Page 241 - Pipelines and Risers

214 Chapter 12

200
~
0
0 1000 2000 3000
Water Depth (m)
I
I + 01 0" + 01 6" --b 024" --)c 036"

Figure 12.31 S-Lay of dry pipeline.

5 800
'G 8 600
5:
I- 0 400
$Z
~ 200
0 1000 2000 3000
Water Depth (m)
I
I + 01 0" + 01 6" +- 024" + 036"

Figure 12.32 S-Lay of wet pipeline.
The difference becomes even more noted when comparing J-Lay capabilities. To install the
same 016" pipeline in 2000m by J-Lay will require a tension of 200 tones, whether installed
wet or dry (Figure 12.33 and 12.34). The big benefit from the wet installation, apart from
requiring only half the material, is that existing equipment can install a 016" pipeline in over
4000m compared to over 2000m in the dry state. An observation from this study is that
installation of a 024" pipeline still requires very large lay tensions - even with J-Lay.
There is scope to reduce the submerged weight of the line by addition of buoyant insulation,
with this and flooding the line there is the potential to reduce lay tensions in 3000m to more
achievable lay tensions.