HAZARD & OPERABILITY STUDIES (1 of 2)

Mike Lihou - Lihou Technical & Software Services

 

INTRODUCTION

The technique of Hazard and Operability Studies, or in more common terms HAZOPS, has been used and developed over approximately four decades for 'identifying potential hazards and operability problems' caused by 'deviations from the design intent' of both new and existing process plants.  Before progressing further, it might be as well to clarify some aspects of these statements.

 

Potential Hazard AND Operability Problems

You will note the capitalised 'AND' in the heading above.  Because of the high profile of production plant accidents, emphasis is too often placed upon the identification of hazards to the neglect of potential operability problems.  Yet it is in the latter area that benefits of a Hazop Study are usually the greatest.  To quote an example, a study was commissioned for a new plant.  Some two years previously, and for the first time, a similar study had been carried out on different plant at the same site which was then in the process of being designed.  Before the latest review commenced, the Production Manager expressed the hope that the same benefits would accrue as before, stating that "in his twenty years of experience, never had a new plant been commissioned with so few problems, and no other plant had ever achieved its production targets and break-even position in so short a time".

Deviation from design intent

To deal firstly with 'design intent', all industrial plant is designed with an overall purpose in mind.  It may be to produce a certain tonnage per year of a particular chemical, to manufacture a specified number of cars, to process and dispose of a certain volume of effluent per annum, etc.  That could be said to be the main design intent of the plant, but in the vast majority of cases it would also be understood that an important subsidiary intent would be to conduct the operation in the safest and most efficient manner possible.

With this in mind equipment is designed and constructed which, when it is all assembled and working together, will achieve the desired goals.  However, in order to do so, each item of equipment, each pump and length of pipework, will need to consistently function in a particular manner.  It is this manner which could be classified as the 'design intent' for that particular item.  To illustrate, imagine that as part of the overall production requirement we needed a cooling water facility.  For this we would almost certainly have

cooling water circuit pipework in which would be installed a pump as very roughly illustrated below.

A much simplified statement as to the design intent of this small section of the plant would be "to continuously circulate cooling water at an initial temperature of xºC and at a rate of xxx litres per hour".  It is usually at this low level of design intent that a Hazop Study is directed.  The use of the word 'deviation' now becomes more easy to understand.  A deviation or departure from the design intent in the case of our cooling facility would be a cessation of circulation, or the water being at too high an initial temperature.  Note the difference between a deviation and its cause. In the case above, failure of the pump would be a cause, not a deviation.

 

Industries in which the technique is employed

Hazops were initially 'invented' by ICI in the United Kingdom, but the technique only started to be more widely used within the chemical process industry after the Flixborough disaster in 1974.  This chemical plant explosion killed twenty eight people and injured scores of others, many of those being members of the public living nearby.  Through the general exchange of ideas and personnel, the system was then adopted by the petroleum industry, which has a similar potential for major disasters.  This was then followed by the food and water industries, where the hazard potential is as great, but of a different nature, the concerns being more to do with contamination rather than explosions or chemical releases.

 

The reasons for such widespread use of Hazops

Safety and reliability in the design of plant initially relies upon the application of various codes of practise, or design codes and standards.  These represent the accumulation of knowledge and experience of both individual experts and the industry as a whole.  Such application is usually backed up by the experience of the engineers involved, who might well have been previously concerned with the design, commissioning or operation of similar plant.

However, it is considered that although codes of practise are extremely valuable, it is important to supplement them with an imaginative anticipation of deviations which might occur because of, for example, equipment malfunction or operator error.  In addition, most companies will admit to the fact that for a new plant, design personnel are under pressure to keep the project on schedule.  This pressure always results in errors and oversights.  The Hazop Study is an opportunity to correct these before such changes become too expensive, or 'impossible' to accomplish.

Although no statistics are available to verify the claim, it is believed that the Hazop methodology is perhaps the most widely used aid to loss prevention.  The reason for this can most probably be summarised as follows:

It is easy to learn. It can be easily adapted to almost all the operations that are carried out within

process industries. No special level of academic qualification is required.  One does not need to be a

university graduate to participate in a study.

