Hazard Hazard Operability Operability

(HazOp)(HazOp)

Hazard Hazard Operability Operability

(HazOp)(HazOp)

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• HAZOP is a highly structured hazards identification system.

• It is extremely basic in its approach• HAZOP can practically be adopted at any

stage. • HAZOP methodology is widely used in

many occupational areas. • With new designs, HAZOP can be carried

out as late as possible in order to be as complete as possible.

• It can also be used for analyzing operating instructions, procedures and in batch operations.

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HAZOP Methodology1. Collect applicable documents and drawings.2. Break facility into manageable sections (Nodes).3. Prepare list of Parameters and Operations to be

examined.4. For each Node create Deviations. 5. List and record causes for each Deviation.6. List and record Consequences for each Cause.7. List and record Safeguards or Controls that may

prevent either the Cause or the Consequence.8. List any future Actions or recommendations you

think should be implemented.

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Hazard and Operability (HazOp) Studies• A HazOp study identifies hazards and

operability problems. • The concept involves investigating how

the plant might deviate from the design. • If in the process of identifying problems

during a HazOp study, a solution becomes apparent, it is recorded as part of the HazOp result.

• HazOp is based on the principle that several experts with different backgrounds can interact and identify more problems when working together.

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Concept• The HazOp concept is to review the occupational place

in a series of meetings.• The multidisciplinary team methodically "brainstorms"

the plant design, following the structure provided by the guidewords and the team leader's experience.

• The primary advantage of this brainstorming is that it stimulates creativity and generates ideas.

• This creativity results from the interaction of the team and their diverse backgrounds.

• Consequently the process requires that all team members participate and team members must refrain from criticizing each other to the point that members hesitate to suggest ideas.

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• The team focuses on specific points of the design (called "study nodes"), one at a time.

• At each of these study nodes, deviations in the process parameters are examined using the guidewords.

• The guidewords are used to ensure that the design is explored in every conceivable way.

• Thus the team must identify a fairly large number of deviations, each of which must then be considered so that their potential causes and consequences can be identified.

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The success/failure of the HazOp depends on several factors: • The completeness and accuracy of drawings

and other data used as a basis for the study • The technical skills and insights of the team • The ability of the team to use the approach as

an aid to their imagination in visualizing deviations, causes, and consequences

• The ability of the team to concentrate on the more serious hazards, which are identified.

• The process is systematic and it is helpful to define the terms that are used

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STUDY NODES • The locations at which the process

parameters are investigated for deviations.

INTENTION • The intention defines how the plant is

expected to operate in the absence of deviations at the study nodes.

• This can take a number of forms and can either be descriptive or diagrammatic; e.g., flow sheets, line diagrams.

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DEVIATIONS • These are departures from the intention which

are discovered by systematically applying the guide words (e.g., "more weight").

CAUSES• These are the reasons why deviations might

occur. • Once a deviation has been shown to have a

credible cause, it can be treated as a meaningful deviation.

• These causes can be hardware failures, human errors, an unanticipated process state (e.g., change of composition), external disruptions (e.g., loss of power), etc.

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CONSEQUENCES• These are the results of the deviations should

they occur (e.g., release of toxic materials).

GUIDE WORDS• These are simple words which are used to

qualify or quantify the intention in order to guide and stimulate the brainstorming process and so discover deviations.

• The guide words are the ones most often used in a HazOp; some organizations have made this list specific to their operations, to guide the team more quickly to the areas where they have previously found problems.

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• Each guide word is applied to the process variables at the point in the plant (study node) which is being examined.

• There are other useful modifications to guide words such as:

• SOONER or LATER for when considering time

• WHERE ELSE for OTHER THAN when considering position, sources, or destination

• HIGHER and LOWER for MORE and LESS when considering elevations, temperatures, or pressures.

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Guidelines for Using Procedure1. Define the purpose, objectives, and

scope of the study 2. Select the team 3. Prepare for the study 4. Carry out the team review 5. Record the results.

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1. Define the Purpose, Objectives, and Scope of the Study.

• The purpose, objectives, and scope of the study should be made as explicit as possible.

• These objectives are normally set by the person responsible for the plant or project, assisted by the HazOp study leader.

• It is important that this interaction take place to provide the proper authority to the study and to ensure that the study is focused.

• Also, even though the general objective is to identify hazards and operability problems, the team should focus on the underlying purpose or reason for the study.

