UFC 4-159-03
3 October 2005
CHAIN AND FITTINGS. Chain is often used in fleet moorings because
6-4
chain:
Is easy to terminate
Can easily be lengthened or shortened
Is durable
Is easy to inspect
Is easy to provide cathodic protection
Has extensive experience
Is available
Is cost effective
Provides catenary effects
DOD commonly uses stud link chain, with each chain link formed by
bending and butt-welding a single bar of steel. Chain used in fleet moorings is Grade 3
stud link chain specifically designed for long-term in-water use (Naval Facilities
Engineering Service Center (NFESC), FPO-1-89(PD1), Purchase Description for Fleet
Mooring Chain and Accessories). This chain is designated as FM3. Properties of FM3
carried in stock are shown in Table 6-4. Anodes for use on each link of FM3 chain,
designed for diver replacement, are described in Table 6-5. Note that oversized anodes
may be used to extend the anode life and increase the time interval required for anode
replacement.
Older ships may use Die-Lock chain (not shown), which was made by
pressing together male and female parts to form each link. Die-Lock is not
recommended for long-term in-water use, because water may seep in between the male
and female parts. The resulting corrosion is difficult to inspect.
Chain routinely comes in 90-foot (27.4-meter) lengths called `shots'. A
number of other accessories are used with chain, as shown in Figure 6-1. For example,
shots of chain are connected together with chain joining links. Anchor joining links are
used to connect chain to anchors. Ground rings provide an attachment point for
multiple chains. Buoy swivels are used to connect chain to buoys. Refer to NFESC
TR-6014-OCN, Mooring Design Physical and Empirical Data and NFESC FPO-1-
89(PD1) for additional information on chain and fittings.
120
Previous Page
