Boilers Page 29-33 Flashcards
List eight mountings found on auxiliary marine boilers.
- [ ] Main-Steam Stop Valve,
- [ ] Safety valves,
- [ ] Auxiliary-Steam Stop Valve,
- [ ] Feed-Water Check Valves,
- [ ] Pressure Gauge connection cock,
- [ ] Boiler Vent Valve,
- [ ] Gauge Glasses,
- [ ] Top and Bottom scum blow-down valves,
- [ ] Remote pressure gauge cock,
- [ ] Remote gauge glass cock.
State four possible reasons for the boiler feed pump failing to maintain the water level in an auxiliary boiler.
- [ ] Severe steam leak on the main steam line,
- [ ] Air induction,
- [ ] damaged section of feed water line,
- [ ] Suction valves closed,
- [ ] filters blocked,
- [ ] Exhaust gas economiser tube leaking.
Describe the start-up sequence of the boiler upon rectification of the fault.
- [ ] Assuming boiler with a safe water level and no lock out alarms activated,
- [ ] the burner force draught fan will run to purge the combustion space up the funnel,
- [ ] fuel pump runs up and pressurises fuel system bypassing burner tip,
- [ ] after correct time, fuel solenoid valve opens and directs pressurised fuel to burner tip where it is atomised and mixed with incoming air,
- [ ] an electric igniter is then actuated causing a spark between two electrodes igniting the mix,
- [ ] a photo-electric cell is activated after approx. 5-7 seconds sensing the flame in furnace,
- [ ] the run green light will then be illuminated on the control panel,
- [ ] if boiler does not run with full pressure it will restart again.
State two consequences of not treating the water in a boiler.
Premature failure of tubes within the boiler or economiser due to corrosion,
Foam and sludge production within the boiler.
Outline two tests which are carried out on boiler water.
- [ ] PH to monitor and control the chemical concentration of boiler water preventing acidic and caustic corrosion,
- [ ] Chloride to monitor and control the concentration of chloride salts within boiler water, indicating the ingress of salt water from coolers.
State the effect on auxiliary boiler operation in the event of a high water level alarm.
Audio & Visual Alarm.
May cause boiler to stop
Risk of poor steam quality (wet)
Reduction in steam space increased pressure affects pressure stability
State the effect on auxiliary boiler operation in the event of a low water level alarm.
Audio & Visual Alarm.
May cause boiler to stop
Risk of overheating
State the effect on auxiliary boiler operation in the event of an extra-low or low-low water level alarm.
Audio & Visual Alarm, Burner Cut Off.
Risk of overheating
What is the procedure for blowing down a low-pressure boiler gauge glass?
- Close both steam and water connections.
- Open the drain valve and clear the glass.
- Open the water check valve to check the passage, then close.
- Open the steam valve to check the passage, then close.
- Close the drain, open the water slowly to fill the glass, then open the steam slowly to settle the gauge at working level.
How often should a low-pressure boiler gauge glass be blown down?
At each watch hand over, or whenever in doubt of boiler water level.
Describe the procedure for blowing through a boiler gauge glass.
- Close S, close W and open D to drain the gauge glass. 2. Open S to prove flow of steam, W shut and D open. 3. Shut S, open W to prove flow of water, D remains open. 4. Shut D, W & S, crack open W to allow to fill gauge glass. 5. When filled with water, crack open S to balance out gauge glass to working pressure of boiler. 6. Open both W & S fully.
W=Water Cock, S=Steam Cock, D=Drain Cock
What occurs when the start button is pressed on an automatically controlled oil fired package steam boiler?
Assuming the boiler has a safe water level and no lock out alarms activated, the burner force draught fan will run to purge the combustion space. The fuel pump runs up and pressurises the fuel system, bypassing the burner tip. After the correct time, the fuel solenoid valve opens, directing pressurised fuel to the burner tip where it is atomised and mixed with incoming air. An electric igniter is actuated, causing a spark between two electrodes to ignite the mix. A photo-electric cell is activated after approx. 5-7 seconds to sense the flame in the furnace, and the run green light illuminates on the control panel. If the boiler does not run with full pressure, it will restart again.
What are three reasons why the boiler would automatically shut down during the starting sequence?
- Ignition transformer electrical supply failure.
