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l -<br />
128<br />
I<br />
PENROD 74<br />
During the construction of Penrod<br />
74 in Singapore, a historic joining<br />
operation took place last December,<br />
five miles at sea near the southern<br />
isle of Pulau Sebarok. No operation<br />
of this kind has previously been<br />
performed outside the USA and<br />
(very recently) Spain, and it was a<br />
considerable achievement for Singapore's<br />
Far East Levingston Shipyard.<br />
The problem was how to place the<br />
upper hull on top of the columns.<br />
It was impossible to lift it into position<br />
due to its tremendous weight,<br />
4,000 tons. The method employed<br />
was to sink the lower section, float<br />
the upper hull over its top, and then<br />
raise t he whole structure by deballasting.<br />
T he combined lower hulls/columns<br />
and the upper hull were towed<br />
separately to the site about 15 miles<br />
from the shipyard. The site was<br />
chosen for its depth of 25 fathoms<br />
w ith a manoeuverin g radiu s of 1500<br />
feet away from sea traffic. T he lower<br />
section was sunk by flooding until<br />
only 12 feet of the columns stood<br />
above the sea surface. Then t he<br />
upper hull, resting on a huge pontoon<br />
was gradually floated across the tops<br />
of t he columns. At t he critical point<br />
of alignment, the lower section was<br />
raised to slot into the upper hull and<br />
welded on. There was a tiny clearance<br />
of only 3 inches for the pontoon<br />
carrying the upper hull to slot in<br />
between the tops of the columns,<br />
b:"Jttling against a choppy sea w ith<br />
swift currents. Clearly the operat:on<br />
was a tremendous achievement in<br />
terms of delicate engineering man-<br />
3 oeuvers.<br />
Shipyard personnel had made elaborate<br />
preparations for this exciting<br />
project. Some 200 men on 2 shifts<br />
worked on t he rig at the sea location<br />
in addition to the details of transportat<br />
ion, accommodation, food, supplies,<br />
equipment power, communications,<br />
safety, emergency arra ngements and<br />
insurance which had to be w orked<br />
out.<br />
l ower hull and columns being towed<br />
out to sea for the joining operation.<br />
2 l ower hull and columns being sunk to<br />
110 ft depth by Electronic Ballasting<br />
Control.<br />
3 Upper hull being positioned over the<br />
columns.<br />
4 l ower section was raised t o slot into<br />
4 the upper hull and welded on.
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