Page 174 - Safety Risk Management for Medical Devices

Integration of Risk Analysis 153

Figure 16.4 Water Pump.

Figure 16.5 Failure Mode of the Pulley.

To this point, we have followed a decomposition model such as what is illustrated
in Fig. 10.1. Now let’s consider the Failure Mode of one of the Water Pump parts:
the Pulley (Fig. 16.5).
If the Pulley breaks up, the water pump can no longer receive torque from the
engine, and it stops pumping water. Not pumping water is the End Effect of the
pulley break-up on the Water Pump. Now let’s move up one level to the Engine.
To the Engine, the Water Pump is a black box component, whose Failure Mode
is: Doesn’t Pump Water. Notice that what was the End Effect: Doesn’t Pump Water from
the Water Pump perspective, has become the Failure Mode of the Water Pump from
the engine perspective, which sees the water pump as a black box component
(Fig. 16.6).