UFC 4-152-01
28 July 2005
a. Pneumatic / Hydro-Pneumatic Fenders. The potential energy in these
fenders is stored by the elastic compression of a confined volume of air.
By varying the internal pressure of air, the energy-absorption
characteristic can be changed. To prevent the air pressure from
increasing to a "blowout" level, pneumatic fenders are provided with a
relief valve or deflection limiter within the body of the unit. The shell
construction for these fenders is similar to an automobile tire with several
laminations to provide the high tensile strength required. The surface
pressure of these fenders is uniform, resulting in uniform hull pressure.
Reaction force is an exponential function of deflection. The basic types of
pneumatic fenders in common use are discussed below:
Air Block and Air Cushion. The shells for these are chemically
bonded and mechanically coupled to a rigid mounting plate that can
be attached to a solid face of the berthing structure. See Figures 5-
11(C) and 5-11(D).
Floating. The floating type is usually cylindrical in shape with
hemispherical ends and is attached to the structure by chains. It
floats on the water and rises and falls with the tide. The unit
requires a backing system to distribute the load. As shown in
Figures 5-11(A) and 5-11(E), large floating pneumatic types are
sometimes covered with a net of used automobile tires and
cylindrical rubber sleeves to protect the fender from puncture and
abrasion. The tire net and chains also form the means for rigging
and attaching the fender to the pier.
Tire. This type consists of a large-diameter tire mounted on an axle
and backed by rollers. The unit can be mounted with its axis of
rotation vertical or horizontal. This type is particularly suited for
pronounced corners of the structure where ships may have
approach difficulties. See Figure 5-11(B).
Hydro-Pneumatic. This type of fender has been developed for use
with submarines and consists of a vertically mounted cylindrical
pneumatic fender partially filled with water and backed by a closely
spaced group of fender piles. A ballast weight is added to adjust
the degree of submergence of the fender to coordinate the vertical
center of the fender with the horizontal center of the submarine hull;
see Figure 5-12. The fender unit floats with the tide and therefore
stays in the same relative position with the vessel. For 11-ft (3.3 m)
diameter by 32 to 35-ft (9.7 to 10.7 m) high submarine hydro-
pneumatic fenders, a vertical and horizontal skin strength of 4,600
lbs/in (82.1 kg/mm) is required. Reduce the hanging counterweight
as much as practically feasible. For the fender size mentioned, a
hanging counterweight around 13,900 lbs (6305 kg) is
recommended.
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