• Automated System Crude Oil Washing (C.O.W.)

Tank cleaning | COW System

Automated System Crude Oil Washing (C.O.W.)

To perform the oil tank cleaning operations, recently our Company has equipped itself with an innovative C.O.W. system (Crude Oil Washing), which allows us to perform any kind of oil tank cleaning, both on floating and fixed roof, with an hydrocarbons recovery from the sludge up to 98%, ensuring a heavy reduction of the waste disposal, as well as a profit coming from the higher quantity of recovered hydrocarbons.

The System allows to perform a safe tank cleaning because it doesn’t require any staff inside the tank until the gas-free condition is reached.

In order to give you a complete overview of the huge capabilities of this automated system, here below we will briefly describe the innovative operating methods of this automated System.

The automated tank cleaning system is divided in modules built into standard 20’ (7 meters) containers, divided as follows:

• suction module
• recirculation module
• separation module
• skimming module

Previously an adequate number of nozzles shall be installed on the roof so that the cutter stock fluid can be injected into the tank, in order to melt the material inside the tank. These nozzles will be inserted on already existing openings on the tank roof or in new openings made using the “SafeTap” tool. The nozzle should be installed according to an installation plan, to be sure that their ranges cover the entire tank surface.

Before starting the cleaning operations, an inert gas (Nitrogen) will be injected into the tank using the previously installed nozzles, in order to reduce the Oxygen level under the 8% and therefore eliminate the risk of explosion. This Oxygen level is held under during the entire cleaning process.

The desludging process may begin when the Oxygen level has fallen below 8%. The recirculation of sludge inside the tank will start, and later on those sludge will be pumped out through the Suction Module (see picture 1), which comprises pre-filters, a vacuum pump and a centrifuge pump.

The product will be sent to the Recirculation Module (see picture 2), which will perform a pre-separation between solids and liquid, using the hydro-cyclones and then the product will be pumped again into the tank. If necessary the product can be heated using the heat exchanger that there is inside the Recirculation Module, in order to help the desludging.

During the desludging, the product at the bottom of the hydro-cyclones will be sent to the separation module, which comprises:

  • n° 1 decanter for the liquid/solids separation
  • n° 1 centrifuge for the liquid/liquid separation (hydrocarbons/water) (see picture 3) for the hydrocarbons recovery.
    This recirculation process will be performed more times.

The water that comes from the centrifuge will be sent to the Skimming Module, where the oil will be skimmed off the water surface and the water will be used for the final water wash of the tank surface

The C.O.W. System is equipped with O2 – H2S - CO detectors and LEL sensor.

picture 1 - suction module

picture 2 - recirculation module

picture 3 - separation module



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