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ERT 322 SAFETY AND LOSS PREVENTION ACCIDENT INVESTIGATIONS

ERT 322 SAFETY AND LOSS PREVENTION ACCIDENT INVESTIGATIONS. Objective. To discuss the method to investigate the accidents in the plant To analyze & evaluate in a case studies. Introduction.

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ERT 322 SAFETY AND LOSS PREVENTION ACCIDENT INVESTIGATIONS

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  1. ERT 322SAFETY AND LOSS PREVENTION ACCIDENT INVESTIGATIONS

  2. Objective • To discuss the method to investigate the accidents in the plant • To analyze & evaluate in a case studies

  3. Introduction • The investigation of accidents and near misses provides opportunities to learn how to prevent similar events in the future. • Accident investigation includes detailed descriptions and recommendations of the events.

  4. Sub-topic • Learning from accidents • Layered investigations • The investigation process • Investigation Summary • Aids for diagnosis • Aids for recommendation

  5. Learning from accidents • Build an investigation team • Every member learns about problems that precipitate accidents • To avoid similar situations in the future • Learn how to prevent future accidents.

  6. Learning from accidents • Fundamental step in accident investigation: 1. Developing a detail description of the accident 2. Accumulating relevant facts 3. Analyzing the facts and developing potential causes of the accident 4. Studying the system & operating method relevant to the potential causes of the accident 5. Developing the most likely causes 6. Developing recommendations to eliminate recurrence of this type of accident 7. fact-finding not fault-finding.

  7. Layered Investigations • First layer: immediate technical recommendations, • Second layer: recommendations to avoid the hazards, • Third layer: recommendations to improve the management system.

  8. Example 12-1 Illustrate the layered investigation process to develop underlying causes of a municipal pool accident. A drowning accident occurred during an open swim period. Approximately 100 children, ranging between 5 and 16 years old, were in and around a pool (3 ft to 9 ft deep). An older child unknowingly pushed a 5-year-old into the deep water. The pool was relatively crowded, and the 5-year-old slipped under the water without being noticed by others, including the lifeguard.

  9. Solution The facts uncovered by an investigation team are 1. the pool did not have deep and shallow markings, 2. the older child was engaged in horseplay, 3. the younger child did not know how to swim, 4. the lifeguard had many blind fields of vision, 5. the pool was overly crowded, 6. the pool did not have an orientation program, and 7. the pool did not offer swimming lessons.

  10. First layer recommendations: Immediate technical recommendations 1. Paint pool depths at the pool edges. 2. Add more lifeguards. 3. Reduce the number of swimmers.

  11. Second layer recommendations: Avoiding the hazard 1. Prohibit horseplay. 2. Zone pool to keep smaller children at shallow end of pool. 3. Add swimming lessons for all age groups. 4. Give all new swimmers (especially young children) a pool orientation. 5. Add a roving lifeguard to monitor and control pool behavior.

  12. Third layer recommendations: Improving the management system 1. Train lifeguards to alert supervision of observed potential problems. 2. Assign the supervisor to make formal (documented) audits on a regular basis.

  13. Investigation Process • Steps • (1) Investigation team – choose team • (2) Brief survey – make overview survey to understand the type and information needed to derive causes of the accident. • (3) Set objectives and delegate responsibilities – based on (1) and (2) • Preincident facts • - gather & organize preincident facts. Use flowsheets, procedures, photograph

  14. Investigation Process • Steps • (5) Accident facts • - make detailed examinations with photos, inspections. • - record extent of damage, hypothesize the sequences of event, cause of accident • Research and analyses • – initiate research-type experiments & analyze facts • Discussion, conclusions and recommendations • - study (2) to (6) to develop conclusion & layered recommendations. • Report • - develop accident investigation report.

  15. Accident Investigation Report • format should be flexible and designed specifically to best explain the accident. • The format may include the following sections: (1) introduction, (2) process description (equipment and chemistry), (3) incident description, (4) investigation results, (5) discussion, (6) conclusions, (7) layered recommendations.

  16. Investigation Summary • Summarizes the events and recommendations in a diagram

  17. Aids for Diagnosis • The data collected during accident are studied and analyzed: - to find the cause of accident - to develop recommendations to prevent a recurrence • Sometimes, the evidence needs added analysis to uncover explanations. • Require special techniques or aid to diagnosis to relate the evidence to specific cause.

  18. Aids for Diagnosis a) Fire b) Explosions c) Sources of ignition in vessel d) Pressure Effects e) Medical Evidence

  19. Aids for Diagnosis a) Fire - identification of the primary source of ignition is one of the major objectives of investigation. - For example; - the depth of wood charring is proportional to the duration of burning - most woods burn at a rate of 1.5 in/hr. - If the time of extinguishment is known; - If the depth of char at various locations is known; - the region of the origin can be approximated.

  20. Aids for Diagnosis b) Explosions - The classification of the explosion as either deflagration or a detonation & magnitude of the explosion may be useful to develop causes and recommendations.

