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Industrial Gas Turbine
                                         Week 8




2.16 – Lubricating Oil Specification
2.17– Types of Lubricating Oil
2.9 & 2.10 – Types of Journal Bearing.
Learning Objective
At the end of this lesson, you should be able to:
• Describe the specification of Gas Turbine Lubrication oil System.
• Describe the types of lubrication oil used on Gas Turbine.
• State the types of bearing used on Gas Turbine without mistake.
• Describe the construction and operation of Journal Bearing.
• State and sketch the types of Journal Bearings used on Gas Turbine
  (at least 2 out of 3 types) without reference.
• Describe the characteristic of elliptical type bearing and how it was
  made.




Learning Objective     Industrial Gas Turbine                        2
Term
Viscosity – a measure of the resistance of a liquid to flow
at a specific temperature.
Viscosity Index – a measure of how much the oil's
viscosity changes as temperature changes.
Low Pour Point – the effect of lowest temperature at which
it will pour or flow under prescribed conditions.
Flash Point – the effect of lowest temperature at which the
oil gives off vapors which can ignite.
Fire Point – the temperature at which it will continue to burn
after ignition for at least 5 seconds.



                                                            3
Term
Foaming – a substance that is formed by trapping many
gas/air bubbles in the L.O.
TBN (Total Base Number) – a measurement of the reserve
alkalinity of an oil to neutralize acids.
TAN (Total Acidic Number) – the measure of a lubricant's
acidity.
Volatility – it is a test to determines the evaporation loss of
lubrication in high-temperature.




                                                             4
2.16 - Specification for Gas Turbine Lubricating Oil System:




                High    High                         High
        Low                                        Oxidation    High
Anti-                             High      High               Carrying    Foaming
        Pour    Fire    Flash   Viscosity             &
                                                                Load      Resistance   Volatility
Wear    Point                    Index      TBN    Thermal     Capacity
                Point   Point                      Stability




                                                                                        5
Principle of Lubrication - Video




                                   6
2.17 - Types of Lubricating oil used on
               Gas Turbine
 Three types of Liquid               Three type of
   Oil used on GT:                  Viscosity Grade:
• Mineral Oil                   • Light Grade
• Semi-synthetic Oil            • Medium Grade
• Fully-Synthetic Oil           • Heavy Grade

Additives are added to enhance the physical and chemical
properties of the lubricating oil.

Recommended Oil: Hydrocarbon/petroleum Base
(Mineral Base) Oil
                                                       7
Comparison between Mineral & Synthetic Oil
•Mineral Oil (Liquid Petrolatum) – It is a by product in the
distillation of petroleum to produce gasoline.
•Synthetic Oil – It provides superior mechanical and chemical
properties than Mineral Oils because the chemical compound
were artificially made from other compounds.
               Property             Mineral Oil     Synthetic Oil
 Max. Temp in the presence of O2       150°C            210°C
 Max. Temp in the absent of O2         200°C            250°C
 Viscosity                             0-140             145
 Boundary Lubrication                  Good             Good
 Suitable material for seals       Nitrile Rubber   Nitrile Rubber

 Resistance to attack by water       Excellent          Good


Note: Mineral Oil composed mainly alkenes (15-40carbon).
                                                                     8
Bearing used on Gas Turbine
There are two type of bearing used:
A. Journal/sleeve Bearings – It is used to support the
   Turbine Rotor weight as well as to support any dynamic
   forces resulting from rotor unbalance and gear tooth
   reactions.
B. Thrust Bearing – it is used to maintain the rotor-to-
   stator axial position.

Both of these main bearings and seals are incorporated in
Two Housing; One at the inlet frame and the other at
exhaust frame.



                                                       9
2.9 - Journal Bearings
• It consist of a Cylindrical shaft section (journal) and a
  mating stationary shell (liner) which surrounds the shaft.




 Journal Bearing for Big Propulsion



                                                         10
2.9 - Journal Bearings
  • In this bearing, it is filled-up with fluid lubricant (lube oil)
    which act as the medium that supports the shaft and
    preventing metal to metal contact.




• Classified as Hydrodynamic in operation - which mean that their
  load supporting capability is derived from a thin oil film wedge.
Operation of Journal Bearings
• Wedge is formed as a result of
  the relative motion between the
  journal and the liner.
• As shaft speedup, the oil film
  pressure increase, gives the oil
  in journal bearing dragged
  behind the pin until the oil film
  break through and separate the
  surface
• Which in turn, supports the
  bearing load.


 Pin – The clearance space between the journal and the liner.
                                                                12
Types of Journal Bearing
1.   Elliptical or two-lobe Bearings




                                       13
Types of Journal Bearing
2. Three-Lobe Bearings




                               14
Types of Journal Bearing
3. Tilting-pad Bearings




                                 15
Elliptical Type Journal Bearing
• Non-cylindrical bores characteristic.
• Design to improve shaft stability at high speed.
• The extra clearance space increase the oil flow and
  reduces the power loses, resulting in lower temperature
  rises in the bearing.




