GP 06-40 - Pipeline Coating Selection

Document No.

GP 06-40

Applicability

Group

Date

15 February 2007

Guidance on Practice for Pipeline Coating Selection

GP 06-40

BP GROUP ENGINEERING TECHNICAL PRACTICES

15 February 2007

GP 06-40 Guidance on Practice for Pipeline Coating Selection

Foreword This is the first issue of Engineering Technical Practice (ETP) BP GP 06-40. This Guidance on Practice (GP) is based on parts of heritage documents from the merged BP companies as follows:

Amoco A CP-COAT-00-E A CP-COAT-00-G

Corrosion Protection—Coatings—General—Selection Specification. Corrosion Protection—Coatings—General—Guide.

ARCO ES 503

Coatings for Buried Steel Piping.

Copyright © 2007, BP Group. All rights reserved. The information contained in this document is subject to the terms and conditions of the agreement or contract under which the document was supplied to the recipient’s organization. None of the information contained in this document shall be disclosed outside the recipient’s own organization without the prior written permission of BP Group, unless the terms of such agreement or contract expressly allow.

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GP 06-40 Guidance on Practice for Pipeline Coating Selection

Table of Contents Page Foreword ........................................................................................................................................ 2 Introduction ..................................................................................................................................... 4 1.

Scope .................................................................................................................................... 5

2.

Normative references............................................................................................................. 5

3.

Symbols and abbreviations .................................................................................................... 5

4.

Surface cleanliness and surface preparation ......................................................................... 5

5.

Pipeline coating systems selection......................................................................................... 6

6.

Line pipe coatings.................................................................................................................. 6 6.1. General....................................................................................................................... 6 6.2. Health and safety considerations ................................................................................ 6 6.3. Resistance to mechanical damage ............................................................................. 6 6.4. Resistance to the operating environment .................................................................... 8 6.5. Compatibility with cathodic protection ......................................................................... 8 6.6. Coating selection ........................................................................................................ 9

7.

Field joint coatings ................................................................................................................. 9 7.1. General considerations ............................................................................................... 9 7.2. Coal tar and asphalt enamels ..................................................................................... 9 7.3. Cold applied tape coatings........................................................................................ 10 7.4. Fusion bonded epoxy powder ................................................................................... 10 7.5. Liquid applied coatings ............................................................................................. 10 7.6. Heat shrink sleeves................................................................................................... 11 7.7. Polyolefin coated line pipe ........................................................................................ 11

Bibliography .................................................................................................................................. 17

List of Tables Table 1 - Comparison of line pipe coating properties .................................................................... 13 Table 2 - Field joint coating options............................................................................................... 14 Table 3 - Comparison of field joint coating properties.................................................................... 15

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GP 06-40 Guidance on Practice for Pipeline Coating Selection

Introduction This Guidance for Practice covers the selection of external line pipe and compatible field joint coatings for new pipelines both onshore and offshore. Coating options for the refurbishment of coatings on onshore pipelines are more limited and are covered by GIS 06-405. For the purposes of this document the term “line pipe” refers to sections of manufactured pipe normally 12 metres (40 feet) in length and usually prepared and externally coated under factory conditions, except for the “cutback” at either end. The coating is stopped short of the pipe ends to facilitate butt welding of adjacent sections of line pipe together without causing coating damage to the line pipe coating. The “field joint” encompasses the butt weld, the cutback area and an area of overlap onto the line pipe coating. The guidance provided is based upon the experience of BP and other major pipeline operators plus information gathered from a number of documented sources. These documents include; independent test reports, national and international standards, published papers, coating manufacturers’ published data, and private communications. A significant amount of the guidance provided in this document is based upon the results from laboratory tests, either directly in accordance with, industry, national, and international standards or slight modifications to them to more accurately represent the conditions experienced in practice. It should be borne in mind that the range of external pipeline coatings that are commercially available covers a number of diverse generic types. As many of the test methods are not universally applicable to every available pipeline coating system, the comparative assessments based on the results of these tests alone are subjective. The most reliable testament to satisfactory performance can only be provided by investigation under the specific conditions to be encountered in practice. Such testing and/or the accumulation of reliable on site performance data is expensive and time consuming and has been very limited to date. It is the responsibility of the reader to ensure that the information used is relevant to his or her specific requirements.

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1.

2.

GP 06-40 Guidance on Practice for Pipeline Coating Selection

Scope a.

This GP provides guidance for the selection of shop applied and field applied external flowline and pipeline coatings for new construction, hereafter referred to as pipeline coatings. The primary purpose is to prevent external corrosion. Coatings which provide thermal insulation are outside the scope of this document.

b.

This document considers the following line pipe coating systems as they are the ones most widely used throughout BP’s pipeline operations: 1.