  21. Aids for Diagnosis b) Explosions Deflagration -The pressure increases during deflagration: for hydrocarbon-air mixtures for hydrocarbon-oxygen mixtures P1 and P2 = upstream & downstream pressure, respectively

  22. Aids for Diagnosis b) Explosions Detonations -In a single vessel detonations increase pressures significantly:

  23. Aids for Diagnosis c) Pressure Effect - Investigation on ruptured pipe and vessel - important to know the pressures required to create the damage - Pressure necessary to produce a specific stress in a vessel depends on: 1. thickness of the vessel 2. vessel diameter 3. mechanical properties of the vessel wall

  24. For cylindrical vessel (pressure p < 0.385SM) • For cylindrical vessel (pressure p > 0.385SM) Where: p is the internal gauge pressure, SM is the strength of the material, tV is the wall thickness of the vessel, r is the inside radius of the vessel.

  25. For spherical vessel (pressure p < 0.665SM) • For spherical vessel (pressure p > 0.665SM)

  26. Example 12-3 Determine the pressure required to rupture a cylindrical vessel if the vessel is stainless 316, has a radius of 3 ft, and has a wall thickness of 0.5 in.

  27. Solution • Because the pressure is unknown, Equation 12-4 or 12-5 is used by trial and error until the correct equation is identified. • Equation 12-4 is applicable for pressures below 0.385SM. • SM for Stainless Steel 316 (from Table 12-3) = 85,000 psi, 0.385SM = 32,700 psi r = 3 ft = 36 in tv = 0.5 in. Therefore Equation 12-4 is applicable, and a pressure of 1170 psi is required to rupture this vessel.

  28. Example 12-4 Determine the pressure required to rupture a spherical vessel if the vessel is stainless 304, has a radius of 5 ft, and has a wall thickness of 0.75 in.

  29. Solution • Equation 12-6 is applicable if the pressure is less than 0.665SM • SM for Stainless 304 = 80,000 psi • 0.665 SM = 0.665(80,000) = 53,200 psi. • Using Equation 12-6 for spherical vessels, • The pressure criteria is met for this equation. • The pressure required to rupture this vessel is 1990 psi.

  30. Aids for Diagnosis (d) Medical Evidence • Medical examinations of the accidents victims may be useful for identifying the source of accidents • Type of medical data: 1. type & level of toxic in the blood 2. location & magnitude of injuries 3. type of poisoning (CO, toluene, etc.) 4. sign of heat exposure 5. sign of eye irritation

  31. Aids for Recommendations • To develop recommendations to prevent a recurrence • To prevent similar accident within the company / industry • 4 principles of investigation recommendation • Safety investments on basis of cost and performance, for the best not worse • Improve management system to prevent safety hazards with proper steps. • Improve management and staff support of safety issues • Develop layered recommendations to eliminate causes of accidents

  32. Aids for Recommendations Control Plant Modifications • Often not given the same attention/concern as a new plant design • Many accidents are result of plant modifications • Recommendations to prevent this problem: a) All modification must be authorized. b) The modification design should have same quality of pipes/equipments as the original design c) Safety review – HAZOP must be conducted while the modification project is in the design phase. d) Training – operators & engineers: to understand the modified operation e) Audit – to ensure the modifications are made & maintain as designed.

  33. User Friendly Design • Not create hazardous conditions • For example: 1. using nontoxic and nonflammable solvent 2. keep temperatures below the flash point & boiling point at atmospheric conditions 3. keep inventories low 4. design for safe shutdown during emergency situations

  34. Block Valves • Install throughout plants to return a process to a safe condition under unusual circumstances • Block valves are often controlled on the basis of analyzer results for: 1. detecting solvent leaks 2. reactor analyzer – detect runaway reactions (block valve can be opened to add a reaction inhibitor) 3. sewer analyzer – detect high concentration of contaminants

  35. Preventive Maintenance - failure of emergency protection equipment such as cooling water pumps, instruments and deluge system can cause major accident. • Protective equipments failed due to no preventive maintenance • Preventive maintenance programs must be organized, managed & fully supported by management. • Must have maintenance schedule

  36. PBL PROJECT- INDUSTRIAL ACCIDENTS

  37. Industrial AccidentsGroup 1:  Flixborough Works Accident, June 1974Group 2: Bhopal, India Accident, December 1984Group 3: Seveso, Italy Accident, July 1976

  38. Group 4: Thailand Toy Factory Fire, May 1993Group 5: Three Mile Island Nuclear Disaster, 1979Group 6: Tokaimura Nuclear Disaster, September 1999Group 7: Piper Alpha Incidents, July 1988

  39. Prepare an Accident Investigation Report. The format may include the following sections: (1) Introduction (2) Process description (equipment and chemistry) (3) Incident description: chronology of event, cause of accident, extent of damage (4) Lesson learned (5) Layered recommendations (6) Conclusions

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