                                                        16
How the Elliptical Bearing is made?
•   Two cylindrical halves brought together.
•   Shims is placed at the horizontal split
•   Machining a cylindrical bore.
•   Removed shim
•   The two halves brought together.




                                               17
Recap
• Describe the specification of Gas Turbine Lubrication oil    √
  System.
• Describe the types of lubrication oil used on Gas Turbine.   √
• State the types of bearing used on Gas Turbine without
  mistake.                                                     √
• Describe the construction and operation of Journal
  Bearing.                                                     √
• State and sketch the types of Journal Bearings used on
  Gas Turbine (at least 2 out of 3 types) without reference.   √
• Describe the characteristic of elliptical type bearing and
  how it was made.                                             √



                                                               18

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Industial gas turbine (week 8)

  • 1. Industrial Gas Turbine Week 8 2.16 – Lubricating Oil Specification 2.17– Types of Lubricating Oil 2.9 & 2.10 – Types of Journal Bearing.
  • 2. Learning Objective At the end of this lesson, you should be able to: • Describe the specification of Gas Turbine Lubrication oil System. • Describe the types of lubrication oil used on Gas Turbine. • State the types of bearing used on Gas Turbine without mistake. • Describe the construction and operation of Journal Bearing. • State and sketch the types of Journal Bearings used on Gas Turbine (at least 2 out of 3 types) without reference. • Describe the characteristic of elliptical type bearing and how it was made. Learning Objective Industrial Gas Turbine 2
  • 3. Term Viscosity – a measure of the resistance of a liquid to flow at a specific temperature. Viscosity Index – a measure of how much the oil's viscosity changes as temperature changes. Low Pour Point – the effect of lowest temperature at which it will pour or flow under prescribed conditions. Flash Point – the effect of lowest temperature at which the oil gives off vapors which can ignite. Fire Point – the temperature at which it will continue to burn after ignition for at least 5 seconds. 3
  • 4. Term Foaming – a substance that is formed by trapping many gas/air bubbles in the L.O. TBN (Total Base Number) – a measurement of the reserve alkalinity of an oil to neutralize acids. TAN (Total Acidic Number) – the measure of a lubricant's acidity. Volatility – it is a test to determines the evaporation loss of lubrication in high-temperature. 4
  • 5. 2.16 - Specification for Gas Turbine Lubricating Oil System: High High High Low Oxidation High Anti- High High Carrying Foaming Pour Fire Flash Viscosity & Load Resistance Volatility Wear Point Index TBN Thermal Capacity Point Point Stability 5
  • 7. 2.17 - Types of Lubricating oil used on Gas Turbine Three types of Liquid Three type of Oil used on GT: Viscosity Grade: • Mineral Oil • Light Grade • Semi-synthetic Oil • Medium Grade • Fully-Synthetic Oil • Heavy Grade Additives are added to enhance the physical and chemical properties of the lubricating oil. Recommended Oil: Hydrocarbon/petroleum Base (Mineral Base) Oil 7
  • 8. Comparison between Mineral & Synthetic Oil •Mineral Oil (Liquid Petrolatum) – It is a by product in the distillation of petroleum to produce gasoline. •Synthetic Oil – It provides superior mechanical and chemical properties than Mineral Oils because the chemical compound were artificially made from other compounds. Property Mineral Oil Synthetic Oil Max. Temp in the presence of O2 150°C 210°C Max. Temp in the absent of O2 200°C 250°C Viscosity 0-140 145 Boundary Lubrication Good Good Suitable material for seals Nitrile Rubber Nitrile Rubber Resistance to attack by water Excellent Good Note: Mineral Oil composed mainly alkenes (15-40carbon). 8
  • 9. Bearing used on Gas Turbine There are two type of bearing used: A. Journal/sleeve Bearings – It is used to support the Turbine Rotor weight as well as to support any dynamic forces resulting from rotor unbalance and gear tooth reactions. B. Thrust Bearing – it is used to maintain the rotor-to- stator axial position. Both of these main bearings and seals are incorporated in Two Housing; One at the inlet frame and the other at exhaust frame. 9
  • 10. 2.9 - Journal Bearings • It consist of a Cylindrical shaft section (journal) and a mating stationary shell (liner) which surrounds the shaft. Journal Bearing for Big Propulsion 10
  • 11. 2.9 - Journal Bearings • In this bearing, it is filled-up with fluid lubricant (lube oil) which act as the medium that supports the shaft and preventing metal to metal contact. • Classified as Hydrodynamic in operation - which mean that their load supporting capability is derived from a thin oil film wedge.
  • 12. Operation of Journal Bearings • Wedge is formed as a result of the relative motion between the journal and the liner. • As shaft speedup, the oil film pressure increase, gives the oil in journal bearing dragged behind the pin until the oil film break through and separate the surface • Which in turn, supports the bearing load. Pin – The clearance space between the journal and the liner. 12
  • 13. Types of Journal Bearing 1. Elliptical or two-lobe Bearings 13
  • 14. Types of Journal Bearing 2. Three-Lobe Bearings 14
  • 15. Types of Journal Bearing 3. Tilting-pad Bearings 15
  • 16. Elliptical Type Journal Bearing • Non-cylindrical bores characteristic. • Design to improve shaft stability at high speed. • The extra clearance space increase the oil flow and reduces the power loses, resulting in lower temperature rises in the bearing. 16
  • 17. How the Elliptical Bearing is made? • Two cylindrical halves brought together. • Shims is placed at the horizontal split • Machining a cylindrical bore. • Removed shim • The two halves brought together. 17
  • 18. Recap • Describe the specification of Gas Turbine Lubrication oil √ System. • Describe the types of lubrication oil used on Gas Turbine. √ • State the types of bearing used on Gas Turbine without mistake. √ • Describe the construction and operation of Journal Bearing. √ • State and sketch the types of Journal Bearings used on Gas Turbine (at least 2 out of 3 types) without reference. √ • Describe the characteristic of elliptical type bearing and how it was made. √ 18

