Assessment of Existing Structures and Repairs - Offshore Structures: Design, Construction and Maintenance - page 529

New member

Clamp Clamp

Damaged member

FIGURE 7.35 Corroded member repair.

Clamp

FIGURE 7.36 Repair using clamps.

7.12.4 Dry Welding
Welding is often regarded as the best modification and repair technique for
strengthening and no doubt would be used even more often if it were not for
the operational difficulties in its execution. Several welding techniques and
welding processes can be considered:

Dry welding topside

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Dry welding at or below the sea surface at one atmosphere using cofferdam
or pressure-resisting chambers. All normal welding processes can be used,
but gas tungsten arc welding (GTAW), shielded metal arc welding
(SMAW) and, to a lesser extent, flux cored arc welding (FCAW) are the
main methods used in practice

●

Hyperbaric welding using habitats. The main processes used are GTAW and
SMAW, although FCAW and gas metal arc welding (GMAW) are some-
times employed.

●

Repairs by both cofferdam and hyperbaric habitat welding techniques have
proven track records. Since 1970, particularly in the North Sea, hyperbaric
welding has been used as an underwater technique.