The LNAPL enters the skimmer system through the floating inlet, flows down through a flexible tube, then is pulled upward by the pump’s suction action during the fill cycle. During the discharge cycle, the bladder is squeezed by the compressed air and the LNAPL is pumped to the collection system at the ground surface. Then, during the fill cycle the compressed air around the bladder is exhausted again and the bladder expands, resuming its original shape. This pulls fluid into the bladder through the check valve at the bottom of the pump.
C100M Pump Controller
The C100M Digital Controller offers easy and flexible control of skimmer system operation in a compact, solar or AC-powered unit. Touch-pad control and digital display simplify its programming. Programmable Genies utilize the C100M Controller which allows the user to not only control the pump fill/discharge cycles, but also to set OFF periods to match the LNAPL pumping rates to the recovery rates of the well. The C100M includes an AC power supply for locations where solar power is either not available or insufficient to support high rate pump operation. In solar-powered mode, the C100M is rated intrinsically safe. See page 39 or consult the factory for more detailed information on the C100M.
The SPG (specific gravity) inlet uses a float with a controlled specific gravity that causes it to float on water but not in the LNAPL. The SPG float has its fluid inlet port positioned near the top so that it is always above water. If the LNAPL layer gets too thin, the SPG inlet will also be above the LNAPL layer and cease recovery of hydrocarbons until more enters the well. To accommodate a range of final LNAPL layer thickness, the SPG float has multiple, variable inlet ports that can be opened or plugged to adjust the level of the inlet port. Why isn’t the SPG always set for the thinnest possible LNAPL layer? The reason is that any float in a small diameter well has a tendency to occasionally stick as liquid levels move up and down, so setting the inlet port too low increases the chance of allowing water to be pumped instead of pumping only LNAPL. So, a trade-off must be made between achieving desired final LNAPL layer thickness and prevention of pumping water.
The SOS inlet uses a float with an inlet port inside a hydrophobic, or water-rejecting, screen. The hydrophobic screen prevents water from being taken in and pumped to the surface, even if the float occasionally sticks or drags as the liquid level fluctuates. While this is a distinct advantage of the SOS inlet over the SPG type, the SOS inlet screen is more subject to plugging due to potential debris or slimes present in the well. The SOS inlet works best on fresh gasoline and jet fuel spills, and less so on weathered diesel.