Vulcan Sinclair Fluid Drive Coupling Overhaul

Once the fluid coupling had been isolated it was removed from its bedplate and oil tank, disconnected from the scoop tube mechanism and all unnecessary pipe work. The fluid coupling was then transported to our workshop in WA.

Once arriving in WA we started the dismantling process, starting with the removal of the couplings and scoop tube assembly, tacking note of all measurements and full photo reports.

The Valcan-Sinclair Fluid Coupling is a scoop trimming type of motor to pump variable speed coupling, it is a scoop trimming type of coupling.

This type of fluid coupling allows the rotational speed of the boiler feed pump in this case to be varied, whilst the motor runs at a constant rotational speed.

The scoop trimming type of coupling operates by oil volume which with maximum oil volume means maximum speed, reducing this oil volume will results in a reduction of speed of the boiler feed pump.

Oil volume control, hence output speed control, is effected by a scoop tube which removes oil from the rotating parts of the fluid coupling. The tip of the adjustable scoop tube is situated in the casing and the scoop trims the oil to the depth determined by the radial position of the scoop tip, which therefore, in turn determines the oil volume and in turn speeds up or slows down the output shaft.

Dismantle, Inspect and Report

• Overall Axial Float- This check could not be obtained due to a failure.
• Main locknut on the output shaft has come undone in service, which has caused the entire internal assemblies to shift.
• Both locknuts will be drilled and tapped to accept two grub screws and a small brass piece to lock onto the thread.
• The scoop tube damaged, due to the internals shifting.  The internal assemblies have been rubbing on the tube.
• Due to the assemblies shifting the internal spherical bearing has been taking all the axial thrust which has caused a catastrophic failure of the bearing.
• Metal particles found throughout the unit due to the bearing failure.
• Bearing outer race has been spinning in the bore of the internal housing.  Internal housing bore is in poor condition and out of specification.
• Bearing support ring has severe pick and rubbing marks due to the failed bearing.
• End of the output shaft has severe pick up marks due to the failed bearing.
• Many internal bolts were excessively tight and had to be destroyed to remove.
• Internal dowels were excessively tight.  Extraction holes had to be drilled and tapped into them to remove.
• Both white metal seals are severely damaged.
• All white metal bearings have scoring and worn appearance.  White metal bearings are not suitable for service.
• White metal bearing thrust pads have minor scoring.  Pads are suitable for service to require minor hand polishing.
• Output shaft end cover is cracked all the way through the flange.
• Pump drive coupling is missing from the bevel gear box output shaft.
• Externals of unit are in poor condition. External blasting is required.

Preliminary Inspection Report – Bore Diameters

Input Shaft and Mating Components

Once the Valcan-Sinclair fluid coupling had been delivered back to the plant in SA it was set back in its original position, coupled up to the motor and boiler feed pump in the correct way which we believed had not been coupled correctly before, this had meant since its last overhaul the fluid coupling had been pulling the balance face of the boiler feed pump together. The Valcan-Sinclair Fluid Coupling was commissioned and is running well.