Wall Thickness DesignAugust 2 – August 28, by Mr. Eng Bin NG
Applicable Codes
Pipe Expansion Calculations
Flexibility Analysis Methodology
5
Pipeline Construction - Conventional & Unconventional
Weekending
Pipe Expansion Calculations, Flexibility Analysis Methodology
Allowable Free Span Calculations, On-bottom Roughness Analysis
Pipeline Protection against Anchors, Wave Liquefaction & Earthquake
Cathodic Protection Design
Pipeline Construction - Conventional & Unconventional
Installation Engineering
1 2 3 4 7 8 9 10 11 14 15 16 17 18 21 22 23 24 25 28
Workshop, revision, exercise
The Power to Deliver™ #*
The purpose of the thermal expansion calculations is to obtain the net thermal expansions at both ends of the pipeline.
Expansion in a marine pipeline is due to:
Pressure Effect
Temperature Effect.
Residual Tension
Longitudinal expansion in a pipeline is dependent on the temperature and pressure differentials, and the frictional resisting force between the pipeline and the seabed. At some distance from the hot and cold ends, the pipeline is virtually anchored when the forces producing the expansion are balanced by the cumulative effects of the soil frictional force.
NRG ENGINEERING
The Power to Deliver™ #*
When the pipeline is long enough, there will be a certain point at some distance from the pipeline end tie-in point, beyond which the pipeline can be considered as completely restrained. This is due to the static equilibrium of the expansion forces, the longitudinal soil friction and restraining forces.
Riser Clamp
Riser Clamp
Analysis Methodology
The methodology used in estimating the pipeline end expansion is based on the first principle of stress-strain relation.
The stresses acting in the pipeline wall resulting from the operating loads and friction resistance depend on whether the pipeline is unrestrained, partially restrained or fully restrained.
Calculation methodology adopted is based on Ling MTS & Palmer A. C. (1981) ’Movement of Submarine Pipelines Close to Platforms’, Paper OTC 4067, 1981.
NRG ENGINEERING
The Power to Deliver™ #*
=
=
=
=
=
=
D = Pipe outside diameter (without coating) (m)
t = Pipe wall thickness (m)
DT = Temperature difference at inlet (°)
x = Distance from ‘hot’ end (m)
l = Decay length over which the temperature difference falls to 1/e of its initial value (m)
Ws = Submerged weight of pipe (N/m) for unburied pipe
= Submerged weight of pipe + cover (N/m) for buried pipe
Ls = Virtual anchor length or ‘friction length’ (m)
A = Steel pipe cross section (m2)
N = Residual lay tension (N)
n = Poison’s ratio for steel
m = Longitudinal friction coefficient between pipe and soil
E = Elastic Young Modulus (MPa)0
NRG ENGINEERING
The Power to Deliver™ #*
=
=
=
The Power to Deliver™ #*
In the pipeline between free end and virtual anchored point, there is some restraint from soil friction, although not sufficient to prevent total movement. The stress-strain relation within the partially restrained section is given by:
=
=
The Power to Deliver™ #*
The end expansions at the hot and cold ends are calculated by integrating the net longitudinal strain and is given by:
Where LAHOT = Virtual anchor point at hot end
LACOLD = Virtual anchor point at cold end
L