Introduction to Phast Risk for Quantitative Risk Assessment

Легендарная Речь Стива Джобса

Как найти причину проблемы с помощью диаграммы Иcикавы (Ишикавы)

ALARP

So what is ALARP?

The ALARP principle

No industrial activity is entirely free from risk and so many companies and regulators around the world require that safety risks are reduced to levels that are As Low As Reasonably Practicable, or "ALARP".

The "ALARP region" lies between unacceptably high and negligible risk levels. Even if a level of risk for a "baseline case" has been judged to be in this ALARP region it is still necessary to consider introducing further risk reduction measures to drive the remaining, or "residual", risk downwards.

The ALARP level is reached when the time, trouble and cost of further reduction measures become unreasonably disproportionate to the additional risk reduction obtained.

ALARP for life

Risk can be reduced by avoidance, adopting an alternative approach, or increasing the number and effectiveness of controls.

At the concept stage of a new project there is the greatest opportunity to achieve the lowest residual risk by considering alternative options, e.g. for an offshore oilfield development, options may range from fixed legged platforms to floating production vessels to subsea facilities.

Once the concept is selected and the early design progresses, the attention shifts to considering alternative layout and system options to optimise inherent safety. In the detailed design phase, the focus moves on to examining alternative options for improving safety systems.

During operations, the attention is on collecting feedback, improving procedures and managing change to maintain the residual risk at an ALARP level. However, with advances in technology, what is ALARP today may not be ALARP tomorrow, so periodic reviews will be necessary.

Conclusion

The key to a convincing ALARP assessment lies in the documented consideration of improvement options, both implemented and discounted, at a level of resolution appropriate to the project phase. ALARP decision making amounts to taking a balanced view and reaching a defensible consensus.

This article first appeared in RISKworld Issue 4.

Принцип ALARP в Великобритании

Разработанный в Англии в рамках закона о Здравоохранении и Безопаснсоти в 1974г. принцип  ALARP основывается на оценке стоимости риска и стоимости задействованных средств, для того, чтобы его снизить.

Здесь исходят из принципа, что нулевой риск физически и финансово недостижим, и что необходимо найти правильное соотношение между затратами и допустимым уровнем риска. Принцип ALARP состоит в том, что риск  должен быть сведен к наиболее низкому уровню, который возможен. Здесь речь идет об анализе стоимость/результат по овладению рисками.

Чтобы провести такую оценку, принцип ALARP опирается на систему глобального анализа рисков, описанную в европейских(EN 50126) и международных (CEI 61508)нормах. С одной стороны он опирается на классификацию рисков по четырем категориям, по пересечению частоты и глубины риска.

Начиная с некоторого уровня, риск рассматривается, как недопустимый и не может быть оправдан ни при каких чрезвычайных обстоятельствах.
Ниже этого уровня существует допустимая зона, в которой действие может произойти, если связанные с ним риски низки насколько это возможно. Допустимый не означает приемлемый: оценка положительного влияния на ситуацию должна быть проведена для того, чтобы определить, стоимость средств или предусмотреть иные меры безопасности. Необходимо, таким образом, быть готовым к тем большим затратам, чем выше степень риска. Поэтому, если степень риска остается высокой, расходы, непропорциональные степени риска, могут быть оправданы. Если риск менее высок, то необходимо уравновесить затраты и получаемое улучшение ситуации.

В приемлемой зоне риски рассматриваются как незначительные, и, следовательно, не являются предметом демонстрации по принципу ALARP. Это не означает, что никакие заградительные меры для рисков не будут предприняты, но, что стоимость их не будет высокой.

The BowTie method in 5 minutes

Four incident analysis methods to choose from

It is a given that in many organizations more than one method is adopted to do incident analysis. If these organizations wish to learn from all incidents, the outcome of these methods needs to be consolidated.

Providing the right method to untangle a complicated incident is crucial if you are to uncover what lessons should truly be learned on both organizational and operational level. Four of the most populair barrier based incident analysis methods were selected for BowTieXP:

• BSCAT
• Tripod Beta
• Root Cause Analysis (RCA)
• Barrier Failure Analysis (BFA)

We observed first three below.

BSCAT

Next generation incident analysis tool

BSCAT is a next generation incident analysis tool that uses barrier thinking to clarify and structure your incident analysis. The BSCAT method can utilize pre-existing BowTies or be used on its own. It is the first method to complete the circle and link risk assessments with incident analysis. BSCAT is built on top of the BowTieXP platform.

Recent insights reveal that improved safety management performance can be obtained if a more focused approach on barrier performance is followed. Advanced Barrier Management is a relatively new concept that addresses the effectiveness of specific barriers that aims to prevent undesired top events from happening and/or that aims to limit the extend of the undesired consequences.

The Bowtie-concept provides a clear visual presentation of several high risk scenarios and how these scenarios can be managed. When applying the bowtie-approach one is triggered to think of available and/or potential barriers that keep control of the hazard scenarios and their effectiveness. Bowtie-based risk analysis is part of mature risk based safety management framework and should be applied by all organizations that aim to have a better understanding and control of their key risks. Allocation of accountabilities and document links can be part of the bowtie-thinking when the software program BowtieXP is applied.

From SCAT to BSCAT

BSCAT links the bowtie-concept to DNV’s classical concept for incident investigation (SCAT), which is already used by many organizations. The Systematic Cause Analysis Technique provides a framework with predefined categories of direct and basic causes that have proven to be important contributions for incidents in a variety of market sectors. By applying this SCAT technique on barrier performance, one can assess the performance of barriers during an incident investigation and come up with specific improvement actions that address the basic causes of failure. The BSCAT-concept supports in particular (complex) incident investigations that are characterized by a variety of events that went wrong. BSCAT is now supported by a software tool – branded as DNV BSCAT – that allows for smart generation of incident diagrams. DNV BSCAT operates under the proven BowtieXP platform.