NGI-Cause Tree Analysis

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NGI-Cause Tree Analysis

  1. 1. oasis International Training Center Presents
  2. 2. CAUSE TREE ANALYSIS
  3. 3. INCIDENT MANAGEMENT WITH THE “CAUSE TREE ANALYSIS” METHOD
  4. 4. INCIDENTS RESULT FROM THE CONJUNCTION OF SEVERAL CAUSES METHODOLOGY OF THE « CAUSE TREE » ANALYSIS THE METHOD IS LOGICAL, CREATIVE AND BASED ON TEAMWORK THE METHOD IS FACT-FINDING, NOT FAULT-FINDING
  5. 5. 1. COLLECTION OF CONCRETE FACTS & PRECISE DESCRIPTION OF THE EVENT FILL IN THE SEVERITY MATRIX 2. BUILD-UP OF THE CAUSE TREE 3. LISTING & SELECTION OF THE PREVENTIVE ACTIONS 4. IMPLEMENTATION & FOLLOW-UP OF THE SELECTED ACTIONS FILL IN THE CAUSE MATRIX METHODOLOGY OF THE « CAUSE TREE » ANALYSIS
  6. 6. THE TREE IN THE THE FOREST METHODOLOGY OF THE « CAUSE TREE » ANALYSIS
  7. 7. 1. COLLECTING FACTS WHO ? <ul><li>TOTAL SITE SUPERVISOR / MANAGER </li></ul><ul><li>HE KNOWS PERFECTLY THE SITE, PEOPLE IN PLACE, INHERENT HAZARDS & RISKS, AND THE RUNNING ACTIVITIES </li></ul><ul><li>THIS IS HIS RESPONSIBILITY (CARE OF PEOPLE HEALTH & SAFETY) AND FALLS WITHIN HIS AUTHORITY & COMPETENCE (CONTROL OF THE SITUATION) CREATION OF AN AMBIANCE OF CONFIDENCE </li></ul><ul><li>HE SHOULD SEEK ASSISTANCE FROM THE CONTRACTOR’S SITE MANAGEMENT TO CARRY OUT THIS TASK </li></ul>
  8. 8. HOW ? <ul><li>LISTEN TO WITNESSES, ONE BY ONE Informations stem from independent sources The average resultant of opinions is avoided </li></ul><ul><li>COLLECT Facts only, without interpretation nor judgement of value (ex.n°2) In the chronological order Look for the « unusual » </li></ul><ul><li>WRITE UP A DETAILED REPORT Gathering all collected informations Reconstructing the undesirable event </li></ul><ul><li>BUILD UP A LISTING OF THE ELEMENTARY FACTS CONTAINED IN THIS REPORT Each fact retains one -and only one- information </li></ul>1. COLLECTING FACTS
  9. 9. WHEN ? <ul><li>AS SOON AS POSSIBLE !! </li></ul><ul><li>memory fades away quite quickly </li></ul><ul><li>witnesses usually build up a sequence of events from the only facts they remember (seeking after a « global » logic) </li></ul><ul><li>one remembers only wilful actions, not spontaneous ones nor reflexes </li></ul><ul><li>IT IS THUS NECESSARY TO QUICKLY RE-ISOLATE THE FACTS SO AS TO RECONSTRUCT THE INCIDENT </li></ul>1. COLLECTING FACTS
  10. 10. EXERCISE 1 Here is a situation which appears to be quite straightforward and which may be encountered at any time in business, family life or in the street. John Smith, a contractor, arrives at the building site in the Boston Street. In the yard a worker is calling out in Spanish, waving his hand around frenziedly and looking up in the air. Then he goes back into the room and plasters the wall. By the porch a young man with a beard is talking affectionately to someone with long hair and wearing blue jeans. <ul><li>Everything in this story is absolutely correct and cannot be doubted. </li></ul><ul><li>Now read the statements listed below and see whether each of them appears to you to be : </li></ul><ul><ul><li>true (T), </li></ul></ul><ul><ul><li>false (F), </li></ul></ul><ul><ul><li>arguable and uncertain (?). </li></ul></ul><ul><li>Ring the one which corresponds to your answer. </li></ul><ul><li>The objective of this exercise is to show that : </li></ul><ul><ul><li>our replies can be modified by the way we “embroider” the facts, </li></ul></ul><ul><ul><li>memory quickly changes, </li></ul></ul><ul><ul><li>we are not always able to distinguish between facts and interpretations. </li></ul></ul>EX. n°1 : COMPANY « SMITH »
