One of our older plants has a burn pit ground flare, and we are trying to validate the purge rate for it.
How does one calculate a purge rate for a flare with this configuration? API521 6th Edition has guidelines for purging the stack, but a burn pit doesn't have a stack - it is just an open pit. The equations in API521 (46 & 47) reference a variable "y" called "column depth at which the O2 concentration is predicted". In the case of a burn pit, would "y" be the depth of the pit, the height of the pilot tip, or some other value?
Eqns 46 & 47 also reference a variable "D", the flare stack diameter. In the case of the burn pit, would this be the flare header diameter?
Are there different methods in another reference or standard that I should use instead?
Thank you in advance for your help.
Are there different equations in another reference or standard that I should use instead? If the API calculations are appropriate, what would I base the value of "y" on - the depth of the pit, the height of the pilot tip, or something else?