1. 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

2. 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

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

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

5. 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

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

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

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

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

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

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

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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

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

21. 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

22. 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

23. Pulsed DC Testing
Signal Return Conductive Mat

24. 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

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

26. 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

27. 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

28. 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

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

30. 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