Production • Processing • Handling
Leg mating units reduce cost of installing offshore platforms
New technology for installing production platforms offshore is providing a welcome reduction in costs.
L
Fig.1. Using LMUs during a float-over process, the loads can be transferred from the barge to the base structure in a controlled manner.
eg mating units (LMUs), deck support units and sway and surge fenders make a valuable contribution to the float-over method of installing the topsides of offshore oil and gas platforms from a barge.
Traditionally the topsides are lifted onto the
support structure or jacket by a floating crane. But the hire rates for such cranes are high, sometimes running into several hundred thousand dollars a day. Te float-over process provides a much less costly solution. But the crucial challenge, according to JP Chia, Engineering Manager at Trelleborg Singapore, is transferring the load from the barge to the jacket. Tis must be done in a controlled manner without causing damage to either structure, even though waves, currents or winds are causing the barge to move. Te LMUs are placed inside steel cans known as transition pieces, which are installed on top of the jacket legs. Meanwhile, surge and sway fenders absorb the impact of the barge on the jacket as it moves forward or sideways during the mating operation. Once the topsides have been safely transferred onto the jacket, the two structures are
welded together. Deck support units, or DSUs, come into play in the fabrication yard. Te topsides are transferred onto the barge on a deck support frame. DSUs positioned on the deck support frame absorb the weight of the topsides as they are placed on the frame. Trelleborg Singapore participated in two recent
float-over projects, including the installation of the BE and BG topsides for Maersk Oil Qatar. Te company performed full custom design, engineering, fabrication and testing. Each of the LMUs for the 13 000 ton BG topsides weighed 24tons, was 2metres in diameter and stood 3.7metres high. Trelleborg worked with technical service provider
GL Noble Denton. Trelleborg supplied 12 LMUs, which showed good performance and reliability during the topside float-over installation. One of the key benefits of the float-over solution is that nearly all the work on the topsides can be done in the fabrication yard, where labour costs are much lower. A floating crane would have had to make several lifts to install the BG topsides, after which extra work would have been required to hook up and commission the various modules. In float-over operations, the topsides of a
production platform, which may vary in size from less than 1000tons to more than 40 000tons, are installed from a barge. Te barge is towed to the field and positioned between the legs of the supporting structure or jacket. Te barge is then ballasted down until the topsides make contact with the jacket legs. When their entire weight has been transferred to the jacket, the barge is towed away In addition to LMUs, DSUs and fenders,
Trelleborg also supplies Orkot bearings to ease the skidding process of the topside onto the transport barge. Runners beneath the deck frame fit into grooves along which the topside is pushed using very strong strand jacks. Te Orkot bearings are placed in the grooves. Tey reduce the force that has to be applied to move the topsides, which may weigh tens of thousands of tons. ●
For more information,
www.trelleborg.com 40
www.engineerlive.com
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 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80