Hazop - A Structured Technique for Systematic Examination of Risks

This article discusses the history and working of Hazop, a technique for identifying potential hazards and operational problems in a process or operation. It also explains the four stages of Hazop and how it differs from LOPA and QRA.

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Hazop
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Hazop
Introduction
Hazard and operability analysis (HAZOP) is a careful and systematic analysis of a
process or an operation with the objective of determining whether deviation from an intended
operation can lead to a hazard or undesirable outcome. In other words, it is a technique of
identifying any potential hazard or any problems in operations that result in risks. Primarily,
HAZOP is based on the theory that assumes that risks are caused by either deliberate or
unintentional deviation from the intended operation. Risk analysis is an important undertaking in
an existing or a new operation. Thus HAZOP is a step by step analysis applicable to both
ongoing and new projects. Thus, the main goal of this paper is to discuss the history of HAZOP
as well as how it is different from techniques such as LOPA and QRA.
A Brief History of HAZOP
The development of HAZOP begun with the pioneering work led by Ellis Knowlton and
Trevor Kletz at the Imperial Chemical Industry (ICI) in the 1960s through the early 1970s.
HAZOP was initially adopted in the chemical industries where it was used to assess the risks
associated with any possible deviation from the intended project. According to Limb (2009),
Kletz has since then ensured the update of the methods through mnemonic demonstrations. The
evolvement of the HAZOP procedure included the use of keywords that were combined to
enable the structuring of a team’s analysis of the newly invented process designs.
Limb (2009), also notes that the use of “keywords” has been replaced with “guidewords”
or “parameters” which are used interchangeably. In other words, the HAZOP process entailed
the combination of the parameters or keywords and guidewords for positive or negative

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deviation from the measured operating variables such as pressure and temperature. Additionally,
following the widespread use of the HAZOP, the HAZOP report was adopted as a document of
legal importance following the HSE focus on the increased publication of accidents in industries.
How HAZOP Works
HAZOP has widely been adopted in different facilities mainly due to its ability to not
only identify hazards but also operational problems. Among the fields where HAZOP has been
adopted include analysis of hazards in photovoltaic field, road safety measures, and medical
diagnostic system. Dunjó et al (2010) connote that the wide use of HAZOP demonstrates how
the approach is considered as a significant technique for improving different types of systems.
Generally, there are four fundamental phases involves in HAZOP analysis. These methods
include; definition phase, preparation phase, examination phase, and documentation and follow-
up phase.
Central to the definition phase is the identification of the risk and operation assessment
team. The team should comprise the members from diverse disciplines because HAZOP calls for
a cross-functional team. Thus, the risk assessment team entails multi-disciplinary specialists
(SMEs) with the relevant experience and skills and who exhibit informed judgment and intuition
(Product Quality Research Institute). Thus, the team members should include individuals with
broad and current knowledge of deviations of the system. The team must, first of all, define the
scope of its study, the main interfaces, and define the assumptions under which the assessment is
performed. Preparation phase, on the other hand, includes such activities as identification and
location of data and information to support the assessment, identifying the audience/users of the

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output, preparing for the project management, agreeing on HAZOP guide words and the template
format to be used during the assessment.
The third step of HAZOP study involves the identification of all the elements set for use
in the system or process. In this stage, the guide words agreed upon by the team members are
assigned to each of the elements. Additionally, the team is engaged in a search for deviations
guided by the rule that the rational use or misuse conditions expected by the user should be noted
and discussed to determine their credibility or whether they should be taken through a further
assessment. The final stage, the documentation and follow-up phase, involves the recording of
the HAZOP analysis. Typically, there is a definite HAZOP template as detailed by the IEC
standard 61882 although the risk assessment team are granted the authority to modify the
template (Product Quality Research Institute). For instance, the template modification may be
guided by such factors as risk rate prioritization, regulatory requirements, audit readiness, or a
company’s documentation policies among other factors.
How HAZOP is Different from LOPA and QRA
HAZOP differ significantly from other techniques such as the Layer f Protection Analysis
(LOPA) and Quantitative Risk Assessments (QRA). LOPA is a risk analyzing technique that
uses complex calculations of the residual risk (Willey, 2014). The residual risk is then used to
examine the safety requirements for the essential instrument tools (de Sali, 2012). Like HAZOP,
LOPA requires a risk assessment team. Nonetheless, de Sali (2012) argues that the number
involves in LOPA’s calculation and the manner in which the calculations are conducted
influences a mounting body of literature thus ignoring the team conducting the Safety Integrity

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Level (SIL). In other words, the primary difference between HAZOP and LOPA is that the
former is team-oriented while the latter largely relies on the calculations.
Similarly, as QRA assesses the potential causes of risks and rates them, HAZOP is a
detailed process that analyses the elements of risk assessment and also looks into the deviations
of the operation system (Holmberg, 2017). The risks identified in the HAZOP process are then
assessed and mitigation measures put in place to curb the risks. According to La and Shah
(2011), HAZOP identifies the hazards/risks while QRA assesses hazards. Additionally, while
QRA is applied in a few projects especially where it is legally required, HAZOP permeates
almost all the projects (Aven, 2015). HAZOP is also qualitative while QRA is quantitative.
Besides, the former calls for multidisciplinary approach while the latter requires one or a couple
of experts with a good command of QRA software.
Conclusion
In summary, this paper has defined HAZOP as a structured technique for systematic
examination of risks in a new or existing project and also assesses the process of operation of a
system. Also discussed is the structure of HAZOP which entails four stages namely;
identification of the team, preparation, identification of elements for use, and documentation and
follow-up phase. Finally, the discussion also shows how HAZOP differs from other techniques
such as QRA and LOPA.

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References
Aven, T. (2015). Risk analysis. John Wiley & Sons.
de Sali, C. F. (2012). HAZOP and LOPA the Odd Couple. Symposium Series, 158:183-186.
Dunjó, J., Fthenakis, V., Vílchez, J. A., & Arnaldos, J. (2010). Hazard and operability (HAZOP)
analysis. A literature review. Journal of hazardous materials, 173(1-3), 19-32.
Holmberg, J. E. (2017). Quantitative Risk Analysis. Handbook of Safety Principles, 434-462.
La, T. S., & Shah, P. D. (2011). Comparative Study between PHA (Process Hazard Analysis)
Evaluation Techniques for Chemical Process Industries. Institute Of Technology, Nirma
University, Ahmedabad, 382 -481.
Limb, D. (2009). HAZOP Studies- A New Approach. Symposium Series, 155:122-129.
Product Quality Research Institute (PQRI). (2012). Manufacturing Technology Committee Risk
Management Working Group Risk Management Training Guides. Accessed on 25th May,
2018 from http://pqri.org/wp-content/uploads/2015/08/pdf/HAZOP_Training_Guide.pdf
Willey, R. J. (2014). Layer of protection analysis. Procedia Engineering, 84, 12-22.

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