Coal tar enamel.

2.

Asphalt enamel.

3.

Cold applied tape wraps.

4.

Single layer fusion bonded epoxy.

5.

Dual layer fusion bonded epoxy.

6.

Two layer polyethylene.

7.

Three layer polyethylene.

8.

Three layer polypropylene.

Normative references The following normative documents contain requirements that, through reference in this text, constitute requirements of this technical practice. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this technical practice are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies.

Deutsches Institut Fur Normung E.V. (DIN) DIN 30670

Polyethylene coatings of steel pipes and fittings; requirements and testing. Polypropylene coatings for steel pipes.

DIN 30678

3.

Symbols and abbreviations For the purpose of this GP, the following symbols and abbreviations apply:

4.

C.D.

Cathodic disbondment

FBE

Fusion bonded epoxy

SCE

Standard Calomel Reference Electrode

Surface cleanliness and surface preparation • •

The importance of surface cleanliness and preparation standard to the long term performance of a pipeline coating cannot be stressed too highly. Poor surface preparation quality resulting from either one, or a combination of the following: inadequate removal of dirt and grease, inadequate removal of mill scale and rust, dust contamination, lack of surface profile angularity, etc. is

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GP 06-40 Guidance on Practice for Pipeline Coating Selection

the major cause of premature coating failure. This is true regardless of the generic coating type selected and the specific conditions under which the coating is applied.

5.

Pipeline coating systems selection Each pipeline shall be considered on its own individual merits in respect of coating systems selection. Under normal circumstances, the selection of an external line pipe coating system is influenced by five principle factors: • • • • •

Health and safety. Resistance to mechanical damage. Resistance to the operating environment and corrosion protection capability, with specific reference to temperature. Compatibility between the line pipe coating, the field joint coating, and the coating used on the bends and fittings. Compatibility of the coating with cathodic protection.

With the exception of health and safety, which is of paramount importance, these factors are not given in order of priority.

6. 6.1.

Line pipe coatings General The selection of the most appropriate line pipe coating is a first priority to ensure the long term integrity of the pipeline. Typically the coating applied to the line pipe protects 98% of the external surface of the pipeline; the field joint coating protects 2%.

6.2.

Health and safety considerations Coal tar enamel and asphalt coatings should not be used unless exceptional circumstances exist which mitigate otherwise. •

•

•

6.3.

At one time, coal tar and asphalt enamels were the mainstay of the pipeline coatings industry. The development of pipeline coatings which are more environmentally friendly and less hazardous during application has seen a dramatic reduction in the use of hot applied enamels over the last 10 to 20 years. Fumes given off during the heating of coal tar contain polycyclic aromatics which are known carcinogens. These are also present during the heating of asphalt enamels, but to a smaller extent. Health and safety concerns have led to some countries prohibiting the use of coating products containing coal tar, while a number of leading paint manufacturers have eliminated coal tar from their liquid coating formulations.

Resistance to mechanical damage a.

Many cases of premature coating failure can be ascribed to mechanical damage to the applied coating system and the coating system either going unrepaired or the repair being of substandard quality. The figures for “relative resistance to mechanical damage” are given in Table 1.

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b.

GP 06-40 Guidance on Practice for Pipeline Coating Selection

For onshore pipelines, specific consideration shall be given to road, rail, river, and other types of pipeline crossings where thrust boring and/or directional drilling operations require the coating to have superior resistance to abrasion and gouging. •

