ICORR Coating Inspector Opt

Pipeline Coatings Inspector ICorr Level 2

Pipeline Coatings Inspector ICorr Level 2

Part A

TABLE OF CONTENTS

PART A

...................................................... ........... ............................................................. POLYOLEFINS & OTHER PLASTIC COATINGS ..................................... ENAMEL COATINGS

FUSION BONDED EPOXY

ELASTOMERIC COATINGS

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MULTI-COMPONENT LIQUIDS MCL'S

WRAPPING TAPES Hot applied tapes . ... . . . . .. . . . . . . . .. . . . .. . . .. . . . . . .. ... .. ... .. . . .. ... ... .. ....... ..........

.. ... .. .. . .. .. .. . . . . ... . .. . . . . . .... ... .. . .. . .. . . .. .......... . . . Grease based tapes . . .... . ... . . .. . . . . . . . . . . . . . . . .. . .. . . . . . .. . ....... . ... .. . . .. ........ ..... Self adhesive overwrap tapes . . . .. .. . .. .. .. . . .. . . .. . . .... . ... . . . . ... ... . .. . . .. .. ... .... . ... BRUSHING MASTICS .................................................................. Cold applied laminate tapes

.................................................. .......................................................... TESTING OF COATINGSIWRAPPINGS ...............................................

FILLERS (MASTICS AND PUTTIES) INTERNAL PIPE COATINGS

Factoryllaboratory based tests .. .... .... . . .. . . . .. . . . .. .. .. . ... .. .. . . . . . .. . . . . . . .. .. . . . . . . . . Tests performed by inspection personnel (factory and site) ... . . .. . .. . .. . . . .. .. . . . . .. . .. .. . . Awareness of other tests .. ............ .... .. ... . .. .. ... . ....... . ... . . . . .. .. . . .. . . . .... .. . ..

INSPECTION

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Duties of a pipeline coating inspector . .. .. ... .. . .. .... . . . . ... . . . . .. . . . . . .. . . . . . .. .. ... . .. . . Reports and records .. ................. ..... . . ... ....... ... . ..... .. .. .. . .. . . .. . . . . ... . . . . .. Examples of possible contractor malpractice . ........ .... . ...... ......... . ... .... . . . . .. ...

. HANDLING, TRANSPORT AND STORAGE OF COATED PIPE ....................... DITCHING AND BACKFILLING .....:. ................................................ PEARSON SURVEY ....................................................................

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When using the term enamels in relation to pipe coatings we are referring to coal tar or bitumen (asphalt) based coatings which are applied as a hot liquid. Coal tar and bitumen enamel coatings for full pipe lengths have largely been superseded by FBE and polyolefin coatings, however, many pipeline users do still specify the use of enamels. Pipeline coating inspectors are also likely to encounter these materials on maintenance work. Bitumen and coal tar enamels must not, in any circumstances, be mixed or applied on top of one another, a loss of properties and poor adhesion respectively will be the result. Both materials are black and are very similar in texture; the following simple test can be used to distinguish between the two materials:

Many other solvent types will also give the desired result when carrvina - out an enamel identijication test.

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Take a very small ball. about 3 mm in diameter, of the unknown enamel and place onto a sheet of white blotting paper or filter paper. Put two or three drops of xylene or toluene solvent onto the ball. The ring of liquid running from the enamel and soaking into the paper will show yellow for coal tar and brown for bitumen enamels.

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Enamel coatings are normally reinforced with two layers of fibreglass to provide a rigid durable coating.

Constituents Coal tar enamels Plasticised coal tar pitch from coal, distilled in coke ovens, is the main constituent to which is added various amounts of coal oil (plasticiser), which modifies the material for viscosity properties and temperature tolerance. Fillers are added, usually in the form of talcum powder or slate flour, in proportions of 25% to 35%, these are classed as inert mineral fillers.

Bitumen enamels Bitumen (asphalt) is a heavy residue from the distillation of crude oil. Inert mineral fillers are added, usually in the form of talcum powder or slate flour as for coal tar. The viscosity of bitumen can be reduced by adding certain waxes and increasing refinement. Herbicides are also added to bitumen enamels to discourage the formation of root growth.

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Advantages and limitations Advantages 1.

Low cost system - low material cost and pipe is not heated.

2. 3.

Relatively simple system. Widely known system - users have a good knowledge of application and performance properties.

Limitations 1.

Overall - poor performance properties when compared to more modern systems; higher CP currents required.

2.

Labour intensive at least three operatives will be required for site applications

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3. 4.

For site work bulky melting pots are required. Coating needs reinforcement.

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Safety hazards - (1) toxic fumes from liquid state; (2) danger of burns from hot enamels especially during field application on welded butt joints; (3) flammablz constituents.

6.

Thermoplastic nature of coating can lead to coating damage during handling, storage and ditching.

7.

Susceptible to breakdown in UV light.

8.

Susceptible to coating damage during soil stressing.

9.

Easy disbonding of coating with impact.

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10. Bitumens need herbicides incorporated. 11. Limitations on bending due to brittle nature. 12. Enamels of both types are not suitable for use over plastics of any type - no adhesion.

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Surface preparation Factory Surface preparation in a factory is normally carried out by dry abrasive blast cleaning using totally enclosed centrifugal blast cleaning units. Chemical cleaning, usually using the Footner process, is an alternative. Typical requirements (blast cleaning) Abrasive used - steel grit or grit and shot mix. Profile requirements - Sa21/2, medium profile or 50-75 p. Inspect blasted areas for surface laminations (slivers); if any exist then remove with a grinder, check for correct contour and wall thickness then reblast the area.

Site Full pipe lengths along with the welded joints may also be prepared and coated on site with puTose built equipment to allow for a continuous operation.