- Low fuel oil pressure.
- Flame eye failure, no flame detected.
Describe the procedure for blowing through a boiler gauge glass image
Describe the procedure of blowing through a boiler gauge glass?
What is the purpose of testing pH in boiler water?
To monitor and control the chemical concentration of boiler water, preventing acidic and caustic corrosion.
What is the purpose of testing chloride levels in boiler water?
To monitor and control the concentration of chloride salts within boiler water, indicating the ingress of salt water from coolers.
Why is water hardness tested in boiler water?
To monitor and control the levels of calcium and magnesium salts within feed water, which could otherwise damage boiler surfaces.
What is the purpose of testing total dissolved solids in boiler water?
To monitor and control the amount of solids within boiler water that gradually build up over time, preventing foaming and damage to the steam plant.
What is a circumstance that would cause the fuel supply to be cut off due to low water level?
Boiler low low water level alarm - This is to prevent overheating of the tubes.
What is a circumstance that would cause the fuel supply to be cut off due to high steam pressure?
High steam pressure - To ensure that the boiler does not over pressure.
What is a circumstance that would cause the fuel supply to be cut off at normal working steam pressure?
Normal working steam pressure - The working pressure has been reached, preventing over pressure.
What is a circumstance that would cause the fuel supply to be cut off due to flame failure?
Flame failure - To prevent fuel from being injected into the furnace.
How can the low water level trip be tested?
The boiler is blown down until the burners cut out, or the connection point to the switch is closed and the body drained.
How can the flame eye sensor be tested?
The sensor may either be covered or unplugged from the control panel, resulting in a burner cut-out.
How can the low fuel oil pressure be tested?
Stop the fuel supply pumps to the boiler, resulting in a loss of pressure and burner cut-out, or isolate the pressure switch and drain the body.
How can the loss of electrical power be tested?
Turn off the electrical supply to either burner or blower; after turning the supply back on, the boiler will not start and will have ‘locked out’.
What should be checked if the boiler locks out before purging is completed?
Low combustion air pressure - Check the condition of any suction filters of the blowers and ensure burner doors and manholes are securely shut.
What should be checked if the ignitors fail to spark and the boiler locks out?
Ignition Transformer or Electrode Fault - Check the electrical supply to the ignition transformer and the condition and gap between ignition electrodes.
What should be checked if the boiler fails to light up after the ignitors spark?
Burner or fuel supply filters fouled - Check the condition of fuel supply filters and line pressure, and check for sludge or carbon build-up in the burner.
What should be checked if the boiler flame flashes up but locks out after 5 seconds?
Faulty flame sensor - Extract the sensor and examine it; use a light source to prove function and clean the protective glass of the sensor housing.
a) Explain the sequence of events that occur on pressing the start button of an automatically controlled oil fired
package steam boiler. (16)
• Assuming boiler with a safe water level and there is no lock out alarms activated
• The burner force draught fan will run to purge the combustion space up the funnel
• Fuel pump runs up and pressurises fuel system bypassing burner tip
• After correct time, fuel solenoid valve opens and directs pressurised fuel to burner tip where it is atomised
and mixed with incoming air
• An electric igniter is then actuated which will cause a spark between two electrodes causing the mix to
ignite
• A photo-electric cell is activated after approx. 5-7 seconds which will sense the flame in furnace
• The run green light will then be illuminated on the control panel
• If boiler does not run with full pressure it will restart again
b) State three reasons why the boiler in Q a) would automatically shut down during the starting sequence (6)
• Ignition transformer electrical supply failure
• Low fuel oil pressure
• Flame eye, failure, no flame detected
What is the purpose of testing pH in boiler water?
To monitor and control the chemical concentration of boiler water, preventing acidic and caustic corrosion.
What is the purpose of testing chloride levels in boiler water?
To monitor and control the concentration of chloride salts within boiler water, indicating the ingress of salt water from coolers.
Why is water hardness tested in boiler water?
To monitor and control the levels of calcium and magnesium salts within feed water, which could otherwise damage boiler surfaces.
What is the purpose of testing total dissolved solids in boiler water?
To monitor and control the amount of solids within boiler water that gradually build up over time, preventing foaming and damage to the steam plant.
