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PAINT SQUARE WEBINAR

FIELD INSPECTION AND REPAIR OF TRANSMISSION

PIPELINE COATINGS

E. BUD SENKOWSKI, P.E.SENIOR CONSULTANT

KTA-TATOR, INC.

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WEBINAR CONTENT

Purpose of pipeline coatings Performance expectations of pipeline coatings Federal/state requirements for corrosion protection Purpose of field inspection Field inspection techniques Field installation and repair of pipeline coatings Protection of girth welds Repair of coating damage prior to burial Field rehabilitation of pipeline coating systems and joints

WHY DO WE NEED PIPELINE COATINGS?

Corrosion is the greatest danger to buried steel pipelines.

Uncontrolled corrosion of the pipe wall leads to leaks,

service interruptions, and even explosions.

Pipeline owners/operators place their

highest priorities on coating systems to

prevent corrosion.

Pipeline coatings are applied to both

pipe runs and girth welds.

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A STACK OF COATED PIPE

PERFORMANCE EXPECTATIONS OF PIPELINE COATINGS

Long-term protection of the pipeline steel surfaces from corrosion.

Compatibility with cathodic protection.

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INSTALLING A COATED PIPELINE IN THE TRENCH

FEDERAL REQUIREMENTS FOR THE CORROSION PROTECTION OF BURIED PIPELINES

All interstate pipelines shall be installed with an exterior coating system.

Additionally, all interstate coated pipelines shall be protected by a cathodic protection system providing:

A minimum pipe-to-soil potential of - 850 mV Or, a minimum polarization shift of 100 mV.

Many states have similar requirements for intrastate pipelines.

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PURPOSES OF FIELD COATING INSPECTION

Verify that the coating application meets the specification requirements for:

Surface cleanlinessSurface profileAllowable ambient conditionsDry film thickness (DFT)Absence of coating holidays (pinholes)Adhesion to steel substrateDegree of cure

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MATERIALS USED IN PIPELINE COATING SYSTEMS

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JOINT COATING AND REPAIR MATERIALS AVAILABLE FOR FIELD USE

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WHY DO PIPELINES HAVE JOINTS?

Pipelines have joints because they are

fabricated from 40’and 80’ coated pipe

sections.

High pressure pipelines require a girth weld at

each field joint.

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SETTING A PIPE SECTION IN THE TRENCH BEFORE WELDING

WHY MUST JOINTS BE COATED?

Each girth weld must be coated because the welds

are made on areas that are bare steel.

The bare area at the end of each pipe section is called the

“cut back” area. It can be up to 12” wide.

All girth welds must be coated before the line is buried.

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WELDING A PIPE JOINT. NOTE THE CUT-BACK AREA BETWEEN THE WELD AND THE YELLOW COATING.

COATING COMPATIBITY ISSUES WITH JOINT AND REPAIR MATERIALS

Coatings selected for a girth applications must be

compatible with the coating applied to the main pipeline.

In addition to chemical compatibility, the girth weld coating must form a tight seal

to prevent water infiltration.

If a generically similar coating is not available, there are

other joint and repair materials that will perform.

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LINE-TRAVELLING UNIT FOR APPLYING LIQUID EPOXY TO GIRTH WELDS ON AN FBE COATED PIPELINE

NEW CONSTRUCTION OR MAINTENANCE WORK?

New construction utilizes automatic line travelling equipment to blast and coat and cure girth welds.

Replacement and recoating of single sections

and their girth welds requires materials that cure under field conditions.

Cold and wet conditions require special material formulations.

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A LIQUID EPOXY APPLICATION TO THE MAINTENANCE REPLACEMENT OF A PIPE SECTION

WHAT IS MICROCRYSTALLINE WAX?

Microcrystalline wax is a solid by-product of petroleum that melts at 160-175°F.

When coating girth welds, the wax is heated in a pot to 270-350°F and applied by the “granny rag” method to reach 40-60 mils. It can also be applied by brush to small areas.

The wax develops excellent adhesion to cleaned steel and exhibits good flexibility.

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APPLYING MICROCRYSTALLINE WAX TO A GIRTH WELD USING A GRANNY RAG

WHAT ARE COLD-APPLIED TAPES?