 

THE BASIC CONCEPT

Essentially the Hazops procedure involves taking a full description of a process and systematically questioning every part of it to establish how deviations from the design intent can arise.  Once identified, an assessment is made as to whether such deviations and their consequences can have a negative effect upon the safe and efficient operation of the plant.  If considered necessary, action is then taken to remedy the situation.

This critical analysis is applied in a structured way by the Hazop team, and it relies upon them releasing their imagination in an effort to discover credible causes of deviations.  In practice, many of the causes will be fairly obvious, such as pump failure causing a loss of circulation in the cooling water facility mentioned above.  However, the great advantage of the technique is that it encourages the team to consider other less obvious ways in which a deviation may occur, however unlikely they may seem at first consideration.  In this way the study becomes much more than a mechanistic check-list type of review.  The result is that there is a good chance that potential failures and problems will be identified which had not previously been experienced in the type of plant being studied.

 

Keywords

An essential feature in this process of questioning and systematic analysis is the use of keywords to focus the attention of the team upon deviations and their possible causes. These keywords are divided into two sub-sets:

Primary Keywords which focus attention upon a particular aspect of the design intent or an associated process condition or parameter.

Secondary Keywords which, when combined with a primary keyword, suggest possible deviations.

The entire technique of Hazops revolves around the effective use of these keywords, so their meaning and use must be clearly understood by the team.  Examples of often used keywords are listed below.

Primary Keywords

These reflect both the process design intent and operational aspects of the plant being studied.  Typical process oriented words might be as follows.  The list below is purely illustrative, as the words employed in a review will depend upon the plant being studied.

  Flow Temperature

  Pressure Level

 Separate (settle, filter, centrifuge)

Composition

  React Mix

  Reduce (grind, crush, etc.) Absorb

  Corrode Erode

Note that some words may be included which appear at first glance to be completely unrelated to any reasonable interpretation of the design intent of a process.  For example, one may question the use of the word Corrode, on the assumption that no one would intend that corrosion should occur.  Bear in mind, however, that most plant is designed with a certain life span in mind, and implicit in the design intent is that corrosion should not occur, or if it is expected, it should not exceed a certain rate.  An increased corrosion rate in such circumstances would be a deviation from the design intent.

Remembering that the technique is called Hazard & Operability Studies, added to the above might be relevant operational words such as:

  Isolate Drain

  Vent Purge

  Inspect Maintain

  Start-up Shutdown

This latter type of Primary Keyword is sometimes either overlooked or given secondary importance.  This can result in the plant operator having, for example, to devise

impromptu and sometimes hazardous means of taking a non-essential item of equipment off-line for running repairs because no secure means of isolation has been provided.  Alternatively, it may be discovered that it is necessary to shut down the entire plant just to re-calibrate or replace a pressure gauge.  Or perhaps during commissioning it is found that the plant cannot be brought on-stream because no provision for safe manual override of the safety system trips has been provided.

Secondary Keywords

As mentioned above, when applied in conjunction with a Primary Keyword, these suggest potential deviations or problems. They tend to be a standard set as listed below:

  Word Meaning

  No The design intent does not occur (e.g. Flow/No), or the operational aspect is not achievable (Isolate/No)

  Less A quantitative decrease in the design intent occurs (e.g. Pressure/Less)

  More A quantitative increase in the design intent occurs (e.g. Temperature/More)

  Reverse The opposite of the design intent occurs (e.g. Flow/Reverse)

  Also The design intent is completely fulfilled, but in addition some other related activity occurs (e.g. Flow/Also indicating contamination in a product stream, or Level/Also meaning material in a tank or vessel which should not be there)

  Other The activity occurs, but not in the way intended (e.g. Flow/Other could indicate a leak or product flowing where it should not, or Composition/Other might suggest unexpected proportions in a feedstock)

  Fluctuation The design intention is achieved only part of the time (e.g. an air-lock in a pipeline might result in Flow/Fluctuation)

  Early Usually used when studying sequential operations, this would indicate that a step is started at the wrong time or done out of sequence

  Late As for Early

It should be noted that not all combinations of Primary/Secondary words are appropriate.  For example, Temperature/No (absolute zero or -273ºC !) or Pressure/Reverse could be considered as meaningless.

 

HAZOP STUDY METHODOLOGY

In simple terms, the Hazop study process involves applying in a systematic way all relevant keyword combinations to the plant in question in an effort to uncover potential problems.  The results are recorded in columnar format under the following headings:

DEVIATION CAUSE CONSEQUENCE SAFEGUARDS ACTION

         

In considering the information to be recorded in each of these columns, it may be helpful to take as an example the simple schematic below.  Note that this is purely representational, and not intended to illustrate an actual system.

Deviation The keyword combination being applied (e.g. Flow/No).

CausePotential causes which would result in the deviation occurring. (e.g. "Strainer S1 blockage due to impurities in Dosing Tank T1" might be a cause of Flow/No).

ConsequenceThe consequences which would arise, both from the effect of the deviation (e.g. "Loss of dosing results in incomplete separation in V1") and, if appropriate, from the cause itself (e.g. "Cavitation in Pump P1, with possible damage if prolonged").

Always be explicit in recording the consequences.  Do not assume that the reader at some later date will be fully aware of the significance of a statement such as "No dosing chemical to Mixer". It is much better to add the explanation as set out above.

When assessing the consequences, one should not take any credit for protective systems or instruments which are already included in the design.  For example, suppose the team

had identified a cause of Flow/No (in a system which has nothing to do with the one illustrated above) as being spurious closure of an actuated valve.  It is noticed that there is valve position indication within the Central Control Room, with a software alarm on spurious closure.  They may be tempted to curtail consideration of the problem immediately, recording something to the effect of "Minimal consequences, alarm would allow operator to take immediate remedial action".  However, had they investigated further they might have found that the result of that spurious valve closure would be over pressure of an upstream system, leading to a loss of containment and risk of fire if the cause is not rectified within three minutes.  It only then becomes apparent how inadequate is the protection afforded by this software alarm.

SafeguardsAny existing protective devices which either prevent the cause or safeguard against the adverse consequences would be recorded in this column.  For example, you may consider recording "Local pressure gauge in discharge from pump might indicate problem was arising".  Note that safeguards need not be restricted to hardware… where appropriate, credit can be taken for procedural aspects such as regular plant inspections (if you are sure that they will actually be carried out!).

ActionWhere a credible cause results in a negative consequence, it must be decided whether some action should be taken.  It is at this stage that consequences and associated safeguards are considered.  If it is deemed that the protective measures are adequate, then no action need be taken, and words to that effect are recorded in the Action column.

Actions fall into two groups:

1. Actions that remove the cause. 2. Actions that mitigate or eliminate the consequences.

Whereas the former is to be preferred, it is not always possible, especially when dealing with equipment malfunction.  However, always investigate removing the cause first, and only where necessary mitigate the consequences.  For example, to return to the "Strainer S1 blockage due to impurities etc." entry referred to above, we might approach the problem in a number of ways:

Ensure that impurities cannot get into T1 by fitting a strainer in the road tanker offloading line.

Consider carefully whether a strainer is required in the suction to the pump.  Will particulate matter pass through the pump without causing any damage, and is it necessary to ensure that no such matter gets into V1.  If we can dispense with the strainer altogether, we have removed the cause of the problem.

Fit a differential pressure gauge across the strainer, with perhaps a high dP alarm to give clear indication that a total blockage is imminent.

Fit a duplex strainer, with a regular schedule of changeover and cleaning of the standby unit.

Three notes of caution need to be borne in mind when formulating actions.  Do not automatically opt for an engineered solution, adding additional instrumentation, alarms, trips, etc.  Due regard must be taken of the reliability of such devices, and their potential for spurious operation causing unnecessary plant down-time.  In addition, the increased operational cost in terms of maintenance, regular calibration, etc. should also be considered (the lifetime cost of a simple instrument will be at least twice its purchase price… for more complex instrumentation this figure will be significantly greater).  It is not unknown for an over-engineered solution to be less reliable than the original design because of inadequate testing and maintenance.

Finally, always take into account the level of training and experience of the personnel who will be operating the plant.  Actions which call for elaborate and sophisticated protective systems are wasted, as well as being inherently dangerous, if operators do not, and never will, understand how they function.  It is not unknown for such devices to be disabled, either deliberately or in error, because no one knows how to maintain or calibrate them.