•

•

•

•

•

The mechanical damage sustained by the coating on a pipeline can take many forms. During pipe handling, transportation, and pipeline construction, the pipe coating can suffer impact damage from momentary heavy contact with foreign objects and abrasion damage from more prolonged contact and relative movement against the same. If the coated pipe has a tortuous route between the coating plant and the construction site involving many stages of handling, resistance to impact and abrasion is a key parameter to consider when selecting the external pipe coating. Experience has shown that coating repairs carried out in the field remain areas of weakness due to the constraints on coating application quality achievable in the field compared to the optimum coating application conditions in the factory. On buried pipelines in particular, these locations are invariably those where coating breakdown occurs first. In general terms, the extent to which the coating suffers mechanical damage in service is likely to be much less for subsea pipelines than for those buried on land. The environment surrounding a subsea pipeline is likely to change very little with time, and mechanical damage in service is not normally a significant issue in the absence of unwitting third-party intervention. By contrast, the coating on an onshore pipeline, buried beneath a minimum of 1 to 2 metres (3 to 7 ft) of backfill of often dubious quality, can suffer varying degrees of impact, shear, abrasion, indentation, and penetration during backfilling. Pipe settlement, cyclic fluid temperatures, and seasonal changes in the water content of the surrounding soil all conspire to place additional forces on the coating in service. It is regularly found that areas of significant external metal loss on existing buried pipelines are associated with the steel having become exposed to the environment as a direct consequence of the coating suffering mechanical damage due to contact with the ground. The figures for “relative resistance to mechanical damage” given in Table 1 in the “impact”, “indentation”, and “abrasion” columns, are based upon a comparative assessment. The value 1 is ascribed to the coating with the lowest resistance to that form of damage in each case. The figures given for all of the others reflect the relative amount by which they are more resistant to the specific damage type. The coating with the highest figure in each column has the greatest resistance to that form of damage. Both the value 1 (least resistance) and the highest figure (greatest resistance) in each column are highlighted. The impact resistance values are based upon the energy required (Joules per mm (ft-lb/in) of coating thickness) to impart a holiday in the coating. The test method used to derive the majority of this data is in accordance with the method described in ASTM G14 and/or a modified version of this test using angular tups in addition to the standard hemispherical tup. The coating with the lowest resistance to impact is single layer FBE (at both 20 and 50°C (68 and 122°F)) with three layer FBE-polypropylene having the highest resistance. The values for indentation/ penetration reflect the relative resistance of each coating to point loading in accordance with DIN 30670, DIN 30678, ASTM G17, and/or a modified version of ASTM G17 which uses angular indentors. The values are based upon the physical measurement of the actual depth of the indentation. Cold applied tapes and coal tar and asphalt enamels are particularly prone to penetration damage as reflected in the much higher values ascribed to the alternative coating systems at the same temperatures.

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GP 06-40 Guidance on Practice for Pipeline Coating Selection

•

6.4.

Resistance to the operating environment •

•

•

•

6.5.

The figures for abrasion resistance are based upon a series of full size tests in which the effect of reciprocal pipe movement relative to the soil was simulated [1]. The maximum depth of penetration was assessed by physical measurement. The greater resistance of fusion bonded epoxies, particularly ruggedised duallayer formulations, to this type of damage compared to polyolefins is evident from a comparison of the figures for the different coating systems.

Since most of the materials used as protective coatings for pipeline externals are chemically inert, a major consideration regarding the performance of the coating system is likely to be the operating temperature and its influence upon the mechanical properties of the coating. The data in Table 1 clearly shows how temperature can have a significant effect upon the mechanical properties (including adhesion) of the external coating, its resistance to the stresses acting upon it in service, and the likelihood that the coating will be breached within the required design life. While the majority of the line pipe coatings show a gradual decrease in mechanical integrity with temperature, fusion bonded epoxies also undergo a step change in physical properties at the glass transition temperature. This usually involves a significant fall in the adhesion quality and a change in the coating itself from a rigid to a rubbery material with a much higher tendency for water uptake. The “standard” range of fusion-bonded epoxies which have been available for 20 to 30 years have glass transition temperatures between 95 and 110°C (203 and 230°F). In general terms, the maximum operating temperature of a pipeline which has an external stand alone “standard” FBE coating should not be higher then 5°C (9°F) below the established glass transition temperature. Newer developments have included fusion bonded epoxy coatings with significantly higher glass transition temperatures (125 to 150°C (257 to 302°F)) and lower application temperatures than the standard range. At this time, there is insufficient data available on which to base any firm guidance with regard to the selection of these coatings. Notwithstanding the above, three layer fusion bonded epoxy-polypropylene coatings incorporating certain standard fusion bonded epoxies as the first layer have shown satisfactory performance at operating temperatures up to 125°C (257°F)4.

Compatibility with cathodic protection a.

Most, if not all, pipelines should be protected from external corrosion by a combination of a protective coating and cathodic protection. Therefore, an important property of any pipeline coating is its ability to withstand C.D.

b.

The coating adhesion shall be resistant to the elevated pH in the immediate vicinity of any holiday in the coating and the diffusion of water through the coating film due to the applied voltage across it. The elevation in pH is due to the electrochemical reactions taking place at the cathodically-protected steel surface. The majority of data that exists concerning the compatibility of line pipe coatings with cathodic protection has been derived from small scale, short-term laboratory tests of the type used to verify the quality of factory applied line pipe coatings. There is a wealth of such data for fusion bonded epoxy and fusion bonded epoxy polyolefin coatings, which demonstrates that in coating systems with fusion bonded epoxy as

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GP 06-40 Guidance on Practice for Pipeline Coating Selection

the first layer, the coatings are extremely resistant to C.D. at ambient temperatures if applied in accordance with the manufacturer’s recommendations to correctly prepared substrates. The resistance to C.D. of the alternative coating systems at any temperature and fusion bonded epoxy based coatings at elevated temperatures is less well documented. 6.6.

Coating selection •

•

7. 7.1.

