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

2. 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

3. 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

4. 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

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

6. 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

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

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

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

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

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

12. The Problem Incorrect Coating Thickness
Profile peaks through thin coatings
Cracking due to excess coating thickness
Reduced service life

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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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.

23. 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

24. 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

25. 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

26. 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

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

28. 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

29. 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

30. 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

31. 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.

32. 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

33. 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

34. Pulsed DC Testing
Signal Return Conductive Mat

35. 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

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

37. 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

38. 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

39. 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

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

41. 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

42. 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