Cold–applied tapes are prefabricated materials made from a polymer backing attached to an

adhesive film. Some may also use a liquid primer.

• Petroleum wax

•Polyethylene (PE)

•PE/PP blends

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WHAT IS PETROLEUM WAX TAPE?

Petroleum wax is a by-product of crude oil that is mixed with

mineral fillers, plasticizers, and corrosion inhibitors.

The wax is applied to a polyester mesh and used as a tape product over

pipeline and girth weld surfaces.

An additional wax-based filler with glass micro beads is used

to smooth out irregular shapes prior to coating.

The tape can be applied over tight rust. It contains no toxic

materials and can be placed in service immediately after application. 15

PETROLEUM WAX TAPE

WHAT IS POLYETHYLENE (PE) TAPE?

Polyethylene (PE) tape is a cold-applied joint covering that

has an elastomeric or butyl rubber-based adhesive.

Tapes use a high-density version (HDPE)for better resistance to mechanical damage.

HDPE tapes are compatible with most pipeline coatings in

current use.

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HDPE TAPE WRAPPED OVER A TEE IN AN FBE COATED PIPELINE

WHAT IS A MULTI-POLYMER ALLOY (MPA) TAPE?

Multi-polymer alloys (MPA)are proprietary blends of

polymers like polyethylene (PE) and polypropylene (PP)

They are applied cold with a pressure-sensitive

adhesive.

MPA tapes have temperature resistance to 250°F.

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HIGH TEMPERATURE TAPE APPLICATION

WHAT ARE HEAT-SHRINK PRODUCTS?

Heat-shrink products are made from specially-processed

PE or PP that will shrink when heated.

The reverse side of the sleeve is coated with an adhesive.

The adhesive layer becomes molten when heated and

upon cooling completes the seal to

the pipe surface.

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APPLYING A HEAT-SHRINK SLEEVE

WHAT KINDS OF HEAT-SHRINK PRODUCTS ARE AVAILABLE?

Heat –shrink products include tube sleeves, wrap-around sleeves and tape.

Shrink ratios are in the 2:1 and 3:1 with minimal change in

the linear direction along the pipe.

Some wrap-around sleeves have metal closure strips that

hold them together during application.

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COMPLETED HEAT-SHRINK SLEEVE OVER A GIRTH WELD

WHERE CAN HEAT SHRINK PRODUCTS BE USED?

Heat shrink products are available for pipe diameters

in the range of 2” to 60”.

They can be used with virtually all of the pipeline coatings in current use.

Depending upon the sleeve material and adhesive

they can be used on pipelines operating to 230°F.

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CONTINUOUS HEAT-SHRINK SLEEVES APPLIED OVER A SECTION OF DAMAGED ASPHALT PIPELINE COATING

WHAT IS LIQUID EPOXY?

Epoxy is a two-part liquid coating made by mixing a resin with a hardener.

After mixing and curing, a hard, tough,

chemically- resistant coating is formed.

Epoxy has excellent resistance to water penetration and cathodic disbondment damage.

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APPLYING LIQUID EPOXY TO A GIRTH WELD

HOW IS LIQUID EPOXY USED FOR JOINTS?

Epoxy is made to work in many field conditions. It is applied at 10-20 mils DFT using brush, roller, or spray.

Surface preparation requires a surface cleaned to an SSPC- SP10, Near-White condition.

Air and surface temperature should be at least Is

50°F.

Lower temperature versions are available. 22

CURED LIQUID EPOXY COATING ON A GIRTH WELD

COATING IN COLD WEATHER

Conventional epoxy formulations will

not cure in cold weather.

Supplemental heat must be used to heat the

pipe and cure the resin.

However, low temperature epoxies are available that can be applied and cured over a 4°F to 32°F temperature range.

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APPLYING LIQUID EPOXY IN COLD WEATHER

HOW IS FUSION-BONDED EPOXY (FBE) USED AS A JOINT COATING?

FBE is used the same way that the material is applied at the mill, except that the process is done in the field.

The weld area is cleaned to SSPC-SP10, Near-White Metal condition, heated by induction, and the FBE applied by electrostatic spray.

Heat completes the cure.

