U.S. Navy Ship Salvage Manual Volume 6 - Oil Spill Response

S0300-A6-MAN-060The operating principles, procedures and capabilities of both classes of skimmer is the same. TheClass V oil recovery system can operate in conditions up to sea state three or four and recover oilat rates up to 300 gallons per minute. At this recovery rate, the skimmer sump will be filled in afew minutes. Without a towed bladder or other oil receiving vessel, skimming operations willhave to cease until the oil can be offloaded. The skimmer may be maneuvered independently witha hydraulically powered 360-degree rotatable thruster or towed with one or two ESSM Systemboom-handling boats. The skimmer is built for high-speed towing to reach distant skimming areasquickly. The pilothouse contains communications equipment. The vessel can be operated by asfew as two people, but more are required when the skimmer operates in the boom and bladderconfiguration.These skimmers recover oil by inducing oil onto a rotating sponge-like filter belt that picks the oilup and transfers it to a sump. The filter belt is composed of reticulated polyurethane foam withlarge cells. Like the general belt designed recovery systems discussed in Paragraph 5-2.1.1, thismaterial is oleophilic and hydrophobic. That means oil is attracted to the belt material and water isrepelled. The oil remains on the belt and water passes through it. The belt can work with or withoutthe polyurethane foam depending on the oil’s viscosity. The foam belt is for light and mediumviscosity oils. The foam is removed and the filter backing used for skimming high-viscosity oils.As the belt moves through the oil-water interface, the oil adheres to it and moves to the top of thebelt where it is scraped off—squeezed off the foam belt—into a sump.Hydraulically powered transfer and offloading pumps and hoses are required for continuousrecovery because the onboard storage capacity of the skimmers is only 32 or 43 barrels, dependingon the class of skimmer. Pumping recovered oil into barges or bladders accompanying theskimmer permits continuous operation.In a free-skimming mode, the sweep width is increased from 3 feet to 12 feet by deploying aluminumsweep arms on both sides of the bow. Sweep coverage may be improved significantly byattaching containment boom to the skimmer and towing the boom and skimmer as a single unitthrough the oil. Connecting hardware for skimmer and boom configurations always is deployedwith the boom and skimmer equipment. Figure 5-13 illustrates the modular characteristics of theClass VB skimmer. Figure 5-14 shows the skimmer belt operating specifications of the Class Vand VB skimmers. Figure 5-15 shows the V-boom skimming configuration.5-4.2 SUPSALV Vessel-of-Opportunity Skimming Systems. Vessels with good tank capacityor deck space for portable tanks, but without installed skimming systems, can be outfitted withvessel-of-opportunity skimming systems (VOSS). The ESSM-stored VOSS system is a floating,vertically adjustable weir-type recovery system. Oil flow over the weir is enhanced by a screwpump that moves the oil from the weir sump to a storage tank. Debris passes through the pumpeasily after passing through a cutting blade.The Class XI oil recovery system is another ESSM vessel of opportunity skimmer system. The oilrecovering apparatus is the same as the Class V and VB skimmers. The oleophilic pickup filterbelt, induction pump and offload pump make up the portable oil skimmer. The unit is attached tothe side of the ship and operated by hydraulic fluid from an accompanying portable hydraulicpump. The system is handled by a portable crane or other suitable lifting system. The operating5-18