Spring 1998
Seaward solves a unique berthing problem with a Floating Donut Fender
A worker puts finishing touches on the interior of the floating DONUT Fender before it is shipped from the Seaward plant.
Nearly four years ago, a major domestic manufacturer of lubricants completed an installation of Seaward’s Floating DONUT dock fender. A risk assessment and feasibility study previously conducted for the company by the Frederic R. Harris Co., of New York, had revealed the potential for damage to berthing oil tankers by the riprap near the end of its pier and concluded that a dolphin should be installed.
Subsequently, an engineering analysis of dolphin styles by Han-Padron Associates, LLP, of New York, found the monopile and Seaward DONUT to be the right combination. This system utilizes a single pile driven into the earth, which is then fitted with a floating ‘donut’ shaped fender that slips over it.
Since its installation, the dolphin has operated problem-free and without the need for maintenance, according to the customer. “Tankers, which bring base stock lube oils from southern refineries, berth at the pier an average of four times a month. Although it is not part of berthing operations, tankers occasionally come in contact with the dolphin. There have been no complaints from the tanker captains or crews since its installation.”
In this application, the steel pile supporting the DONUT Fender is 48 inches in diameter and 109 feet long, with a wall thickness varying from 3/4 inch at the top to 1-1/2 inches at the base. Driven to a refusal depth of 50 feet below the mud line in a water depth of 40 feet, the pile at the top extends 19 feet above mean low water and 7 feet above the deck of the pier. The pile is protected from corrosion by a cathodic protection system and a marine coating. Following the installation of the pile, marine contractor Spearin, Preston and Burrows, Inc., of Staten Island, NY, lowered the Floating DONUT fender over the top of the driven pile and installed a stop to prevent loss from excessively high tides.
The same Floating DONUT Fender, nearly four years later, standing sentry for the pier it is protecting.
The ease of installation of the monopile DONUT Fender, coupled with years of maintenance-free service, makes this fendering system an obvious choice for many unique berthing problems. Seaward works with the customer and its design engineering firm to custom design and fabricate each DONUT Fender system for its particular application. Our computer aided design capabilities enable our designers to insure timely and accurate products tailored for each situation.
Seaward’s manufacturing process of these products includes fitting the steel core of the unit with multiple UHMW wear pads to protect the surface of the monopile and insure continued rotation. Closed-cell foam is bonded to the core and laminated in successive layers until the designed diameter is achieved. Finally, a nylon fiber reinforced polyurethane outer skin is created by simultaneously introducing nylon reinforcing strands and spray-applied polyurethane, thus allowing the reinforcing fibers to be completely embedded in the outer skin.
This process provides superior puncture resistance and more than six times the tear resistance of an unreinforced skin. Further, the flexible closed-cell foam body provides an unsinkable construction.
For more information on Seaward Floating DONUT Dock Fenders and their applications, please contact Seaward.