 

Considering all Keywords - The Hazop procedure

Having gone through the operations involved in recording a single deviation, these can now be put into the context of the actual study meeting procedure.  From the flow diagram below it can be seen that it is very much an iterative process, applying in a structured and systematic way the relevant keyword combinations in order to identify potential problems.

 

FULL RECORDING versus RECORDING BY EXCEPTION

In the early days of Hazop Studies, it was usual to record only the potential deviations which carried with them some negative consequence.  This might well have been because such studies were only for internal use within a company.  Also, with manually handwritten records, it certainly reduced the time taken, both in the study itself and the subsequent production of the Hazop Report.  Such methodology is classed as "Recording by exception", where it is assumed that anything not included is deemed to be satisfactory.

Latterly, it has become more the accepted practice to set down everything, stating clearly each keyword combination applied to the system.  Where applicable, this would be followed by a statement indicating either that no Cause could be identified, or alternatively that no Consequence arose from the Cause recorded.  This is classified as "Full recording", and it results in a Hazop Report which demonstrates unambiguously to outside parties that a rigorous study has been undertaken.  In addition, it produces a comprehensive document which will greatly assist in the speedy assessment of the safety and operability of later plant modifications (do they impinge upon a potential deviation which was originally recognised as being credible, but which involved at that time no negative consequences ?).

Bearing the above in mind, it is recommended that "Full recording" is instituted.  With the use of a computer, the previous concern regarding time, both in the study and the reporting, is all but eliminated.  To make this methodology easier to handle efficiently, text macros should be set up as follows:

1. No potential causes identified. 2. No significant negative consequences identified. 3. No action required - existing safeguards considered adequate.

These macros can be used in the appropriate circumstances to quickly set down the reason for not pursuing a keyword combination.

In addition to the above, the pseudo Secondary words 'All' and 'Remainder' are often used.  These are employed in the following circumstances:

For a particular Primary Keyword (e.g. Flow), some combinations have been identified as having credible Causes (e.g. Flow/No, Flow/Reverse).  Having explored all other relevant combinations (Flow/Less, Flow/More, Flow/Other, etc.), no other Causes could be identified.  The combination "Flow/Remainder" is therefore used, with the macro in (1) above.

Having explored all relevant combinations for a particular Primary word, no potential deviations could be identified.  The combination "Flow/All" is therefore used, with the macro in (1) above.

Use of these pseudo Secondary Keywords greatly improves the readability of the final report, as it eliminates countless repetitive entries, all with a similar format (i.e. Keyword combination with "No potential causes identified").  However, to make it a robust system, the introduction to the Hazop Report must list clearly the Secondary Keywords which were globally applied to each Primary Keyword; in other words, the 'relevant combinations'.  This will give an unambiguous meaning to the words 'All' and 'Remainder'.

Note that such an approach should only be adopted where no credible Cause is identified. In cases where the potential deviation is considered possible, but no significant consequence ensues, then both keywords should be recorded, together with the actual Cause identified, and macro (2) in the Consequence column.

 

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HAZARD & OPERABILITY STUDIES (2 of 2)

Mike Lihou - Lihou Technical & Software Services

 

THE HAZOP TEAM

The team who will conduct the Hazop study should consist of personnel with a good understanding of the process and plant to be reviewed.  The group should ideally contain about six members, with perhaps an absolute upper limit being set at nine.  In a study in which both contractor and client are participating, it is desirable to maintain a balance between the two in terms of team membership so that neither side feels outnumbered.

The participants should consist of people from a range of disciplines, and this aspect is one of the strengths of the Hazop methodology:

With a team of people, each with differing backgrounds and experience, potential problems are likely to be identified which would be missed by one or two people working on their own. 

It is often the case that one person's solution can become a problem to another department within the project.  For example, a Process Engineer conducting his own review in isolation may identify a potential problem for which he considers that another instrument and alarm would be desirable.  When this requirement is

passed to the Control & Instrumentation Engineer, it transpires that no suitable channels are available within the appropriate section of the electronic control system, which has already been ordered and is currently being manufactured by the vendor.  A protracted inter-departmental discussion and correspondence then ensues as to possible alternative remedies, and the potential cost penalty of re-specifying the control system.  All of this could have been settled within a few minutes had both departments participated in the study. 

