• Petro-Pile Sump Caisson

    The Petro-Pile™ Sump Caisson is the most effective device available today for collection, treatment, and discharge of wastewater from offshore platforms. The patented design includes a Quite Oil Spillover chamber which provides an oil collection area that is unaffected by wave action, tidal changes or storm surge. 

    We are currently operating successfully on over 135 offshore facilities including tension leg, semi-submersible, and spar platforms while remaining unaffected by the motion of the platform. The first choice of environmentally responsible companies, the Petro-Pile Sump Caisson is operating across the globe -- from Nigeria to Mexico, the US to the Caspian Sea.



    Operation Details:

    The incoming oily water is introduced into the caisson through the downcomer pipe. The downward velocity is interrupted by the dispersal plate located below the outlet of the pipe. The mixture flows into the caisson below the oil-water interface, which is set by the adjustable weir pipe.

    The oily water then begins its flow downward toward the bottom of the caisson. The oil particles that have a large enough diameter to provide them with an upward velocity greater than the downward velocity of the water begin to float to the surface. As they rise upward through the water, they contact and bond with smaller diameter oil particles and carry them to the surface.

    Baffles are provided on opposite sides of the caisson and extend to the center. These plates are sloped at 45° toward the bottom of the caisson and provide a means of rolling any sand entering the caisson to help strip it of oil. The plates are spaced to create negligible dead volume below and no constrictions, which could cause high velocities or points of clogging. Each plate is provided with a weep hole at the high point where it contacts the caisson wall, so that oil trapped under the plate can continue its upward flow.

    As the oil reaches the surface of the fluid level in the caisson, it spills over into the oil quiet chamber through slots in the weir pipe. The slots are provided to keep trash out of the oil chamber. (If a large amount of trash should accumulate at the slots, the top of the caisson can be removed and the trash scooped out.)

    The oil chamber is provided with bubbler tubes or level switches and either a submersible pump, diaphragm pump, blow case or a discharge line with a foot valve. As the oil level increases in the quiet chamber it reaches a preset point where the sensors send a signal to start the pump or blow case operation. The oil is then removed from the chamber until it reaches a preset level that shuts off the pump or blow case operation. If there is a failure of the blow case or pump and the oil level keeps rising in the chamber, another preset level is reached and a high level alarm sounds.

    Samples of the water leaving the caisson are taken through a 3/8" stainless steel sampling line whose inlet is located near the bottom of the caisson and fitted with a check valve. The oil is forced out of the tube by gas introduced through another 3/8" stainless steel tube that connects just above the check valve on the sampling line.


    • Quiet Oil Spillover chamber provide oil collection area that is unaffected by wave action, tidal changes, or storm surge
    • Provides a large contained volume, and therefore a long settling time, without taking up any deck space
    • Helps prevent pollution during process upsets in the produced water treating equipment
    • Deep discharge point reduces the likelihood of a sheen being created when waste waters enter the sea
    • Imparts minimal loads to the platform due to its low elevation and cylindrical shape
    • Typically has lower installation costs than conventional sump tanks
    • Equipped with non-clogging baffles which help remove oil from the sand which then exits the pile without any build-up
    • Allows for precise setting of the oil-water interface so that the influent can enter the pile below the interface, thereby not disturbing the oil which has already separated from the water 
    • The oil weir spillover pipe can be easily adjusted to change the elevation of the oil-water interface
    • All of the controls such as level switches, floats, bubbler tubes, pumps or blow cases are located in the oil wetted quiet chamber where they never come in contact with the seawater, reducing corrosion and maintenance 
    • The level controls are also located in their own stilling wells so as to further minimize pump cycling