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SP0169-2007

Standard Practice

Holiday Detection of Fusion-Bonded Epoxy External Pipeline Coatings of 250 to 760 µm (10 to 30 mil)

This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone, whether he or she has adopted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not in conformance with this standard. Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This standard represents minimum requirements and should in no way be interpreted as a restriction on the use of better procedures or materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE International assumes no responsibility for the interpretation or use of this standard by other parties and accepts responsibility for only those official NACE International interpretations issued by NACE International in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual volunteers.

Users of this NACE International standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE International standard may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard.Users of this NACE International standard are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard.

CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may be revised or withdrawn at any time in accordance with NACE technical committee procedures. NACE International requires that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication. The user is cautioned to obtain the latest edition. Purchasers of NACE International standards may receive current information on all standards and other NACE International publications by contacting the NACE International FirstService Department, 1440 South Creek Drive, Houston, Texas 77084-4906 (telephone +1 [281] 228-6200).

Reaffirmed 2007-08-07 Reaffirmed March 2001 Reaffirmed March 1995

Approved April 1990 NACE International

1440 South Creek Drive Houston, Texas 77084-4906

+1 281/228-6200

ISBN 1-57590-119-6 ©2007, NACE International

NACE SP0490-2007 (formerly RP0490-2001)

Item No. 21045

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SP0490-2007

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Alberto Espino

________________________________________________________________________

Foreword Detection and correction of defects in protective coatings are important factors in an effective corrosion control program. High-voltage electrical inspection of pipeline coatings prior to installation is one method in general use. Prior to issuance of this NACE International standard, there had been no U.S. standard for electrical inspection of fusion-bonded epoxy pipeline coatings. Although several specifications have been written by operating companies for high-voltage electrical inspection of protective coatings, they apply only to specific coatings. This standard is intended to serve the needs of pipeline owners, coating applicators, coating inspectors, and other interested parties in the electrical inspection of fusion-bonded epoxy pipe coatings. This standard practice was originally prepared in 1990 by NACE International Work Group T-10D-9c on Electrical Inspection and its parent, Task Group T-10D-9 on Coating Inspection, a component of Unit Committee T-10D on Protective Coating Systems. This standard was developed through the joint efforts of representatives of coating manufacturers and applicators, holiday detector equipment manufacturers, corrosion specialists, and others concerned with the construction of underground pipeline facilities. Unit Committee T-10D reaffirmed the standard in 1995. This standard was reaffirmed in 2001 by Specific Technology Group (STG) 03 on Protective Coatings and Linings— Immersion/Buried. It was reaffirmed by STG 03 in 2007 and is issued by NACE International under the auspices of STG 03. These recommendations apply only to fusion-bonded epoxy pipeline coatings, which are generally applied at a dry-film thickness of 250 to 760 µm (10 to 30 mil). For other types of patching materials and joint wrap, the manufacturer of the material should be consulted for holiday detection voltages. Conformance to the principles of this standard improves methods of holiday detection and, therefore, the effectiveness of the coating.

In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph 7.4.1.9. Shall and must are used to state mandatory requirements. The term should is used to state something considered good and is recommended but is not mandatory. The term may is used to state something considered optional.

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SP0490-2007

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Alberto Esp

________________________________________________________________________

NACE International Standard Practice

Holiday Detection of Fusion-Bonded Epoxy External Pipeline Coatings of 250 to 760 µm (10 to 30 mil)

Contents

1. General ............................................................................................................................... 1 2. Definitions ........................................................................................................................... 1 3. Testing Voltages ................................................................................................................... 1 4. Grounding ............................................................................................................................. 2 5. Exploring Electrode............................................................................................................. 3 6. Travel Speed of Exploring Electrode ..................................................................................... 3 7. Test Voltage Measurements .................................................................................................. 3 8. Condition of Coating Surface............................................................................................... 3 9. Care of Equipment................................................................................................................. 4 References ................................................................................................................................ 4 Table 1....................................................................................................................................... 2

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Alberto Espin

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Section 1: General

1.1 This standard presents recommended techniques in the operation of holiday detector equipment currently used on fusion-bonded epoxy (FBE) pipeline coatings following shop application of the coating and prior to on-site installation of the coated pipeline. It also presents recommended voltages for various coating thicknesses. Guidelines for establishing minimum requirements to ensure proper application and performance of plant-applied, fusion-bonded epoxy coatings are presented in NACE Standard RP0394.1 1.2 Electrical inspection (holiday detection) is a test of the continuity of a protective coating. This type of inspection is not intended to provide information on coating resistivity, bond, physical characteristics, or the overall quality of the coating. It detects voids, cracks, foreign inclusions, or

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contaminants in the coating that are of such size, number, or conductivity to significantly lower the electrical resistance or dielectric strength of the coating. 1.3 Use of a holiday detector shall be under the direction of a qualified coating inspector, such as a NACE-certified coating inspector. An initial holiday detector inspection, performed as soon as practical after the application of the coating, assists in verifying conformance to specifications for the materials and the application procedures. Before the coated pipe is placed in the ground, a final electrical coating inspection discloses coating discontinuities or damage that may have occurred during the shipping, storage, or construction period.

