Page 363 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

151338 Risk Management
Consequence (receptor) Probability
~~~ ~~~ ~
Never Has Has Happens Happens
heard of in occurred occurred several several
industry in industry in company times per times per
year in T year in

No health No No effect No impact
effect damage

Minor Minor Minor Limited
injury damage effect impact
potential

Major Localized Localized Considerable
injury damage effect impact
potential

Fatality Major Major National
damage effect impact

Multiple Extensive Massive International
fatalities 1 damage I effect I impact

Figure 15.2 Example of qualitative risk criteria matrix.

The ALARF’ principle recognizes that no industrial activity To define the transitions between the zones, two levels of crite-
is entirely free from risk. It attempts to gauge the point where ria are set:
risk reduction has gone far enough. Achieving ALARF’ levels
involves balancing reduction in risk against the time, trouble, 1. A maximum tolerable criterion (or intolerable level), above
difficulty, and cost of achieving them. The point at which the which the risk is intolerable
time, trouble, difficulty, and cost of further reduction measures 2. A negligible criterion (or broadly acceptable level), below
become unreasonably disproportionate to the additional risk which the risk is insignificant.
reduction achieved is ALARP
A widely referenced ALARP framework for risk acceptabil- The phrase acceptable risk has been defined as “a risk which
ity is from the Health and Safety Executive (HSE) in the United has been evaluated in accordance with accepted practices and
Kingdom, which divides risks into three bands (Figure 15.3). for which an informed decision to accept the frequency and
consequence that comprise that risk has been made and docu-
1. An unacceptable region, where risks are intolerable except mented” [91]. This is obviously a difficult definition to apply.
in extraordinary circumstances, and risk reduction measures In the UK, the procedure to show whether the risks on an
are essential. installation are ALARF’ is as follows:
2. A middle band, where risk reduction measures are desirable,
but may not be implemented if a costhenefit analysis shows 1. Estimate the risks and compare with appropriate risk crite-
that their cost is disproportionate to the benefit achieved. In ria. If they exceed the maximum tolerable criterion, then
the United Kingdom this is known as the ALARP region, and measures must be taken to make them tolerable; otherwise
risks are considered tolerable providing they have been operations must cease. If they are broadly acceptable, the
made “as low as reasonably practicable” This ALARF’ con- risks are ALARP and no further risk reduction measures
cept can be seen in many other regulatory risk criteria. need be considered, provided appropriate diligence is
3. A negligible region, within which the risk is tolerable, and applied to maintain risks in this region. If they are in the
no risk reduction measures are needed. In the United ALARF’ region, continue as follows.
Kingdom this is known as the broadly acceptable region, 2. Identify a complete range of practicable risk reduction
suggesting that the activity would be acceptable to a broad measures, based on best modern practice, focusing prima-
majority ofthe public, and the term negligible is reserved for rily on large risk contributors. Assess the feasibility and cost
still lower risks. of the risk reduction measures.