Wednesday, 16 November 2011


Hazard and Operability Analysis (HAZOP) is a structured and systematic technique for system examination and risk management.  In particular, HAZOP is often used as a technique for identifying potential hazards in a system and identifying operability problems likely to lead to nonconforming products.  HAZOP is based on a theory that assumes risk events are caused by deviations from design or operating intentions.

Identification of such deviations is facilitated by using sets of “guide words” as a systematic list of deviation perspectives.This approach is a unique feature of the HAZOP methodology that helps stimulate the imagination of team members when exploring potential deviations.

This document presents some guiding principles in the execution of  HAZOP analyses.Successful application of any risk management model requires that tools are used in concert with the overall quality risk management process.

This guide will present the principles of HAZOP in the context of the accepted Quality Risk Management process consisting of Risk Assessment, Risk Control, Risk Review and Communication and is intended to compliment (not replace or repeat) the guidance available within IEC International Standard 61882.

1.1 Definitions. 
When describing the HAZOP methodology, the following definitions1 are useful:

Hazard -   Potential source of harm. Deviations from design or operational intent may constitute or produce a hazard. Hazards are the focus of HAZOP studies, and it should be noted that a single hazard could potentially
lead to multiple forms of harm.

Harm -  Physical injury or damage to the health of people or damage to property or the environment.  Harm is the consequence of a hazard occurring and may take many forms: patient or user safety, employee safety, business risks, regulatory risks, environmental risks, etc.

Risk -   Combination of probability of occurrence of harm and the severity of that harm.  In a strict sense, “risk” is not always explicitly identified in HAZOP studies since the core methodology does not require identification (also referred to as rating) of the probability or severity of harm.  However, risk assessment teams may choose to rate these factors in order to further quantify and prioritize risks if needed.

1.2 Usage 

HAZOP is best suited for assessing hazards in facilities, equipment, and processes and is capable of assessing systems from multiple perspectives:
·                     Assessing system design capability to meet user specifications and safety standards 
·                     Identifying weaknesses in systems.
 Physical and operational environments.
·                     Assessing environment to ensure system is appropriately situated,supported, serviced, contained, etc.

 Operational and procedural controls:

·                     Assessing engineered controls (ex: automation), sequences of operations, procedural controls (ex: human interactions) etc. 
·                     Assessing different operational modes – start-up, standby, normal operation, steady & unsteady states, normal shutdown, emergency shutdown, etc. 
·                     Helpful when confronting hazards that are difficult to quantify 
·                     Hazards rooted in human performance and behaviors 
·                     Hazards that are difficult to detect,analyze, isolate, count, predict, etc. 
·                     Methodology doesn’t force you to explicitly rate or measure deviation probability of occurrence, severity of impact, or ability to detect 
·                     Built-in brainstorming methodology 
·                     Systematic & comprehensive methodology 
·                     More simple and intuitive than other commonly used risk management tools.
·                     No means to assess hazards involving interactions between different parts of a system or process. 
·                     No risk ranking or prioritization capability. 
·                     Teams may optionally build-in such capability as required 
·                     No means to assess effectiveness of existing or proposed controls (safeguards). 
·                     May need to interface HAZOP with other risk management tools (ex: HACCP) for this purpose. 

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