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Section 2: Definitions

Continuous Direct Current (DC) Voltage Holiday Detector: A holiday detector that supplies a continuous DC test voltage. The continuous DC-type holiday detector is often used in very arid, sandy, or rocky areas and in coating plants where moisture and contamination conditions are controlled. The continuous DC test voltage holiday detector cannot be used where continuous moisture is present on the surface of the coating. For proper inspection using continuous DC output test voltage, other than in coating plant operations, the fusion-bonded epoxy coating surface must be dry. Generated Test Voltages: With two types of commercially available detectors, generated output test voltages are used for the electrical inspection of fusion-bonded epoxy pipeline coatings. They are commonly described as pulse-DC and continuous-DC test voltages.

Holiday: A discontinuity in a protective coating that exposes unprotected surface to the environment. For the purpose of this standard, the term is used interchangeably with discontinuity. Holiday Detector: An electrical device that locates discontinuities in the protective coating. Pulse-DC Voltage Holiday Detector: A holiday detector that supplies a high DC voltage pulse of a very short duration (such as 0.0002 seconds at a rate of 30 pulses or more per second). The pulse-type holiday detector is the most common type used in the industry.

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Section 3: Testing Voltages

3.1 All holiday detector output test voltages in this standard refer to pulse-DC and continuous-DC values. 3.2 The minimum effective applied output test voltage is dependent on coating thickness, atmospheric conditions, electrode configuration, and grounding conditions. Therefore, the applied test voltage varies from case to case. 3.3 To determine the minimum effective applied test voltage for a given set of field conditions, the following field calibration should be performed daily:

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3.3.1 Make a holiday 790 µm (0.031 in.) in diameter through the FBE coating. Ensure that the hole extends completely through the coating to the metal substrate. 3.3.2 Start with the lowest test voltage setting of the holiday detector and slowly increase the test voltage until the manufactured holiday can be positively detected at normal operating speeds (see Paragraphs 5.3 and 9.2 and Section 6). 3.3.3 This method of test voltage adjustment shall be performed while the exploring electrode and grounding are in the expected operating positions. If the above

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conditions change, it may be necessary to readjust the test voltage setting.

3.4 Alternatively, the pipe-to-electrode test voltage can be adjusted to the minimum test voltages described in Paragraph 3.5, which are commonly used in the pipeline industry. Output test voltages may be somewhat higher than these test voltage settings; the differential depends on grounding conditions and detector type.

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3.5 The minimum testing voltage for a particular coating thickness shall be within 10% of the value determined by Equation (1):

TKV VoltageTesting == (1)

where V = peak voltage in volts, T = nominal coating thickness in µm, and K = 104 (constant)(1) Table 1 gives calculated voltages for coating thicknesses of 250 to 760 µm (10 to 30 mil).

TABLE 1 Recommended Test Voltages for Various FBE Coating Thicknesses

Coating Thickness Test Voltage(A)

250 µm (10 mil) 1,650 V

280 µm (11 mil) 1,750 V

300 µm (12 mil) 1,800 V

330 µm (13 mil) 1,900 V

360 µm (14 mil) 1,950 V

380 µm (15 mil) 2,050 V

410 µm (16 mil) 2,100 V

510 µm (20 mil) 2,350 V

640 µm (25 mil) 2,650 V

760 µm (30 mil) 2,900 V ______________________

(A) Rounded to the nearest 50 V.

3.5.1 The test voltage should be verified periodically (see Paragraph 3.3.3). 3.5.2 If an outerwrap is applied over the primary coating, the thickness and dielectric strength of the outerwrap material must be considered when determining or specifying the test voltage. Certain

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outerwrap materials may have electrical insulating properties equal to or greater than the coating. 3.5.3 Consumer-specified test voltages used at the coating site at the time of coating application shall not be exceeded during the on-site electrical inspection of the coating.

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Section 4: Grounding

4.1 Proper electrical grounding of the holiday detector to the coated pipe under inspection is necessary to complete the electrical circuit.

