
c) opening the safety valve.
d) raising steam pressure.
e) shutting off the feedwater.
e) shutting off the feedwater.
CH006 Q09
Simulate a low water condition in the boiler by shutting down the feed pump and feedwater supply valve. On steam heating boilers, the valve on the condensate return line should be closed so the boiler will not get any replacement water. Allow the boiler water level to drop and note the level at which the cutoff switch shuts down the burner. The blowoff valve can be opened to hasten the operation. If the fuel is not shut off when there is about 25 mm of water remaining in the gauge glass, the boiler should be shut down and the low water cutoff repaired.
The low-water fuel cutoff
a) controls the water level in the boiler.
b) shuts off the fuel and water supply.
c) shuts off the fuel if the water level is too low.
d) shuts off the fuel if the water pressure is low.
e) shuts off the water flow if the fuel pressure is low.
c) shuts off the fuel if the water level is too low.
CH006 Q10
The ASME Code and CSA B51 require that every automatically fired boiler which is not under continuous attendance by a certified operator shall be equipped with an automatic low-water fuel cutoff device that automatically shuts off the fuel supply when the water level drops to about 25.4 mm (1 in) in the gauge glass. This corresponds to a level approximately 76.2 mm (3 in) above the lowest permissible water level as specified by the manufacturer. The installation shall be such that the device cannot be rendered inoperative and can be tested under operating conditions.
The drain on a hot water boiler low-water fuel cutoff should be opened to flush out any build up of sediment
a) annually.
b) monthly.
c) weekly.
d) daily.
e) each shift.
c) weekly.
CH006 Q04
Weekly: to check the low-water fuel cutoff mechanism, open the drain on the float chamber while the burner is in operation. The water level should drop enough for the float to open the mercury switch and shut down the burner. Carefully observe the water level at which the fuel cutoff switch shuts down the burner. If this cutoff level is not at or slightly above the lowest permissible level specified by the manufacturer, the low-water fuel cutoff should be serviced immediately or replaced if necessary.
Equalizing lines on a condensate receiver float chamber
a) eliminate the need for a make-up level control valve.
b) keep receiver level equal to boiler level.
c) maintain equal flow of condensate to multiple boilers.
d) maintain make-up flow equal to condensate flow.
e) dampen level fluctuations.
e) dampen level fluctuations.
CH007 Q15
An externally mounted float controller feeder valve is preferred on most installations. The float chamber is attached to the receiver by equalizing lines which dampen the level fluctuations in the chamber resulting in a smooth flow of make-up water.
If the feed water check valve on a steam heating boiler fails to close, steam pressure could force the boiler water back into the return line, causing an unsafe water level. To prevent this, many boilers are fitted with a
a) stop valve.
b) Hartford loop.
c) electric feeder valve.
d) high pressure limit switch.
e) combination low-water fuel cut off and feeder valve.
b) Hartford loop.
CH007 Q07
In older, small steam heating systems the condensate from the various parts of the heating system is piped to a common condensate return line or return main which feeds the condensate directly back into the boiler by gravity. The condensate is fed into the boiler through a return or Hartford loop. If the condensate return line would be directly connected to the feed connection in the lower part of the boiler, the possibility would exist that the steam pressure would force the boiler water back into the return line should the check valve fail to close, and the water level in the boiler could drop below the safe minimum level. The Hartford loop prevents this. The return line is connected to the loop at the height of the lowest safe water level. At that level the heights of the water in the boiler and in the loop will be equal and the steam pressure above the water in boiler and loop will be the same. Since water height and steam pressure in both boiler and loop are balanced, no water can be forced out of the boiler and sufficient water will cover the heating surfaces to prevent overheating.
At normal boiler steaming rates, the condensate receiver should contain water equivalent to the water evaporated by the boilers in
a) 30 minutes.
b) 60 minutes.
c) 2 hours.
d) 4 hours.
e) 8 hours.
a) 30 minutes.
CH007 Q18
An important requirement of a well-designed boiler feedwater system is a condensate receiver of adequate size together with a reliable method of makeup water supply to the receiver. An undersized receiver may cause loss of condensate, while an unreliable makeup feeder could result in boiler shutdowns due to low water conditions if the boilers are not equipped with feeder valves.
As a general rule, the size of the receiver should be sufficient to hold a volume of condensate equivalent to the water evaporated by the boiler in a 1/3 to 1/2 hour period at normal load. The smaller sized receiver may be used when the condensate returns easily, as in heating systems used in high-rise buildings. In systems extended over a large area (factories, warehouses, etc.), condensate return will be lengthy and the larger size tank should be used.
