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Sugar Mill Turbines > Turbine Theory > Flashcards

Turbine Theory Flashcards

1
Q
  1. What is eccentricity? Possible causes?
A

A bent shaft (out of roundness). Can be caused by hogging or sagging due to uneven heating or cooling (generally measured below 300RPM)

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2
Q
  1. What is on a SDS?

5 answers

A
  1. Storage requirements
  2. Handling procedures
  3. PPE
  4. Clean up
  5. Fire fighting etc
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3
Q
  1. What is a SOP? What is it used for?
A

Standard Operation Procedures

- To make sure plant is in safe working order before start up.

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4
Q
  1. When should turbine speeds be monitored?

6 answers

A
  1. Startup
  2. After a trip
  3. During abnormal operating conditions
  4. Shutdown
  5. During testing
  6. When synchronising (power gen)
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5
Q
  1. Define critical speed.
A

Refers to a specific speed at which very high vibration naturally occurs.

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6
Q
  1. Define differential expansion.
A

Difference between the casing expansion and the rotor expansion.

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7
Q
  1. Prior to starting a turbine, list a few things to look at other than workplace hazards.
    5 answers
A
  1. Logbooks - any defects?
  2. Specific equipment e.g. any PPE required?
  3. SOP’s
  4. Risk Assessments completed.
  5. Maintenance records.
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8
Q
  1. Name some hazards at start up.

6 answers

A
  1. Insufficient steam drainage.
  2. Steam leaks.
  3. Slips & trips.
  4. Poor lighting.
  5. Missing lagging e.g. causing hot surfaces.
  6. Hot lube oil.
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9
Q
  1. Apart from safety checks, what else should an incoming Operator check? 5 answers
A
  1. Operational checks e.g. any changes to operational instructions.
  2. Check logbooks with outgoing Operator
  3. All alarms / faults.
  4. Any plant undergoing maintenance.
  5. Load requirements.
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10
Q
  1. What is the difference between back pressure & condensing turbines?
A

Back Pressure: Works above atmospheric pressure.

Condensing: Works belong atmospheric pressure.

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11
Q
  1. Who should you seek advice from if there are hazards on a handover?
A

Chemists, other Operators, Supervisors, WPHS Rep, Manager.

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12
Q
  1. Define dry saturated steam.
A

Saturated steam, NOT in the presence of water.

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13
Q
  1. Define water hammer.
A

The rapid change in pressure when moving fluid is forced to stop or suddenly changes direction.

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14
Q
  1. List 5 causes of water hammer. 5 answers
A
  1. Poor steam line drainage.
  2. Sudden operation of valves.
  3. Poor system design.
  4. Incorrect warm through of pipes.
  5. Sudden changes in load from the Boiler.
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15
Q
  1. Why are steam traps used? 4 answers
A
  1. Reduce risk of water ingress
  2. Remove non-condensable gases.
  3. Maintain dry steam lines.
  4. Auto drain condensate to improve efficiency.
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16
Q
  1. List 5 classifications of Steam Turbines.
A
  1. Shaft position (horizontal or vertical)
  2. Type of blading (impulse of reaction)
  3. Method of drive (direct or geared)
  4. Exhaust pressure (back pressure, condensing, pass-out, reheat)
  5. No of stages (single or multi)
  6. Type of flow (axial or radial)
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17
Q
  1. What are the three main requirements for steam in Turbine?
A
  1. Enough superheat to stop condensate?
  2. Clean steam, free of contaminants
  3. Chemically treated - correct pH & conductivity
  4. Free from air & non condensable gases
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18
Q
  1. List 3 efficiency factors that can’t be controlled by an Operator i.e. Platform Attendant?
A
  1. Steam temp.
  2. Steam pressure.
  3. Back pressure.
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19
Q
  1. Define steam turbine governing.
A

The procedure of monitoring and controlling the flow rate of steam into the turbine to maintain a constant speed of rotation. As load increases, so does speed. The governor senses these changes adjusts steam flow accordingly.

