5 - nrg - flexibility
DESCRIPTION
NRG - FlexibilityTRANSCRIPT
Wall Thickness Design8 August 2006
The Power to Deliver™ #*
Purpose: To examine the stress levels under worst loading combinations and determine the adequacy of the riser/expansion spool wall thickness, expansion spool length, and verify that lower riser clamp location is acceptable.
NRG ENGINEERING
The Power to Deliver™ #*
Stresses are developed in the riser/expansion spool as a result of various environmental, operational and design factors. These include:
Pipeline expansion at the riser/spool end
Expansion of the riser/expansion spool due to pressure and thermal effects,
Stresses developed as a result of the internal pressure, expansion of the pipeline on the seabed due to pressure and thermal effects,
Jacket movement
Hydrodynamic loads acting on the riser/expansion spool,
NRG ENGINEERING
The Power to Deliver™ #*
A number of commercial programs are available in market to perform the flexibility stress analysis of riser and expansion spool, such as Autopipe and Caesar II.
The commercial program CAESAR II is used as illustration here.
This CAESAR software package is an engineering tool used in the mechanical design and analysis of piping system. The user creates a model of the piping system using simple beam elements and defines the loading conditions imposed on the system. It performs pipe stress analysis based on parameters such as temperature changes, pressure, system weight, anchor, support restraint, movements, wave, soil stiffness, flanges and the effect of support friction/guide support gaps. With this input, CAESAR II produces results in the form of displacements, loads, and stresses throughout the system. Additionally, CAESAR II compares the stress output with stress allowable specified by recognised codes and standards.
NRG ENGINEERING
The Power to Deliver™ #*
CAESAR II allows individual pipe elements to experience loading due to hydrodynamic effects. These fluid effects can impose a substantial load on the piping elements. The force calculation is based on riser diameter that includes the coating and marine growth thickness. The wave and current forces acting on the riser is calculated for the still water depths at the platform, in order to maximise the force.
Wave and current forces acting on the riser/dog leg are determined using Morison's equation. The drag and inertia force component is considered using the vector summations of the water particle instantaneous velocity (associated with the wave) and the steady current velocity.
NRG ENGINEERING
The Power to Deliver™ #*
The riser/expansion spool is modelled as a system of finite elements (nodes) supported by a system of anchors, restraints and seabed supports.
The design pressures and temperatures are specified as input-data, and the program calculates the resultant stresses and expansion of the riser/expansion spool.
The hydrodynamic loads acting on the riser/expansion spool are internally calculated using the Morison equation by CAESAR II, wave generator module are directly applied to the riser/expansion spool individual pipe elements to simulate loading on the riser due to hydrodynamic effects.
NRG ENGINEERING
The Power to Deliver™ #*
Nodal points are located at specific locations of the riser/expansion spool system such as riser clamp/support locations, platform displacements and marine growth.
The riser model limits are modeled as anchor points and the expansion of the pipeline on the seabed due to pressure and thermal effects is modeled as fixed displacements.
The platform displacements as defined are applied at the riser clamp locations.
The expansion spool is modeled as a system of finite elements (nodes) supported by a system of seabed supports with soil vertical spring stiffness.
The pipeline approach angles, riser slopes and bend angles are correctly represented in the 3-dimensional model.
NRG ENGINEERING
The Power to Deliver™ #*
(Elsie: to provide better example. This one doesn’t look impressive)
Node 1000, EL (+) 7.5 m
Hanger Clamp
Guide Clamp
The Power to Deliver™ #*
Elsie, we need one slide to show allowable stresses based on various codes, eg DBV 1981, DNV 2000, etc.
Also, a better 3-D model showing riser-spool before and after operation would good.
NRG ENGINEERING
The Power to Deliver™ #*
Purpose: To examine the stress levels under worst loading combinations and determine the adequacy of the riser/expansion spool wall thickness, expansion spool length, and verify that lower riser clamp location is acceptable.
NRG ENGINEERING
The Power to Deliver™ #*
Stresses are developed in the riser/expansion spool as a result of various environmental, operational and design factors. These include:
Pipeline expansion at the riser/spool end
Expansion of the riser/expansion spool due to pressure and thermal effects,
Stresses developed as a result of the internal pressure, expansion of the pipeline on the seabed due to pressure and thermal effects,
Jacket movement
Hydrodynamic loads acting on the riser/expansion spool,
NRG ENGINEERING
The Power to Deliver™ #*
A number of commercial programs are available in market to perform the flexibility stress analysis of riser and expansion spool, such as Autopipe and Caesar II.
The commercial program CAESAR II is used as illustration here.
This CAESAR software package is an engineering tool used in the mechanical design and analysis of piping system. The user creates a model of the piping system using simple beam elements and defines the loading conditions imposed on the system. It performs pipe stress analysis based on parameters such as temperature changes, pressure, system weight, anchor, support restraint, movements, wave, soil stiffness, flanges and the effect of support friction/guide support gaps. With this input, CAESAR II produces results in the form of displacements, loads, and stresses throughout the system. Additionally, CAESAR II compares the stress output with stress allowable specified by recognised codes and standards.
NRG ENGINEERING
The Power to Deliver™ #*
CAESAR II allows individual pipe elements to experience loading due to hydrodynamic effects. These fluid effects can impose a substantial load on the piping elements. The force calculation is based on riser diameter that includes the coating and marine growth thickness. The wave and current forces acting on the riser is calculated for the still water depths at the platform, in order to maximise the force.
Wave and current forces acting on the riser/dog leg are determined using Morison's equation. The drag and inertia force component is considered using the vector summations of the water particle instantaneous velocity (associated with the wave) and the steady current velocity.
NRG ENGINEERING
The Power to Deliver™ #*
The riser/expansion spool is modelled as a system of finite elements (nodes) supported by a system of anchors, restraints and seabed supports.
The design pressures and temperatures are specified as input-data, and the program calculates the resultant stresses and expansion of the riser/expansion spool.
The hydrodynamic loads acting on the riser/expansion spool are internally calculated using the Morison equation by CAESAR II, wave generator module are directly applied to the riser/expansion spool individual pipe elements to simulate loading on the riser due to hydrodynamic effects.
NRG ENGINEERING
The Power to Deliver™ #*
Nodal points are located at specific locations of the riser/expansion spool system such as riser clamp/support locations, platform displacements and marine growth.
The riser model limits are modeled as anchor points and the expansion of the pipeline on the seabed due to pressure and thermal effects is modeled as fixed displacements.
The platform displacements as defined are applied at the riser clamp locations.
The expansion spool is modeled as a system of finite elements (nodes) supported by a system of seabed supports with soil vertical spring stiffness.
The pipeline approach angles, riser slopes and bend angles are correctly represented in the 3-dimensional model.
NRG ENGINEERING
The Power to Deliver™ #*
(Elsie: to provide better example. This one doesn’t look impressive)
Node 1000, EL (+) 7.5 m
Hanger Clamp
Guide Clamp
The Power to Deliver™ #*
Elsie, we need one slide to show allowable stresses based on various codes, eg DBV 1981, DNV 2000, etc.
Also, a better 3-D model showing riser-spool before and after operation would good.
NRG ENGINEERING