Retrofit of Real Time Impressed Current Cathodic Protection · Retrofit of Real Time Impressed...

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© 2016 Aquatec Group Retrofit of Real Time Impressed Current Cathodic Protection MAKING LIFE EXTENSION A VIABLE OPTION Andy Smerdon CEO, Aquatec Group Oceanology International, London, 16 March 2016

Transcript of Retrofit of Real Time Impressed Current Cathodic Protection · Retrofit of Real Time Impressed...

Page 1: Retrofit of Real Time Impressed Current Cathodic Protection · Retrofit of Real Time Impressed Current Cathodic Protection ... IMPRESSED CURRENT CATHODIC PROTECTION ... •Standard

© 2016 Aquatec Group

Retrofit of Real Time

Impressed Current Cathodic

Protection MAKING LIFE EXTENSION A VIABLE OPTION

Andy Smerdon – CEO, Aquatec Group

Oceanology International, London, 16 March 2016

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© 2016 Aquatec Group

Overview

• Introduction to Aquatec

• Cathodic Protection (CP) Primer

• The Problem

– Ageing Offshore Structures

• The Solution

– Retrofit CP System

– Real-Time CP Monitoring

– Controlling the System

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© 2016 Aquatec Group

Aquatec Group Ltd

• Founded in 1990

• Headquartered in Basingstoke UK

• Design and manufacture all products and engineered solutions

• Products sold worldwide

• ISO 9001, ISO 14001 BS OHSAS 18001

Customers in the offshore market

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Cathodic Protection Primer

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Steel in Sea Water WHY DOES STEEL CORRODE IN SEA WATER?

• Galvanic corrosion – requires three conditions:

1. Two dissimilar metals

2. Both immersed or in contact with the same electrolyte

3. An electrical connection or joining of the two metals

• The two dissimilar metals may be different – for example

steel and aluminium.

• They may be a single piece of the same metal with

metallurgical differences at the surface

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Corroding Steel

• Two similar steel plates welded together and immersed in sea water fulfil the three conditions for galvanic corrosion because the conditions at the surface vary according to depth and water composition

• The following corrosive reaction takes place at more active sites:

• The free electrons travel through the steel to less active sites, where the following reaction takes place:

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Corroding Steel

• Recombination of these highly reactive ions at the active

surface produces the iron corrosion product ferrous

hydroxide:

• This reaction leads to current flow through the sea water

from the more active site (anode) to the less active site

(cathode), and the iron is depleted

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© 2016 Aquatec Group

Control of Corrosion FOUR METHODS

– Material selection – design

avoid galvanic cells

– Coatings

isolate metal from oxygen

– Environment

remove the oxygen

– Change the potential

cathodic protection

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© 2016 Aquatec Group

Cathodic Protection (CP)

• CP controls corrosion of a metal surface by making all of

it work as the cathode of an electrochemical cell

• CP prevents corrosion by converting all of the anodic

(active) sites on the metal surface to cathodic (passive)

sites by providing free electrons (electrical current) from

another source.

• There are two types of CP…

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© 2016 Aquatec Group

Sacrificial Anode CP (SACP)

• Sacrificial Anode CP

supplies the

protective current

through the

attachment of

preferentially

corrosive metals

(e.g. Zinc,

Magnesium,

Aluminium).

The anode metal is sacrificed and depleted over the lifetime of the installation.

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© 2016 Aquatec Group

Sacrificial Anode CP (SACP)

• Sacrificial Anode CP

supplies the

protective current

through the

attachment of

preferentially

corrosive metals

(e.g. Zinc,

Magnesium,

Aluminium).

The anode metal is sacrificed and depleted over the lifetime of the installation.

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© 2016 Aquatec Group

Impressed Current CP (ICCP)

• Uses permanent, non-corroding anodes supplied with an

external power supply

• Power supply acts

as ‘electron pump’

• Electrons are driven

from the anode to

the cathode

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© 2016 Aquatec Group

ICCP In Practice

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The Problem

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© 2016 Aquatec Group

The Problem

• Exploitation of offshore oil expanded in the 1970s.

• Platform design life based on estimates of reservoir yield

• 5-25 year life extensions now needed thanks to – Extended discoveries, satellite wells

– Enhanced oil recovery techniques

– Tax breaks for “brown field” development

– Small lean operators taking over from majors

• Sacrificial CP on older platforms now depleted and protection is failing

• Older ICCP systems often damaged or failing

• Regulators require reinstatement of adequate protection levels

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© 2016 Aquatec Group

An Example

• UK North Sea platform

• 38 years old

• Requirement for 15

year life extension

• ICCP selected as

optimum method

• Near real-time updates

of cathodic protection

potentials required for

closed-loop control

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© 2016 Aquatec Group

An Example

• UK North Sea platform

• 38 years old

• Requirement for 15

year life extension

• ICCP selected as

optimum method

• Near real-time updates

of cathodic protection

potentials required for

closed-loop control

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© 2016 Aquatec Group

The Solution

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© 2016 Aquatec Group

The Solution IMPRESSED CURRENT CATHODIC PROTECTION (ICCP)

• ICCP Anode Skids

• ICCP Power Supply

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© 2016 Aquatec Group

Component Locations

1

2a

2

3

4

100A SKID

200A SKID

100A SKID ALTERNATIVE POSITION

JUNCTION BOX

POWER CABLE ALTERNATIVE

1

2a

POWER CABLE

KEY:

590m

30m

60m

40m

45m

NOTES:

ICCP SYSTEM CONCEPT ANNOTATIONS ADDED

BY FRAZER-NASH CONSULTANCY.

