What is the minimum safe distance between flare stacks and electric high line? Please specify the related code and standard.
Answers
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20/07/2009
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Graham Bennett, DNV , graham.bennett@dnv.com
It would be useful to know why you ask this question: is it related to the ignition risk from the HV lines? If so, I am not aware of any safe separation distances quoted in standards for this parameter. Usually, safe separation distances are determined only for thermal radiation either by using the methodology in API 521, or by using a dispersion/radiation calculation tool such as the DNV PHAST program.
Usually, you would not expect significant quantities of unignited hydrocarbons to be released from the flare unless there was a problem with the flare ignition package, so consideration of secondary ignition sources beyond the flare igniter are not normally a major consideration.
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19/07/2009
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keith bowers, B and B Consulting, kebowers47@gmail.com
API 510 is the flare and relief system section. The length elevation, and direction of the flame during max relieving case with prevailing wind rose will show you how far the flame reaches. Adding at least 150' from the boundary of the flame to the power line conductors will usually get heat flux down to less than 3000 BUT/hr-ft2 (like right at fireplace front plane with a real good roaring fire). That will cause some line sagging of course, but not failure. The probabilities of max relieving at worst case wind direction and velocity may be vanishingly low, but impact of that condition must be delineated to ensure a rational decision can be made. One has to consider radiant heating loads for flames with lots of olefins as they burn with very high radiance as compared to methane, propane or butanes.
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