Full Width Weir Plate Design
A separator’s performance depends on more than how water flows through it. It also depends on how oil is removed from it. Mercer’s Full Width Weir Plate is engineered for one job—to remove accumulated oil smoothly, evenly, and without disturbance, so it cannot fall back into the separator and contaminate the effluent.
Most oil–water separators use narrow skimming slots, makeshift overflow edges, or shallow “lip style” overflows that splash, funnel, or surge. These designs routinely re-entrain oil during flow changes or when an operator tries to skim accumulated layers.
Mercer’s design eliminates those problems with a full-width, fixed-elevation weir constructed to overflow the entire width of the tank. No turbulence. No eddies. No oil slugs dropping back into the separation chamber.
This is not a cosmetic difference. It’s a mechanical advantage that directly affects effluent consistency, operator workload, and long-term system reliability.
Most manufacturers treat the weir as an afterthought. Mercer learned the hard way—forty years of field data—that the wrong weir design destroys overall performance.
Common industry problems include:
When the weir destabilizes the oil layer, the operator pays the price in carryover, higher O&M, and compliance headaches. Mercer’s long-term position is simple: a separator without a proper weir is a separator that will fail in the field.
Every part of the Mercer weir system exists to maintain a stable, gentle, predictable overflow of waste oil.
Oil is skimmed across the entire width of the tank, reducing the chance of collapse, backmixing, or agitation. This allows oil layers to be removed without disturbing the separation zone below.
The weir height is matched to the tank geometry and plate pack assembly. This ensures the separator stores enough oil to maintain separation, then removes it slowly and consistently as it accumulates.
The weir plate is designed to overflow gently—no splashing, no liquid slugs, no vortexing. This maintains a clean transition into the oil reservoir or skim trough.
Mercer uses thick-gauge, corrosion-resistant materials that hold their geometry over decades. No warping, no distortion, no surprises.
The weir plate is fully removable, allowing inspection, maintenance, and full access to the oil removal zone—something welded-in designs cannot provide.
This is not theory. It’s based on thousands of installations and over 40 years of field-proven design refinement.
Operators get a system that removes oil the same way every time. No splashing, no sudden dumps, no “mystery” carryover.
The full-width design ensures that the oil layer exits cleanly and predictably, helping maintain consistent performance even during flow variation. In tanks that see heavy, fluctuating, or emulsified oils, stable oil removal is the difference between compliance and nonstop troubleshooting.
If you want predictable, stable oil removal backed by real engineering, start with a free evaluation. Mercer will review your system, your operating conditions, and your effluent requirements with no pressure and no guesswork.
If testing shows Mercer’s solution will not deliver meaningful improvement, you will know before you commit to anything. Free testing and evaluation are included.
A wider skimming surface removes oil more gently and prevents disturbance of the oil layer, reducing re-entrainment.
Typically no. Mercer fixes the elevation based on the tank’s internal geometry and storage volume requirements to maintain predictable oil removal.
Heavy-gauge, corrosion-resistant materials designed to hold shape and survive long-term industrial service.
If oil collapses back into the water phase or is agitated during removal, it will re-enter the separation zone and can show up as higher TOG/TPH.
Yes. Mercer provides free testing and honest evaluation. If your current weir is not the bottleneck—or if Mercer’s design won’t deliver meaningful improvement—you will know before committing.