Notes de l'éditeur

  1. Recap from previous week lesson:Purpose of Lubricating Oil Cooler -To take away the heat from the lubricating oil before recycle back to the system.The need of Oil Filter - To filter any Impurities and Particles. - Type of filter used is Duplex filter. - Type of Catridge used is Resin-impregnated pleated paper elements type. - The need of 2 filter is for backup purposes (1 standby & 1 running).The need of Protection Devices - To onitor the temperature & pressure of the Lubricating oil system. - The need of low pressure switch is to detect low lube oil pressure in the lube oil feed piping. - The need of high Temperature switch is to detect high lube oil temperature in the lube oil feedsystem.Describe inspection & maintenance procedure for Gas Turbine.
  2. Viscosity - a measure of the resistance of a liquid to flow at a specific temperature. "thickness of L.O“Viscosity Index - a measure of how much the oil's viscosity changes as temperature changes such as; Viscosity become thin as temperature increase and thicken as temperature decrease.Low Pour Point – the effect of lowest temperature at which it will pour or flow under prescribed conditions which the oil easily to flow.Flash Point - the effect of lowest temperature at which the oil gives off vapors which can ignite. It is dangerous for the oil in GT to ignite and burn, so a high flash point is desirable.Fire Point - the temperature at which it will continue to burn after ignition for at least 5 seconds. At lower temperature, a substance will ignite, but vapor might not be produced to sustain the fire.
  3. Foaming - a substance that is formed by trapping many gas/air bubbles in the L.O. (corrosion occur due to oxidation).TBN (Total Base Number) - a measurement of the reserve alkalinity of an oil to neutralize acids.TAN (Total Acidic Number) – the measure of a lubricant's acidity.Volatility- it is a test to determines the evaporation loss of lubrication in high-temperature service. The more oil vaporize, the thicker the oil become which contributing to poor circulation, reduced fuel economy, increased oil consumption, causing wear on bearings.
  4. As previously mention, the Lubricating oil is primarily used for lubricating and cooling of the Main Bearings. It also used for Hydraulic Fluid to operate the accessories fitted with Gas Turbine.Why is it important to maintain the operating temperature of the main bearings?Refer back on the purpose of Lube oil Cooler (Topic 2.4)! During operation, L.O temperature rises due to coming in contact with the hot bearings. If this process continue the temperature will keep increasing , then the bearing may overheat and crack/damage.
  5. Grades:Example of light Grade viscosity Oil; 29-36cSt(centistrokes) at a temperature of 38⁰C.Turbine oils usually use the ISO VG range 32, 46, and 68 (cSt at 40°C). Medium GradeMotor Oil Grades (just for share)The Society of Automotive Engineers(SAE) has established a numerical code system for grading motor oils according to their kinematic viscosity. SAE viscosity grading include the following: 0, 5, 10, 15, 20, 25, 30, 40, 50 or 60. Some of the numbers attached with the letter W, stand for "winter" or cold-start viscosity, at lower temperature.Viscosity is graded by measuring the time it takes for a standard amount of oil to flow through a standard orifice, at standard temperature. The longer it takes, the higher the viscosity, and thus higher SAE code.
  6. Difference between Semi-synthetic and fully-synthetic: Semi synthetic (synthetic blends) - is a mixture of petroleum oil and synthetic oil (no more than 30%) . The advantage is that it has very small molecules that contribute to its "lubricity" (small molecules fit into little pits on the metal surface more easily). Trouble is, when things get hot, these little molecules are the first thing to burn up and turn to sludge!Advantage of Fully-synthetic:Better low and high temperature viscosity performance. Better chemical & shear stability.Decreased evaporative loss. Resistance to oxidation, thermal breakdown and oil sludge problems.Extended drain intervals with the environmental benefit of less oil waste. Improved fuel economy in certain engine configurations.Better lubrication on cold starts
  7. Two cylindrical halves brought together so that their centers are displaced several mm from the bearing centre.Shims is placed at the horizontal split, then machining a cylindrical bore.Shim then removed, then two halves brought together to foam the elliptical bearing.