  11. 11. EXERCISE 1 - RULES OF THE GAME - answer the questions in numerical order. - do neither go back and re-read propositions after replying, nor correct a previous answer. PROPOSITIONS REPLIES 1. Smith is a contractor 2. There are only four people on the building site in the Boston Street 3. The contractor is on the building site in the Boston Street 4. The contractor saw the worker cry out 5. One of Smith’s employees was plastering the wall 6. There was a Spanish worker in the yard 7. The worker who calls out in the yard is addressing a workmate on an upper floor 8. He is calling out to warn his workmates that the contractor had arrived 9. After calling out the workman starts plastering again the room wall 10. The workman who cried out in the yard does not then go back into the room 11. The plasterer is plastering the room wall 12. The bearded workman is having a short rest 13. The bearded man is talking affectionately to the woman in blue jeans 14. If the person with long hair and wearing blue jeans is a young man, could it be that the bearded man is in love with him ?  Has the picture which you had formed of the scene changed having answered these questions ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? YES NO
  12. 12. PROPOSITIONS REPLIES 1. Smith is a contractor 2. There are only four people on the building site in the Boston Street 3. The contractor is on the building site in the Boston Street 4. The contractor saw the worker cry out 5. One of Smith’s employees was plastering the wall 6. There was a Spanish worker in the yard 7. The worker who calls out in the yard is addressing a workmate on an upper floor 8. He is calling out to warn his workmates that the contractor had arrived 9. After calling out the workman starts plastering again the room wall 10. The workman who cried out in the yard does not then go back into the room 11. The plasterer is plastering the room wall 12. The bearded workman is having a short rest 13. The bearded man is talking affectionately to the woman in blue jeans 14. If the person with long hair and wearing blue jeans is a young man, could it be that the bearded man is in love with him ?  Has the picture which you had formed of the scene changed having answered these questions ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? T F ? YES NO SOLUTION TO EXERCISE 1
  13. 13. ref 239 A AMONG THE FOLLOWING HEADLINES, UNDERLINE THOSE WHICH, IN YOUR OPINION, TRANSLATE JUDGEMENTS OR INTERPRETATIONS RATHER THAN FACTS : 1. Non-use of the individual protection made available 2. Inadequacy of work organization 3. Lack of instructions on working methods 4. Dangerous omission 5. Physical failure 6. Proceeding without adequate precautions 7. Work instruction not observed 8. Acting without giving warning 9. Neglecting to use individual protection 10. Working in a not very safe position 11. Inadequate vocational training 12. Dangerous act 13. Neutralizing a safety device Only facts, no interpretation, no judgement ! EXERCISE 2
  14. 14. IN BOLD : WORDING NOT TO BE USED 1. Non-use of the individual protection made available 2. Inadequacy of work organization 3. Lack of instructions on working methods 4. Dangerous omission 5. Physical failure 6. Proceeding without adequate precautions 7. Work instruction not observed 8. Acting without giving warning 9. Neglecting to use individual protection 10. Working in a not very safe position 11. Inadequate vocational training 12. Dangerous act 13. Neutralizing a safety device 1, 7, 8 and 13 are facts (5 is under medic competence) 2, 3, 4, 6, 9, 10, 11 and 12 are judgements / interpretations SOLUTION TO EXERCISE 2
  15. 15. 2 BUILDING THE CAUSE TREE WHERE ? : For a given incident, several CTA can be done, provided that all causes are found and prevention targets identified. <ul><li>WHEN ? : 2 to 3 days after the event, as </li></ul><ul><li>soon as possible, in order to : </li></ul><ul><li>Implement immediate corrective actions </li></ul><ul><li>Avoid the changes of memories </li></ul><ul><li>Even in the case of a very simple story. </li></ul>METHODOLOGY When 2 causes are simultaneously necessary to produce an incident: look for what could have prevented these two to combine. A protection device, like a safety helmet, for instance. This absence of the safety barrier constitutes in itself a particular cause.
