Technical Presentations at the April 2011 Meeting

1.1  Corrosion Fatigue Testing of Tensile Wires for Flexible Pipelines’, Paul Wood, CAPCIS 

CAPCIS has developed corrosion fatigue testing facilities to determine the behaviour of armour wires used to give strength to flexible flowlines in both production and water injection flowlines. 

The purpose of fatigue testing is to determine the fatigue properties of the pressure armour and tensile armour wires located in the annulus of flexible pipelines.  The results are used by the client in collaboration with full scale testing to make service life predictions of flexible lines. The result from a corrosion fatigue test is an S-N Curve (stress range plotted against the log of the number of cycles to failure). 

CAPCIS currently has 12 fatigue rigs set up at its Trafford Park Testing facility: 

Number

of Rigs

Manufacturer

Capacity

Pressure

Rating

Power

System

1

SI Plan

10kN

Ambient

Air

2

Instron

25kN

Ambient

Hydraulic

5

Instron

25kN

Up to 20bar

Hydraulic

1

Servotest

100kN

Up to 70bar

Hydraulic

3

Instron

100kN

Up to 70bar

Hydraulic

Corrosion fatigue testing is carried out in environments specified by the client (flexible pipeline manufacturer) according to the end users requirements. Information on well fluids, pressure and temperature conditions are supplied by the end user to the manufacturer.  The manufacturer then carries out permeation calculations and environment predictions and specifies the environment to CAPCIS to carry out the corrosion fatigue testing. Typical environments include, 

·        Deaerated, gas-containing liquid.

·        Aerated seawater.

Saturation of the aqueous environment with a gas mixture simulates permeation of gases from the bore into the annulus of the pipe.  Testing in aerated seawater simulates rupture of the outer sheath.

 

1.2    Optimization of Retrofit CP Systems using Mathematical Modeling by Evaluating Performance of Remnant and Retrofit CP Systems, Taking into Account Long-term Polarization Effects’, John Baynham, BEASY  

Installation of retrofit sacrificial anode CP systems to aging structures is routinely performed to provide life extension of offshore assets in matured fields.  Sometimes earlier retrofit systems are now being replaced or supplemented. 

It is important to understand when the remains of previous CP systems can no longer prevent depolarization, because timely intervention can reduce overall retrofit cost.  Life of the new CP system must be some required number of years, and ideally the design should take into account performance of any remaining anodes and the state of calcareous deposits on the structure.  Data which can be used to help identify the state of calcareous deposits and remaining anode mass is generally available from past surveys. 

During design of a retrofit system, simulation can be used firstly to gain quantitative understanding of the state of the structure, remaining life of existing anodes and estimated date at which serious loss of calcareous deposits will occur.  Secondly, it can determine the short-term effect of a new CP system on structural potentials.  This information can be used to modify the numbers, positions and mass of new anodes in a revised design.  This process optimizes distribution of potential and anode mass loss rates. 

The same techniques can be used to weigh up the benefits of fewer large versus several smaller anodes. 

Finally, simulation can be used to determine the long-term effects of new, old, and combined CP systems, for example to identify when individual anodes reach their utilization factor and the consequent effect on the remainder of the structure. 

The aim of this presentation is to demonstrate the above techniques using a case study for which simulation has been applied to a jacket structure, using “long-term” polarization curves to represent accumulation of calcareous deposits.  [j.baynham@beasy.com]

A pdf version of this presentation has kindly been provided for staff of MCF member companies – please contact the Secretariat for a copy  

Back to Minutes

1.3   Is There Value in Translating New Wireless Corrosion Monitoring Technologies to Upstream Oil and Gas?’, Adrian Bowles, QinetiQ 

Recent years have seen an increase in the commercial availability of advanced corrosion monitoring systems that promise greater convenience and the provision of improved quality data.  This presentation will be a brief overview of these advanced monitoring techniques and the advantages they can bring over more traditional methods of monitoring corrosion. 

The first half of the presentation will review the deficiencies of traditional corrosion monitoring techniques before putting forward criteria for the perfect technology.  Eight of the most advanced permanently installed corrosion monitoring systems will then be evaluated against these criteria.  

A limited number of corrosion monitoring technologies offer a wireless data transmission solution to reduce the costs of installing cabling and performing manual interrogation.  Industrial facilities are harsh environments for radio frequency communication and the second half of the presentation will explore reliable wireless technologies designed to operate in heavy industry and the unique challenges that may be presented by upstream oil and gas facilities.   Finally, traditional and advanced corrosion monitoring techniques will be compared using data from manual ultrasonic measurements and an automated, wireless, permanently installed system to illustrate the value a wireless corrosion monitoring technology could bring.  [arbowles@qinetiq.com]

 

3.1    An Introduction to Asset Corrosion Management in the (Offshore) Oil Industry’, Ali Morshed, Wood Group Integrity Management 

This presentation started by providing definitions for both corrosion engineering and corrosion management in the oil and gas industry and then focused on the ten corrosion management products which if are missing or are not applied properly, could adversely affect the overall integrity management (of the associated pressure systems) of an offshore asset.  All discussions were based on past cases encountered either in the UK’s North Sea Sector or elsewhere.  [Ali.Morshed@wgim.com]

A pdf version of this presentation has kindly been provided for staff of MCF member companies – please contact the Secretariat for a copy. 

 

3.2   QA/QC Tools for Duplex Stainless Steels – How to Get What You Ordered’, Roger Francis, Rolled Alloys 

It has long been understood that the heat treatment of duplex and superduplex stainless steels is critical to obtain the optimum structure and the desired properties.  Over the last twenty years there have been a number of cases where inadequately heat treated components have been delivered by the manufacturer and then subsequently identified as defective further down the supply chain.  In some cases the problem was identified and resolved prior to fabrication and installation, in others fittings have leaked in service due to poor microstructure from incorrect heat treatment. 

Common to all these cases is that the cast and batch production test certificate indicated that the goods met specification requirements in all respects.  Hence the similitude between cast and batch specific test pieces and the production parts has been called into question.  There has been extensive discussion on how best to test individual components non-destructively to detect unsatisfactory material.  Some have suggested that magnetic measurement of the ferrite content is adequate, whilst others believe the test to be insufficiently discerning, resulting in too many good parts falsely being identified as “suspect” and causing unnecessary remedial action.  Various electrochemical tests to assess individual item quality have also been proposed.  

The present paper described the strengths and limitations of magnetic ferrite measurements and showed how the readings are affected by manufacturing route, product form, surface roughness and radius of curvature.  The paper went on to show how the test can be used to identify material that may contain sigma phase and that in-situ metallography is then required on these suspect areas to either release the part or condemn the part to remedial heat treatment.  The results of five years successful experience with this combination of tests was discussed.

 Back to Minutes