8.4 CLOSED FAIRLEADS AND
PANAMA ... TVPE FAIRLEADS
Although the terms 'closed fa,irlead' and Panama fai.rlead' a,re often used interchange.ably, not all
closed chocks a,re 'Panama chocks'. Panama chocks must comply with Panama Canal reguJatiODS,
which slipuJate, among others, a nli.rumum sw-face radius (178 mm), a minimum throat opening
(300 x 250mm for single, 350 x 250mm for double type) and a safe working load (32t for single,
64t for double type (314 kN or 628 kN)).Closed chocks or Panama·type chocks are either deck mourued or bulwark mounted. BS MA 19
shows suitable standards for both types. The three sizes shown conform with Panama Canal regu-
lations, although the footnotes indicate that only (he IWO larger sizes are suitable.SmaUer size closed chocks whicb do not comply with Panama Canal regulations, can be found in
JIS F2005. The Japanese Industrial Standard also covers true Panama·type fairleads (liS F2017
gives sLx differem sizes from 310 x 260llun to 500 x 260mm, for both deck mounting and bulwark
mounting).
Information on allowable loads is scant. Neither 8S nor JlS lists the direction or number of applied
ropes. The BS lists tbe wire rope breaking load and JIS F2005 the diameter of 'applicable' wire and
soft ropes. Strength of these fittings does not appear to be a problem due to their substantial de ign.
Nevertheless, the method of altachmenJ to the deck or buJwark is important, and it is recommended
(hat the criteria listed in Table 4.3 of Section 4 be applied.
Some standards quote 'enlarged' type closed chocks. These are usually large tluoat opening size and
large radius fittings. They are especially useful with large diameter wires where the effect of bend
radius are significant. Where soft rope tails are used, [he size of the throat opening may have to be
of the enJarged type to allow fo r connector shackJes.8.5 ROLLER FAIRLEADS AND PEDESTAL FAIRLEADS
Tbe roHers resemble sheaves and may be mounted near the edge of the deck to serve as mooring
fairleads; or they may be mounted upon a pedestal elsewhere on the deck to provide a fair lead 10 a
winch drum or warping head. Deckside fairleads may be of the open or closed type. In the case of
the open type the roller pin is a cantilever attached at tbe base oruy. Almost all pedestal fairleads
are of the cantilever pin type. Expericnl:e has shown Lhat the cantilever pin and its attachment are
very critical: pin failure has been the cause of serious accidents. Pedestal fairlcads have also failed
at the pedestal-ta-deck connection due to improper design or workmanship.Roller fairleads and pedestal fairleads should be designed to meet the strength requirements of Table
4.3 of Section 4. Strength data avajlable for existing standard fillings i,~ inadequate to determine
the actual strength. Table 8.2 compares the BS and liS standards.As no clear design criteria are given in the standards, it is recommended that a prototype of an
aCLUaJ filling be strength tested to confirm compliance with the proposed criteria in Table 4.3 of
Section 4. Since the pin conne tion is the critical pan, the prototype testing must be carried out
using Ihe method of connection actually intended for the ship.Figure 5.5 in Section 5 shows an example of a pedestal fairlead designed for a wire breaking strength
of 85 [ (834 kN) with wire wrapped 1800 (170t IOtaJ load (J 667 kN)) and a safety factor as listed in
Table 4.3 of Seclion 4.