HAZARD & OPERABILITY STUDY (HAZOP)

WHAT IS HAZOP?

It is a study that identifies hazard and  operability problems by investigating how the plant might deviate from the design.

By definition:-

The application of a formal systematic critical examination to the process and engineering intentions of the new facilities to asses the hazard potential of mal-operation or malfunction of individual items of equipment and the consequential effects on the facility as a whole.

WHY WE NEED HAZOP?

  • Chemical Industry handling hazardous substances.
  • Manufacturing unit with complex reaction(s).
  • Deviations may have serious effects.
  • Responsible corporate organisation.
  • Law abiding company.
  • Care for community in and around the unit.

WHERE WE NEED TO APPLY HAZOP?

Limited resources results in method of selection Factors considered;

  • Abnormal occurrences, accidents in the past
  • Some study has indicated “High Potential Risk”
  • Extensive modification have been done
  • Statutory requirement

WHEN HAZOP SHOULD BE DONE?



  • Ideally to be done when design is firm, before construction & start up.
  • Technically can be extended to existing plants to improve operating methods

WHO SHOULD CARRY OUT HAZOP?

  • Normally to be done by multi-disciplinary teams.

Two types of teams,

  1. a) Technical contribution
  2. b) Supporting & structuring role
  • Should not be too large, ideally 3 to 5 members.

WHO SHOULD CARRY OUT HAZOP?

(a)Technical team

– Chemical,Mechanical,Instrument,Electrical.

– Detailed knowledge of process, plant, equipment.

– Technique of guide words generate questions,    that need to be answered without resource to further expertise.

  1. (b) Supporting team,

– Some one to control discussion, called ‘Study leader’.

– Guides systematic questioning.

– Should not be closely associated with the subject, danger of developing blind spots.

HOW TO CARRY OUT HAZOP?

Main steps are,

  • Define the purpose, objectives, scope of study.
  • Select the team.
  • Prepare for the study.
  • Carry out the team review.
  • Record the results.

Step 1- Define the purpose, objectives, scope:-

  • The purpose, objective, scope should be explaned.
  • Focus on underlying purpose or reasons.
  • Examples of reasons,

– Check the safety of a design.

– Check operating/safety procedures.

– Improve safety of existing facility.

– Verify that instrumentation is adequate.

  • Define specific consequence to be considered e.g.

– Loss of equipment/production.

– Liability.

– Public safety/Environmental impact.

  • If last one considered, study should focus on

deviations which result in off site hazards.

Step 2- Select the team

  • Ideally five persons, one each from one discipline.
  • Too large – group approach fails.
  • Too small – may lack breadth of knowledge.
  • Members to have knowledge of process, equip.

Step 3- Prepare for the study

Three steps:

–  Drawings (line diagrams, flow sheets, layouts).

–  Operating instructions,logic dia, instr.controls.

–  Plant manuals ,equip manuals, history cards.

– Divide the process into sections with activities.

– Start at beginning & progressively downstream.

– Establish study nodes(points where temp/press

have identified design intent).

-Apply guide words at specific study nodes.

-Estimate the team hours (Roughly a vessel with

two inlets & two exits,a vent should take 1.5 hrs



or three hrs for each major piece of equip.

-Each session should not last for more than 3 hrs at a stretch.

Step 4- Cont… Important Terminologies

Study nodes :Location at which process paramete is investigated.

Intention       :Defines how plant is expected to operate in absence of deviations.

Guide word  :Simple word to qualify intention to guide,stimulate brainstorming

Deviation      :Departure from intention discovered by systematic applying guidewords

Cause             :Reason why deviation might occur

Consequence :Result of deviation should it occur

Step 4- Cont… GUIDE WORD APPLICATION

Each guide word is applied to the process variable

Guide words       Parameter      Deviation

No                      & Flow                No flow

More               & Pressure           High Pressure

As Well As      & One phase       Two phase

Other Than     & Operation      Maintenance

Step 4- Continued….

  • Deviations with cause, consequence are recorded.
  • Two extreme situations,

-A suggested action found for each hazard before

-No search for action until all hazards detected

  • If solution is straightforward, decision is easy
  • The study may expose gaps of information or knowledge of technical team members.
  • Thus it may be necessary to call for specialist.
  • Once the section has been examined mark copies.

Step 5- Record results

  • Some of the causes may be unrealistic, so derived Consequence will be rejected as not meaningful
  • Some of the causes may be trivial hence considered no further.
  • Some deviation with both causes that are conceivable & consequences that are potentially hazardous are noted for action.
  • The team will make recommendations.
  • Some of them require significant changes.
  • Clarity needed for responsibility in actions.
  • Follow up & ‘Progress chasing’ procedure needed’

Saurabh Ranjan is Founder of rlshumancare.com. I have dedicated & committed to publishing some innovative content and useful topics regarding Health, Safety & Environment, which will help and awareness to people for daily life. Also trying to continually improve my content for better awareness and suit to dedicated people.

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