What is a circumstance that would cause the fuel supply to be cut off due to low water level?
Boiler low low water level alarm - This is to prevent overheating of the tubes.
What is a circumstance that would cause the fuel supply to be cut off due to high steam pressure?
High steam pressure - To ensure that the boiler does not over pressure.
What is a circumstance that would cause the fuel supply to be cut off at normal working steam pressure?
Normal working steam pressure - The working pressure has been reached, preventing over pressure.
What is a circumstance that would cause the fuel supply to be cut off due to flame failure?
Flame failure - To prevent fuel from being injected into the furnace.
How can the low water level trip be tested?
The boiler is blown down until the burners cut out, or the connection point to the switch is closed and the body drained.
How can the flame eye sensor be tested?
The sensor may either be covered or unplugged from the control panel, resulting in a burner cut-out.
How can the low fuel oil pressure be tested?
Stop the fuel supply pumps to the boiler, resulting in a loss of pressure and burner cut-out, or isolate the pressure switch and drain the body.
How can the loss of electrical power be tested?
Turn off the electrical supply to either burner or blower; after turning the supply back on, the boiler will not start and will have ‘locked out’.
What should be checked if the boiler locks out before purging is completed?
Low combustion air pressure - Check the condition of any suction filters of the blowers and ensure burner doors and manholes are securely shut.
What should be checked if the ignitors fail to spark and the boiler locks out?
Ignition Transformer or Electrode Fault - Check the electrical supply to the ignition transformer and the condition and gap between ignition electrodes.
What should be checked if the boiler fails to light up after the ignitors spark?
Burner or fuel supply filters fouled - Check the condition of fuel supply filters and line pressure, and check for sludge or carbon build-up in the burner.
What should be checked if the boiler flame flashes up but locks out after 5 seconds?
Faulty flame sensor - Extract the sensor and examine it; use a light source to prove function and clean the protective glass of the sensor housing.
State FOUR tests which are required for boiler water, giving a reason for EACH test (16).
PH to monitor and control the chemical concentration of boiler water preventing acidic and caustic corrosion Chloride to monitor and control the concentration of chloride salts within boiler water, indicating the ingress of salt water from coolers
• Water Hardness, to monitor and control the levels of calcium and magnesium salts within feed water, that would otherwise damage boiler surfaces
• Total Dissolved Solids, to monitor and control the amount of solids within boiler water that gradually build up overtime. These would otherwise cause foaming within the boiler water and carry over that would damage steam plant severely
State four circumstances under which the fuel supply to the burners of an auxiliary boiler would be automatically cut off, giving a reason why each circumstance requires the fuel to be cut off. (16)
Boiler low low water level alarm - This is to prevent overheating of the tubes
High steam pressure - To ensure that boiler does not over pressure
Normal working steam pressure - The working pressure has been reached, this is to prevent over pressure Flame failure - To prevent fuel from being injected into the furnace
List four safety or alarm devices fitted to an automatically controlled auxiliary boiler indicating how each of these devices may be tested. (16)
• Low water level trip.
The boiler is blown down until the burners cut out, alternatively the connection point to the
switch is closed and the body drained the burners should now cut.
• Flame eye sensor, the sensor may either be covered or un-plugged from the control panel resulting in a burner cut-out.
• Low Fuel Oil Pressure, either stop the fuel supply pumps to the boiler resulting in a loss of pressure and burner cut out or, Isolate the pressure switch and drain the body
• Loss of electrical power, Turn off the electrical supply to either burner of blower if not combined the boiler will now shut down; after turning the supply back on the boiler will not start and will have “locked out” follow normal start procedure.
State the possible cause, and outline the remedial action that should be taking when each of the following faults occur during starting up of an automatic package boiler.
a) The boiler starts and the fan runs with the control dampers correctly positioned, the boiler then locks out
before purging is completed; (4)
• Low combustion air pressure, check the condition of any suction filters of the blowers
• Check that the burner door and all manholes are securely shut and sealed correctly
State the possible cause, and outline the remedial action that should be taking when each of the following faults
occur during starting up of an automatic package boiler.