  16. 16. <ul><li>HOW ? : </li></ul><ul><li>From right to left </li></ul><ul><li>Using proper symbols </li></ul><ul><li>Note that, in conjunctions, all causes have not the same “weight”. Eliminating one cause will have an effect on the risk which may differ from another cause. </li></ul>METHODOLOGY WHO ? : The investigation Team with the the Site Manager 2 BUILDING THE CAUSE TREE
  17. 17. 2. BUILDING UP THE CAUSE TREE - METHODOLOGY HOW ? (2) : FOR EACH FACT, ASK THE FOLLOWING 3 QUESTIONS : A POSITIVE ANSWER TO THE 3rd QUESTION MEANS THAT ALL POSSIBLE ANTECEDENTS HAVE BEEN TAKEN INTO ACCOUNT It is strongly recommended to be creative at that stage, looking in particular for non-listed but plausible and widely admitted facts, e.g. the absence of any kind of safety barrier related to hardware or human awareness. « WHAT HAS BEEN REQUIRED ?… to get the incident » « WAS IT NECESSARY ?… to its occurrence » « WAS IT SUFFICIENT ?… aren’t there other antecedents ? »
  18. 18. HOW ? (3) : FOLLOW THE « CHAINING » METHODOLOGY : THESE SIMPLE FACTS, WHICH ARE THE SOUGHT-AFTER ELEMENTARY AND INDEPENDANT CAUSES, REPRESENTS THE PREVENTION TARGETS . <ul><li>Using the detailed report and related list of elementary facts, start from the ultimate undesirable event(s) </li></ul><ul><li>and seek for the logical and direct antecedents of each fact </li></ul><ul><li>going back, in the chronological order, to the single facts beyond which nothing can be done or for which there is no plausible nor known antecedent </li></ul>2. BUILDING UP THE CAUSE TREE - METHODOLOGY
  19. 19. 2. BUILDING THE CAUSE TREE - OPERATING STRATEGY ref 354 A HOW ? (4) : BUILD UP THE TREE COLUMN BY COLUMN, ANTECEDENT BY ANTECEDENT, TICK OFF FACTS FROM THE LIST AS SOON AS INTEGRATED INTO THE TREE, <ul><li>prevents from rushing straightforward to so-called obvious targets, and from missing a lot of things, </li></ul><ul><li>prevents from forgetting some facts, if for instance a fact leads to several other ones </li></ul>CHECK THE TREE FROM THE LEFT TO THE RIGHT. EXAMPLE OF LOGICAL CHAINING : ex.n°3 TRAINING FOR THE METHOD : ex.°4
  20. 20. DOCUMENT TYPES OF CONNECTIONS BETWEEN FACTS - SYMBOLIC SYSTEM B has a single cause A, which is necessary and sufficient for it to happen. 1. LINK <ul><li>An event has a number of causes : </li></ul><ul><li>either independent : A or B are necessary and sufficient for D to happen, </li></ul><ul><li>or necessary simultaneously A and B simultaneously are necessary for D to happen. </li></ul>2. CONJUNCTION 3. DISJUNCTION A number of events have the same cause : C is necessary and sufficient to produce A and (or) B. A B A B D C A B C A B D C
  21. 21. EXERCISE 3 (1/2) Exercise A 1. Receives phone call. 2. Does not turn the oven off. 3. Talkative caller. 4. Roast burned. A B C 3 1 2 4 2 4 3 1 4 1 2 3 Exercise B 1. Misses train. 2. Car breaks down. 3. Arrives late at station. 4. Forgets to fill up with petrol. A B C 4 2 3 1 1 2 3 4 1 2 3 4
  22. 22. EXERCISE 3 (2/2) Exercise C 1. Forgets to put on his safety helmet 2. Does not change footwear. 3. Arrives late. 4. Fog. A B C 1 2 3 4 2 4 3 1 4 3 1 2 Exercise D 1. Forflift truck driver absent. 2. Foreman drives truck. 3. Urgent loading job. 4. No replacement forklift truck driver. A B C 2 4 3 1 4 1 3 2 1 3 4 2
