| Tweet |
Custom Search
|
|
|
||
 TB 55-1900-232-10
(Text continued from page 2-5)
a.
Energy absorption
b.
Durability
c.
Handling characteristics
d.
Ease of storage aboard ship
e.
Ease of maintenance when not in use
f.
Required support equipment
g.
Weight
h.
Size
1.
Standoff distance
j.
End fittings
k.
Time required for deployment and recovery
l.
Capability of being used if damaged
Low-pressure and high-pressure pneumatic fenders have similar characteristics. However, because they are
filled with air they must be larger than foam-filled fenders to absorb the same amount of energy. On the other
hand, equal capacity and quality foam-filled fenders will likely be more expensive and heavier than pneumatic
fenders.
2-3.4.3 Operating Problems. In addition to the larger size of pneumatic fenders, other attending
disadvantages are the extra equipment needed to pressurize them and to check the internal pressure. Patch
kits and special slings to support the fender's mid-section when being deployed and retrieved are also
necessary for the low-pressure types. All pneumatic fenders have safety valves. When these valves relieve
under high fender loads, the fenders lose nearly all their energy absorption capability. There- fore, foam filled
fenders are recommended when there is a choice.
One major operating problem, with side fenders especially, arises when either the tug or the tow has a low
freeboard relative to the other ship When the heaving or rolling motions of the two ships get out-of-step, the
fender can be rolled upward between the two ships and pop out onto the deck of the one with the lower
freeboard.
When the freeboards are more nearly equal, the out- of-step motions of the two ships can create a great deal of
frictional heating on the surfaces of the fenders. It is often necessary to spray seawater onto the rubbing
surfaces to help lubricate them and keep them cool
Care must also be exercised in the fore and aft placement of the fenders to ensure that they do not bear
against relatively large areas of side plating that are not well supported by internal framing and longitudinal
structural members. This is especially important in quartering seas when swells will cause the two ships to
pivot about the bow or stern and then slam the sides together at the other end.
SECTION IV
2-4 TOWLINE CONNECTION
The towline connection between the tug and the tow is a complete system composed of many components.
Although the tow hawser has often been considered to be the "towline" or "towline connection, " it rarely is. In
reality, it is only one of the components in the complete towing connection system illustrated in Figure 2-9. The
towline connection system extends from the attachment point on the towed vessel to the tug's attachment point.
It includes the attachment points, the connecting components and end terminations of the ropes, chains and
other tension components that make up the various pendants, hawsers, etc. Each of these components is
defined and discussed briefly in the following paragraphs and more fully in succeeding sections of this manual.
24.1 ATTACHMENT POINT IN THE TOW. The attachment point on the tow may be a hard point specifically
intended for towing, such as a
2-15
|
||
|
||
