Application of Risk Theory in Man–Machine–Environment Systems - Fundamentals and Assessment Tools for Occupational Ergonomics - page 168

TABLE 8.1
Part of Gearbox Sign

Pinion bearing Rlp

Pinion Rp

Bearing and pinion Rl þ p

Countershaft bearing Rlpr

Countershaft gearing Rpr

Countershaft shaft Rhpr

Whole block Rcb

Big gear Rlvk

Output gear Rvk

Bearing and output gear Rlvk þ vk

with thickness from 5.6 to 12.5 mm and with length from 9 to 12 m. The arrangement of pipe mill hallis
shown in Figure 8.4.

8.2.2.2 Risk Level Determination
To obtain the values of technical risk levels in this technological complex we need to know the values
of probability P and consequence D. Number of failures or the frequency of failures equals to the
probability of risk state occurrence. The kind of accident equals to the range of health-injury, that
is, equals to the consequence or to the weight factor. We can see all the important parts of pipe
mill hall in the next table. For each part, the frequency of failures and the consequence of accident
are determined. Combination of these two parameters is the risk level. Operation is with three levels
of failure frequencies: low, middle and high. Three kinds of consequences are taken into consideration:
accident light, accident difficult and deadly accident. Hence three risk levels are also obtained: low,
middle and high (Table 8.2). It is possible to determine from this table the so-called weak points
in the whole technological complex. From the analysis of maintenance costs and the technical risk
it is evident that the most important subject of interest is the ultrasonic welding 1. Therefore, it is
very useful to perform the technical risk analysis for all components of this machine for ultrasonic
welding 1 (Figure 8.5).
The result is shown in the graph in Figure 8.5. In this graph the risk level becomes equal to the point
evaluation: 1-5 is unacceptable risk; 6-9 is undesirable risk; 10-17 is risk acceptable with control and
18-20 is risk acceptable without control.
It is necessary to take into consideration that during the process of risk determination two aspects were
combined together: technical factor — frequency of failures and human factor — kind of accident.

0.016

optimal parameters
unsufficient maintenance

0.014

0.012

0.01

0.008

0.006

0.004

0.002

0

Rlp Rp Rl+p Rlpr Rpr Rhpr Rcb Rlvk Rvk Rlvk+vk

Parts of Gearbox

FIGURE 8.3 Comparison of risk values.