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20
Q
  1. List 2 examples of when a regulator may direct a HRWL holder to obtain reassessment.
A
  • The training or competency assessment didn’t meet the standard.
  • Regulator receives info that licence holder has been incompetent when carrying out high risk work.
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21
Q
  1. What can result from a licence holder failing to work safely?
A
  • Suspension
  • Cancellation
  • Failure to renew by regulator
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22
Q
  1. Define under the Workplace Health & Safety Act the duties of a worker.
    4 answers
A
  1. To take reasonable care for his/her own health & safety.
  2. Take reasonable care that his/her acts don’t adversely affect the health & safety of co-workers.
  3. Comply with work instructions given by Managers.
  4. Co-operate with Managers policies & procedures.
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23
Q
  1. What must the employer provide when you are working on a new/unfamiliar Boiler? 4 answers
A

Info, Training, Supervision & Instructions

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24
Q
  1. List 5 sources of safety info.
A 
Site SOP's
Codes of Practice
Site Work Procedures
Site WPHS Policy
Site WPHS Representatives e.g. Safety Adviser
Operating Manuals
Australian Standards
Federal & State WPHS Acts & Regulations
25
Q
  1. Define a hazard.
A

A situation or thing that has potential to cause harm.

26
Q
  1. Define a risk.
A

The possibility that harm might occur when exposed to a hazard.

27
Q
  1. List the hierarchy of control in order.
A

Every Saturday I Eat Apple Pie

  • Elimination
  • Substitution
  • Isolation
  • Engineering
  • Administration
  • PPE
28
Q
  1. List the 4 sides of a Fire Tetrahedron.
A

Fuel, Heat, Chemical Reaction, Oxygen

29
Q
  1. In case of a fire around a turbine, list your action plan.
A
  • Raise the alarm
  • If safe, try to extinguish it.
  • Make sure everyone is safe, evacuate if necessary
  • Activate site procedures.
  • Trip turbine.
  • Turn lube off if its a lube fire.
30
Q
  1. List 3 things to ensure steam quality.
A
  • Clean
  • Dry
  • Free from silica
  • Free from air & incondensable gases
  • At the correct pressure.
  • At the correct temperature.
31
Q
  1. What’s the difference between impulse and reaction.
A

Impulse blades have no pressure drop as steam passes through the blades, whereas reaction blades the pressure drops as it passes through the blades

32
Q
  1. As steam passes through a reaction turbine what happens to pressure and volume?
A

Pressure drops, volume increases.

33
Q
  1. Explain a pass-out condensing turbine.
A

Where a portion of the steam used by the turbine is extracted at an intermediate pressure from the turbine, with the remainder being fully condensed before it’s exhausted at the exit.

34
Q
  1. What is journal bearing?
A

They support the turbines rotor shaft and consist of a horizontally split shell lined with white metal.

35
Q
  1. What is a thrust bearing?
A

They absorb unbalanced steam thrust on the turbine therefore minimising axial movement on the shaft to avoid fixed and moving blades from contacting each other.

36
Q
  1. What is a michell thrust bearing?
A

It’s used to absorb thrust, it consists of a series of kidney shaped pads which tilt to create an oil wedge. They can absorb large force on a small surface. They also handle reverse thrust when a turbine trips.

37
Q
  1. What is the function of glands and seals? What is the result of them failing/leaking?
A

They’re used to stop steam leakage. If they fail, the steam at the high pressure end will leak out, while at the low pressure end of condensing turbines air will be sucked in, which may cause the shaft to shrink causing differential expansion problems.

38
Q
  1. List 4 things lube oil does.
A
  1. Reduce friction
  2. Minimise wear
  3. Reduce heat
  4. Helps exclude water and contaminants from the bearing components.
39
Q
  1. List 5 possible causes for a drop in oil pressure.
A
  1. Oil pump failed.
  2. Bearing failed.
  3. Water
  4. Foaming
  5. Blocked strainer.
  6. Hot oil.
  7. Pipework failure.
  8. Oil tank heaters staying on when not required.
40
Q
  1. List 4 things that cause oil to deteriorate.
A
  1. Water
  2. Oxidisation
  3. High temp
  4. Any foreign matter e.g. dirt/metal
41
Q
  1. What is the process of starting and stubbing the lube oil cooler?
A

To avoid water leaking into the oil, always start the oil system first then the water (oil under high pressure will leak into water not the other way around).