Table 1 compares the adhesion strength and the resistance to mechanical damage and C.D. for the line pipe coating systems listed above. In some cases, this data extends over a range of temperatures. The final column provides guidance on the maximum operating temperatures for these generic coating types. The values for adhesion strength are minimum values measured during the production coating of line pipe and/or required by international standards. Apart from the three layer FBE-polyolefin coatings, there is little documented quantified information on the effect of substrate temperature upon adhesion strength that can be used to determine appropriate upper temperature limits.

Field joint coatings General considerations a.

Table 2 summarizes the field joint coating options available for each generic line pipe coating system discussed in clause 6 above. Two major factors influence the selection of the field joint coating; compatibility with the line pipe coating and the service conditions. Adequate performance of both the line pipe and field joint coating is needed the projected life of the pipeline (usually 30 years minimum).

b.

The method of application shall be conducive to the environmental conditions and the rate at which the pipeline is laid. While historically the simplicity of the field joint coating application procedure has been paramount, in recent years tremendous strides have been made in the development of on-site, automated coating application equipment by field joint coating contractors. When operated and maintained correctly, this equipment ensures consistency of field joint coating quality while optimizing the production rate.

c.

Table 3 gives a comparison of the properties of the field joint coatings reviewed in this clause. The same comments made in clause 6.6 in respect of Table 2 are also applicable with respect to Table 3, with one exception. In Table 3, the comparative rankings for Indentation and Penetration are given in 2 separate columns. The “Indentation” column rankings are based upon standard test methods described in DIN 30670, DIN 30678, or ASTM G17. The “Penetration” column rankings are based on a modified version of ASTM G17, in which angular indentors were used and which more closely represent the conditions experienced in practice on a buried pipeline.

7.2.

Coal tar and asphalt enamels The early “over the ditch” methods of applying asphalt and coal tar enamel coatings meant that field joints were not in themselves a specific concern, as the coating could be applied in a continuous manner along the pipeline way leave. It was only when these materials began to be applied to individual lengths of pipe under factory conditions that field joints became a subject of specific attention. At Page 9 of 17

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GP 06-40 Guidance on Practice for Pipeline Coating Selection

first, the field joints were coated in an analogous manner to the line pipe; that is, using hot enamel and fabric reinforcement applied as a full circumferential wrap or “granny ragging,” as it was commonly known. This procedure, which has significant health, safety, and environmental risks, has been largely superseded over the last 30 years by the application of cold applied tapes, two component liquid applied coal tar epoxy, or coal tar urethane, or radiation cross linked polyethylene (HSS PE) shrink sleeves. 7.3.

Cold applied tape coatings •

•

•

7.4.

Fusion bonded epoxy powder •

•

7.5.

By the very nature of their composition and temperature limitations, the only viable field joint coating option on line pipe coated with cold applied tape wrap is to use an identical material to the line pipe coating at the field joints. Due to the thermoplastic nature of cold applied tape wraps, the terminations adjacent to the field joint are easily damaged by pre-heating and post-heating operations. Cold applied tapes are regarded as the simplest coatings to apply at field joints, as less skill is required compared to the alternatives available. Nevertheless, there are a minimum number of application parameters that need to be satisfied during their application, if they are to provide external corrosion protection over a reasonable time frame. Due to their comparatively poor resistance to soil stressing particularly at elevated temperatures (> 40°C (> 104°F)), their use should be limited to smaller diameter pipelines (< 18 in), pipelines conveying non-hazardous products, and ambient operating temperatures.

One of the major advantages of fusion bonded epoxy powder coatings is that they can be applied to line pipe, bends and fittings, and field joints, alike. This enables just one coating system to be specified for the entire pipeline, eliminating problems with the selection of the external coating at field joints in situations in which two generically different coatings may have otherwise been applied to the parent pipe on either side of the field joint. However, as standalone field joint coatings, they are not compatible with any line pipe coating other than fusion bonded epoxy. Unlike coal tar and asphalt enamel coatings and cold applied tapes, the application of FBE coatings in the field requires sophisticated equipment in the form of induction heating coils, fluidized beds, and flock spraying equipment. A satisfactory long-term coating performance is reliant upon a high quality of surface preparation and a rigid adherence to established coating application procedures in the field.

Liquid applied coatings To combat extreme weather conditions, liquid polyurethane and epoxy field joint coatings normally comprise 100% solids materials applied at elevated temperatures by “mix at the gun” hot twin airless spray equipment, often with pipe pre-heat and sometimes post-heat to accelerate the curing rate even further. Induction heating is the preferred method for both pre- and post-heating for optimum control and reproducibility of the heat profile. As with fusion bonded epoxy coatings, the performance of liquid applied coating systems at field joints is reliant upon a high quality of surface preparation and adherence to established coating application procedures.

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7.6.

