Flow Assurance Vessel Calcs and Structural Analysis 

Finite Element Analysis

We carry out Finite Element Analysis FEA and other analysis to characterise  structural response of buildings and other structures to various loads including : Fires and explosions dropped objects impacting subsea infrastructure ship energy and consequence. Analysis includes fatigue and creep as well as cycled creep associated with elevated temperatures. Material models used includes metals as well as nonlinear materials such as concrete.

Modelling includes transient loading with explicit solver for explosion loads and transient stress wave propagation. 

Software packages used include ANSYS, ABAQUS, NASTRAN, and others. 

Vessel Calculations 

We carry out analytical vessel fire risk studies for different types of pressure vessels. We are also able to take a more detailed approach by carrying out coupled FEA and CFD analysis with modelled jet fires impinging on the vessel and an FEA carrying out the heat up calculations for the vessel. We also assess the radiant heat loads as a result of impinging jet fire on  targets of concern with view to assessing requirements for PFP.

Blowdown (duration or pressure threshold), cladding vessel liquid evaporating contents are also taken into effect in this type of calculation.

Flow assurance - PIPESIM OLGA HYSYS CFD

Our company specialises in  complex flow problems. Our expertise extends to venting flaring and Depressurisation calculations where the purpose is often to calculate the lowest temperature of steel/alloy  fittings piping and vessels reach in order to prevent embrittlement which can cause catastrophic failures. 

In addition the formation of liquid droplets in gas pipeflows can also cause heavy damage at pipe bends or junctions and vibrations can also be induced from high speed flows. 

In general these problems are tackeled using PIPESIM HYSYS or OLGA. More complex problems where 3D fluid effects, turbulence or multiple flow  phases (liquid gas and foam ) are present can be tackled by the use of computational Fluid Dynamics CFD. 

Our staff have worked with companies around the world including BP Shell Woodside ADNOC Sour Gas ADNOC Gas Processing ADNOC Onshore ADNOC offshore Carigali Hess WorleyParsons FLUOR Technip Genesis and many other companies around the world. 

 

Flow Assurance Methodology

 

OLGA Study

 

The methodology for an OLGA study is relatively straight forward. A model of the pipeline system including inlets and outlets and other features such as restrictions/orifices are created.

 

 Model information should include the pipeline lengths and elevations as well as other physical dimensions such as diameter and roughness.

 

Information for pipeline materials including the pipe material itself (e.g. steel or aluminium) as well as insulation (if applicable) should also be included in the model. Thsi can automatically specify heat transfer coefficients ( specific heats etc) as well as pipe roughness which is important for turbulence quantification. 

 

Mass flow rates, fluid properties (such as density, specific heats and others) are added to the model and initial conditions including initial pressures temperatures, composition and quality are also specified.

 

Flow scenarios are then modelled to obtain relevant pressures and temperatures. Typical scenarios involve pressure checks temperature checks and low temperature effects for high speed gas flow (such as venting, depressurisation or flaring) causing embrittlement are typical outcomes that are verified with these types of studies.  Slugging is also a typical feature of the flow that is commonly investigated. This results in high internal forces on pipelines particularly at bends or high gradient elevation changes.

 

Recommendations are made with reference to material selection for piping as well as flow parameters or design features which can prevent or mitigate the elevated pressures or temperatures in the class of investigated scenarios.

 

Surge Study

A model of the crude or water pipe system is created in the software (such as TLNET / Pipeline Studio-Liquid or Bentley Hammer) is created.

 

This includes pipe lengths, diameters, restrictions and connections such as valves and pumps.

 

Important features of the model include the pipeline profile (especially the elevations and location of  high points), Pipeline and lining Material, inventory locations, connections (such as valves or pumps). Pump characteristics (performance curves and operating speeds as well as moments of inertia) are also included in the model. 

 

Scenarios where Surge is a risk are then investigated using the model set up.  These include among others:

 

– Pump Start-up/ Shut down

– Loss of power

– Valve Shutdown

– Air pocket or vacuum creation or rapid removal

 

Surges associated with the above cases can be identified and recommendations made with regard to prevention and mitigation such as flow rate control or surge control are usually the conclusions of such a study.

 

PIPESIM Overview

PIPESIM is a flow simulation software program that’s used for modeling multiphase flows. Mid-sized and large companies in both the oil and gas industry use PIPESIM to understand the behavior of fluids in their systems. As part of normal use, PIPESIM can optimize production and identify and diagnose operational challenges with the help of its computational fluid dynamics (CFD) capabilities. more at 

 

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