Vertical or Horizontal Gravity Skim per API Publication 421
Size a simple atmospheric skim tank for bulk oil removal from produced water — typically the first stage after a free-water knockout or as a slop-handling vessel. Stokes settling for 150 µm design droplet (API 421 default), with Hazen overflow check for vertical tanks and retention-time check for horizontal.
Process Stream
BWPD
mg/L
mg/L
µm
—
°API
°F
cP
Vessel
min
📚 Theory
API 421 design basis, Stokes Vt, Hazen overflow, retention time.