Page 494 - Pipelines and Risers
P. 494
Pipe-in-Pipe and Bundle Systems 461 '
HOOP stress
The hoop stress criterion is in principle applicable for the bundle system with the following
special considerations.
The allowable hoop stress for flowlines and heat-up lines in Safety Zone 1 and those inside
the bundle carrier in Safety Zone 2 shall be limited to O.S*SMYS.
The allowable hoop stress for the riser pipe, spool pieces and towhead piping in Safety Zone 2
shall be limited to 0.67*SMYS.
Collapse due to extern1 hydrostatic pressure
Wall thickness shall be designed to avoid pipe collapse due to external hydrostatic pressure. A
collapse analysis may be performed in accordance with Chapter 3. The carrier pipe and the
sleeve pipe shall be pressurized to a pressure one bar greater than the maximum external
pressure at the deepest point in the installation area to prevent collapse.
Local buckling
The flowlines, sleeve pipe and carrier pipe shall be designed to withstand local buckling due
to the most unfavorable combination of external pressure, axial force and bending. The design
may be carried out in accordance with Chapter 4.
On-bottom stability
The wall thickness design shall be adequate to ensure the on-bottom stability of the bundle
without any additional means.
Installation stress
The wall thickness shall be adequate to withstand both static and dynamic loads imposed by
installation operations.
Hydrotest and operational stresses
The wall thickness shall be adequate to ensure the integrity of the flowlines, sleeve pipe and
canier pipe under the action of all combinations of functional and environmental loads
experienced during hydrotest and operation.
On-Bottom Stability Design
The bundle system shall be stable on the seabed under all environmental conditions
encountered during installation, testing and throughout the design life. The bundle shall be
designed with sufficient submerged weight to maintain its installed position, or to limit
movement such that the integrity of the bundle system is not adversely affected.
On-bottom stability shall be verified in accordance with Chapter 8 for the following cases:
