Rudarski radovi br 4 2011 - Institut za rudarstvo i metalurgiju Bor

ing to the overall economy. However,<br />
risks in this field have become a<br />
social reality and society has learned to<br />
live with them.<br />
These lead to a fact that risk assessment<br />
has to be a continuous process, since<br />
time can bring new techniques for reduction<br />
the residual risk and existence of such<br />
process itself has a positive effect to the<br />
public consciousness. It should be underlined<br />
that our society has low level of tolerance<br />
towards risks in mining and that<br />
people are prone to perceiving a "serious<br />
injury" as a "catastrophic injury".<br />
Figure 2 gives a graphic representation<br />
that would be used as an aid in decision<br />
making regarding risk tolerability. Lower<br />
left region represents the region of low<br />
risk and all risks in this region are considered<br />
tolerable and require constant supervision.<br />
Upper left is the region of high<br />
risk. All risks in this area are intolerable<br />
and the system in question (mining) can<br />
only function if they are eliminated using<br />
appropriate measures and transferred to<br />
the central region, known as ALARP[10]<br />
(As Low As Reasonably Possible). This is<br />
the region where the most decision mak-<br />
Fig. 2. Risk level regions<br />
ing regarding risks takes place. The basic<br />
principle is to transfer each risk towards<br />
the lower left angle, as much as it is practical<br />
and feasible and as long as the costs<br />
of such transfer are proportionally to the<br />
improvement gained, i.e. reasonable. In<br />
practice, this means the increase of production<br />
indicators at all levels, with the<br />
maximum safety of employees. Also, it<br />
should be noted that introduction of measures<br />
which increase the safety of a system<br />
also increases its complexity and, in most<br />
cases, negatively influences its reliability<br />
and general safety level.<br />
Making decision on what is reasonable<br />
and what isn't is crucial to the entire process.<br />
This decision includes the cost of implementation<br />
of risk reduction measures,<br />
the extent of reduction and the improvement<br />
gained. Such decisions are often<br />
subjective, and it is recommended that<br />
they should be made by interdisciplinary<br />
team, which has multiple perspectives of<br />
the same problem.<br />
Table 4 shows classification of risks<br />
according to the IEC 61508-5 Standard<br />
which defines 4 classes of risks in terms<br />
of tolerability.<br />
No 4, 2011. 127<br />
MINING ENGINEERING