TABLE OF CONTENTS The general objective of a hazard and risk assessment is the identification of machinery features which could threaten the safety of personnel, property, or the environment. Hazard and risk assessment methods are evaluated in Table 9-1. Hazard is defined as the source of harm, and risk is the possibility of experiencing this harm. For example, the hazard around a pumping service for toxic material could be the failure of the shaft seal. Two designs are suggested to prevent a leakage of the toxic material. Design B uses multiple mechanical seals (Fig. 9-1B), whereas design A calls for a single mechanical seal (Fig. 9-1A). Both designs may fail during operation of the pump. However, the probability of a toxic release for the multiple seal design (Fig. 9-1B) is much less than for the design incorporating only a single seal. Consequently, for the same hazard level, design B poses less risk for the plant operators and the public than design A.
| Method | Characteristic | Advantages | Disadvantages |
|---|---|---|---|
| Preliminary hazards analysis | Defines the system hazards and identifies elements for FMEA and fault tree analysis; overlaps with FMEA and criticality analysis | A required first step | None |
| Failure mode and effect analysis (FMEA) | Examines all failure modes of every component. Hardware oriented | Easily understood. Well accepted, standardized approach, non-controversial, non-mathematical | Examines non-dangerous failures. Time-consuming. Often combinations of failures not considered |
| Criticality analysis | Identifies and ranks components for system upgrades. May be part of FMEA | Well-standardized technique. |