GP 06-40 Guidance on Practice for Pipeline Coating Selection

Heat shrink sleeves •

•

Radiation cross linked heat shrink sleeves require pre-heating of the field joint followed by post-heating after fit up of the sleeve to shrink the sleeve down to fit snugly on the pipe. The traditional method of heat application is by manually operated open flame torch. Apart from inherent health and safety risks, this method results in a non-uniform heat input across the field joint. This nonuniform heating pattern produces differential shrinkage rates across the field joint, leading to wrinkling and blistering of the sleeve and widely differing qualities of adhesion. In cases of extreme heat input, the sleeve may char and/or the adjacent line pipe coating may be damaged due to overheating. A significant improvement in the heating pattern and consistency of adhesion can be achieved by using induction heating in place of open flame torches to apply the preheat. Polypropylene shrink sleeves provide a step change in the quality of the adhesion that can be achieved to both steel and polypropylene line pipe coatings and resistance to mechanical damage compared to their polyethylene based counterparts. In order to fully realize the capabilities of polypropylene heat shrink sleeves, induction heating is required to provide uniform pre-heat to the pipe. As these field joint coatings are a comparatively recent development, track records are limited to date.

7.7.

Polyolefin coated line pipe

7.7.1.

General

•

•

7.7.2.

The generic coatings listed above have limited adhesion to polyethylene and abrasive blast cleaning or mechanical roughening of the surface of the polyethylene is a minimal requirement in order to attain a measure of adhesion in the case of liquid applied coatings, cold applied tapes, and heat shrink sleeves. With cold applied tapes and radiation cross linked polyethylene heat shrink sleeves; this is offset to a small extent at ambient temperatures by the rigidity of the plastic backing. There is some evidence that the adhesion level between the field joint coating and the polyethylene can be optimized by judicious selection of the type and particle size distribution of the abrasive, but this has not been reliably documented. Attempts to enhance the adhesion of coatings to polyethylene by flame treatment of the polyethylene substrate have given variable results in general and moderate improvements in adhesion at best.

Fusion bonded epoxy-polypropylene

•

•

•

Three layer fusion bonded epoxy-polypropylene coatings are the only pipeline coatings with an established operating temperature limit in excess of 90°C (194°F), and their use is confined mainly to preventing external corrosion of pipelines operating between 90 and 125°C (194 and 257°F). To date, five different field joint coating systems have been used on line pipe coated in the factory with three layer fusion bonded epoxy-polypropylene. All of these systems incorporate the application of FBE as the first coating layer in an identical manner to that described in clause 7.4, followed by a flock sprayed layer of polypropylene copolymer adhesive within the gel time of the FBE to ensure adequate cross linking. Good interlayer adhesion is dependant upon a chemical reaction between the fusion bonded epoxy and the polypropylene co-polymer adhesive. This can only take place when the fusion bonded epoxy is in a liquid state but has not had time to cure. This period is normally of the order of 20 to 40 seconds following application of the FBE. Page 11 of 17

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GP 06-40 Guidance on Practice for Pipeline Coating Selection

•

The principle difference between each of the field joint coating types is the manner in which the outer layer(s) of polypropylene/ polypropylene copolymer is(are) applied. There are six different types as follows: - Sintered polypropylene copolymer. - Co-extruded polypropylene sheet plus polypropylene welding. - Flame sprayed polypropylene copolymer. - Injection moulded polypropylene. - Co-extruded polypropylene tape. - Polypropylene heat shrink sleeve.

•

•

•

•

•

The sintered polypropylene copolymer field joint coating application method involves the build up of the copolymer coating by flock spraying as a dry powder, the residual heat in the pipe from the fusion bonded epoxy application process being used to melt and coalesce the copolymer particles. As polyolefins have a low thermal conductivity, the thickness that can be achieved is limited to less than 1 mm (0,04 in) with the added risk that the final copolymer layer may be porous, unless supplementary heating is applied externally. Without the supplementary external heating, this type of coating is likely to be extremely poor quality by comparison with the alternatives available and described below. The co-extruded polypropylene sheet method gives a sound field joint coating with properties equivalent to that of the line pipe coating, but requires precise cutting of the sheet to fit the field joint area, preheating of the sheet, and then preparation and sealing of the longitudinal and circumferential edges of the sheet to the line pipe coating by extrusion welding using a polypropylene consumable. This field joint coating system is, therefore, time consuming to apply correctly. Of the five systems described, flame spraying is perhaps the most versatile as it can also be used to coat fittings and pre-formed bends at a wide range of coating thicknesses. The polypropylene co-polymer powder is propelled under gas pressure through a flame. The individual particles and the coated surface are heated by the flame enabling a fully fused coating to be produced. The application technique requires a high degree of skill in order to apply the coating to a uniform thickness without slumping. Injection moulding of polypropylene at field joints has been used only rarely and exclusively on offshore pipelines. It requires bulky and sophisticated equipment and has a reputation for being more costly compared to the alternative systems available. Nevertheless, it gives an extremely robust field joint coating almost equal in properties to the line pipe coating. Polypropylene tape wrapping is the most recent development and may be regarded as an extension of the co-extruded sheet method. Being of a single material and more flexible than the sheet, it is applied to the field joint as a spiral wrap in an analogous way to cold applied tape, rather than as a single sheet. Good adhesion both between successive spirals, to the pipe, and the line pipe coating requires preheating of the tape and the substrate as the tape is applied, followed by post heating.

