INDUSTRIAL GAS TURBINE2.11 & 2.12 – Type of Thrust Bearings

2.13 & 2.14 –Gas Turbine Main Bearing Housing

2.15 – Main Bearing Examination procedure

2.18 – Bearing problem diagnosis

National Diploma Year 1

in Marine Engineering

LEARNING OBJECTIVE

Describe the type of Thrust Bearing without

reference.

Explain the purpose of Bearing Housings.

Describe the examination procedure for

Industrial Gas Turbine Bearings.

Diagnose any bearing problems.

2.11 – THRUST BEARING

It support any loads that directly parallel to the

rotor axis.

It consists of a collar or thrust runner rotating

against a mating stationary plate surface

(bearing).

THRUST BEARING OPERATION

Hydrodynamic operation.

The Oil film supports the thrust load and prevent

metal-to-metal contact of the bearing surfaces.

THRUST BEARING OPERATION

The thrust load of a rotor assembly is unidirectional.

Direction of thrust load only in reverse during the

starting-up & shutdown period.

2 thrust bearing required.

Why required 2 bearings?

o To support thrust load

imposed in either direction.

2.12 – TYPES OF THRUST BEARING

1. Tilting pad self-equalizing bearings.

2. Tilting pad non-equalizing bearings.

3. Tapered Land Bearings.

4. Flat land bearings.

TILTING PAD SELF-EQUALIZING THRUST

BEARING

Employed as “Loaded” thrust bearing.

Capable of sustaining high load.

Capable of handling shaft and housing

misalignment.

TILTING PAD NON-EQUALIZING THRUST

BEARING

Used for Inactive (unloaded) application.

Capable of carrying high thrust loads…

But less tolerant of misalignment than tilting

pad self-equalizing bearing.

TILTING PAD NON-EQUALIZING THRUST

BEARING CONTINUE…

Thick in size.

Have “Leveling Plates”.

Much thinner in the axial dimension.

TAPERED LAND THRUST BEARING

Used for loaded or unloaded thrust bearing.

Consist of a steel ring faced with Babbitt.

CONSTRUCTION OF TAPERED LAND

THRUST BEARING

Bearing surface divided by radial oil groves into a

number of individual pad.

Radial oil grooves not fully extend to the outer

periphery of bearing…

But instead, partially blocked. Why?

CONSTRUCTION OF TAPERED LAND

THRUST BEARING CONTINUE…

Each surface is tapered.

A portion of the surface near the trailing edge of

the pad left un-tapered.

FLAT LAND THRUST BEARING

Consist of a steel ring faced with white metal.

The bearing surface is divided by radial oil grooves

into a number of individual segment (pads).

2.14 - PURPOSE OF BEARING HOUSING

Incorporate the oil baffles.

Prevent excessive leakage along the shaft.

Provide passages for admitting lubricating oil to

the bearing.

Locates the bearing lobes both axially and radials

with respect to the shaft.

Key in place together with bearing lobes.

2.15 - EXAMINATION PROCEDURE FOR MAIN

BEARINGS OF GAS TURBINE:

Support the shaft.

Removes Top half housing.

Slide out the bottom half of the bearings.

Clean bearings with light oil (with clean rags).

Visual inspect the bearing and journal surface.

Inspect the conditions of the seals.

Check oil and air passages in the housing are clear.

Check & clean the sump.

Replace the lower half bearing (if necessary).

Replace top half bearings (if necessary).

Remove shaft support.

Note to remember: Take care not to damage any bearing

surfaces (avoid contact with shaft object during handling). .

2.18 - DIAGNOSIS BEARING PROBLEMS

1. Scratch or Scores

• Due to lack of lubrication and not correct viscosity(temperature) during start-up.

• Due to foreign matter (such as; grit or metal chips)comes in contact with the bearing surface (if notfiltered efficiently).

2. Uneven Wear (high/low spots)

• Due to vibration which is caused by misalignment orexcessive gap between space.

3. Discoloration and Crack of bearing surface

• Due to overheating which caused by highlubricating temperature (might cause from faultylube oil cooler).

RECAP

Describe type of Thrust Bearing.

Explain the function of Bearing Housings.

Describe the examination procedure for

Industrial Gas Turbine Bearings.

Explain Diagnose bearing problems.

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