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.

1. Fired Heater Safeguarding
Survey
Edward M. Marszal
President, Kenexis

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. Survey Scope
• Automatic Trips
• Alarms
• Permissives
• Shut off valves
• Pilots
• Post-Purge

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. 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. 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. 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. Pilot Gas Shutdowns
Alw ays Alw ays
3 3
2 Som etim es 2 Som etim es
2.3
2.1
1 1 Alm ost
Alm ost
Never Never
0
0 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. Loss of Flame
Alw ays Alw ays
3 3
2 Som etim es 2 Som etim es
1 1.4 Alm ost 1 1.4 Alm ost
Never Never
0 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. 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. 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. Combustion Air Shutdown
3 3
2 Alw ays 2 Alw ays
2.3 2.1
Som etim es Som etim es
1 1 Alm ost Never
Alm ost Never
0 Study Result
0 Study Result
Result
Result
• Almost always address for FD/ID systems
• Detection methodology varies
• Fan motor speed also used

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. Temperature Alarms
3
2.5 2.8 2.8
2.6
2 Always
1.5 Sometimes
1 Almost Never
0.5 Study Result
0
High Bridge Wall Temp High Stack Temp High Outlet Temp

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. 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. 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. 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. Flame Proven Permissive
Alw ays Alw ays
3 3
2 Som etim es 2 Som etim es
1 1.6 1
Alm ost 1.2 Alm ost
Never Never
0 0
Result Study Result Result Study Result
Main Pilot
• Not common
• Only used where loss of flame trip is employed

20. Double-Block and Bleed
Alw ays Alw ays
3 3
2 2.4 Som etim es 2 Som etim es
2.3
1 1 Alm ost
Alm ost
Never Never
0 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. 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. 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. 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. 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. 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