Regional Sales Manager The use of High Voltage Holiday Detectors for field testing of pipeline coatings Presenter: Craig Woolhouse Regional Sales Manager Elcometer Limited © Elcometer Limited 2011

Contents Introduction The Problem - Flaws & Defects Standards for Porosity Detection Continuous DC High Voltage Testing Pulsed DC High Voltage Testing AC High Voltage Testing Conclusions and Questions

Introduction High Voltage Holiday Detection is used on cured coatings to ensure there are no flaws Continuous DC Pulsed DC AC

The Problem Flaws in cured coatings reduce service life in: Internal and External pipeline coatings Tank linings Immersed applications

The Problem The Test Principle: Be aware of the dielectric strength of the coating Be aware of the film thickness of the coating Apply a controlled voltage to the surface of the coating The presence of a defect will result in current flow through the coating enabling detection of the flaw to be possible

The Problem Some Examples of Coating Flaws Runs & Sags Pinholes Cratering Cissing Incorrect Coating Thickness

The Problem Runs & Sags Caused by excessive film local thickness prior to cure

The Problem Pinholes Caused by air or blast media inclusions in the coating

The Problem Cratering Caused by air release from the partially cured coating

The Problem Cissing Caused by contamination of substrate by oil or grease also known as crawling or fisheyes

The Problem Incorrect Coating Thickness Profile peaks through thin coatings Cracking due to excess coating thickness

Test Standards NACE SP0188:2006 “Discontinuity (Holiday) Testing of New Protective Coatings on Conductive Substrates” Test Voltage Table

Test Standards NACE RP0274:2004 “High Voltage Electrical Inspection of Pipeline Coatings” Voltage Formula or Table Where: V = test voltage and T is the thickness in mm

Test Standards NACE SP0490:2007 “Holiday Detection of Fusion-Bonded Epoxy External Coatings of 250 to 760 µm” Voltage Formula or Table Where: V = test voltage and T is the thickness in µm

Test Standards ASTM D5162:2008 “Practice for Discontinuity (Holiday) Testing of Nonconductive Protective Coating on Metallic Substrates ” Voltage Formula or Table Where: V = test voltage, Tc is the thickness in mm and M is a constant dependant on the range of the thickness

Test Standards ASTM D4787:2008 “Continuity verification for liquid or sheet linings applied to concrete substrates ” Voltage Formula or Table Where: V = test voltage, Tc is the thickness in mm and M is a constant dependant on the range of the thickness

Test Standards ISO BS EN ISO29601:2011 “Paints and varnishes – Corrosion protection by protective paint systems – assessment of porosity in a dry film” Test Voltage Table

Test Voltage for 500 µm Coating Test Standards Test Voltage Comparisons Standard Test Voltage for 500 µm Coating NACE SP0188 2.5 kV NACE RP0274 6.0 kV NACE SP0490 2.3 kV ASTM D4787 (Formula) ASTM D4787 (Table) 2.7 kV BS EN ISO 29601 2.9 kV

Continuous DC Testing Test Set-up Signal return cable connected to uncoated substrate Menu Operated Standards Voltage Calculator Integrated Jeep Tester DC Voltage from 0.5 to 30 kV Conductive Electrodes

Continuous DC Testing Test Electrodes Insulated Handle Rolling Spring Internal Pipe Brush Metal or Conductive Rubber Brush Electrodes Extension rods

Pulsed DC Testing Test Set-up Capacitive (Trailing) Signal Return Cable Menu Operated Standards Voltage Calculator Integrated Jeep Tester 35 kV Test Voltage Range Conductive Electrodes

Pulsed DC Testing Electrodes options Stainless Steel Rolling Springs Phosphor-Bronze Rolling Springs Band Brushes Wire Brushes up to 1 m wide Internal Pipe Brushes Conductive Rubber Strip up to 1m wide Electrode Adaptors

Pulsed DC Testing Signal Return Conductive Mat

AC Testing AC High Voltage Testers are also available Typically mains operated (inconvenient for site work) Surface contamination & moisture can cause AC sparks High AC voltage is more hazardous than DC

The use of High Voltage Holiday Detectors for field testing of pipeline coatings Conclusions © Elcometer Limited 2011

Conclusions The key to successful high voltage holiday detection is the selection of the correct test voltage for the dielectric strength of the coating: Too low a voltage and flaws will be missed Too high a voltage and the coating will be burnt

Care must be taken with low dielectric strength coating Conclusions Care must be taken with low dielectric strength coating Thin sections may not resist the high voltage if the dielectric strength is low Breakdown voltage of air is 4 kV/mm Some coatings have a dielectric strength of 6 kV/mm

Continuous DC or Pulsed DC Testing? Conclusions Continuous DC or Pulsed DC Testing? Determined by practical issues Pulsed DC when direct connection to substrate is not possible Pulsed DC when coating is damp or dirty Continuous DC recommended when accurate voltage setting required especially with lower dielectric strength coatings

Care when referencing a standard Conclusions Care when referencing a standard The different standards produce different test voltages for the same thickness

Thank you for your attention The use of High Voltage Holiday Detectors for field testing of pipeline coatings Thank you for your attention Questions? © Elcometer Limited 2011