  23. 23. EXERCISE 3 - SOLUTION Exercise A 1. Receives phone call. 2. Does not turn the oven off. 3. Talkative caller. 4. Roast burned. A B C 3 1 2 4 2 4 3 1 4 1 2 3 Exercise B 1. Misses train. 2. Car breaks down. 3. Arrives late at station. 4. Forgets to fill up with petrol. A B C 4 2 3 1 1 2 3 4 1 2 3 4
  24. 24. EXERCISE 3 - SOLUTION Exercise C 1. Forgets to put on his safety helmet 2. Does not change footwear. 3. Arrives late. 4. Fog. A B C 1 2 3 4 2 4 3 1 4 3 1 2 Exercise D 1. Forklift truck driver absent. 2. Foreman drives truck. 3. Urgent loading job. 4. No replacement forklift truck driver. A B C 2 4 3 1 4 1 3 2 1 3 4 2
  25. 25. EXERCISE A 1 - Floor wet 2 - Falls 3 - Slips 4 - Injures himself EXERCISE C 1 - Deep trench, slides not shored 2 - Collapse 3 - Heavy rain 4 - Heavy vehicle passes close to the edge of the trench (just before the collapse) EXERCISE B 1 - Floor wet 2 - Véhicle breakdown 3 - Drivers slips 4 - Drivers walks EXERCISE D 1 - Another accident 2 - No warning of first accident 3 - Crowd gathers 4 - Traffic accident EXERCISE 4
  26. 26. EXERCISE A 1 - Floor wet 2 - Falls 3 - Slips 4 - Injures himself EXERCISE C 1 - Deep trench, slides not shored 2 - Collapse 3 - Heavy rain 4 - Heavy vehicle passes close to the edge of the trench (just before the collapse) EXERCISE B 1 - Floor wet 2 - Véhicle breakdown 3 - Drivers slips 4 - Drivers walks EXERCISE D 1 - Another accident 2 - No warning of first accident 3 - Crowd gathers 4 - Traffic accident 1 3 2 4 2 4 1 3 4 1 3 2 4 3 2 1 EXERCISE 4 - SOLUTION
  27. 27. CTA - OCIAR INTERFACE 1° INCIDENT REPORT 2° CTA SEVERITY MATRIX CAUSES MATRIX     REAL SEVERITY  LEVEL 3 OR POTENTIAL SEVERITY  LEVEL 4
  28. 28. 3 - LISTING & SELECTING PREVENTIVE ACTIONS WHO ? The investigation team, plus the concerned technical manager and someone who can « decide » on investments WHEN ? <ul><li>After completion of the CTA </li></ul><ul><li>Within 2 weeks time </li></ul><ul><li>No need for rush, let things get mature as long as immediate corrective actions aimed at preventing the re-occurrence of the incident have been implemented </li></ul>WHERE ? At the affiliate’s office
  29. 29. HOW ? USING THE BRAIN-STORMING TECHNICS <ul><li>Look for solutions to the identified prevention targets (at least one per target) </li></ul><ul><li>List all realistic & workable suggestions </li></ul><ul><li>Give free rein to imagination, avoid « sterilizing » & systematic criticism </li></ul><ul><li>Check, through the multicriterion decision matrix, if the proposed solutions : </li></ul><ul><li>Do no shift / transfer the problem elsewhere (imagine the possible negative consequences, hence the new resulting risk level). Appeal mainly to common sense and practical field experience </li></ul><ul><li>Comply with legal requirements </li></ul><ul><li>Are long lasting, i.e. are stable (if not it’s only “partial” prevention) </li></ul><ul><li>Are widely applicable (general in scope) </li></ul><ul><li>Are acceptable to operators (who should thus be part of the brain storming session to be motivated) </li></ul><ul><li>Estimate their potential efficiency (i.e.  large probability to eliminate the undesirable event) </li></ul><ul><li>Evaluate cost & deadlines </li></ul><ul><li>Additional site-specific criteria may be added </li></ul><ul><li>Eventually decide </li></ul>
