Patented Separator Design Eases Maintenance

March 11, 2002

Traditionally, the separations process was one which involved frequent and often complicated maintenance. Wastewater Diversion Systems, Inc. of Mechanicsville, Va., has developed and patented the FOX VGS (Vertical Gravity Separator) to remove free oil, grease and suspended solids from wastewater, while significantly reducing the frequency and difficulty of maintenance.

This separator features high efficiency, low cost oil water separator technology that continuously meets the performance standards, is able to handle high concentrations of oil, effectively removes the suspended solids, reduces vapor content to acceptable levels, and requires less floor space.

The FOX VGS operates by control of both fluid velocity and pressure, which gently coaxes non-emulsified impurities from water — allowing high density contaminants to fall into a sludge retaining area and oil droplets/low density suspended solids to rise where they float off into a sludge tank.

This separator is effective because the FOX VGS Skimmer skims only a few millimeters from the surface of the oily water, dealing with the most relevant fraction of liquid.

Often with conventional oil/water separators, cleaning can be a messy process. Someone first has to remove the plates or filters, then use a high pressure hose to wash them —with grease and oil everywhere.

However, with the FOX VGS, there is no lifting plates or filters out, no filter disposal, no reblocking the system, and no oil and grease splatter. The user simply turns a valve and is back in operation within minutes.

This separator is designed to operate efficiently. A pump delivers oily water into the top of the main body via the inlet leg, flowing down this central column before being redirected upward through the chimney of the truncated conical spiral pack (SPAK).The oily water supply to the pump is from either a skimmer or a fixed suction in the pit, depending upon the application. At the top of the main body, free oil and suspended solids are built up, eventually flowing out for collection and suitable disposal.

The partially cleaned water is directed to the outside (perimeter) of the conical SPAK and follows a tortuous path while cascading down and around the SPAK. If this fluid while passing down the main body encounters a set of conditions where the density of the fluid below is greater than itself, then this lower density (oilier) fluid is drawn preferentially up the inside of the inclined coalescing surface of the SPAK and into the lower pressure center (chimney). Here it co-mingles with the incoming fluid and is thus redirected again to the top of the main body and the process is repeated.

As a result of this process, the lightest fluid phase is trapped within the hydraulics of the FOX VGS. This “convection current” is created and maintained within the SPAK by the density variations down the fluid column and the upward flow of the incoming oily water. At the point that the fluid is most free of oil droplets, then this “cleaned water” will enter the outlet leg — flowing up and out of the system — while the heavy solids will drop to the base of the main vessel.

The depth of the separated oil and surface sludge trapped in the top of the main body of the FOX VGS is regulated by adjustment of the height of the “cleaned water” outlet. This level is set by rotation of a T-Bar assembly (adjuster) at the time of startup or at anytime that the flow rate through the VGS is varied.

Construction of the unit is such that the SPAK is hung from a support plate which bears onto the top edge of the main body and is free to revolve. This support plate also has paddles on its underside that protrude into the oil and sludge phase. Because the conical SPAK forms a continuous spiral, its rotation produces a violent pumping action of the internal fluids and causes the surfaces to be cleaned of any sludge build up. The paddles fluidize any encrustation of the surface sludge and makes it suitable for discharge with the oil.

Maintenance and cleaning requires about one minute. A worker closes off the water outlet and, with fluid flowing into the separator, rotates the SPAK counter clockwise for three revolutions to flush it. Oil, water and surface sludge buildup will flow out of the oil outlet for collection. This usually is the only action required to maintain optimum performance of the FOX VGS. The frequency of this cleaning action depends on each application. Once per month is suggested until experience dictates otherwise.

The trash basket will indicate that emptying is required if inlet fluid is seen to flow over the top of the main body. This fluid is contained by the top berm initially, and will enter the main body via the hollow paddles. Build-up of any heavier sludge in the base of the main body may be drained off through the bottom valve.

For further information, phone Wastewater Diversion Systems, Inc. at 804-730-1280.

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