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

Contents Introduction What is Porosity detection? 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 Holiday Detection is used on cured coatings to detect the presence of flaws Wet Sponge Pinhole Detection Continuous DC High Voltage Detection Pulsed DC High Voltage Detection AC High Voltage Detection

Introduction Low Voltage Wet-Sponge Detection finds pinholes through the coating High Voltage Holiday Detection identifies defects Testing can be applied on site to internal and external coatings

The Problem Flaws in cured coatings reduce service life in: Internal and External Pipeline Coatings Tank Linings Immersed applications etc.

The Problem The High Voltage 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 Reduced service life

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

Selecting a Test Voltage Optimum Test Voltage Breakdown Voltage of air – 4kV/mm Typical Dielectric Strength of Paint – 6kv/mm Optimum Test Voltage for 1 mm of coating – 5 kV Optimum Test Voltage for 500 µm (0.5 mm) – 2.5 kV

Selecting a Test Voltage ASTM G62 (1) Dielectric Strength of Coating x Thickness (mm) e.g. For Dielectric Strength = 6kV/mm and Thickness = 500 µm (0.5 mm) Test Voltage = 3kV

High Voltage Pinhole Detection Test Options High Voltage Pinhole Detection The ‘High Voltage Technique’ is a method of locating flaws in insulating coatings on conductive substrates. A Pulsed DC or Continuous DC high voltage is passed over the coating with a probe. If the probe crosses a defect in the coating a spark is generated triggering an audible and /or visual alarm, identifying areas of the coating where defects are present.

Pulsed DC & Continuous DC Explained Test Options Pulsed DC & Continuous DC Explained ‘Pulsed DC (Voltage)’ is a time dependent voltage signal with specific periods of applied fixed voltage (with associated direct current (DC) flow), interspaced by periods of no applied voltage. Voltage Applied Time

Pulsed DC & Continuous DC Explained Test Options Pulsed DC & Continuous DC Explained ‘Continuous DC (Voltage)’ is a voltage level of unvarying, time independent nature caused by direct current (DC) flow. The word Continuous is used to reinforce the unchanging character and so differentiate against Pulsed DC. Voltage Applied Time

Pulsed DC & Continuous DC Explained Test Options Pulsed DC & Continuous DC Explained ‘Pulsed DC (Voltage)’ : Voltage Applied Time The Elcometer 280 operates using this principle ‘Continuous DC (Voltage)’ : Voltage Applied Time The Elcometer 236 and 266 operate using this principle

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 Safety – voltage generated in handle

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 Safety handle

The Voltage Calculator Pulsed DC Testing The Voltage Calculator The voltage calculator function within the Elcometer 280 is designed to automatically calculate the test voltage. Select the required standard from the list Adjust the dry film thickness to the required value Press OK to set the instrument voltage to the calculated value

Pulsed DC Testing The Voltage Calculator Alternatively, the voltage can be adjusted manually Switch the gauge on Adjust the voltage to the required level Press OK to set the instrument voltage

The 2 Key Advantages of the Pulsed DC System Pulsed DC Testing The 2 Key Advantages of the Pulsed DC System 1) Direct metal-to-metal ground contact is not required As a pulsed DC system does not need the direct metal-to-metal ground contact that a continuous DC system requires, it can be used with a trailing lead. This means that you do not always need to connect the earth to the component – ideal in many test situations such as testing on large surface areas or on pipelines.

The 2 Key Advantages of the Pulsed DC System Pulsed DC Testing The 2 Key Advantages of the Pulsed DC System 2) Pulsed DC systems can be used on damp or dirty surfaces Using Pulsed DC technology, the Elcometer 280 is designed to ensure that the energy is contained within very short pulses. Each pulse having more energy than an equivalent Continuous DC System. This means that the Elcometer 280 can be used to test for holidays over slightly conductive coatings, or dirty or damp surfaces

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

Conclusions Portable equipment is available for field testing of coatings for discontinuities Low Voltage testing using a moist sponge only detects holes in the coating High Voltage testing can be safely and simply with the latest design of equipment

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