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Segmentation of Workflow for Secure Human Check

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Why do we fail in checking? How can we improve them?

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Segmentation of Workflow for Secure Human Check

  1. 1. Toru Nakata National Institute of Advanced Industrial Science and Technology (4th CCPS Global Summit on Process Safety, pp.37-38, September, 2017) Segmentation of Workflow for Secure Human Check 1
  2. 2. Why do we fail in checking? Common causes of the failures, which I have found so many times in industry scenes. 2
  3. 3. Common Defects on Check 3 1. Check about actions (not about results) 2. Triggering by completion of the previous operation 3. “Double check” as an identical repeat 4. “Closed question” (Yes/No questioning)
  4. 4. 1) Check about Actions 4  “Do A. Then, check whether you have done A.”  Almost meaningless!  Tautology. Very boring.  Able to neglect by answering “yes”  Not verified from different viewpoints nor independent information.  But, this is very popular among actual operations of the industry.
  5. 5. 2) Triggering by completion of the previous operation  "Do A. After that, check B.“  Vulnerable against omission If you forget to do A, the check will be forgotten too.  Actions and checks must be triggered independently. 5 Action A Check BTrigger
  6. 6. 3) “Double check” as an identical repeat 6  Can identical multiplexing make operation more reliable?  Success rate = (1-Pfail^N)?  “Yes” for mechanical equipment  “?” for human operators  Every operators may commit the same mistake. “Even worse”, if each operator rely on others do check correctly and do own check vague. Criticism among people is required.
  7. 7. 4) “Closed question” (Yes/No questioning)  Closed question is simple, but it can be used for easy quick checks with low risk.  We usually have prejudice answering “Yes” is OK, so closed question is less reliable.  We normally face many “yes” than “no” in workplace.  Better solution: to make the checker answer something varies each time: i.e. “when”, “how many”, “who”, etc. 7
  8. 8. How to improve check: Segmentation of Workflow and Interruption for check 8
  9. 9. Ope 1Aroused Ope 2 CheckOpe 3 Done Ope 1Aroused Ope 2 Check Done Time OpeAroused Check DoneTask1 Task 2 Task 3 Bad Design: Asynchronous, dependent-triggered  Two Defects  Who does check? : Same person may undertake both of operation and check. (Sectionalism)  Vulnerable against Omission. If operation is forgotten, check will be forgotten too. 9
  10. 10. Ope 1 Arou sed Ope 2 Ope 3 Done Ope 1 Arou sed Ope 2 Done Time Ope Arou sed DoneTask1 Task2 Task3 Good Design: Simultaneous, independent-triggered  Trans-sectional checking. Same timing allows swap of workers for checks.  Triggered by  Particular time or Particular phase10 Check Check
  11. 11. Case 1: Checkpoint at 4 PM  A company has a rule that stops all employees' operation at 4PM to make them concentrate on checking situation of their tasks.  Swap works among the workers. Check by different person.  If they find mistakes at 4PM, they can correct them before the end of working hours. 11
  12. 12. Case 2: Checkpoint of a Tray  In a food factory,  Novice operators put each material into the machine at different timing as soon as the material is ready.  Skillful operators place a tray in front of the intake of the machine, put each material on it,  and wait until all materials are prepared,  then they check aligned composition of the materials in stillness. 12
  13. 13. Case 3: Shepherding Tourists  A tour conductor guides the group of his customers, he usually appoints some meeting places before the final goal.  Appointing the final goal is weak against disturbances, since it is rather difficult to remember long way to the goal and to reach there without trouble.  Appointing near place as a rendezvous point is much easier and robust. 13
  14. 14. Conclusion 14
  15. 15. Points  Ordinary styles of check are often wrong. 1. Check on actions (not on results) 2. Triggering by completion of the previous operation 3. “Double check” as an identical repeat 4. Yes/No questioning (“Closed question”)  Segmentation / Interruption style can eliminate the defeats. 15

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