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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
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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.
A STACK OF COATED PIPE
 Pipeline coatings are applied to
both pipe runs and girth welds.
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PERFORMANCE EXPECTATIONS
OF PIPELINE COATINGS
 Long-term protection of the
pipeline steel surfaces from
corrosion.
 Compatibility with cathodic
protection.
INSTALLING A COATED
PIPELINE IN THE TRENCH
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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 cleanliness
 Surface profile
 Allowable ambient conditions
 Dry film thickness (DFT)
 Absence of coating holidays (pinholes)
 Adhesion to steel substrate
 Degree 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.
SETTING A PIPE SECTION IN THE
TRENCH BEFORE WELDING
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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.
WELDING A PIPE JOINT. NOTE THE CUTBACK AREA BETWEEN THE WELD AND
THE YELLOW COATING.
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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.
LINE-TRAVELLING UNIT FOR APPLYING
LIQUID EPOXY TO GIRTH WELDS ON AN
FBE COATED PIPELINE
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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.
A LIQUID EPOXY APPLICATION TO
THE MAINTENANCE
REPLACEMENT OF A PIPE
SECTION
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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 270350°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.
APPLYING MICROCRYSTALLINE
WAX TO A GIRTH WELD USING A
GRANNY RAG
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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.
PETROLEUM WAX TAPE
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WHAT IS POLYETHYLENE (PE) TAPE?
 Polyethylene (PE) tape is a coldapplied joint covering that has an
elastomeric or butyl rubberbased 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.
HDPE TAPE WRAPPED OVER A TEE
IN AN FBE COATED PIPELINE
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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.
HIGH TEMPERATURE TAPE
APPLICATION
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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.
APPLYING A HEAT-SHRINK SLEEVE
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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.
COMPLETED HEAT-SHRINK SLEEVE
OVER A GIRTH WELD
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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.
CONTINUOUS HEAT-SHRINK SLEEVES
APPLIED OVER A SECTION OF
DAMAGED ASPHALT PIPELINE
COATING
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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, chemicallyresistant coating is formed.
 Epoxy has excellent
resistance to water
penetration and cathodic
disbondment damage.
APPLYING LIQUID EPOXY TO A GIRTH
WELD
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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 SSPCSP10, Near-White condition.
 Air and surface temperature
should be at least Is 50°F.
 Lower temperature versions
are available.
CURED LIQUID EPOXY COATING ON A
GIRTH WELD
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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.
APPLYING LIQUID EPOXY IN COLD
WEATHER
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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.
A LINE-TRAVELLING FBE SPRAY UNIT
FOR GIRTH WELD COATING
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HOW ARE FBE JOINTS APPLIED
UNDER 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.
HEATED SHELTERS FOR GIRTH WELD
WORK IN COLD WEATHER
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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.
MAGNIFIED VIEW OF IMPACT DAMAGE
ON AN FBE COATING
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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.
HAND-WRAPPING PE TAPE
 A primer may be necessary to
optimize the adhesive bond of
the tape.
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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.
APPLYING HEAT-SHRINK TAPE AT A
GIRTH WELD REPAIR
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PRECAUTIONS WHEN USING HEATSHRINK 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 reapplying 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.
LIQUID EPOXY APPLICATION TO A
PIPELINE AREA
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MAKING REPAIRS TO FUSION-BONDED
EPOXY WITH LIQUID/PASTE EPOXY
 Small areas of damage in an
FBE coating can be repaired
with a fast-curing, 100% solids,
2-component chemically-cured
epoxy paste supplied in a dualcomponent 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.
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
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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.
TESTING A HDPP HEAT-SHRINK
SLEEVE APPLIED OVER A 3LPP
COATING
33
JOINT COATING AND REPAIR
MATERIALS AVAILABLE FOR FIELD USE
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QUESTIONS?
QUESTIONS?
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