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Emergency Relief System Design: Managing Vessel Overpressure Risks in Chemical Processes

This workshop by Gary Van Sciver, held on September 20, 2005, addresses emergency relief system (ERS) design focusing on vessel overpressure scenarios. It highlights historical hazardous releases, such as the Bhopal disaster and incidents in Pasadena and Allentown, emphasizing the necessity of protecting both onsite and offsite personnel. The workshop outlines the process of identifying and selecting design bases for ERS, considering various failure scenarios like runaway reactions and fire. It serves as a guideline for ensuring safety and compliance with industry codes.

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Emergency Relief System Design: Managing Vessel Overpressure Risks in Chemical Processes

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Presentation Transcript

  1. Selectingan ERSDesign Basis SACHE Workshop Gary Van Sciver September 20, 2005

  2. EmergencyReliefSystem

  3. Vessel Overpressure

  4. Concept Sciences 1999 Allentown, PA 5 fatalities high concentration and temperature of hydroxylamine

  5. Hazardous Release

  6. Phillips Pasedena, Texas 1989 23 fatalities Vapor cloud explosion of ethylene and other gases Explosion occurred ~ 2 minutes after release started

  7. Bhopal Union Carbide 1984 2,500 fatalities large ERS release of methyl isocyanate

  8. Venting Policy: ERS must protect on-site people AND off-site people

  9. Balance:

  10. What is aDesign Basis?

  11. Design Basis:Simple way to express system capacity

  12. FailureScenario

  13. Fire Scenario

  14. Runaway Scenario

  15. Failure Scenario: Series of events leading to high vessel pressure.

  16. How high?

  17. Codes require that the maximum pressure not exceed the vessel design pressure

  18. Design Basis: Most severe failure scenario which complies with the Codes.

  19. How do we do it?

  20. Procedure: 1. Identification 2. Selection

  21. 1. Identification(of all important failure scenarios)

  22. ideas

  23. Non-reactiveSystems

  24. Product Tank Example

  25. Non-Reactive Checklist 1. Heat addition a. Normal breathing b. Fire c. Excessive heating 2. Pressurized liquid addition 3. Pressurized gas addition

  26. 1a. Normal breathing(atmospheric temperature and pressure changes)

  27. 1b. Fire Exposure

  28. 1c. Excessive heating(steam valve failures, coil leaks)

  29. 2. Pressurized liquid addition(usually accompanied by some flashing, especially if hot)

  30. 3. Pressurized gas addition(line blowing, pressure transfers, pads or purges)

  31. ReactiveSystems

  32. Is there an exothermic or gas-generating reaction?

  33. Generic Emulsion Compatibility Matrix

  34. Reactive Chemistry Worksheetdeveloped by EPA and NOAA (National Oceanic and Atmospheric Administration)http://response.restoration.noaa.gov/chemaids/react.html

  35. OSHA Chemical Reactivity Websitehttp://www.osha.gov/dep/reactivechemicals/

  36. Bretherick’sHandbook of Reactive Chemical Hazards

  37. LabExperiments

  38. Emulsion Reactor Example

  39. NormalReaction Checklist 1. Inadequate cooling 2. Inadequate heat sink 3. Excessive reactant 4. Poor reactivity

  40. 1. Inadequate cooling

  41. 2. Inadequate heat sink

  42. 3. Excessive reactant (continuous)

  43. 3. Excessive Reactant (batch)

  44. 4. Poor reactivity

  45. Abnormal Reaction Checklist • Too hot • Wrong composition

  46. 1. Too hot

  47. 2. Wrong composition

  48. System ________________

  49. 2. Selection(of a design basis from the important failure scenarios)

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