Evaluation of Subsystem Hazard Risk

The SSHA has identified two possible conditions that could cause the passenger car to slip in the shaft once it has come to a stop at a designated floor landing. 

Hamrd Condition Item 1 Loss of Hydraulic Pressure 

The required design safety factors and hydraulic pressure bleed-off rates will not permit a catastrophic result in the event of pressure loss. At most, in the event of a continuous oil pressure loss, the elevator would descend slowly to the ground floor level at a rate consistent with that of the loss. Therefore, a severity level of marginal has been assigned and a probabihty of occurrence level of remote has been determined. 

Recommendation 1 Even though an RAC of 3D is considered acceptable with review, hazard risk reduction is still warranted, especially in consideration of the two reported incidents. In order to ensure maximum possible reduction of the hazard risk associated with a failure of the plunger joint components, it is recommended that routine preventative maintenance inspections include replacement of the plunger joint o-ring component. This action would further reduce the probability of occurrence to the improbable level. Once recommended control actions are in place, a controlled RAC of 3E (marginal/improbable) can be assigned. 

Hazard Condition Item 2 Loss of Hydraulic Pressure 

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