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GP 06-40 Guidance on Practice for Pipeline Coating Selection

Table 1 - Comparison of line pipe coating properties

Generic Type

Total Coating Thickness (µm (mil))

Adhesion Strength

Relative Resistance to Mechanical Damage (1-Lowest Resistance) [3]

Temp (°C (°F))

Peel (N/mm (lb/in))

Pull off (MPa (psi))

C. D. Resistance –1,5 V. v. SCE (mm (in) max.) 23°C (73°F)

65°C (149°F)

Temp °C (°F)

Impact *

Indentation/ Penetration #

Abrasion §

28 days

48 hrs

Recommended Maximum Operating Temperature (°C (°F))

Asphalt Enamel

4 000-6 000 (160-240)

25 (77)

5 (29)

N/A

20 (68)

-

1∞

-

10 (0,4)

-

50 (122)

Coal Tar Enamel

4 000-6 000 (160-240)

25 (77)

5 (29)

> 2,4 (> 350)

20 (68)

-

1∞

-

10 (0,4)

-

65/80 (149/176) €

Cold Applied Tape 3 000 (120)

22 (72)

2 (11)

N/A

20 (68)

3 (56) ∞

1∞

-

12 (0,5)

-

40 (104)

20 (68)

1 (19)

220

(2) ♂

1 (19)

180

5

5 (0,2)

5 (0,2)

90 (194) †

5 (0,2)

5 (0,2)

90 (194) @

-

-

50 (122)

5 (0,2)

5 (0,2)

75 (167)

5 (0,2)

5 (0,2)

125 (257)

FBE Single Layer

350-600 (14-24)

25 (77)

N/A

> 21 (> 3 000)

50 (122)

FBE Dual Layer (Ruggedised)

750-1 350 (30-54)

25 (77)

N/A

> 21 (> 3 000)

20 (68)

7 (131)

250

5

50 (122)

7 (131)

180

12

2 Layer Polyethylene

1 000-2 000 (40-80)

23 (73)

4 (23)

NA

20 (68)

14 (262) ♀

10 ♀

1♀

50 (122)

7 (131) ♀

10 ♀

1♀

23 (73)

20 (224) [4], [5]

20 (68)

14 (262)

10

1

40 (104)

15 (86)

60 (140)

8 (46)

80 (176)

5 (29)

3 Layer FBE- HD Polyethylene

3 Layer FBEPolypropylene

2 500-3 500 (100-140)

2 500-3 500 (100-140)

N/A 50 (122)

7 (131)

10

1

23 (73)

20 (114)

20 (68)

16 (299) ∞

20 ∞

-

70 (158)

15 (86)

50 (122)

15 (281) ∞

13 ∞

-

90 (194)

8 (46)

110 (230)

-

8

-

125 (257)

2 (22)

125 (257)

-

4

-

N/A

* # §

Impact rankings based upon the energy required to produce a holiday in J/mm (ft-lb/in) of coating thickness ∞ Figures relative to 2 Layer Polyethylene Extrapolated from Privately Communicated Data Indentation rankings compares the resistance to penetration under constant load € Upper temperature limit for coal tar enamel depends upon enamel grade. Abrasion ranking compares depth to which the coating is penetrated for a fixed load and No. of cycles Higher temperatures (< 100°C (< 212°F)) possible beneath concrete weight † Depends upon the specific FBE product used coat. ♀ Performance assumed to be the same as for three layer FBE-PE @ Upper temperature limit for dual layer FBEs needs to be established from ♂ Single layer FBE suffered through film penetration independent test data.

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GP 06-40 Guidance on Practice for Pipeline Coating Selection

Table 2 - Field joint coating options Line Pipe Coating

Coal Tar or Asphalt Enamel

Field Joint Coatings

Comments

Hot Coal Tar or Asphalt Enamel Wrap

HSE concerns mitigate against the use of hot enamel wrap in the field.

