Our Tank Cleaning Process
The process begins with the installation of equipment according to a thorough site plan approved by the tank owner. The Suction, Recirculation, Separation and Skimming modules, plus required auxiliary equipment, are set up in compliance with the prevailing regulations concerning potentially hazardous zones.
To avoid the risk of explosion, an inert gas – typically nitrogen – is injected into the tank before the cleaning process is started to reduce the oxygen level to below 8 percent. This level is maintained throughout the entire tank cleaning process.
Tank Cleaning Nozzles
Depending on the tank’s diameter, the required number of nozzles is installed in the roof – either through existing or new perforations made with the SafeTap® tool. Specially designed, patented Single Nozzle Sweepers (SNS) use the re-circulated oil as their primary cleaning media; low pressure, high volume jetting technology makes the process extremely efficient.
The hydrocarbon recovery and cleaning process starts with desludging. Depending on the nature and complexity of the sludge, it is customary to use a compatible crude oil as "cutter" stock to begin liquefying the sludge. The sludge is taken in by the Suction module, passing through pre-filters to strain off foreign objects before entering the Suction Modules vacuum tank, where gases, if any, are returned to the tank.
The oil is then pumped to the Recirculation module where it feeds through hydrocyclones to separate heavy solid particles from the recirculating cleaning media. A booster pump returns the cleaner oil through the jetting nozzles in the storage tank where it is used to re-liquefy more sludge.
The nozzles play a vital part in the cleaning process. The jetting nozzles can be programmed, via a PLC, to focus on areas that require more intensive desludging; a hydraulic unit controls their speed and movement. The process of mixing cutter stock with the sludge is continued until all sludge has been removed.
The entire BLABO process is automated and personnel do not enter the tank before or during cleaning period. Easy to operate, BLABO is monitored by trained operators (certified) using the built-in PLCs and user-friendly control panels on the modules themselves.
Separation and Recovery of Oil
If the oil from the bottom of the hydrocyclones matches the tank owner’s specifications, it is pumped directly to the pipeline. Should the oil need further treatment, the Separation module is used. Separation of the sludge takes place simultaneously with desludging and is separated into clean oil, solids and water. BLABO recovers close to 100% of the hydrocarbons.
There are two separate steps. First, a liquid/solids separation takes place in the decanter whereby solids are removed from the oil. The solids are deposited into roll-off containers for disposal or treatment, if required. If recovered oil still contains water, a further oil/water separation is performed via the high-speed separator (also in the module). The clean oil may be pumped to the pipeline while the water can be pumped directly to a local waste water treatment facility; heat exchangers are used to facilitate the separation process. Cinatra Operators regularly test samples to ensure the separated oil conforms to the tank owner’s specifications.
Final Water Wash
At this stage, there is no sludge remaining in the tank, only a small layer of liquid which may contain sediments (sand, rust) on the bottom and the walls and some oil. To clean the tank completely, a water wash is needed; the Skimming module is then introduced into the process.
Fresh water is introduced via the nozzles and pumped through the Skimming module where coalescing plates perform the last oil/water separation. The oil is skimmed off and returned to the tank owner as recovered oil; this procedure is repeated until there is not oil left in the tank.
Ventilation and Demobilization
After the water wash, the manholes are opened to vent the tank. Once the tank atmosphere has been approved by a safety officer, personnel are free to enter. It may, however, be necessary to manually remove some sand or rust scales so the tank can be readied for maintenance and hot work.
Text and images © Oreco A/S
View Our BLABO Animation
See for yourself how the BLABO® system effectively cleans an oil storage tank and simultaneously recovers the oily sludge. Follow the entire process from installation of the BLABO units, installation of cleaning nozzles, desludging, washing, oil recovery and on to the final water wash.
Cinatra's cleaning nozzles are inserted in tank rooftops through holes created using SafeTap, a unique cold-tapping tool that provides a safe, fast and effective cutting method. All stages of the tapping process are performed under cold conditions to prevent the risk of ignition that exists when cutting metal in potentially hazardous areas.