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Examples of reasons for a study might be to:

• Check the safety of a design • Decide when and where to build • Develop a list of questions • Check operating/safety procedures • Improve the safety of an existing

facility • Verify that safety instrumentation is

reacting to best parameters.

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It is also important to define what specific consequences are to be considered:

• Employee safety (in plant or neighboring places)

• Loss of plant or equipment • Loss of production (loose competitive

edge in market) • Liability • Insurability • Public safety • Environmental impacts.

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2. Select the Team.• Ideally, the team consists of five to seven

members, although a smaller team could be sufficient for a smaller plant.

• If the team is too large, the group approach fails.

• On the other hand, if the group is too small, it may lack the breadth of knowledge needed to assure completeness.

• The team leader should have experience in leading a HazOp.

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The rest of the team should be experts in areas relevant to the plant operation.

For example, a team might include:• Safety engineer • Design engineer • Process engineer • Operations supervisor • Instrument design engineer • Chemist • Maintenance supervisor

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• The team leader’s most important job is to keep the team focused on the key task: to identify problems and to solve them.

• There is a strong tendency for engineers to launch a design or problem-solving mode as soon as a new problem comes to light.

• Unless obvious solutions are apparent, this mode should be avoided or it will detract from the primary purpose of HazOp, which is hazard identification.

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• In addition, the team leader must keep several factors in mind to assure successful meetings:

1. Do not compete with the members; 2. Take care to listen to all of the

members 3. During meetings, do not permit

anyone to be put on the defensive; 4. To keep the energy level high, take

breaks as needed.

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3. Prepare for the Study• The amount of preparation depends upon

the size and complexity of the plant. • The preparative work consists of three

stages:

a) obtaining the necessary data; b) converting the data to a suitable form and c) planning the study sequence; and arranging

the meetings.

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a. Obtain the necessary data.• Typically, the data consist of various drawings in the form of line diagrams, flow sheets, plant layouts, and fabrication drawings.

• Additionally, there can be operating instructions, instrument sequence control charts, logic diagrams, and computer programs.

• Occasionally, there are plant manuals and equipment manufacturer’s manuals.

• The data must be inspected to make sure they pertain to the defined area of study and contain no discrepancies or ambiguities.

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b. Convert the data into a suitable form and plan the study sequence.

• The amount of work required in this stage depends on the type of plant.

• With continuous plants, the preparative work is minimal.

• The existing, up-to-date flow sheets or pipe and instrument drawings usually contain enough information for the study, and the only preparation necessary is to make sure that enough copies of each drawing are available.

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c. Arrange the necessary meetings.• Once the data have been assembled and the

equipment representations made (if necessary), the team leader is in a position to plan meetings.

• The first requirement is to estimate the team-hours needed for the study.

• As a general rule, each individual part to be studied, e.g., each main pipeline into a vessel, will take an average of fifteen minutes of team time.

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4. Carry Out the Team Review.• The HazOp study requires that the plant schematic be divided into study nodes and that the process at these points be addressed with the guide words.

• If there are obvious remedies, these too are recorded.

• As hazards are detected, the team leader should make sure that everyone understands them.

• The degree of problem-solving during the examination sessions can vary.

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5. Record the Results.• The recording process Is an important part of the HazOp.

• It is impossible to record manually all that is said, yet it is very important that all ideas are kept.

• It is very useful to have the team members review the final report and then come together for a report review meeting.

• The process of reviewing key findings will often fine-tune these findings and uncover others.

• The success of this process demands a good recording scheme.

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• First, a HazOp form should be filled out during the meeting.

• This form is best filled out by an engineer who can be less senior than the team members.

• This recorder is not necessarily part of the team but, as an engineer, can understand the discussions and record the findings accurately.

• Other means of recording can be developed as best suits the organization.

• It has also been found useful to tape-record the sessions and have them transcribed.

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Assignment1. What are the Industrial Accidents? Also state &

explain causes of industrial accidents.2. Explain industrial hazards, give types of industrial

hazards toxicity. Also enlist most toxic industrial hazards & explain any five of them in detail.

3. What are the common types of fires? Suggest important fire prevention methods which you think are effective.

4. Describe leading causes of industrial fires and state the consequences of industrial fires in detail.

5. What is safety auditing? Explain main elements undertaken in safety audits.