A spirit of co-operation and common purpose is engendered which crosses departmental boundaries, and this will persist even after the Hazop Study has been completed.  Personnel will understand better the views, concerns and constraints within which other disciplines have to work, and will take these into account when making decisions affecting the project.

The actual composition of the Hazop team will vary according to the type of plant being reviewed.  One person who should always be included is a representative from Operations.  He or she should have first hand experience of day-to-day operations on either the plant being reviewed, or one that is very similar in nature.  The contribution of this team member to the discussion can be invaluable, as it introduces an operational perspective to other participants who may have never, for example, had to climb down into a vessel wearing breathing apparatus to carry out repairs or an inspection.

To summarise, a team should be selected so that a balanced approach to the study is ensured.  In addition, the intention should be that questions raised during the meeting can be answered immediately, rather than having to resort to the time consuming process of referring to outside expertise.  It is not of course necessary for the same people to participate in the study from beginning to end.  If the "core" of the group consisted of five people, for example, additional members could be called in from session to session as and when their particular expertise was needed.

As with all group activities, there needs to be a person appointed who will be in overall charge; with Hazop Studies this person is usually called the Chairman or Study Leader.  Ideally, he should not have been too closely associated with the project under review as there might be a risk of him not being sufficiently objective in his direction of the team.  As the Chairman's role is of vital importance in the smooth and efficient progress of the study, he should be carefully chosen and be fully conversant with the Hazop methodology.

Another important member of the team will be the Secretary.  His contribution to the discussion may well be minimal, as his main function during the sessions will be to record the study as it proceeds.  He will therefore need to have sufficient technical knowledge to be able to understand what is being discussed.

 

PREPARATORY WORK

It is most important that, before a study commences, work that can be conveniently done beforehand is carried out.  This is not only essential in some respects for the proper structuring of the study and the team, but will also greatly increase the efficiency of the Hazop and thus retain the interest and enthusiasm of the participants.

This preparatory work will be the responsibility of the Chairman, and the requirements can be summarised as follows:

1. Assemble the data 2. Understand the subject 3. Subdivide the plant and plan the sequence 4. Mark-up the drawings 5. Devise a list of appropriate Keywords 6. Prepare Node Headings and an Agenda 7. Prepare a timetable 8. Select the team

 

Assemble the data

All relevant documentation should be collected beforehand.  Typically this might consist of:

1. A Process Flow Diagram. 2. A comprehensive Process Description containing operating parameters, flow

rates, volumes, etc., as well as a brief summary of how each plant item functions. 3. P&IDs. 4. Cause & Effect Charts setting out how control and trip systems operate. 5. Details of vendor packages if available. 6. Plant layout diagrams.

 

Understand the subject

The Chairman should take as much time as is necessary to gain a good understanding of how the plant is meant to operate, by studying the assembled data and if necessary talking to the design personnel involved.  As he performs this task, it is very likely that he will notice potential problem areas.  Private notes should be made of these, as they might possibly be missed during the course of the study.  In such an event, it can only serve to enhance the Chairman's standing if he demonstrates his grasp of the subject by pointing out potential problems that the team have overlooked.

This stage of preparation is perhaps the most important, because it is the foundation upon which the other steps in the preparation process will be built.  Without a reasonable

understanding of how the plant functions, it will be impossible to plan a sensible study strategy, decide how long the review is likely to take, or who needs to be included in the study team.

Some proponents of the Hazop methodology state that there is no need for the Chairman to have any knowledge of the plant being reviewed, his function being only to ensure that the meeting progresses smoothly.  An analogy to this approach would be a leader attempting to guide an expedition without a map, no plan of action other than to get to the destination, and with no knowledge of the terrain to be traversed.  Such a leader would command very little respect from other members of the team, and at the first sign of trouble he would likely be sidelined and marginalised by those with a better understanding of the situation.  Once that has happened it will be almost impossible for him to regain control of the group.

