ASK Piearcey

HAZOP Service Launched
September 16, 2014, 1:09 pm
Filed under: Uncategorized | Tags: , , , , , , ,

ASK Piearcey Ltd have developed their own in-house, database driven, HAZOP process. We can now facilitate entire HAZOP events or attend as a contributor or scribe. So What is a HAZOP??

According to the  Health and Safety at Work Act 1974 (HASAW) and for Major Hazardous processes COMAH (1999) regulations, it is the responsibility of the OPERATOR or end user to identify risks associated with a plant.


There numerous regulations and protocols to refer to ( example see HSE website: ) but in our view, the End-User or operator of the plant must facilitate and attend a HAZOP for the plant as a minimum and must fully discharge their responsibilities under HASAW and where appropriate, COMAH.


A HAZOP is a study and NOT a document. Any HAZOP documentation is a product of a HAZOP study.


The HAZOP study should include but not be limited to a team of individuals with responsibility within the project to be studied as follows:


  • An electrical engineer
  • A control/software engineer
  • A mechanical engineer
  • A process engineer
  • An operator (as in person who will be physically operating that plant)
  • Project manager(s)
  • Engineers relating to specific plant items (e.g. a representative from a reactor manufacturer
  • Persons in positions of responsibility for the End User
  • Persons in positions of responsibility for the Principal contractor
  • Persons in positions of responsibility for the Planning Supervisor
  • An independent chairperson
  • An independent scribe


The HAZOP centres around the “frozen” process and instrumentation diagram (P&ID). It is a rigorous, painstaking and methodical study of each and every line within the P &ID diagram (referred to as “nodes”). Each node has a list of guide words applied to it and each guide word has a list of deviations applied to it in turn.




Guide word is “Flow”


Deviations maybe :




“Less than”

“More than”

Each application of a deviation will generate scenarios, discussion, questions about the risk and consequence of the deviation and at each stage the plant is questioned for its robustness and suitability to prevent, minimise or handle such deviations. This in turn generates actions for individuals present to rectify any perceived flaw or weakness in the design.

We have never encountered a HAZOP which has not changed the design in some manner and hence it is extremely important that a HAZOP is carried out.

HAZOP image 1 HAZOP image 2

A HAZOP may take some weeks to organise, some days to complete and some further weeks to sign-off any actions. The Actions may result in the change of the P&ID, operational instructions, drawings and design. A design cannot therefore be fit for purpose unless it has undergone a formally recorded and signed-off HAZOP.

With our  in-house designed HAZOP program, we  can carry out formal HAZOP studies. We have successfully managed and chaired HAZOPs using our database centred system. There are also companies and individuals who specialise in HAZOPs and indeed other Structured What-If Techniques (SWIFT) and they  also have fully contained database driven HAZOPS that include the procedures for issuing and signing off actions. We advise that end-users formally engage  ourselves or other specialists to facilitate HAZOPs if they do not have the capability in-house.

The HSE also advise a HAZAN (for COMAH) is undertaken as part of the hazard identification process. This is a study of the severity of a hazard in the event the risk of the hazard is realised.  In our experience, HAZANs are often not a formal, separate study but are split into actions for groups of individuals. It is advisable to fully explore the consequences of a hazard actually occurring as it may well significantly affect the methods of mitigation put in place. An example would be the potential for cross filling of sulphuric acid into a chemical tank containing sodium hypochlorite. In this event chlorine is formed and this is a highly toxic gas. At a HAZOP measures would be suggested to minimise the risk of the cross filling occurring. The HAZAN looks at what would happen to chlorine if it were formed and what consequences this would have. If the implications included  multiple fatalities then the HAZOP actions may well be made even more robust and the “budget” for mitigation increased accordingly.

It should be noted that in our experience as attendees, the “OP” part of HAZOPs is often left relatively unexplored (particularly when operators are not involved in the study) and another study known as an ALM (Access Lifting and Maintenance) can be useful in identifying and eliminating operational issues. Of course Access, Lifting and Maintenance would  simply be added as guide words to the HAZOP  if we were managing  the event and they would probably have no deviations.

For complicated projects, especially those involving several stages of treatment and with numerous interfaces with other equipment, it is advisable to implement a HAZCOM. This is a “big picture” SWIFT technique which looks at a whole process rather than individual lines on a P&ID. The purpose of a HAZCOM is to identify hazards that may arise as a result of commissioning activities. The HAZCOM needs to involve representatives from any party involved in concurrent commissioning activities. It becomes particularly relevant when there is dependency between various parties during the commissioning phase.

ASK Piearcey Ltd have attended HAZCOM events and found them to be useful in raising awareness of concurrent commissioning activities and their associated hazards.