  30. 30. MULTICRITERION DECISION TABLE (1/2) CRITERIA PROPOSED PRENVENTIVE ACTIONS 1a 1b 1c 2... Legal compliance Non-transfer of the risk Long-lasting (i.e. stable) measure Deadline (compatible with operations) Cost Widely applicable Potential efficiency Acceptable to operators OVERALL RANKING COMPULSORY DESIRABLE
  31. 31. USED RATING + O - COST DEADLINE EFFICIENCY OTHERS CHEAP SHORT EXCELLENT YES RELATIVELY EXPENSIVE RELATIVELY LONG AVERAGE DOUBTFUL TOO EXPENSIVE TOO LONG POOR NO MULTICRITERION DECISION TABLE (1/2)
  32. 32. ELIMINATION OF INCIDENTS CAUSES it’s freezing no sweater doesn’t know has forgotten CAUGHT A COLD MAKES A MISTAKE TO AVOID : ELIMINATE : A B A B C C « C » « C » & or « A » « B » or « A » « B » &
  33. 33. CREATES AN AMBIANCE OF CONFIDENCE THE FOLLOW-UP PHASE IS FUNDEMENTAL : There is usually a large gap between the number of decided actions and the number of actual achievements. « Many safety initiatives fail because they never succeed in turning enthusiastic commitment into actions. » The rigorous implementation of the CTA method should allow to not exclusively depend on the personnel’s enthusiasm, but to get convincing result thanks to a clever and efficient management of the incidents. HAVING A BETTER KNOWLEDGE AND ASSESSMENT OF THE RISKS TAKING ADEQUATE MITIGATING & PREVENTIVE MEASURES 4 - IMPLEMENTATION & FOLLOW-UP
  34. 34. IMPLEMENTATION AND FOLLOW UP MATRIX Prevention Target Contributing factor (cause matrix) Action selected Priority Approval from Management Implemented by Follow up by Target Date Closed Yes / No
  35. 35. EXERCISE 7 BUILD UP THE CAUSE TREE FOR THE FOLLOWING INCIDENT : FATAL CAR ACCIDENT On 23/3/94, at around 18h30, a fatal car accident occurred between RlO CULLEN and CANADON ALPHA (Argentina). In a road bend, the driver of the car - a NISSAN pick-up, apparently in good condition - lost control of the latter, meanwhile he was driving at a speed of about 80-100 km/h. The car overturned and rolled over several times. The driver has been ejected at about 5m away from the vehicle, and has been deeply injured. He died a few days later. The passenger has not been ejected, and suffered only light injuries. None of them had the safety belt fastened. The road was a stony track, narrow and dry. There was no wind nor rain, visibility was good. These two people were working for a local company, just contracted by TOTAL AUSTRAL for the construction of a guardroom at the Canadon Alpha plant entrance. The purpose of the trip to RlO CULLEN was to meet with TOTAL staff and to define the electrical hardware and set-up. TOTAL standard contractual terms clearly specifies as follows : The driving speed shall not exceed 60 km/h on non-asphalted roads, The use of the safety belt is compulsory. NB At the time of the accident, wearing of safety belts was not yet compulsory in Argentina.
