corrpro ac mitigation
TRANSCRIPT
2016 OCC Pipeline Safety Conference2016 OCC Pipeline Safety Conference2016 OCC Pipeline Safety Conference2016 OCC Pipeline Safety ConferenceMay 10 through 13, 2016May 10 through 13, 2016May 10 through 13, 2016May 10 through 13, 2016
Corrpro
Hector Hernandez
Matthew Coburn
Who is Corrpro?
• The world’s leading provider of corrosion control and integrity engineering services
• Exclusively involved in condition assessments and corrosion prevention with over 50 years of experience
• Corrpro offices:• US = 26• Canada = 10• UK = 3• Saudi Arabia = 1
• 887 employees (500+ engineers, technicians and support staff) • Specific expertise in pipeline / tank integrity and asset management
Corrpro Technologies & Services
• Corrosion prevention engineering
• Corrosion and soil/groundwater laboratory testing
• Material selection
• Cathodic protection design and construction (EPC)
• AC and DC interference modeling and mitigation
• Internal corrosion control programs
• Protective coating technology
• Condition assessments
• Corrosion monitoring systems
• Pipeline integrity management programs
An Introduction to AC Interference Effects on Pipelines
• Background
• Utilidors
• Criteria
• Options
• Testing
• Mitigation
• Monitor
Many Complex Factors Contribute to AC Interference & Determining Effective Mitigation
• Coating Quality and Cathodic Protection
• Pipeline vs. Transmission Line Geometry and Proximity
• Length of Parallelism and Crossings
• Variations in Soil Resistivities
• Electrical Breaks in Pipeline, e.g. Isolation Flanges
• Transmission Line Conductor Configuration
• High Steady State Current / High Voltage Magnitude
• Transmission Line Phase Transpositions
• Electrical Fault Currents
• Tower grounding and Shield/Sky Wires Connecting Towers
Causes:“Utilidors” - Joint Utility Corridors
• Rights-of-way are increasingly difficult to obtain for new pipeline projects and for new power line projects
• An attractive option is shared rights-of-way, i.e. “Utilidors”
• Future projections are for more and more Utilidors
• Utilidors can range from a few thousand feet to 1000+ miles
Causes: “Utilidors” - Joint Utility Corridors
• Shared ROW
• Congestion
• Demand
• Coatings
• Growth
• Regulated
AC Mitigation & Control - North American Standards/Codes and Regulations
• NACE International SP0177
• IEEE – Institute of Electrical Electronic Engineers
• CSA – Canadian Standards Association
• CFR 192 & 195
• OQ, Operator In-House
• 15 VAC Above and Below Grade
• AC Current Density: 20 A/m² - 100 A/m²
• Coating Stress Voltage: 3,000 to 5,000 volts for FBE
Safety: AC Interference Concerns
Safety – Step & Touch Potentials
• General Public
• Company Personnel
• Livestock & Other Animals
Pipeline Integrity / Asset Protection
• Impact on CP effectiveness & monitoring
• AC Corrosion
• SCADA & Other Equipment Reliability
• Coating Damage
• Pipe Wall Integrity
Steady-State AC Interference on Pipeline from Changing Electromagnetic Field
Magnetic Field Produced By
AC Current In Overhead Lines
Pipeline
Soil
Options and Solutions
• AC Interference Causes & Concerns
• Induced AC
• Power Line Faults
• AC Current Densities
• AC Interference Mitigation Solutions
• Front-End Engineering Analyses
• Materials and Methods
• Safe Construction Practices
AC Impact From A Power Line Fault
Fault Current
Shield (“Sky”) Wire To
Adjacent Towers
Counterpoise Cable To
Adjacent Towers
Underground High-Voltage AC Transmission Systems
PipelinePipeline
A
B
C A
B
C
Copper Ground Cable (Typ.)
PipelinePipeline
A
B
C A
B
C
Steady-State
Power Line to Ground
Fault
Help! Help! Help!I need criteria for AC corrosion!
• AC Safety:• NACE SP0177 – 15 Volts
• AC Corrosion:• European Standard CEN-EN 15280 – Almost done
• PRCI AC Corrosion Research (Elsyca/Corrpro/MetriCorr)
• NACE TG430 – Standard practice is under construction
Common AC Corrosion Thresholds
AC Current Density AC Corrosion Significance
Less than 2-3 A/Ft.2 (20-30 A/m2) No or Low Likelihood
3 – 10 A/Ft.2 (30-100 A/m2) Medium Likelihood
Greater than
10 A/Ft.2 (100 A/m2)
Very High Likelihood
Even in the Presence of Apparently Effective CP
Qualitative only! Nothing about rate of corrosion, which is what really counts! Right?
Factors that Influence AC Corrosion
Likelihood of AC corrosion can be determined by approximating the AC current density using Ohm’s Law:
where,
i = AC current density
VAC = AC voltage of pipeline to remote earth (which is where?)