b) The boiler purges correctly, but the ignitors fail to spark and the boiler locks out; (4)
• Ignition Transformer or Electrode Fault, Check the electrical supply to the ignition transformer
• Check the condition and gap between ignition electrodes
State the possible cause, and outline the remedial action that should be taking when each of the following faults
occur during starting up of an automatic package boiler.
c) The boiler purges correctly, the ignitors spark, but the boiler fails to light up and locks out; (4)
• Burner or fuel supply filters fouled, Check the condition of fuel supply filters and line pressure
• Check the condition of burner, sludge or carbon build-up
State the possible cause, and outline the remedial action that should be taking when each of the following faults
occur during starting up of an automatic package boiler.
d) The boiler flame flashes up but after about 5 seconds the automatic control locks the boiler out. (4)
• Faulty flame sensor, extract sensor and examine.
• Use a light source to prove function clean the protective glass of sensor housing
What is the purpose of the feed water header tank in an auxiliary boiler?
Allows for expansion of water.
What does the auxiliary feed pump do in an auxiliary boiler?
Allows for leakage.
How does scale form on the heating surfaces of an auxiliary boiler?
High concentrations of calcium and magnesium salts within hard water decompose by heat, coming out of solution as scale forming carbonates.
The bicarbonates of calcium and magnesium are decomposed by heat and come out of the solution as scale forming carbonates
Scale forms as carbonates adhere to heated surfaces due to “coming out of suspension”
Due to the scale covering surfaces heat increases and the process intensifies
Why is scale undesirable in a boiler?
- Reduction in heat transfer efficiency.
- Local overheating of boiler tubes and damage.
How is scale prevented from forming in steam boilers?
By keeping hardness salts in suspension and preventing impurities from sticking to heat transfer surfaces.
By keeping the hardness salts in suspension in the solution to prevent scale formation
By stopping any suspended salts and impurities from sticking to the heat transfer surfaces
What is the name given to the water level indicators mounted on a boiler?
Water Level Gauge Glass.
Why are water level gauge glasses fitted on a boiler?
- To monitor the level of boiler water in the event of glass failure.
- To allow monitoring during severe roll.
List five boiler mountings subject to survey, other than water level gauge glasses.
- Pressure Gauge Connections.
- Boiler Vent Cock.
- Main Steam Stop Valve.
- Safety Valves.
- Blow Down valve connection.
What action should be taken if no water level is visible in the gauge glass?
Stop burner, blow down gauge glass to ensure it is not blocked, and check reading.
This prevents damage to tubes and overheating.
With reference to an auxiliary boiler, state for EACH of the following circumstances the action to be taken,
giving a reason for EACH action;
a) No water level visible in gauge glass; (4)
Stop burner, blow down gauge glass to make sure not blocked, make sure reading correctly
Can cause damage to tubes & prevent overheating
With reference to an auxiliary boiler, state for EACH of the following circumstances the action to be taken,
giving a reason for EACH action;
Safety valve lifting; (4)
Shutdown boiler burner to stop over pressurising
Make sure stop v/v is open as this could cause boiler pressure to rise
With reference to an auxiliary boiler, state for EACH of the following circumstances the action to be taken,
giving a reason for EACH action;
c) Excessive smoking during firing; (4)
Checking fuel & air ratio proportion are correct; this is too much fuel can lead to black smoke during combustion
Check fuel temp to make sure you are getting correct combustion
With reference to an auxiliary boiler, state for EACH of the following circumstances the action to be taken,
giving a reason for EACH action;
Excessively high chloride content of boiler water. (4)
Check returns from condenser. If contamination is coming from condenser one of the tubes may have failed and S.W entering condenser
Check evaporator water level, Blow down boiler and top up
Make sure distilled water has no chloride content in system
With reference to Auxiliary Boiler,
Sketch an open feed system suitable for an auxiliary boiler, labelling the component parts.(12)
What does a feed water header tank and an auxiliary feed pump allow for?
Feed water Header tank allows for expansion
Auxiliary feed pump allows for leakage
Boiler start up sequence shirt version
- [ ] Boiler safe water level?
- [ ] Draught fan purge combustion space
- [ ] Fuel pump runs
- [ ] Fuel solenoid valve opens
- [ ] Electric igniter - sparks
- [ ] Photo electric cell activates
- [ ] Green light on control panel
- [ ] If Boiler does not run with full pressure it will restart again