ANNOTATIONS ADDED TO TRIDENT OFFSHORE

DUNLIN APPROACH CHART (REF: TRI-MAR-5549

rev.A 20/07/2008)

DRAWN BY

DATE

CHECKED BY

SHEET

P.MUTTON

12/06/13

J.HORTON

REV A

Frazer-Nash Consultancy,

Stonebridge House,

Dorking Business Park,

Dorking,

Surrey RH4 1HJ, UK

Tel. +44 (0)1306 885050

1 of 1

Skid 1

Skid 2

Skid 3

Skid 4

PSU

J-Tube + JB

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© 2016 Aquatec Group

How to Control the System?

• Existing SACP provides some residual protection

• ICCP must be set to supplement this

• Should not ‘over protect’ the steel as this can cause

damage

• Standard practice is to monitor the Cathodic Protection

potential

• Goal: to provide automated monitoring with remote

access

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© 2016 Aquatec Group

Monitor CP Potential

• Use reference electrode as datum to form half cell with

the cathode (steel structure)

• Reference electrode

– Maintains constant

potential

• Practical electrodes:

– Silver/Silver Chloride

+0.27 V re Hydrogen

– Zinc -0.77 V

– V2-V1 1.04V

Cath

ode (

ste

el)

Ag/AgCl

Zn Sea

V1

V2

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© 2016 Aquatec Group

Monitor CP Potential

• AQUAmodem 500CP real-time CP

potential monitor units

• Measure steel potential with respect to

Zinc & Silver/Silver Chloride electrodes

• Transmit data up to every 15 minutes

using acoustic telemetry

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© 2016 Aquatec Group

Monitor CP Potential

• Steel case in contact with

cathode (steel platform)

through:

– Mechanical clamping

arrangement (ROV or diver

installed) 900mm clamp shown,

or

– Mechanical banding, or

– Friction welding

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© 2016 Aquatec Group

Acoustic Telemetry: Pros & Cons

Pros Cons

Long range potential Slow

Cheaper than long

cable runs

Needs power:

especially for 2-way

Cheaper to install

than cable

Busy communication

channel

Can be more robust

than cable

Acoustic path can be

problematic

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© 2016 Aquatec Group

‘Send and Forget’ concept

• System Analogies

1. Static meter display - check when passing or on a schedule

2. Heartbeat monitor - periodic tick shows system is healthy - alarm and increased data when faulty

• Measure data at preset rate

• Transmit data infrequently if all is well

• Increase update rate when alarm conditions are met

• Transmission is automatic – no interrogation needed from the surface

• Only powered up when reading data or transmitting

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© 2016 Aquatec Group

Monitor Units at Key Positions

1

2a

2

3

4

100A SKID

200A SKID

100A SKID ALTERNATIVE POSITION

JUNCTION BOX

POWER CABLE ALTERNATIVE

1

2a

POWER CABLE

KEY:

590m

30m

60m

40m

45m

NOTES:

ICCP SYSTEM CONCEPT ANNOTATIONS ADDED

BY FRAZER-NASH CONSULTANCY.

ANNOTATIONS ADDED TO TRIDENT OFFSHORE

DUNLIN APPROACH CHART (REF: TRI-MAR-5549

rev.A 20/07/2008)

DRAWN BY

DATE

CHECKED BY

SHEET

P.MUTTON

12/06/13

J.HORTON

REV A

Frazer-Nash Consultancy,

Stonebridge House,

Dorking Business Park,

Dorking,

Surrey RH4 1HJ, UK

Tel. +44 (0)1306 885050

1 of 1

M1

M2

M3

M4

M5

M6

M7

M8

M9

M10

M11

M12

M13

M14

Mobile

Rx

Skid 1

Skid 2

Skid 3

Skid 4

PSU

J-Tube & JB

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© 2016 Aquatec Group

AQUAmodem 500CP Acoustics

• ‘Send and forget’ principle

• Read data infrequently e.g. every 15 minutes

• Transmit every hour unless alarm condition is detected

• Transmit every 15 minutes if alarm is detected

• Message collision avoidance:

– Two transmissions every update period

– Separated by random interval

• Message includes error checking and correction

• Decoding includes multiple validation stages to minimise

false alarms

• Range up to 600 m

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© 2016 Aquatec Group

Closed-Loop Control

• Monitor all potentials

– continuously in near real-time

– using acoustics

• Adjust current output on each skid

• Calibrate system response

• Control current on basis of measured potentials

• Ensure adequate but not excessive protection

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© 2016 Aquatec Group

Complete System

• Fully integrated system

• Monitoring

• Impressed Current CP

• Closed-loop control

Monitor 1 of 14

ICCP Anode Skid 1 of 4

Hydrophone

CP data to PSU

Current from PSU

JB

PSU

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© 2016 Aquatec Group

What About Sacrificial?

• Potential Monitoring

• Current Monitoring

• Sacrificial Anode CP

• Data logging

• Allows refinement of model

Potential Monitor

Sacrificial Anode Skid Current Monitor + Data Logger

Hydrophone

Return Current

Sense Potential Drop

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© 2016 Aquatec Group

AQUAmodem Op1 FOR REAL TIME DATA AND DATA RECOVERY

Optical Modem

for rapid data

download

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© 2016 Aquatec Group

Summary

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© 2016 Aquatec Group

Summary

• Retrofit CP solution for ageing offshore platforms and pipelines

• Compact and efficient power supply

• Easily installed seabed equipment

• Acoustic comms removes need for cabled monitoring

• Real-time acoustics provides closed-loop control

• Capability for sacrificial current monitoring and logged data retrieval

• A viable CP solution for life of field extension

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© 2016 Aquatec Group

Thank you

Any questions?