Heating plants with multiple boilers often have
a) separate condensate receivers.
b) feed water pressure regulating valves for each boiler.
c) individual feed water systems.
d) a common feed water control valve.
e) independent boiler feed water control from a header.
e) independent boiler feed water control from a header.
CH007 Q08
In multiple boiler heating plants, the control of the water level in each boiler is independent from the other boilers but the feed water is usually supplied through a common feed line by a single pump. When one of the boilers requires water, its float operated control switch closes, energizing the motorized valve in the feed water branch line to the boiler. As soon as this valve reaches the open position, it closes an attached pump starting switch, and the condensate starts flowing from the receiver to the boiler. When the water in the boiler reaches its maximum level, the pump control switch opens the circuit, the motorized valve closes and the pump stops.
In heating plants with multiple boilers that are supplied from a single condensate receiver, all boilers commonly share a single
a) boiler feed pump.
b) water column and gauge glass.
c) drum level control valve.
d) burner.
e) low water fuel cutoff.
a) boiler feed pump.
CH007 Q10
In multiple boiler heating plants, the control of the water level in each boiler is independent from the other boilers but the feed water is usually supplied through a common feed line by a single pump. This pump supplies water to a header that supplies all the boilers. Individual feeder valves on each boiler control the level of water in that boiler.
When a combination low water cutoff and feeder valve is used to control water level in a boiler, the code requires that
a) the device is installed at the lowest safe water level.
b) the device be fitted with a gage glass.
c) a second low water fuel cutoff device is installed.
d) isolation valves be installed on the steam and water connections.
e) the feeder valve open before the low water cutoff device is activated.
c) a second low water fuel cutoff device is installed.
Float operated low-water fuel cut-offs are often combined with a valve assembly that is used to control the flow of feed water to the boiler. A cut-away view of this combination cut-off is shown in Fig.
Since control of the feed water supply is now the primary function of the cut-off device, a second cut-off is again required by code.
Which of the following controls would you expect to find on a low pressure steam boiler?
1. Operating pressure control.
2. High limit temperature control.
3. High limit pressure control.
4. Operating temperature control.
a) 3 and 4 only.
b) 1, 2, 3 and 4.
c) 2 and 4 only.
d) 1 and 3 only.
e) 1 and 4 only.
d) 1 and 3 only.
There are four distinct methods of burner operation control, they are:
- On-Off Control - The burner fires at a constant rate which is sufficient to maintain boiler pressure or temperature at full load. When operating at less than full load, the burner is shut off when the upper pressure or temperature limit is reached and it is lit up again when the pressure or temperature drops to the lower limit. Thus the burner operates on an on-off cycle. This type of control is the simplest and is commonly used on low capacity boilers. However, it has the disadvantages that the pressure or temperature swings between the upper and lower set limits and that the boiler will not operate at maximum efficiency unless fired continuously.
- High-Low Control - Two firing rates are available with the rate used depending on the boiler load. Operation with this type of control is more efficient than with the on-off control and pressure or temperature fluctuations are smaller.
- Modulating Control - The firing rate is continuously adjusted to match a varying boiler load. The boiler pressure or temperature is maintained at a constant value and operation is most efficient.
- High Limit Control (High Steam Pressure Fuel Cut-Off) - This control is used to shut down the fuel supply in the event of too high a steam pressure. This will help prevent a possible explosion.
On a multi nozzle boiler the high fire nozzle will
a) be ignited by an independent pilot flame.
b) be in operation on start up.
c) operate continuously when steam demand exceeds capacity of low fire nozzle.
d) operate regardless of where the manual over-ride switch is set.
e) respond to electrical resistance.
c) operate continuously when steam demand exceeds capacity of low fire nozzle.
CH008 Q12
When steam demand is higher than the amount of steam produced by firing the low fire nozzle, the operating limit control will keep the low fire nozzle in continuous operation but the high-low fire control will now come into action and start the high fire nozzle(s) when pressure drops to 72 kPa, the cut-in point of this control. The pressure will then rise and when it reaches 86 kPa, the cut-out point, fuel supply to the high fire nozzle(s) is shut off again. Thus, at higher loads, the low fire nozzle is in operation continuously but the high fire nozzle(s) will be on on-off cycle and the operating pressure will vary between 72 kPa and 86 kPa. The high fire nozzle(s) will only be in continuous operation when steam demand equals or exceeds maximum boiler output.
When a lead-sulfide cell is used in a flame scanner it is sensitive to
a) the presence of carbon monoxide in the flame.
b) infrared radiation.
c) furnace temperature.
d) visible light.
e) ultraviolet radiation.
b) infrared radiation.