  36. 36. Rescue means ? Driving skills ? Road bend Stony track Narrow track OR OR OR OR EXERCISE 7 - SOLUTION It is 18h30 Not informed Has forgotten Motivation ? Does not apply instructions No speed limitation device Urgent meeting Comfort speed ? High speed Tiredness ? Car condition ? Lost control of the car No roll over bar Car overturned Not informed Has forgotten Frame deformation Door opens Ejection force Safety instructions not enforced No control Meeting in R.Cullen Does not know instructions Ejected from the car Deep injuries Death Hits car equipment Passenger injured Has no safety belt OR OR Drives the car
  37. 37. EXERCISE 8 BEAM'S INCIDENT TOTALEX <ul><li>After completion of the drilling operations, heavy beams are stacked on the roof of a porta-cabin with a large crane (20 m boom) located at 15 m from the porta-cabin. The purpose is to transport these beams laying on top of the porta-cabin to the next drilling location. </li></ul><ul><li>The operation is supervised by the crane driver ‘X’, and the helper ‘Y’ stands on the roof of the porta-cabin to receive and position the beams. </li></ul><ul><li>The porta-cabin is 3 m wide and is located at 1.5 m out of the vertical of a 20 kV electrical line supplying power to the site. </li></ul><ul><li>During the lifting operation, the crane wire came too close to this line : an electrical arc was created and burnt ‘Y’, who consequently Iost his balance. He then fell down onto the ground and was injured. </li></ul><ul><li>NB (non-reported but plausible facts, which rnay help to build the cause tree): </li></ul><ul><li>‘ X’ and ‘Y’ probably knew that the electrical line was under tension, but didn’t take this fact into consideration. </li></ul><ul><li>‘ X’ (crane driver) cannot simultaneously watch the top of the boom (to check if it comes close to the electrical line) and the Iift itself when the latter comes close to the porta-cabin’s roof. </li></ul><ul><li>Hazardous areas where the crane should not be allowed to work in are not properly identified and marked. </li></ul><ul><li>‘ Y’ had no safety harness. </li></ul><ul><li>Apparently, this was the only usual way of transportation for these beams... </li></ul>1/3
  38. 38. 2/3 EXERCISE 8 CRANE PORTA-CABIN 20kV LINE RD 373 1,5 m 20kV LINE 1,5 m 10 m 3 m 15 m
  39. 39. 3/3 EXERCISE 8 BUILDING AND CIVIL ENGINEERING WORKS AND ALL OTHER WORKS CONCERNING BUILDINGS. Works near electrical lines, ducts or installations must comply with prescriptions of title 12 of decree 65-48 of 8 January 1965 MANOEUVRE NEAR BEAR LIVE PARTS 50 000 V or more : 5m less than 50 000 V : 3m
  40. 40. EXERCISE 8 - SOLUTION 7 Beams transported to next location End of drilling Heavy beams No other mean of transportation ? Has no protection Using wire slings 10 2 No other crane available ? Site power supply Not known No pre-job reminder No PTW reminder No visual warning 4 X drives the crane Unknown regulation OR OR No TOTAL safety supervision 2 8 9 9 5 6 Known but forgotten 20 kV not taken into account 11 Non-isolated line Line under tension Crane's wire too close Electrical arc Holds the beam Receives & positions the beams Loses his balance Is on the roof Falls down Y injured Y burnt Beams stacked on roof Impossible to watch Need a crane Porta-cabin below HT line Hazardous area not delimited Saf. instr. not complied with Crane gets closer to the line Crane high enough 20kV line @ 10m 3 1
  41. 41. EXERCISE 11 - PROPOSED PREVENTIVE ACTIONS
  42. 42. Thank you for your attention.

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