• The HAZOP study should be an integral part of an overall SMS that includes the other appropriate studies described in Chapter 2.

• The process must have the full backing and support of senior management.

• The study must be initiated by a person who has authority and who will also receive and implement the actions. If the person does not have authority and the actions are not implemented, the study is a waste of time.

• The design must be well developed and “firm”—that is, the sections examined are not being simultaneously developed. In the case of a modification, the P&IDs must be verified as “as built” with the changes highlighted within a “cloud.” A study cannot be carried out on a partly-developed design as the subsequent changes will undermine the HAZOP study. Freezing of the P&IDs is critical to a study. Also, the drawings must be well prepared. The drawings are the record of what was studied, and if they are inaccurate or incomplete the HAZOP study is worthless. Equally, the study must not be delayed too long as the options for change will become very limited. Premature study where the P&IDs are still not finalized is wasteful of time and effort. Equally, the freeze of the P&IDs stops further development of the drawings and may hinder further design work. The balance is a careful judgment.

• A skilled and suitably experienced team leader should be chosen.

• The leader must be given a clear scope, objectives, and terms of reference from the initiator for this study (including delivery date and recipient); if this is not done, the study may be incomplete in some aspects and not fulfill the requirements of the initiator.

• The leader should choose a route plan (see Section 5.3) through the P&IDs to ensure that all necessary sections are covered effectively with special care taken at branches and interfaces with services. The route should be clearly defined with well thought out starts and ends.

• The study should not be required to make project decisions; nor should the design team adopt the approach of “leave it to the HAZOP study to decide what should be done!” If a problem is known, then it needs to be addressed during the design.

• The study team must be balanced and well chosen to combine knowledge and experience. A study group that is drawn entirely from the project team will not be capable of critical creative design review. Equally, a team which has no operations input may lack objectivity.

• The team must be given adequate notice of the study so that they can carry out their own preparation in readiness for the study itself. This may require some preliminary reading of any relevant hazard databases and analysis of the P&IDs.

• The extent to which problems are evaluated, ranked, and solved should be defined.

• The team must be motivated, committed, and have adequate time to complete the examination.

• Team continuity is important—only essential variations and substitutions should be accepted (see Section 5.2.3).

• The boundary of the study must be clearly analyzed and studied. A change on item “one” may have an effect on item “two.” The item may be two different processes or an operation upstream or downstream on the same process. If the potential impact is not perceived correctly, the boundary may be placed wrongly.

• The boundary of a study on a modification is equally complex—a change in the temperature of a reactor may affect the by-product spectrum and have a more far-reaching impact than the immediate modification.

• A clear description, design intention, and design envelope must be given to every section or stage examined.

• The study uses a creative thought process. If it becomes a mechanistic process and simply works through a checklist, or if fatigue sets in, the study must be halted and restarted when the team is refreshed.

• Proposing, developing, and finalizing actions is the responsibility of the team, not the leader.

• Each action must be relevant, clearly defined, and worded with no ambiguity. The person who follows up the action may not have been at the meeting and could waste time and effort if there is a misunderstanding.

• The study must accept a flexible approach to actions. Not all actions are centered on hardware changes—procedural changes may be more effective.

• The study team members must be aware that some problems ranked and identified during the study may be caused by human factors.

• There are potential pitfalls, which must be treated individually, when planning the route around branched systems. These branches may be recycle lines, junctions in the process, or vents and drains.

• Every action raised must be analyzed and answered accurately.

• Many of the actions raised will require no further change but all must be signed off as “accepted” for action or no action, as described in Sections 6.4 and 6.5.

• Actions that require a positive change should be subject to an MOC process (which may require a new HAZOP of the change) and put into a tracking register.

• Action reply sheets should be clearly linked to the original study reports, including the reference number, the node, the intent, and the deviation. This greatly helps follow-up and audit. They should also reference any calculations carried out.