 

Subdivide the plant and plan the sequence

In all but the simplest of plants, it is too much to expect any study team to deal with all aspects and operations in the process simultaneously.  Therefore, it must be split into manageable sections (commonly referred to as Nodes, but sometimes called Tables because of the tabular means of recording the study).  Also, the sequence in which these sections are studied is important.

With continuous plant, one usually progresses from upstream to downstream, with services such as drains, vent headers, instrument air, cooling water, etc. being considered separately and last.  With regard to splitting the plant into sections, there is no need to consider each line and every single minor item of equipment under a separate Node.  This will be wasteful of time, and boring and tedious for the team.

Instead, endeavour to group smaller items into logical units.  Therefore, a minor pump with its suction, discharge and kick-back lines might be grouped together in a Node.  However, with a major compressor, the recycle line and its in-line cooler should perhaps be studied separately.  Also, when studying a vessel the Node should encompass those inlet/outlet lines up to and including any control/isolation valve/s, all level bridles, as well as vent lines up to the PSV.

If a number of streams converge on a vessel, the study sequence should if at all possible deal with all of those streams before the vessel is considered.  The rule is "never study a vessel until the incoming deviations are known".

With batch operations, an entirely different approach is needed.  In such a case the plant drawings are an accessory rather than the prime focus of the study.  Of greater importance instead will be a detailed flowchart or operational sequence of steps to be accomplished.  It is these batch sequences which will need to be split into manageable sections, and keywords may well target sequential operations such as Prepare, Charge,

React, Transfer, Centrifuge, Dry etc.  This methodology is required because an individual plant item is very likely to be put into differing states and serve different purposes at various stages of the sequence.

 

Mark the drawings

When the study strategy has been decided, the plant items encompassed by each Node should be marked in distinctive and separate colours, with the Node Numbers alongside in the same colour.  Lines should be paralleled, and equipment and vessels outlined in the chosen colour.  Where a Node spans two or more drawings, the colour used should remain constant.

This prior marking is a departure from the more usual practise of doing such work whilst the study progresses.  However, it serves two purposes.  Firstly, it will save time during the meeting, both in the actual marking and the discussion as to where a Node should begin and end.  Secondly, the Chairman will be assured that in planning the study strategy nothing has been inadvertently missed.

 

Devise a list of appropriate Keywords

Having completed the work above, it will be a simple matter to formulate a comprehensive list of the Keywords required to cover all aspects of the process to be studied.

Some companies, because most of the plant that they operate is of a similar nature, will have a standard set of Keywords.  Such a list should be checked to ensure that it is covers all aspects of the system to be studied.  Any redundant Keywords should be removed.  For example, if the subject of the review is to be a pumping station, the inclusion of a keyword such as 'Absorb' is unnecessary.

The finalised list should be duplicated and a copy given to every team member.  Also included should be a schedule of appropriate keyword combinations (i.e. which Secondary keywords will be applied with each Primary keyword).  Where there are likely to be semantic problems as to what meaning/s a particular combination is intended to convey, then a full explanation should be given.

When devising the list, bear in mind that the smaller the number of words utilised, the more speedy the study.  That is not to say that aspects of the process should be discounted.  Instead, to illustrate what is meant, imagine a plant containing a separation vessel, some pump suction filters, and an environmental scrubber.  Rather than have three keywords 'Separate', 'Filter', 'Absorb', have instead one keyword 'Separate'... that, after

all, is the basic function of all those equipment items.  Similarly, 'Temperature' can cover heat transfer aspects of Heaters, Coolers, and Heat Exchangers.

 

Prepare Node Headings and Agenda

Node Headings reference the relevant drawings, and contain a brief description of the design intent of the relevant plant section, with process parameters, flow rates, and any other potentially informative details.

The agenda is a list of those headings.  A copy should be handed to each team member.  In addition to being informative and an aid to full participation, it will serve to put into perspective the amount of work to be accomplished in the time allotted.  Hopefully this will induce an appropriate sense of urgency.

 

Prepare a timetable

For all but a one day study, the Chairman should devise a timetable showing what needs to be accomplished at each study meeting if the schedule is to be maintained.  In devising this schedule he will need to call upon his experience when assessing how much time the review will take.  A great deal will depend upon the complexity of the plant as well as the experience of the team.

