PART SEVEN: ANCHORING SYSTEMS
can corrode and fail, so some recommend the
round pin, which uses a standard cotter pin
to secure it. The round-pin shackle also has
slightly less bulk to catch on things. The
safety pin is seldom used in anchor systems,
as the excess bulk makes it more likely to
snag.Swivels
Swivels on the anchor rode pose a conun-
drum. You can see that the strength of a swivel
is lower than that of a comparable shackle or
chain. Thus, you need to use the largest swivel
that will fit in order to match the WLL of the
rest of the rode. Further, galvanizing is proneto grind off a swivel, leading to faster corro-
sion. In general, I recommend that swivels be
avoided unless you expect to be anchored for
many days at the same location.
Because there is no galvanizing to come
off, stainless anchor swivels are generally su-
perior. Suncor makes stainless anchor
swivels with and without built-in toggles to fit
right on the anchor (Figures 23-6 and 23-7).
Note that Tables 23-9 and 23-10 for stainless
anchor swivels list their breaking loads, not
their working load limits (WLL): half-inch
( 1 3 mm) proof coil has a WLL of 4,500 pounds
(2,040 kg). Four times that (to get the break-
ing load) is 18,000 pounds (8,160 kg), which
matches well with the stainless swivel’s
breaking load. However,^3 / 4 - inch (19.8 mm)
high test is 20,200 pounds (9,160 kg) WLL.
Three times that (to get the breaking load for
high test) is 60,600 pounds (27,500 kg), which
is well over the breaking load of the stainless
swivel supposedly for^3 / 4 - inch (19.8 mm)
chain. So consider the strengths of the various
components and the chain carefully.Figure 23-4.
Chain or
D-shackle
(Courtesy Chicago
Hardware and
Fixture Co.)
TABLE 23-7. STAINLESS ANCHOR “BOW” SHACKLE SPECIFICATIONS
Inside Inside
Width@ Width@ Inside Inside Working Working
Nominal Wire Dia. Wire Dia. Pin Dia. Pin Dia., Eyes Eyes, Length Length Load Limit Load Limit
Size inches inches mm inches mm inches mm inches mm lbs. kg
(^3) / 16 3 / 16 4.76 (^1) / 4 6.35 (^3) / 8 9.95 (^7) / 8 22.22 650 295
(^1) / 4 1 / 4 6.35 (^5) / 16 7.94 (^15) / 32 11.91 11 / 16 26.98 1,000 454
(^5) / 16 5 / 16 7.94 (^3) / 8 9.52 (^1) / 2 12.70 11 / 4 31.75 1,500 681
(^3) / 8 3 / 8 9.52 (^7) / 16 11.11 (^5) / 8 15.87 17 / 16 36.51 2,000 907
(^7) / 16 7 / 16 11.11 (^1) / 2 12.70 (^3) / 4 19.05 15 / 8 41.27 3,000 1,361
(^1) / 2 1 / 2 12.70 (^5) / 8 15.87 (^7) / 8 22.22 113 / 16 46.04 4,000 1,815
(^5) / 8 5 / 8 15.87 (^3) / 4 19.05 11 / 16 26.98 25 / 16 58.74 6,000 2,722
(^3) / 4 3 / 4 19.05 (^7) / 8 22.22 13 / 16 30.16 27 / 8 73.02 8,000 3,630
(^7) / 8 7 / 8 22.22 1 25.40 11 / 2 38.10 37 / 16 87.31 10,000 4,537
1 1 25.40 11 / 8 28.57 15 / 8 41.27 33 / 4 95.25 12,000 5,445
Figure 23-5. Assorted shackles (Courtesy
Chicago Hardware and Fixture Co.)