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Figure 5-14. Example of flexible pipe and couplings.

Two-part expandable polyurethane foams are also available. With these foams the buoy must first be pumped free of water. The two parts of the foam are then mixed together according to die manufacturer's directions and poured into the buoy. Care must be exercised to make sure that too much foam is not mixed. Also, gases given off from some of these foams may be hazardous. The user should check with the manufacturer before using these types of products.

5.4.1.1 Buoy Replacement. Partial replacement of the components of a fleet mooring is often all that is required to bring the mooring up to a level of normal service capacity. A defective riser mooring buoy (Figure 3-32) can be exchanged in place without removing the entire mooring.

• The mooring buoy is lifted by a surface-platform-mounted crane into the air and washed down with a high-pressure stream of seawater.

• The single riser chain is then secured to a corner bitt or cleat, and the buoy is separated from the riser chain by removing the detachable chain joining link or safety shackle located directly under the buoy on the padeye. If necessary, the chain may be cut with a cutting torch.

• New or refurbished joining links should be used to secure the replacement buoy to the riser chain.

• If new or refurbished joining links are not available, the existing joining link should be cleaned, coated with a preservative grease, and reused to secure the replacement buoy.

• The new mooring buoy is then lowered back into position.

The in-place exchange of telephone-type buoys is more complicated because of the increased number of connections of the ground leg chains to the buoy, but the procedure is essentially the same.

5.4.1.2 Mooring Leg Overhaul. In-place repairs may also include overhauling mooring legs. For this operation, a work barge should be outfitted with a double drum winch for chain inhaul and reinstallation and a work crane for anchor retrieval and reinstallation. To detach die bitter end of the mooring leg chain, slack must be provided at the padeye by rigging either the double drum winch or crane to take the load off the chain. Once the chain is slack, the bitter end can be detached, either by the chain joining link or safety shackle or, if necessary, by cutting with a cutting torch.

Mooring leg recovery, as illustrated in Figure 5-15, uses the double drum winch to recover the mooring leg over the bow of the work barge in a hand-over-hand fashion over a bow-mounted anchor chain roller.

• With the chain load transferred to a 1-inch winch inhaul wire, the chain is inhauled over the roller. The recovery should be accomplished with the in-water chain hanging vertically to the maximum extent possible, which requires the barge to transit backwards over the mooring leg.

• When the inhaul wire line is brought to the right-angle snatch block, die inhaul wire from the other winch is attached to the chain at the bow, the inhauled length of chain is secured to a 25-ton padeye near the snatch block, and the previous inhaul wire is removed.

Picture Snatch Block Operations

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