Welded joints are blast cleaned using pressure blasting equipment and dry expendable abrasive. Typical requirements (welded joints) Remove solar protective coating and all extraneous material from the existing coating (150 mm is typical requirement). Degrease only if necessary. Chamfer coating by 50 mm or 100 mm as specified, using a blow torch and scraper. Blast clean using dry expendable abrasive -profile requirements - Sa21/2, medium profile or 50-75 pm. Inspect blasted areas for surface laminations (slivers) - if any exist: remove with a grinder, check for correct contour and wall thickness then reblast area. Check for disbonded coating; if any exists then remove and reblast the area.

Coating application Factory In a pipe coating factory (mill) the enamel coating process is often done as a continual process by using spacer collars placed between the pipes, so that in effect, one long continuous pipe length is being coated. Some coating factories will treat each pipe separately. Q Ruane & T P O'Neill Issue 1 :28/04/97

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The sequence of events for coating (showing typical requirements) are as follows: 1.

Residual dust from the abrasive blast cleaning operation is removed from the pipe by soft brush andlor clean dry compressed air or by vacuum suction.

2.

As the pipe is rotating and moving forward, an overhead spray applies the appropriate primer. For coal tar enamel, a fast drying synthetic (chlorinated rubber) type B would be used and for bitumen enamels, a synthetic or bitumen based primer would be used. In both cases the DFT required would be in the region of 15-25 pm. The primers are low volume solids materials and dry in approximately 5-15 minutes, sometimes facilitated by blowing warm air through the pipe.

3.

When the primer is dry, a flood coating of hot enamel is applied using afiood box. The enamel should be constantly agitated and, as a general rule, should not L_ exceed 205"C, especially when there is a delay in application. Maximum application temperature for coal tar enamel: 250°C; discard enamel if temperature exceeds 260°C. Maximum application temperature for bitumen enamel: 230°C; discard enamel if temperature exceeds 240°C.

4.

Simultaneously, two reinforcements are applied in a spiral fashion, using a 150 mm wide strip of glass fibre inner wrap and a 150 mm to 230 mm wide strip of impregnated glass fibre outer wrap. The spiral overlap on each wrap should be at least 25 mm. The inner wrap should be embedded approximately half way into the enamel and should not be within 1 mm of the pipe surface. The outer wrap should be visible on the surface of the pipe coating.

5.

The wrapping (enamel plus reinforcement) should be trimmed back 150 mm from each end of the pipe and possibly bevelled, e.g. by at least 25 rnm.

6.

A solar protective coating should be applied whilst the pipe is still warm. White wash for coal tar enamels; blue wash for bitumen enamels. The washes should terminate 300 mm from each end of the wrapping.

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Typical thickness requirement: 4-7 mm.

Site application (welded joints) In the field, enamels can only be used on welded butt joints when the adjoining pipes are enamel coated.

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The sequence of events is essentially a manual reproduction of the factory system except now the pipes cannot be rotated or moved in any way. Sequence of operations

1. 2. 3.

Remove dust. Apply primer by brush.

4.

When primer is dry, apply the 1st flood coat of enamel. This is poured from a bucket and the coating is smoothed off (preventing icicles) by using a sling which is pulled back and forth around the joint by two operatives.

5.

Apply 2nd flood coat of enamel simultaneously with the application of a fibreglass inner wrap overlapping the existing coating by at least 75 mm.

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Blast clean to Sa2Y2.

Apply a 3rd flood coat of enamel and apply an enamel impregnated outer wrap. 6 Typical thickness requirement: minimum 4 mm.

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Safety When using coal tar enamels, due regard should be paid to the hazardous and irritant fumes. Barrier creams should be applied to all areas of bare skin and ideally masks worn. Contact with coal tar can cause warts. Medical advice should be sought at the first suspicion. It is not advisable to use enclosures during inclement weather because of the fumes. Coal tar and bitumen enamels should normally be used at temperatures below their spontaneous ignition temperature but even so, the vapour space is frequently within the flammable range, therefore smoking or naked flames should not be allowed in the vicinity of a tank or drum containing hot material and no source of ignition should be put into a tank or drum which has contained this material until the tank or drum is gas free.

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Tests on the primer 1.

Viscosity measurement using a flow cup at a specified temperature.

2.

Film thickness measurement.

Tests on the enamel material

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1.

Enamel temperature measurements.

2.

Softening point (ring and ball).

3.

Penetration.

4.

Viscosity measurement using a Zahn flow cup at 230°C.

Tests on the enamel coating 1.

Preliminary adhesion.

2.

Tapping tn check for laminations.

3.

Holiday detection.

4.

Bond strength test.

5.

Thickness of wrapping.

6.

Visual check for uniformity of coating contour, e.g. no icicles, ensure outer wrap is not disbonded and bleed through has taken place and ensure no coking exists.

7.

Coupons taken to ensure inner wrap is correctly positioned in enamel. Laminations may also be evident.

Determination of filler fineness, filler content, enamel specific gravity, peel resistance, sag resistance, flexibility (bend tests), low temperature disbondmentlcracking, impact resistance and cathodic disbondment, are other tests carried out at less frequent intervals, e.g. once a year or at the start of a project. The inner and outer wraps must also meet specified requirements for various tests.

Repairs Repairs to enamel coatings can be carried out by various methods depending on the nature and size of the coating fault. Pinholes are sometimes repaired using a hot knife whereas extensive damage would normally require full circumferential removal of the wrapping over the affected area. The bare area may then be repaired with the same enamel (normally incorporating reinforcement), heat shrinkable material, hot applied Q Ruane & T P O'Neill Issue 1 :28/04/97

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tape, cold applied laminate tape or a grease based t a F c . u m ~ ~ y ;.:& .3 2 & adhesive overwrap tape as specified. Multi-component hquids