Mi Swaco 414

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1.3 The centrifuge rotating assembly consists of the bowl, the conveyor and the planetary
gearbox. All these items are described in Paragraph 1.1.1, 1.1.2 and 1.1.3.
1.4 The following safety components are incorporated in the Swaco 414 Centrifuge
1.4.1 Torque Limiter
The torque limiter is a combination of mechanical and electrical controls. The
small sunwheel shaft has a spring loaded coupling (G.S. Coupling - See
Figure 12) which will limit the torque that can be applied to the shaft. If this
limit is exceeded the coupling will disengage and will, by axial movement of
the coupling, trip a limit switch, Item 224, Diagram 1. This will disconnect
power from the bowl drive motor and the feed pump when controlled by
Centrifuge Control System.
1.4.2 The mass of the rotating assembly is very high. To bring this assembly up to
operational speed takes from 90 to 100 seconds. A fluid coupling is installed
between the drive motor and the rotating assembly to allow the motor to attain
full operating speed almost immediately and allow the bowl to reach
operational speed gradually.
Without the fluid coupling, the motor current on startup would be excessively
high and could result in damage such as overheating of connectors and cable
or motor overload protectors or could overload the power plant if it was
operating near full load.
Should a high load on the rotating assembly cause excessive slip in the fluid
coupling, the heat so generated will melt a fusible plug in the coupling causing
the oil to be dumped. This will unload the motor before any damage is done.
1.4.3 Overspeed of back drive motor
The small sunwheel is driven by a back drive motor (Paragraph 1.1.3).
Overspeed of the back drive motor could occur if the back drive motor is
turned off before or immediately after the main drive motor. This would
allow the conveyor to assume the bowl speed. The rotation would be
transferred through the gearbox to the small sunwheel shaft and through the
belts to the back drive motor to rotate at higher than designed motor speeds
and could cause the motor armature to fly apart resulting in property damage
and/or personal injury or death.