Gears Flashcards
State why epicyclic reduction gearing may be used in the same gearbox as double helical reduction gears.
Are used to provide double/ triple reduction in gear ratios.
On inspection of a gearbox the following defects may be found on gear teeth, state how each is apparent on visual inspection and the likely cause of each defect:
i) pitting on new gear following sea trials;
Along the pitch line due to high and hard spots on the surface when most the initial loading takes place.
On inspection of a gearbox the following defects may be found on gear teeth, state how each is apparent on visual inspection and the likely cause of each defect:
scoring;
High spots on the gear tooth sit proud of the oil film and score the mating surface causing a rough finish.
On inspection of a gearbox the following defects may be found on gear teeth, state how each is apparent on visual inspection and the likely cause of each defect:
scuffing.
Scuffing is due to a failure of lubrication film. This allows metal to metal contact resulting in local fusion or welding, which the welded metal gets torn apart.
Explain how in the event of an electrical power failure the turbine bearings and gearbox continue to be supplied with oil until the plant comes to a stop;
In the event of an electrical power failure then oil will be supplied from a gravity tank at a low pressure. The sprayers are driven from the engine drive pumps.
Identify three tests carried out on the lubricating oil to ensure that it remains fit for service.
Water contamination
Viscosity
Total Acid Numbers TAN
State THREE precautions to be taken prior to carrying out a gearbox inspection, assume the gearbox and main engine have been shut down and are ‘cold’.
Oil spray nozzles clear
Markings on teeth
General cleanliness
Identify FIVE gear tooth faults that may be found when undertaking a gearbox inspection.
Abrasion Pitting Corrosion Destructive pitting Scoring
List the Four main factors looked for during lubricating oil tests.
Water contamination
Viscosity
Total Acid Number TAN
Insolubles
State the main purpose of the lubricating oil system gravity tanks .
To provide a low pressure oil supply to the bearings in case of a power failure.
Define EACH of the following terms:
i) Tip circle;
Radial height of the teeth
Define EACH of the following terms:
Root circle;
Radial depth of the teeth
Define EACH of the following terms:
Addendum;
Tip circle minus pitch circle
Define EACH of the following terms:
Dedendum;
Root circle plus pitch circle
Define EACH of the following terms:
Involute.
Shape of the load face of the gear teeth