Cold Applied Tape Wrap

Limited resistance to soil stressing particularly at above ambient temperatures. †

Liquid Applied Coal Tar Epoxy or Coal tar Urethane

Fully automated coating application available. Superior adhesion to steel, mechanical properties less affected by temperature

Radiation Cross Linked PE Heat Shrink Sleeves Inconsistent adhesion quality due to method of heat input. Limited resistance to soil (PE HSS) stressing at above ambient temperatures.* Cold Applied Tape Wrap

Cold Applied PE/PVC Tape Wrap Single or Dual Layer Fusion Bonded Epoxy

Single & Dual Layer Fusion Bonded Epoxy

Two layer Polyethylene

Three Layer FBEPolyethylene

Three Layer FBEPolypropylene

Liquid Applied Epoxy or Urethane. Radiation Cross Linked PE Heat Shrink Sleeve (PE HSS) with Epoxy Primer

See above † Adhesion strength of FBE and liquid applied coatings less affected by temperature than PE HSS. FBE & liquid applied coatings have superior mechanical damage resistance at above ambient temperatures compared to PE HSS.

Radiation Cross Linked PE Heat Shrink Sleeves Limited adhesion between primer and PE in the line pipe coating restricts the field joint (PE HSS) with Epoxy Primer coating options. Cold Applied PE/PVC Tape Liquid Applied Epoxy, Urethane, or Coal Tar Urethane.

Superior adhesion to steel, mechanical properties less affected by temperature

Radiation Cross Linked PE Heat Shrink Sleeves See comments above *

Limited adhesion of all of the field joint coatings to PE. Requires careful selection of blast abrasives to try to optimize the coating adhesion at the overlap.

Cold Applied Tape Wrap

See comments above †

FBE-Sintered Polypropylene Co-Polymer

Limited thickness is achievable (< 1 mm (0,04 in)) & coating porosity a significant risk

FBE-Flame Sprayed Polypropylene Co-Polymer

Good field joint-line pipe coating continuity achievable. Slow manual PP application process, although automation possible. Risk of the PP coating slumping during application.

FBE-Tape Wrapped Polypropylene

Good field joint-line pipe coating continuity achievable. Fully automated process capable of consistent field joint coating quality.

FBE-Cigarette Wrapped Polypropylene

Good field joint-line pipe coating continuity achievable. Semi-automated process, manual PP sleeve application

FBE-Injection Moulded Polypropylene

Good field joint-line pipe coating continuity achievable. Closest to factory application quality. Level of equipment sophistication required makes this coating system difficult to justify for onshore pipelines.

Radiation Cross Linked PP Heat Shrink Sleeve (PP HSS) with Epoxy Primer

Coating adhesion values of the same order of magnitude as for FBE-PP field joint coatings achievable, providing that induction heating used to provide uniform pipe pre-heat.

Page 14 of 17

15 February 2007

GP 06-40 Guidance on Practice for Pipeline Coating Selection

Table 3 - Comparison of field joint coating properties

Generic Type

Total Coating Thickness (µm (mil))

FBE Mono Layer

350-600 (14-24)

FBE Dual Layer (Ruggedised)

750-1 350 (30-54)

Liquid Applied Epoxy

Liquid Applied Polyurethane

Liquid Applied Coal tar Urethane

750-1 000 (30-40)

750-1 000 (30-40)

750-1 000 (30-40)

Temp (°C (°F)) 25 (77)

25 (77)

23 (73)

23 (73)

23 (73)

Peel (N/mm (lb/in))

Pull off (MPa (psi))

N/A

> 21 (> 3 000)

N/A

> 21 (> 3 000)

N/A

N/A

N/A

> 21 (> 3 000)

> 17 (> 2 500)

> 10 (> 1 500)

Cold Applied PE/PVC Tape

2 500-3 000 (100-120)

22 (72)

2 (11)

N/A

Heat Shrink SleeveRadiation X Linked PE Mastic

1 500-2 500 (60-100)

23 (73)

1,5 (9)

N/A

Heat Shrink SleeveRadiation X Linked PE Adhesive/ Epoxy Primer

1 500-2 500 (60-100)

23 (73)

3 (17)

N/A

C. D. Resistance –1,5 V. v. SCE (mm (in) max.)

Relative Resistance to Mechanical Damage (1-Lowest Resistance) [6], [7], [8], [9]

Adhesion Strength Temp (°C (°F))

Impact

Indent #

20 (68)

8 (150)

-

50 (122)

10 (187)

Penetration ¥ Abrasion § Gouging § 223

4

-

50

4

-

0 (32)

6 (112)

-

400

-

-

20 (68)

10 (187)

-

250

8

-

50 (122)

12 (225)

-

100

5

-

80 (176)

10 (187)

-

33

-

-

0 (32)

4 (75)

177

201

-

201

20 (68)

6 (112)

233

107

7

107

50 (122)

10 (187)