ρ = soil resistivity (at holiday, not bulk soil – how do I measure?)
d = diameter of a circular holiday having an area equal to that of the actual holiday (million $ question!)
d
Vi
AC
ρπ
8=
Dangerous Equation! Use at your own risk!
Datalogging reveals conditions overlooked by instantaneous (“spot”) measurements
0
5
10
15
20
25
30
12:00 PM 6:00 PM 12:00 AM 6:00 AM 12:00 PM 6:00 PM 12:00 AM
AC
PIP
E-T
O-S
OIL
PO
TE
NTIA
L (V
olts)
AC Interference Modeling
• Soil Conditions
• Pipeline Characteristics
• Pipeline and Power System Alignments
• Power System Characteristics• Operating Voltage
• Fault Currents
• Phase Transpositions
• Tower Configurations
• Static Wire
• Grounding Design
• Counterpoise Data
• Substation Locations
AC Interference Modeling
• Computer Aided Predictive Modeling• CDEGS / Right-of-Way Software
• Accurate Predictions of Real-life Pipeline Phenomena
• Mitigation Designs Verified with Models
• Graphical and Text Output
• Design of Mitigation Systems• Innovative Grounding System Configurations
• Proven, Established Engineering Solutions
Modeling Output
RIGHT OF WAY SCHEMATIC
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 20 40 60 80 100 120 140 160
AC Circuit 3 - 115KV AC Circuit 7 - 500KV
AC Circuit 2 - 230KV AC Circuit 6 - 500KV
AC Circuit 1 - 500KV AC Circuit 5 - 115KV
Cypress Pipeline AC Circuit 4 - 230KVCrossings not shown for clarity
STEADY STATE PIPE TO EARTH VOLTAGE
15-Volt Maximum
0
30
60
90
120
0 20 40 60 80 100 120 140 160
CONSTRUCTION MILEPOST
VOLTS
No MitigationSingle Ribbon MitigationDouble Ribbon Mitigation
AC Mitigation & Control - What’s the Solution ? Parallel Mitigation, e.g. Zinc Ribbon(s) or Copper Cables(s)
MINIMUM MEASURESCP Personnel Safety – Dead-Front Test Stations
Design Tip:
Test heads can be designed & supplied with custom terminal ID labeling
Personnel SafetyEquipotential Gradient Control Mats at Test Stations
Test Station
Pipeline
Parallel Zinc Ribbon
7’x7’ Zinc Ribbon Mat “Spiral” – 8 inches below grade under well-drained gravel pad
Parallel Ribbon & Mat connected to pipe through DC-decoupler, a.k.a “PCR”
Solid-State DC Decouplers
Across Isolation Flanges Between Pipe & Zinc Ribbon or Copper Cable At Test Stations
Various Types & Ratings – Use The Appropriate Device For The Particular Application
AC Interference Quiz
1. Do you have AC concerns or problems?
2. What tools/technologies do you use to monitor for AC interference
and the effectiveness of your AC interference mitigation system?
3. Do you believe induced AC causes/increases corrosion?
4. How many of you use coupon technology for CP monitoring? For
AC interference monitoring? For DC interference monitoring?
5. If you are concerned about AC corrosion, is increasing the level of
CP a suitable solution?
Coupon Potential & Current Measurements
mAac/dc(+)(-)
PIPE COUPON REF.
Vac/dc
on / instant-off(+) (-)
AC Current Density
(A/sq.m or A/sq.ft) = Measured Current / Coupon
Surface Area
How Best to Detect/Monitor ACand DC Interference?
OR OR
Simple Coupon
Simple Electrical Resistance (ER) Corrosion Rate
Probe
Complete Monitoring System – Sophisticated
Technology but Straightforward to Use
Pipeline
MetriCorr Probe
Rod typeFlush type
Ref.Electrode
MetriCorr Logger with Remote
Monitoring Option
Corrosion rate
DC ‘On’ potential
DC IR compensated Potential
DC current density
AC potential
AC current density
Measuring is knowledge
Time-stamped, simultaneous data collection, as frequent as 1 set of readings (7 channels of data) every minute
Evolution of Technology
Technology ReleaseProbe – 2004, Qty. = 2400Logger – 2005, Qty. = 750
M-Link RMU – 2010M-Report software/database - 2011
Unique, mature “fit for purpose” multi-channel
corrosion monitoring system based on multi-year industry
sponsored research
CONCLUSIONS – AC CORROSION
1. AC corrosion is real!
2. The mechanisms causing AC corrosion can be quite complex and are not completely understood, but proven, straightforward instrumentation to monitor the corrosion & the effectiveness of any mitigation does exist
3. AC corrosion can be controlled in part by optimizing CP levels – not too little, not too much, just enough
4. In the presence of AC, excessive CP or cathodic DC interference can increase corrosion rates dramatically
5. Instantaneous electrical measurements alone can be misleading
• Datalogging corrosion rate determines if there is a problem
• Concurrently logging various AC and DC electrical parameters determines the cause(s) of the problem and helps establish a suitable mitigation strategy