42
Q
  1. List 5 causes of water contamination in oil.
A
  1. Cooler tube leaks.
  2. Condensed steam.
  3. Failed oil tank heaters.
  4. Atmospheric condensation.
  5. Failed vapour extraction fan.
43
Q
  1. List the main components of a turbines oil system.
A
  1. Main oil pump
  2. AC auxillary oil pump
  3. DC emergency oil pump
  4. Jacking oil pump
  5. Seal oil pump/s (when coupled to a generator)
  6. Oil tank
  7. Oil strainers
  8. Centrifuge
  9. Oil tank vapour extraction fan
  10. Oil coolers
    See Picture
44
Q
  1. When do you remove oil systems from service? (turn them off).
A
  1. When the shaft is at rest.
  2. When the oil is no longer required to manage bearing temp.
  3. HP inner metals are less than 200 degrees celcius
  4. Once the jacking oil system is out of service
  5. If cooling water is shutdown.
45
Q
  1. What is the function of a condenser?
A
  1. Maintain vacuum.
  2. Remove non-condensable gases.
  3. Condense the steam existing the turbine.
46
Q
  1. At what pressure are explosion diaphragms designed to lift at?
A

35kpa above atmospheric pressure

47
Q
  1. List 4 things that contaminate condensate.
A
  1. Leaking condenser tubes
  2. Lube oil
  3. Contaminated makeup water
  4. Air ingress
48
Q
  1. Why is barring or turning gear placed into service prior to roll?
A

To minimise eccentricity and thus vibrations by removing any sagging or hogging.

49
Q
  1. Why must critical speeds be avoided.
A

Running at critical speed only for a few minutes can cause enough vibration to shatter the blades and other components. Very important to accelerate through critical speeds smoothly. Do not hold in a critical area.

50
Q
  1. Explain a double valve isolation.
A

ESV (emergency stop valve) and MSV (main stop valve) must both be isolated to work on the turbine. Open drain to ensure no steam is coming through.

51
Q
  1. Name a few in service tests operators should complete.
A
  • Test stop & throttle valves (every day)
  • Valve tests (forced closed non-return)
  • Oil pump cut in test (once a week)
  • Thrust bearing wear test (once a week)
  • Feedwater heaters bled steam forced closed non-return valves
52
Q
  1. What causes turbine cycles to lose performance?
A
  1. Excessive throttling
  2. Exhaust steam moisture
  3. Worn blades
  4. CAN’T READ ANSWER
  5. Worn seals
  6. Poor condenser performance
  7. Poor quality steam
  8. Feed heaters out of service
53
Q
  1. What is the importance of extraction steam non-return valves?
A

In the event of a trip, they stop steam flowing back to the turbine and causing an overspeed.

54
Q
  1. Possible causes of differential expansion.
A
  1. Warming too fast.
  2. Changes in steam temp.
  3. Water ingress.
  4. Load chances on the generator.
  5. The difference in mass between rotor & casing
55
Q
  1. If differential expansion is approaching the limits, list the corrective action to take for each cause.
A
  1. Hold run up till back in limits
  2. Increase heat & hold run up.
  3. Return to previous load.
  4. Correct steam conditions.
  5. Identify source of ingress - maximum turbine drainage
  6. Trip turbine.
56
Q
  1. What is axial expansion? How do you accommodation for it?
A

The expansion of the rotor lengthwise, it’s accommodated by the casing being allowed to heat up, then because it’s mounted on sliding feet or a flexible beam this allows expansion of the casing.

57
Q
  1. If a turbine trips from load what should you check?
A
  1. That it tripped safely and is running down.
  2. All valves are shut (MSV & ESV)
  3. All driven elements are correctly unloaded (gen circuit breaker)
  4. All standby devies have started (oil pumps, turning gear).
  5. Find out cause of trip and log all details.
58
Q
  1. In the event of critical plant failure (ancillary plant failure) what should the Operator do?
A
  1. Follow all site procedures (SOP’s)
  2. Check alarms.
  3. Check standby plant has started
  4. Check tripped plant has shut down safely.
  5. Check protection devices have operated.
  6. Respond to alarms.
  7. Trip the turbine if required.
  8. Log and report all actions.

Sugar Mill Turbines (1 decks)

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