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A LINE-TRAVELLING FBE SPRAY UNIT FOR GIRTH WELD COATING

HOW ARE FBE JOINTS APPLIEDUNDER FIELD CONDITIONS?

Girth weld completion must go on regardless of

weather conditions.

When FBE is applied to welds it may be necessary

to erect environmentally controlled structures along the right-of-way.

Welding and coating takes place within the structures.

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HEATED SHELTERS FOR GIRTH WELD WORK IN COLD WEATHER

WHY DO WE REPAIR SMALL COATING DEFECTS?

Small coating defects can occur at any time on mill coated pipe from the point of manufacture to final burial in the trench.

Electrical testing (jeeping) can also reveal holidays that require repair.

Any unrepaired defect can become a point of

corrosion on the coated pipe.

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MAGNIFIED VIEW OF IMPACT DAMAGE ON AN FBE COATING

REPAIRING PIPELINE COATINGS WITH POLYMER-BASED TAPES

Defects or damage in many pipeline coatings can be repaired with cold-applied polymer-based tapes.

The tapes may utilize PVC, HDPE, HDPP, or MPA

polymers.

The areas to be repaired can be prepared by wire

brush.

A primer may be necessary to optimize the adhesive

bond of the tape.27

HAND-WRAPPING PE TAPE

REPAIRING PIPELINE COATINGS WITH HEAT-SHRINK SLEEVES

A variety of coated pipelines, including FBE and composite, 3-layer HDPE And HDPP, can be repaired using heat-shrink sleeves or tape.

Areas to be repaired can be cleaned by power-driven

wire brush.

The interior sleeve or tape surfaces will have a modified butyl rubber adhesive that will complete the adhesive bond.

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APPLYING HEAT-SHRINK TAPE AT A GIRTH WELD REPAIR

PRECAUTIONS WHEN USING HEAT-SHRINK PRODUCTS

The applications of heat shrink sleeves and tapes must be closely monitored to ensure that both

the preheating of the steel surface and heat applied to achieve the shrinking of the material is adequate to maximize the adhesive bond.

If the temperatures are below levels specified by the manufacturer, an insufficient bond will

form and lead to failure by water penetration. Pull-off peel tests provide a means to evaluate the adhesive bond of heat-shrink products in the field.

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MAKING REPAIRS TO LIQUID-APPLIED EPOXY AND POLYURETHANE

Pipelines originally coated with liquid epoxy or polyurethane coatings can be repaired by re-

applying the same materials.

Exposed metal should be cleaned to a near-white condition.

Weather conditions at the time of repair may require the

use of low temperature tolerant formulations.

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LIQUID EPOXY APPLICATION TO A PIPELINE AREA

MAKING REPAIRS TO FUSION-BONDED EPOXY WITH LIQUID/PASTE EPOXY

Small areas of damage in anFBE coating can be

repaired with a fast-curing, 100% solids, 2-component chemically-cured epoxy paste supplied in a dual-

component dispenser.

Once dispensed, the epoxy paste is mixed with a

spatula and applied to complete the repair.

Epoxy products develop a strong adhesive bond to FBE.

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A HAND-HELD GUN FOR DISPENSING A 2-COMPONENT EPOXY REPAIR PASTE

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REPAIRS WITH PLURAL COMPONENT HIGH SOLIDS SPRAY (HSS) UNITS

Field repairs can also be made by spraying plural component epoxy with a high solids spray (HSS) unit.

HSS units are scaled-down, disposable spray units that use compressed air at 40-50 psi to mix and spray the contents (40-1000 mL) of a dual (resin/hardener) cartridge pack.

For best results, the cartridges should be heated to approximately 120-130°F before use.

HSS DISPOSABLE SPRAY UNIT

FIELD REPAIRS TO 3-LAYER COMPOSITE COATINGS

Composite, 3-layer polypropylene (3LPP) and polyethylene (3LPE) coatings can be repaired using hot microcrystalline wax, cold applied tape, and heat-shrink products.

HDPP heat-shrink products match the thermal and mechanical resistance of

the original 3LPP composite coating.

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TESTING A HDPP HEAT-SHRINK SLEEVE APPLIED OVER A 3LPP COATING

JOINT COATING AND REPAIR MATERIALS AVAILABLE FOR FIELD USE

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QUESTIONS?

QUESTIONS?