The main principle of the NES system for tank cleaning and oil recovery is to give the tank owner a safe efficient and cost effective system of returning there tanks to service whilst reducing the environmental impact of the system by reducing the overall disposables.

The basic operation of the NESL system can be broken down into three stages to make it easier to understand the principles involved

1. Desludging.

The method for the removal of the sludge from the tank is dependant on the type of sludge and the configuration of the tank itself. Some tanks will be easier to desludge using the MOVer system whilst others especially those with steam coils will be more easily cleaned using the remote manway cannon. There also may be occasions when circumstances require a combination of both methods.

The NES MOVer is a hydraulically driven tracked vehicle specifically designed for the slurrying of sludge to a condition suitable for pumping from the tank. It is a well proven reliable method which when used in conjunction with the supplied rotary lobe pump can efficiently remove heavy sludge from tanks up to 300 ft diameter.

The NES Manway cannon is a remote operated jetting system, which is fitted to the tank manway and can wash the tank down using a jet of hot or cold water or cutter stock. It has an explosion proof camera and lighting system, which allows the operator to efficiently operate the machine from the control system. The Cannon can remove heavy sludges by dilution and can also wash and degrease the tank afterwards using water and detergents. See also the latest NES Roverjet

The supply of jetting fluid for the camera is by a hydraulically powered centrifugal pump giving up to 250 PSI at 250 GPM. Again a lobe pump is used to pump the diluted sludge from the tank. Hydraulic power for both systems is supplied by diesel driven hydraulic power packs.

Both of these methods are designed as the first stage of operation to remove the sludge from the tank and to transport it to either the Pre-treatment system or to a holding tank should the processing system be located remotely from the tank.

If a holding tank is used the sludge is transferred onto the pre-treatment unit using the hydraulically powered screw pump (Booster pump).

 

2. Pre-treatment

 

In simple terms the pre-treatment unit modifies the viscosity and temperature of the sludge to render it to an optimized condition for solids removal and oil recovery.

It does this by first removing large contaminates (bolts stones etc) in the filter system and then raising the temperature in the first mixer tank. The heated oil is then pumped into the blending and stabilization tank for the addition of cutting stock and or chemical surfactants or emulsion breakers as required.

Once blended the slurry is pumped to the centrifuge feed tank ready for treatment and polymer injection at the decanter inlet.

The temperature is maintained at all times during the operation and has gauges to monitor the operation. All mixers, pumps etc are hydraulically powered and the unit is self contained with all pipe work valves and controls integrally mounted.

Hydraulic power for this unit is supplied from a hydraulic power pack.

3. Oil Recovery

The feed pump on the pre-treatment unit feeds the slurry into the decanter inlet where it is separated into recovered oil , water and solids. The machine is adjusted to optimize the treatment and operates on a continuous basis. The water is discharged through a weir tank fitted in the unit to give a final polish to the water quality , and the solids are conveyed to a skip for disposal. The recovered oil is discharged from the decanter under pressure and is piped to the clean oil holding tank for testing and load out. The unit is self contained and has an inbuilt power pack to drive the decanter skid.

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