1. Field of the Invention
This invention relates to a depending skirt for oil tankers and the like, wherein a barrier of liquid impervious material can be very rapidly deployed around a ship's hull to contain leaking or spilling liquid cargoes which are less dense than water (such as oil), preventing any substantial spread of the cargo into surrounding water.
2. Description of the Prior Art
Catastrophic spills of oil from oil tankers are evidence of the need for an effective oil containment device which can be carried directly on an oil tanker, barge, etc., for prompt deployment to contain a spillage of oil or other such pollutants. Petroleum products, for example, are normally less dense than water and when escaping from a ship will rise to the surface and spread outwardly from the ship, causing environmental damage. Floating barriers (i.e., oil booms) have been developed to define a perimeter along the surface, and can be effective in containing expanding oil slicks when they are available, when wave and weather conditions are calm, and when they are deployed quickly. The barriers keep the floating oil in a limited area where skimmers can collect the oil.
A problem is presented in how to deploy the floating barrier to contain the spill. As time passes after a spill (e.g., from a rupture in the hull of the ship), the spreading oil requires a larger and larger barrier to encompass its expanding perimeter. Whereas a tanker cannot be moved when a spill occurs (to avoid dispersing the spill) and in any event is unlikely to be sufficiently maneuverable, the oil boom is typically deployed from an auxiliary ship which manuevers around the perimeter of the spill while dispensing the barrier linearly into the water, e.g., from the deck of the auxiliary ship. The barriers can be carried on the tankers themselves. Even in that case any delay in deployment allows the spill to expand to a point where a larger barrier is needed, and a larger barrier of course takes even more time to deploy. A delay of crucial minutes, hours, or even days, allows the spillage to spread before the barriers are deployed and may allow the spill to expand to a point where the required barrier is so long as to be unpractical and/or ineffective. In cases where barriers are carried on the tankers themselves, they are typically stowed in inconvenient protected storage areas which are remote from the point of deployment and are neither easily nor quickly deployed. As a result of delay, a larger barrier is needed, leading to further delay, etc. Speed and ease of deployment are crucial in preventing what could have been a contained minor spill from becoming a major ecological disaster.
Attempts have been made to solve the containment problem by providing floatable booms and the like which are carried to the scene of the spill or which are carried in a storage area on the ship and deployed by hand from the ship while it is in the water. Preus U.S. Pat. No. 4,073,143 discloses a barrier for pollutants which comprises a separable series of end-to-end floatable boom segments. The boom segments are connected to the ship at only a few points, whereby the ship's hull defines part of the barrier to the oil, and are connected to each other in a variable pattern. In order to deploy the boom and also to benefit from the various possible configurations of the boom structure, the Preus structure is assembled at the time of deployment and attached to a ship only then.
Niemi U.S. Pat. No. 4,129,989 discloses a floating ballasted oil containment boom which comprises boom elements interconnected end-to-end by overlapping joints. There is no provision in Niemi for attaching the boom to a ship or for deploying the boom from the ship. However the ballast in the boom assists in keeping the barrier vertical, to thereby maximize the depth of containment.
Fuxelius U.S. Pat. No. 4,333,726 discloses a flotation barrier comprising a floating curtain and weights to maintain the curtain in a vertical position. The curtain is constructed of flammable paper for easy disposal. The Fuxelius curtain is to be deployed from a helicopter, suggesting that a large curtain may be needed to enclose a spill. The curtain is not intended to be attached to or deployable from a sea-going vessel.
The present containment apparatus is attached to a ship's hull for storage as well as deployment, and is arranged to be instantly deployable immediately adjacent the hull. Bouvier U.S. Pat. No. 4,249,834 discloses an oil spill containment boom for ships including a deployable skirt which surrounds the periphery of a ship. The device is arranged to be spaced from the ship's hull by radial rib members which extend between the hull and a plurality of curtain segments which attach at vertical stems. When assembled, a flotation collar is maintained at a constant distance from the ship to provide a containment space for spilled oil. The curtain or boom can be assembled and taken apart at will to provide a perimeter of the required length.
The Bouvier boom is carried on board and kept in protective storage. In a time of need, the boom must be assembled and deployed, which takes time and necessitates means to encompass an area much larger than the hull. Although Bouvier addresses one problem by having the containment device immediately available by storing it on the hull of the ship, the need for rapid deployment is not fully addressed. Since many spills take place close to shore, and since the dimensions of the containment device needed increase over time, a more rapid deployment would be advantageous to better confine the oil. The delay caused when a containment device is not immediately deployable, as well as the aggravation of the problems associated with containing the expanding spill which are caused by delay, may account for the spread of great quantities of pollutant into the surrounding water.
There is, therefore, a need for a rapidly deployable containment system which is carried at all times on a ship and which is simple to operate and deploy to provide a containment curtain residing close to the ship.