CASE STUDIES Ӏ DECOMMISSIONING
could then be lifted from the main deck to a supply vessel for later disposal or recycling. Located on the top deck there
were 14 large components weighing between 10 to 40 tonnes, as well as a number of smaller components of various weights below 10 tonnes. Since the existing platform crane capacity and reach radius was not sufficient for the project Thunder’s TC90 modular rental crane was proposed, which has a maximum capacity of approximately 60 tonnes for offboard lifts. The client had explored other
options for module removal; one such was to hire a barge crane. However, Thunder Cranes’ modular rental crane was the best solution from the viewpoint of ensuring safe static lifting, as well for cost and time savings.
The option of using the
platform’s own cranes for topside preparation and clearance was also considered. This would have involved 150 days of removal work by the platform crane. Since its capacity was limited, many lighter lifts would have been required, and modules would have had to be sectioned and removed one part at a time; this would have also involved the extra work of isolating and disconnecting all lines connected to equipment. 15 lifts over seven days by a heavy lift vessel would also have been needed; the total decommissioning would have taken 157 days. The alternative was to instal a
rental TC-90 crane to be used in addition to the platform’s crane. With this option the schedule would reduce to: 30 days of
Auto-Service
Safar removing a boiler
removal by platform crane alone; 90 days of removal by the platform crane and the TC-90 working together; and three lifts, over two days, by the heavy lift vessel. The total decommissioning would then take 122 days. The saving in time is therefore over a month; the saving in heavy lift vessel time (and associated costs) is a not inconsiderable five days; and the total cost saving was in the region of $USD 1.5-2.0 million. Not surprisingly, this was the option that was adopted. Performing the operation
was not straightforward. The platform had very limited space for rigging up and no exposed beams on which Thunder Cranes could apply its TC90 clamping system. Therefore welding with dog plates was required to
CRANES TODAY 37
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53