As a rough guide, with straightforward plant and with P&IDs which are not too 'cluttered', on average three drawings can be studied in a day.  If the system to be reviewed is complex, or if each P&ID seems to have been drawn with the intention of not wasting any space (i.e. as many plant items as would fit are included on the drawing), then almost certainly only two or perhaps even one drawing will be completed in a day.

Be prepared for time slippage at the start of the study.  Progress is always slow to begin with, whilst the team are acclimatising themselves to this novel role of casting critical eyes over their own or their colleague's design efforts.  After the first day everything will speed up, and the schedule should be on target by the end of the week.  Do not, however, allow the timetable to reflect this expectation of a slow start... better for the team to realise that they must increase their efforts, rather than go home thinking that this first slow day is the norm.

 

Select the team

Having gained a good appreciation of what will be involved in the study, both in terms of content and timetable, the Chairman can ensure that the core team members have suitable

expertise and will be available for the duration of the review.  In addition, he can also ascertain which personnel with additional expertise are likely to be needed during the course of the meetings, and when their assistance will be required.  With regard to the latter aspect, in certain circumstances the study sequence may need to be tailored around the availability of such personnel.

 

RUNNING A HAZOP STUDY

After all the above preparation, the Chairman should be in a position to easily guide an efficient and comprehensive study through to a successful conclusion.  However, there are a few guidelines to remember:

It is always a temptation for team members to illustrate their ideas by quickly drawing on the master P&ID which has been so painstakingly marked up.  Establish the rule right at the beginning that this is forbidden, even in pencil. 

Similarly, with tie-ins and vendor packages, a team member may endeavour to help by roughly illustrating the upstream/downstream plant or the internal workings of the package.  Be firm in the rejection of such help... it is dangerous to pretend to have studied something when all that is available is a few scribblings on a sheet of paper. 

If the schedule is slipping, resist the temptation to hasten the process by listing potential causes/consequences yourself.  All that results is that the team sits back and listens to you dictating to the Secretary, and they will continue to do so until you force them to participate again. 

Do not allow a separate meeting to develop, with two team members conversing in low voices at the corner of the table.  If this happens, stop the general discussion and ask them to share with the rest of the team the benefit of their deliberations (always assume that they are discussing something directly relevant to the study, although the likelihood is otherwise).  This will usually elicit an apology and bring them back to full participation. If they persist, request that the rest of the team members be completely silent whilst the private discussion continues.  If even this does not produce the required result, call a coffee break.  Then speaking privately to the persons concerned, politely but firmly insist that they leave the meeting.  Such members usually have nothing to contribute to the study, and they will only irritate and demotivate the remainder of the team. 

Ensure that all team members participate, even those who might well feel unsure of themselves.  Do this by asking questions such as "Do you agree with that solution, Bob?", or "What severity would you attach to this consequence, Fred?". 

Alternatively, and less potentially contentious, you could request "John, could you help the Secretary by summarising in a few words the agreed action".  Once such team members realise that they are not going to be contradicted as soon as they open their mouths, they participate to the best of their ability. 

Recognise and reward with praise the team member/s who contribute to the discussion wholeheartedly and sensibly.  However, do not allow them to overshadow the rest of the team. 

If discussion wanders away from the matter under consideration, re-focus the attention of the team either by requesting that the Secretary read out what he has recorded, or by asking for an action to be formulated.  The latter usually concentrates the mind and encourages the team members to get to the heart of the problem. 

Where a particularly intractable problem arises, or consequences of a serious nature are uncovered, too often an inordinate amount of time is devoted to formulating potential remedies.  Solutions and counter solutions are proposed and discussed, there is much speculation as to costs and other related aspects, and generally no satisfactory conclusion is reached.  Before too much time is wasted, such situations should be dealt with by placing an action upon a specific person to investigate and report upon what alternatives are available, together with the advantages/disadvantages of each.  Any discussion, gathering of additional data, reliability calculations, etc. can thereby be accomplished outside of the Hazop meeting, allowing the team to progress steadily with the review. 