4.1.1 The coated pipe metal must have electrical contact to earth at one or more points. An electrical ground of the pipe can be made by electrically connecting the pipe metal to a metal grounding rod driven into the earth to a depth of 0.6 to 0.9 m (2 to 3 ft).

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4.1.2 The holiday detector can, in most cases, be effectively grounded electrically by the use of a flexible ground wire of approximately 9 m (30 ft) in length that is connected to the ground terminal of the holiday detector and trailed along the surface of the earth. The first 1 to 1.5 m (4 to 5 ft) of the ground wire extending from the ground terminal of the holiday detector must be adequately insulated to prevent possible electrical

___________________________ (1) For coating thickness in mils, use K = 525.

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shock to the operator. In some instances, the bare end of the ground wire must be attached to an independent driven earth rod to ensure adequate electrical grounding. 4.1.3 In arid, sandy, or rocky areas where earth resistivity prevents effective holiday detection by

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creating high circuit resistivity, a direct wire connection between the pipe metal and holiday detector ground terminal shall be maintained. Additional ground wire (0.324 mm2 [22 AWG] minimum) of any length may be used in making connections between the holiday detector ground terminal and the pipe metal.

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Section 5: Exploring Electrode

5.1 The exploring electrode is the means by which the electrical potential is applied to the surface of the coating. 5.2 Typically, electrical holiday detector exploring electrodes are manufactured in two basic forms. The most common electrode is the full-circle wire spring type, which, when placed around the coated pipe in operating position, allows for complete circumference inspection with one pass by rolling the spring electrode over the coated surface. The second type is in the form of a brush made of conductive rubber or brass bristles such that there is no more than 250

µm (10 mil) lateral distance between the spring coils or brass bristles at the area where the electrode contacts the coated surface. 5.3 The exploring electrode shall maintain contact with the coated surface at all times. 5.4 The exploring electrode shall be kept clean and free of coating material and rough surfaces that might damage the coating.

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Section 6: Travel Speed of Exploring Electrode

6.1 Pulse-type holiday detector: The output test voltage pulse rate must be considered in determining the travel speed of the exploring electrode over the coated surface. Faster pulse rates allow a higher speed of travel of the exploring electrode over the coated surface.

6.2 The proper travel speed for a particular set of conditions shall be determined by making holidays in the coating and attempting to detect the holidays at various electrode travel speeds (see Section 3, particularly Paragraph 3.3.2).

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Section 7: Test Voltage Measurements

7.1 Test voltage measurements of pulse-type holiday detectors shall be made with a peak reading kilovoltmeter or with a capacitance or resistance voltage divider and suitable indicator such as an oscilloscope or voltmeter. 7.2 Test voltage measurements of continuous DC-type detectors shall be made with a high-resistance DC voltmeter.

7.3 The exploring electrode must be in the normal operating position on the coated surface in a holiday-free area. 7.4 The holiday detector and the coated pipe must be electrically grounded (see Section 4). 7.5 The test voltage shall be measured between the electrode and the pipe metal.

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Section 8: Condition of Coating Surface

8.1 Electrically conductive material, such as contaminating moisture, in or on the surface of the coating system can cause appreciable DC leakage through the holiday detector circuit, producing false signals. This may lower the effective test voltage or falsely indicate holidays. The contamination must be removed or dried prior to electrical inspection.

8.2 All foreign materials that cause an increase in the distance between the exploring electrode and the coated surface must be removed prior to electrical inspection (see Section 5). 8.3 The maximum temperature at which FBE coatings shall be electrically inspected is 90°C (195°F).

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Section 9: Care of Equipment

9.1 All parts of the holiday detector shall be kept clean at all times.

9.1.1 The electrode shall be kept free of coating material and in suitable mechanical condition to maintain contact with the coated surface at all times. 9.1.2 All electrical contacts and connectors on the holiday detector shall be kept clean and free of corrosion.

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9.1.3 The trailing ground wire shall be kept free of coating material and kinks and shall be in suitable condition to maintain electrical grounding with the earth. The ground wire shall be of sufficient length to ensure proper grounding (see Paragraph 4.1).

9.2 Batteries should be in full charge condition at the start of the inspection day. Batteries shall be maintained in accordance with the manufacturer's recommendations.

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References

1. NACE Standard RP0394 (latest revision), “Application, Performance, and Quality Control of Plant-Applied Fusion-Bonded Epoxy External Pipe Coating” (Houston, TX: NACE).

NACE International ISBN 1-57590-119-6

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