fallah,
QUOTE (fallah @ Nov 28 2007, 11:58 AM)

- what is the min. slope in main header and the subheaders and based on which references?
I have seen 1:500 for both on one project and 1:200 for sub-header and 1:500 for main header for another project.
QUOTE
- what is the normal height difference between piperack on which flare header lied, and the knock-out drum inlet?
Other than optimum design maintaining free draining slope towards KO drum and no low pocket, i can't think any requirement on height difference...
If you got any special advice/requirement by other, let forum know...
JoeWong