The Chairman should be independent and unbiased, and should not be perceived as constantly favouring one section of the team as opposed to another.  This is of particular importance when personnel from both client and contractor are participating.  If a difficult situation arises, where, for example, there is a heated dispute over whether an action should be undertaken, in some cases one of the parties to the dispute will request that the Chairman makes the final decision.  If, in the Chairman's estimation, the reasons on one side of the argument are so strong as to be indisputable, then he should say so.  On the other hand, should the situation be finely balanced, then the dispute can be defused by careful wording of an action. Take as an example the situation where the client wishes to have an additional High Level Alarm, but the contractor strongly disputes its necessity.  Consider the following actions: 

o "Fit a High Level Alarm".  In the view of the contractor, the Chairman has sided with the client.  He may, wrongly or otherwise, perceive this to be a biased decision. 

o The action "Justify the requirement for a High Level Alarm" is addressed to the client.  The Chairman favours the contractor's argument, but is not dismissing altogether the views of the client.  Both parties are likely to be content with this formula. 

o The action "Justify the absence of a High Level Alarm" is addressed to the contractor.  The Chairman favours the client's argument, but is not dismissing altogether the views of the contractor.  As before, neither party will have cause to feel aggrieved. By effectively postponing a final decision until a later review of Action Responses, it is often the case that the two sides will get together after passions have cooled to discuss the matter rationally.  Almost invariably the situation will then be amicably resolved.

 

THE REPORT

The Hazop Report is a key document pertaining to the safety of the plant.  The number of man-hours spent on the study is usually considerable.  It is crucial that the benefit of this expert study is easily accessible and comprehensible for future reference in case the need arises to alter the plant or its operating conditions.

The major part of such a report is of course the printed Minutes, in which is listed the team members, meeting dates, Keywords applied, and of course every detail of the study teams findings.  However, it is usual to include with this a general summary.  The contents of such a summary might typically be:

An outline of the terms of reference and scope of the study.  

A very brief description of the process which was studied. 

The procedures and protocol employed.  The Keyword combinations applied should be listed, together with the explanatory meanings given to the team at the start of the study.  Also the fact that Action Sheets have been produced and responses will be recorded should be explained.  A brief description of the Action File (described in the following section) should be included. 

General comments.  If, for example, the team were assured that high point vents and low point drains would be universally provided, mention that statement and its source.  If certain details of vendor packages were not available, explain and list the items which were not reviewed. 

Results.  This usually states the number of recommended actions.

Also included in the Hazop Report would be an Appendix containing:

Master copies of the drawings studied. 

Copies of technical data used. 

Cause and Effect charts (i.e. matrices showing the executive action of safety related instruments and trips). 

Any calculations produced. 

Relevant correspondence between departments, from contractor to vendor, or client to contractor.

Each of the above should be signed and dated by the Chairman.

 

THE ACTION FILE AND REVIEW MEETINGS

The Hazop Report is compiled as soon as possible after the end of the study, and once completed does not change.  On the other hand the Action File is only started at the end of the study, and its contents will continue to change perhaps for many months, until the very last action has been reviewed and accepted as having been satisfactorily discharged.

Essentially, this Action File is a binder.  Initially, at the end of the study, it will be empty.  As completed and signed Action Response Sheets are returned, they are housed in the binder.  Periodically, the returned responses will be input into the data file (either manually or electronically, according to the system being used).

By the time the first review meeting is convened there should be no outstanding (i.e. overdue) responses.  The Secretary would prepare a listing of all responses received, making a copy for each review team member.  During the review meeting responses will either be accepted and marked as having been discharged, or in a small number of cases further action would need to be taken.

At the end of the first review, where further action had been required, Action Sheets for these would be produced for distribution.  In due course these would be completed, signed and returned, and these further responses would be input into the data file and housed in the Action File as before.

The procedure for the second review meeting is the same as for the first, except that the number of responses would of course be much smaller.  If some of those responses were still not found to be satisfactory, then the process as outlined above would be carried out again.

It can be seen that the Action File represents a hard copy record of the state of completion of Hazop recommendations at any point in time.  When all action responses have been reviewed and accepted, it finally becomes a static record containing the complete history of the implementation of the Hazop Study's findings.

 

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