CH009 Q09
Infrared Scanner: The scanner illustrated in Fig. contains a lead-sulphide cell which reacts to infrared rays. The cell is a semiconductor whose electrical resistance decreases instantaneously with an increase in the amount of infrared light from the main burner or pilot flame. Fluctuation of its resistance produces a fluctuating voltage across the cell. This voltage, called the “flame signal”, is amplified sufficiently by an electronic amplifier to hold an electromagnetic switch or flame relay in closed position.
When testing a gas burner with flame scanner, the scanner is removed and the main gas valve should trip closed within
a) 1/2 second.
b) 4 seconds.
c) 6 seconds.
d) 10 seconds.
e) 15 seconds.
b) 4 seconds.
CH009 Q03
Gas Burner With Electronic Flame Scanner (Photoelectric Cell)Method 1: same as (Gas Burner With Electronic Flame Rod and Interrupted Pilot) below
Method 2:
1. Remove the scanner from its sighting tube and cover it. Note the time it takes for the automatic gas valve on the main burner supply to close. This should take no longer than four seconds.
- If the test is successful, reset the controls, light the burner, and verify correct operation. Gas Burner With Electronic Flame Rod and Interrupted Pilot1. With the main burner in normal operation, close the main gas cock. Note the time it takes for the automatic gas valve to close. This should take no longer than four seconds.
- If the test is successful, open the main gas cock, relight the burner, and check the burner for correct operation.
With automatic gas-fired boiler programmed control, the normal firing period begins approximately
a) 105 seconds after FD fan starts.
b) 75 seconds after FD fan starts.
c) 60 seconds after FD fan starts.
d) 47 seconds after pre-purge.
e) 10 seconds after pilot extinguishes.
a) 105 seconds after FD fan starts.
CH090 Q10
105: End of starting cycle. Beginning of normal firing period. Timer motor stops. Burner and blower remain in operation until heat demand is satisfied and operating control reaches its cutout point.
During the start-up of a boiler equipped with an automatic control system and flame scanning device, the manual fuel supply valve
a) must be closed before ignition.
b) can be opened before the flame scanner sees a flame.
c) must be opened before ignition can take place.
d) can be opened any time during start up sequence.
e) should be open as soon as pilot valve opens.
c) must be opened before ignition can take place.
CH010 Q13
Before a steam or hot water boiler can be started by a programming control, the following conditions must be fulfilled: all manually operated valves in the fuel lines to the pilot and main burner must also be open…
Compare with the following extracted from startup logic which relates to the automatic valve:
End of purge period. Ignition energized. Pilot gas valve opens. Start of trial period. When scanner sights pilot flame, flame relay closes. Main gas valve energized, main burner lights. Start of main burner ignition trial period.
On automatic boilers, liquid-fuel manual valves should be opened
a) with the automatic main burner fuel valve.
b) after the automatic main burner fuel valve opens.
c) prior to pre-purging.
d) after pre-purge and just prior to pilot ignition.
e) immediately after completion of the pilot flame trial.
c) prior to pre-purging.
CH010 Q08
Before a steam or hot water boiler can be started by a programming control, the following conditions must be fulfilled: All manually operated valves in the fuel lines to the pilot and main burner must be open…
The function of a programming control is to
a) regulate the fuel supply to the burner.
b) regulate fuel, air, and water supply to the boiler.
c) control the boiler blowdown rate.
d) regulate combustion controls during start-up.
e) supervise feedwater supply to the boiler.
d) regulate combustion controls during start-up.
CH010 Q07
The programming control includes safety features related to boiler start-up. If any part of the starting sequence is not properly completed, it terminates the start-up sequence and purges the furnace. In addition, it orchestrates a controlled shut down of the boiler when the pressure rises to the cut-out point or other interlocks take out the boiler.
If a shutdown occurs during normal firing of a boiler and the steam pressure is below the normal cut-out value, the problem could be
a) ignition transformer failure.
b) the sensing line to the combustion air proving switch is plugged.
c) pilot flame trial failure.
d) high steam pressure limit switch tripped.
e) main flame trial failure.
b) the sensing line to the combustion air proving switch is plugged.
CH010 Q06
If shutdown occurs during firing, it may be caused by faulty interlock. Each time the operating control or a limit switch such as the low water fuel cut-off opens and shuts down the boiler, or when the power fails, the boiler will automatically start up again when the switch closes or power has been restored. In these cases the lock-out switch will not be actuated. When the air flow to the burner is established, the low air pressure switch is closed. If the low pressure switch opens during boiler operation it will shut down the boiler. By process of elimination, the only correct answer is that the air proving switch has failed although other interlocks could cause the same condition.
