Fired Heater Safeguarding Survey

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Refiners use a wide array of process heaters. The operation of these heaters poses a number of hazards that must be controlled, and are typically controlled using safety instrumented functions. The number and type of safety instrumented functions that are employed vary to a great degree from refiner to refiner and from site to site. This paper presents a summary of some of the results of a benchmarking study that was performed to determine the most prevalent practices in industry and establish the degree of adoption for some of the more common safety instrumented functions.

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Fired Heater Safeguarding Survey

  1. 1. Fired Heater Safeguarding Survey Edward M. Marszal President, Kenexis
  2. 2. Introduction• Most refiners employ fired heaters and are interested in standard designs• API 556 is a common basis• Benchmarking desired, address limitations – Improper bypass – Open block valves at light off – Improper fuel/air ratios
  3. 3. Survey Scope• Automatic Trips• Alarms• Permissives• Shut off valves• Pilots• Post-Purge
  4. 4. Survey Participants• Pure-play refiner or integrated oil and gas• Large market capitalization• Multiple refineries• Large processing volume capacity• Data set is limited – Acquisitions cause inconsistency – Attempted to get multiple sites
  5. 5. Results Scope and Format• Practices for new design and for existing equipment• Ranked from 1 to 3 – 3 – Almost always implemented – 2 – Sometimes implemented – 1 – Almost never implemented• Results from multiple sites averaged• Oriented to natural draft
  6. 6. Results – Low FG Pressure 3 3 Alw ays 2 Som e tim e s 1 Alm os t Ne ve r 0 Study Re s ult Re s ult• Almost always for new and existing• Even if not required by standard almost always implemented
  7. 7. High FG Pressure 3 2.9 Alw ays 2 Som etim e s 1 Alm os t Ne ve r 0 Study Re s ult Re sult• High degree of implementation• May address hazard not detected by other means• Some opt out if not a credible scenario
  8. 8. Pilot Gas Shutdowns Alw ays Alw ays3 32 Som etim es 2 Som etim es 2.3 2.11 1 Alm ost Alm ost Never Never 00 Study Result Study Result Result Result High Pressure Low Pressure• Considers that some organizations do not employ pilots in normal operation• Some consider risk posed by pilot misoperation to be minor
  9. 9. Loss of Flame Alw ays Alw ays3 32 Som etim es 2 Som etim es1 1.4 Alm ost 1 1.4 Alm ost Never Never0 0 Result Study Result Result Study Result Main Pilot• Not very common• Feel this is addressed by other means• Expensive, results in high spurious failure rate• More prevalent in forced draft and boilers
  10. 10. Low Pass Flow Shutdown 3 2.8 Alw ays 2 Som e tim e s 1 Alm os t Ne ve r 0 Study Re s ult Re s ult• Extremely common• Required to be reviewed even if not “standard”• Some opt out of consequence shown small
  11. 11. Improper Fuel/Air Shutdown 3 Alw ays 2 Som etim es 1 Alm os t Never 1 0 Study Re sult Re sult• Many are concerned but automatic shutdown very uncommon• Addressed by operator action or BPCS
  12. 12. Combustion Air Shutdown3 32 Alw ays 2 Alw ays 2.3 2.1 Som etim es Som etim es1 1 Alm ost Never Alm ost Never 0 Study Result0 Study Result Result Result• Almost always address for FD/ID systems• Detection methodology varies• Fan motor speed also used
  13. 13. Air Supply Alarms 3 2.9 2.5 2.7 2 2.1 Always 1.5 Sometimes 1 Almost Never 0.5 Study Result 0 High Draft Pressure Low Oxygen High CO or Combustibles• Frequent and consistent• High CO becoming more prevalent due to regulatory involvement
  14. 14. Temperature Alarms 32.5 2.8 2.8 2.6 2 Always1.5 Sometimes 1 Almost Never0.5 Study Result 0 High Bridge Wall Temp High Stack Temp High Outlet Temp
  15. 15. Purge Flow Permissive 3 Alw ays 2 Som e tim e s 1.7 1 Alm os t Ne ve r 0 Study Re s ult Re s ult• Supervised manual function – different from completely automatic purge• Typically completely manual
  16. 16. Shutoff Valve Position Permissive 3 Alw ays 2 2.4 Som e tim e s 1 Alm os t Ne ve r 0 Study Re s ult Re s ult• Common practice although not often addressed in corporate standards• Typically limit switches
  17. 17. Burner Valve Closed Permissive 3 Alw ays 2 Som etim es 1 1.4 Alm ost Never 0 Study Result Result• Not common unless large number of burners are employed (SMR, olefin cracking)
  18. 18. Automatic Firebox Purge 3 Alw ays 2 Som e tim e s 1 1.3 Alm os t Ne ve r 0 Study Re s ult Re s ult• Not common for natural draft• Very common for FD/ID systems
  19. 19. Flame Proven Permissive Alw ays Alw ays3 32 Som etim es 2 Som etim es1 1.6 1 Alm ost 1.2 Alm ost Never Never0 0 Result Study Result Result Study Result Main Pilot• Not common• Only used where loss of flame trip is employed
  20. 20. Double-Block and Bleed Alw ays Alw ays3 32 2.4 Som etim es 2 Som etim es 2.31 1 Alm ost Alm ost Never Never0 0 Study Result Result Study Result Result Main Pilot• Somewhat common but not ubiquitous• Other methods used to achieve goals of positive isolation and low system failure probability
  21. 21. Bypass Valves 3 Alw ays 2 Som e tim e s 1 1.4 Alm os t Ne ve r 0 Study Re s ult Re s ult• Not common and getting less so…• Pressure test systems might employ ¼” “dead man” valve
  22. 22. Continuously Operated Pilots 3 Alw ays 2 2.3 Som e tim e s 1 Alm os t Ne ve r 0 Study Re s ult Re s ult• Some consider continuous pilots strong basis of safety• Some consider unreliable and not installed at all
  23. 23. Pilot Gas Separate Supply 3 Alw ays 2 2.2 Som etim e s 1 Alm ost Ne ve r 0 Study Re s ult Re s ult• Very common where continuous pilots are used and separate supply is feasible
  24. 24. Post Purge 3 Alw ays 2 Som e tim e s 1 Alm os t Ne ve r 1.1 0 Study Re s ult Re s ult• Automatic steam introduction upon shutdown initiation• Not very common• Some concern over consequence of action
  25. 25. Conclusions• Benchmarking powerful tool for clarifying implementation of standards• Assists in determining “Recognized and Generally Accepted Good Engineering Practice”• Results show remarkable consistency for most applications

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