Application of Risk Theory in Man–Machine–Environment Systems - Fundamentals and Assessment Tools for Occupational Ergonomics - page 167

FIGURE 8.1 Gearboxes are one- or two-stage types with helical gears and with a synchronous motor.

8.2.1.2 Method of Solution
To evaluate the technical risk of the above-mentioned gearboxes, one needs to determine the probability
P and the weight factor or consequence D.
There are three information sources available for the determination of P: statistics, expert system,
individual estimate of an expert-worker.
We chose the way of an expert system, which is suitable for our purposes (Figure 8.2). Description of
this flexible observation system is too complicated.
The software is based on the fuzzy groups and this method enables one to perform condition-based
maintenance — CBM. It is a well-known fact that the CBM is the best maintenance method at the
present time.
On the other hand, the consequence D is most frequently expressed in terms of money. Only the primary
consequences are taken into consideration here, that is, price of spare parts and price of work. But the
secondary consequences (losses due to lost time) are often much higher. There is a list of gearbox parts
shown in Table 8.1. Two states of the gearboxes were simulated by means of the expert system:

1. Current operation with optimal parameters
2. Operation with insufficient maintenance

The result of the simulation is the final comparison of risk values for individual parts of the gearbox
(Figure 8.3).

8.2.2 Example 2
8.2.2.1 Risk Evaluation in the Pipe Mill Hall
In the next part the example considered is the pipe mill hall. It is a big technological complex from the
technical risk point of view. Products of this pipe mill are pipes with diameters from 500 to 1420 mm,

R = P . D

Real task

Financial costs

Gearbox conditions

Statistical monitoring Gearbox monitoring

Planned monitoring Non-planned

monitoring

Statistics

Expert system

FIGURE 8.2 The complicated flexible observation system.