35

46

3

46

80 (176)

8 (150)

7

9

-

9

0 (32)

10 (187)

75

151

-

151

20 (68)

12 (225)

17

46

-

46

50 (122)

12 (225)

9

7

-

7

80 (176)

10 (187)

7

7

-

7

0 (32)

6 (112)

61

64

-

64

20 (68)

8 (150)

18

9

-

9

50 (122)

8 (150)

15

4

-

4

80 (176)

4 (75)

13

3

-

3

20 (68)

1 (19)

11

-

-

-

50 (122)

-

-

-

-

-

20 (68)

-

-

-

-

-

50 (122)

-

-

-

-

-

0 (32)

8 (150)

71

6

-

6

20 (68)

8 (150)

62

3

1

3

50 (122)

4 (75)

11

1

1

1

80 (176)

2 (37)

1

1

-

1

Page 15 of 17

Max Service Temp. (°C)

23°C (73°F)

65°C (149°F)

28 d

48 hr

5 (0,2)

5 (0,2)

90 (194) †

5 (0,2)

5 (0,2)

90 (194) @

5 (0,2)

5 (0,2)

90 (194)

5 (0,2)

5 (0,2)

80 (176)

5 (0,2)

5 (0,2)

65 (149)

12 (0,5)

-

40 (104)

8 (0,3)

8 (0,3)

40 (104)

8 (0,3)

8 (0,3)

40 (104)

15 February 2007

Generic Type

GP 06-40 Guidance on Practice for Pipeline Coating Selection

Total Coating Thickness (µm (mil))

Heat Shrink SleeveRadiation X Linked PP/Epoxy Primer

2 500-3 000 (100-120)

3 Layer FBEPolypropylene (Flame Spray/ Tape)

3 000-4 000 (120-160)

* # ¥

Pull off (MPa (psi))

C. D. Resistance –1,5 V. v. SCE (mm (in) max.)

Relative Resistance to Mechanical Damage (1-Lowest Resistance) [6], [7], [8], [9]

Adhesion Strength Temp (°C (°F))

Peel (N/mm (lb/in))

70 (158)

4 (23)

110 (230)

4 (23)

70 (158)

15 (86)

0 (32)

-

-

-

-

-

90 (194)

6 (34)

50 (122)

-

18

-

-

-

110 (230)

2 (11)

90 (194)

3 (56)

4

-

-

-

121 (250)

4 (23)

121 (250)

-

-

-

-

-

N/A

N/A

Temp (°C (°F))

Impact

Indent #

23 (73)

8 (150)

62

-

-

-

110 (230)

8 (150)

10

-

-

-

Impact rankings based upon the minimum energy required in J/mm (ft-lb/in) of coating thickness to produce a holiday Indentation rankings compare the resistance to penetration under constant blunt load in accordance with DIN 30670 & 30678

§

Indentation rankings compare the resistance to penetration under constant angular load representative of typical onshore pipeline backfill

†

Penetration ¥ Abrasion § Gouging §

Max Service Temp. (°C)

23°C (73°F)

65°C (149°F)

28 d

48 hr

5 (0,2)

-

90 (194)

5 (0,2)

5 (0,2)

125 (257)

Abrasion and gouging ranking compares depth to which the coating is penetrated for a fixed load and fixed No of cycles @ Upper temperature limit for dual layer FBEs needs to be established from independent test data. Depends upon the specific FBE product used

Page 16 of 17

Bibliography [1]

ASTM G14 Standard Test Method for Impact Resistance of Pipeline Coatings (Falling Weight Test).

[2]

ASTM G17 Standard Test Method for Penetration Resistance of Pipeline Coatings (Blunt Rod).

[3]

Pipeline Research Council “Coating and Backfill Optimisation Study” May 2004

[4]

M. Alexander. 13 International Conference on Pipeline Protection, Edinburgh, 1999 “Three Layer Epoxy/Polyethylene Side Extruded Coatings for Pipe for High Temperature Application”

[5]

D. Nozahic & L. Leiden 13th International Conference on Pipeline Protection, Edinburgh, 1999 “Advanced-Three Layer HDPE System with Improved Short and Long Term Properties”

[6]

Advantica Report No R5777 “Pipeline Coatings/Trench Backfill System Optimisation Study-Phase 2 Field Joint Coatings” March 2001

[7]

R. Espiner, I. Thompson, J. Barnett, “Optimization of Pipeline Coating and Backfill Selection” Paper 03046, NACE 2003

[8]

Advantica Report No R4302 “Pipeline Coatings/Trench Backfill System Optimisation Study-Small Scale Laboratory Test Programme” January 2003

[9]

Advantica Report No R5426 “BP Pipeline Field Joint Coating Study: Support to Shah Deniz Export Project” July 2002

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