There are many ways of dealing with an oil spill. Direct mechanical removal from the water surface is preferred since it is the fastest solution with the least impact on society and environment. The fastest and most effective way of mechanical recovery of oil spills on open water like lakes, rivers or seas is direct removal by Dynamic oil recovery. This means a ship with sweeping arms to its sides navigates directly through the oil spot. The sweeping arms collect the oil it encounters between the arms and the ship’s hull. By moving forward a thicker layer of oil is build up in front of the skimmers in the inner pontoon of the sweeping arm. The brush or weir skimmers directly skim the oil off the water surface and pump it into the oil recovery tank of the ship, leaving a clean watersurface behind.
The reason why dynamic recovery is so fast is that there is not need to contain the oil before skimming it off the water surface. The forward movement already guides the oil to the skimmer and can then easily be skimmed of directly. This makes it possible to immediately start recovering oil as soon as the the sweeping arms are hoisted in the water. This makes dynamic recovery the fastest and most effective method of recovery of a big spill on open water or for example the cleaning an oil trail in a river.
Why rigid sweeping arms?
Most accidents happen in adverse weather conditions. Major oil spills in the past like the Erika, Prestige and Deepwater Horizon spills showed that sweeping arms are highly performing in these circumstances, because of their large operating window. For more information on the effectiveness of the sweeping arms see at the EMSA website, the recovery data table below from the EMSA report “Action Plan for Oil Pollution Preparedness and Response” (2004), at chapter on the lessons learnt after the Prestige spill (pag. 44).
Part of the exceptional performance of the sweeping arm can be contributed to the high capacity oil recovery pumps used in the sweeping arms. The used pumps are able to pump very viscous oils while being insensitive to debris and running dry. This makes the Koseq pumps reliable to use in any emergency situation. Dutch build quality, also in the harshest conditions proven to be robust and reliable. Koseq sweeping arms have a long life span with low maintenance because the construction material. The system is made from steel with marine coating and stainless steel components like bolds nuts and hydraulic quick couplings. This is why some very early build models still serve and offer preparedness to their owners. The current Koseq sweeping arm models benefit from years of experience as Koseq was, and still is, the frontrunner of the development of the sweeping arms that started in the ’70s.
The high degree of mechanization of the sweeping arms and dedicated cranes makes the total oil recovery process efficient. One reason for this is the very short system set-up or start-stop time. Dedicated cranes make it possible to deploy sweeping arms within minutes. See YouTube movie at Koseq channel. Practically, this means you can sail at high speed to the oil slick with the sweeping arms on board and very quickly start the high capacity oil recovery. This quick start-stop ability make the system very suitable to efficiently recover multiple smaller oil slicks as well.
The high degree of mechanization also makes the system very Safe, easy and efficient to handle. Only one ship and one operator is needed to hoist and operate the system and couple of hands to handle the towing lines.
What does a sweeping arm system look like?
A rigid sweeping arm is a steel construction which consist of two pontoons connected by a bridge piece with oil guiding bulkhead on the front. The length can vary between roughly 12 and 15 meter. But also Compact models as small as 5 meter are available. The inner pontoon houses the skimmer-module with brush or weir skimmer, pump chamber and the oil recovery pump. The oil is pumped through flexible cargo hoses to the recovered oil tank in the ship.
Different types of brush- and weir skimmers are available. A brush-skimmer is used for minimal water-intake in waves or when sweeping a thin layer of oil. For maximum skimming capacity a weir skimmer is available. The skimmers are height adjustable to the thickness of the oil layer. They are installed as modules which makes them quickly interchangeable. In front of the skimmer is a self-cleaning hydraulic debris screen mounted.
Sweeping arms can be permanently installed on the ship or stored on-shore and only temporarily installed on the ship in case of an emergency. They are placed and secured on the ship’s deck with twist locks with underneath an oil drip tray to prevent the ship’s deck from becoming slippery from oil.
The dedicated cranes place the sweeping arms in the water. Permanent installed cranes can be mounted on deck by a pedestal. Dedicated cranes guarantee easy, fast and safe operation. On top of the standard crane the operator console is located with controls both the crane and sweeping arm. From this location the operator has good view over the hoisting and sweeping operations. During hoisting each sweeping arm is lifted by two hoisting lines and held in place by two catchers which prevent the sweeping arm from moving excessively during hoisting in heavy weather. Other types of cranes like Multi-purpose cranes or davids belong to the range of delivery options as well. See “additional equipment” menu for more information.
The crane and sweeping arm can be powered by a hydraulic power pack or the ship’s own hydraulic system. An explosion proof execution of the complete system is available. Once again see “additional equipment” menu for more information.
The sweeping arms float in the water independent from the ship and are held in place under an angle to the ship by two lines. One line to the bow of the ship to pull it forward. An extra line is made to the back of the ship to ensure that the sweeping arm stays against the ship’s hull at all time. Three fenders beside the sweeping arm ensure a leak-proof connection to the hull while protecting the ship from getting damaged.
Using the system.
After the power packs are started the sweeping arms can be lowered into the water and secured with predetermined fixed length lines to the ship. This whole process doesn’t take a few skilled operators more than a couple of minutes. One person operates the crane and sweeping arm. And a couple of hands for handling the lines at the start and finish of the recovery operations. This ability to quickly start en stop the oil recovery process makes it very suitable equipment to recovery big spills that consist of many smaller patches of oil. To get familiar with oil recovery under these and other circumstances a training facility at Willem Barentz Institute at Terschelling, the Netherlands is offering training in a simulator in which Koseq equipment can be used in all possible circumstances.
After the sweeping arm is lowered into the water, secured properly to the ship, the brush or weir skimmer is height adjusted and the pump is turned on. The system is ready to start oil recovery. Oil spill equipment and OSRV that deploy the equipment need to be cleaned after use. Koseq Sweeping arms are made of materials that can be easily cleaned with a hot water pressure cleaner without shortening the lifespan of it.
To learn more about our different models sweeping arms see “Sweeping Arm Model” menu or click here.
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