Page 495 - Pipelines and Risers

462 Chapter 24

I Environmental had Combination I FlowlineContent I Phase I
~~
1 year significant wave and 1 year current Empty Installation
10 year significant wave and 100 year current (if Product filled Operation
current dominates)
100 year significant wave and 10 year current (if waves Product filled Operation
dominates)
Allowable Free Spans Design
Maximum allowable span lengths for the bundle system shall be calculated for both static and
dynamic loading conditions. Analyses shall consider all phases of the bundle design life
including installation, testing and operation. 1 year wave and current shall be considered for
as-installed and hydrotest conditions. Combination of 10 year wave and 100 year current or
100 year wave and 10 year current resulting in the higher environmental load shall apply to
operational conditions.

Bundle Expansion Design
The design shall take into account expansion andor contraction of the bundle as a result of
pressure and/or temperature variation. Design pressure and the maximum design temperature
shall be used in bundle expansion analysis. The presence of the sleeve pipe shall be taken into
account.

Bundle Protection Design
The bundle system shall be designed to against trawl loads outside the trawl free around the
installations. The flowlines and umbilicals shall be protected against dropped objects around
the installations. Carrier pipe and bundle towheads shall offer sufficient protection against the
dropped objects with impact energy of 20 kJ.

Impact loads from dropped objects for the protection structure design shall be treated as a PLS
condition.

Corrosion Protection Design
Cathodic protection design shall be performed according to relevant codes.
Cathodic protection together with an appropriate protective coating system shall be
considered for protection of the bundle external steel surfaces from the effects of corrosion.
Sleeve pipe will be protected from corrosion by provision of chemical inhibitors within the
canier annulus fluid.

Flowlines within the sleeve pipe will be maintained in a dry environment. Therefore, cathodic
protection system is not required.

Bulkheads and Towhead Structure Design
The bulkheads will form an integral part of the towhead assemblies. The towhead structures
shall remain stable during all temporary and operational phases. Stability shall be addressed