The document discusses an offshore project in the Gulf of Arabia near Qatar where CRTS was hired to coat the internal field joints (IFJs) of a new pipeline to prevent internal corrosion. CRTS designed specialized robotic equipment to remotely clean, inspect, and coat the nearly 13,000 IFJs, which represent a small portion of the pipeline but are highly susceptible to leaks and corrosion. The customized equipment allowed for remote, efficient coating of the IFJs in the unique offshore environment. Coating the IFJs provides critical protection from internal corrosion to help ensure the integrity and longevity of the pipeline.

1. THE
OFFSHORE
COATING
TECHNIQUE
Renato Sanchez, Engineering
Manager, and Caroline A.
Fisher, Technical Writer, CRTS,
Inc., USA, examine the use of
internal field joint coatings in
unique, offshore locations.
W
hen building a pipeline of nearly 13 000 welds,
corrosion management is naturally part of the
design. Unfortunately, while the majority of
pipelines are built with reasonable monitoring and
inspection plans in place, little attention is paid to the bare steel
on the internal field joints (IFJs) where leaks and internal corrosion
often occur. This bare steel represents approximately 2% of the
entire pipeline, yet easily becomes the pipeline’s weakest link if
not protected.
To prevent internal corrosion, one of the largest oil
companies in the world awarded CRTS an offshore project in
the Gulf of Arabia near Qatar in 2012. This pipeline crosses the
Hasbah and Arabiyah gas fields and CRTS completed its corrosion
prevention services in January 2015. The operation was based at
the company’s facility in Abqaiq, Kingdom of Saudi Arabia, and
at that time was the largest project ever awarded to CRTS. Why
was IFJ coating chosen over other corrosion prevention methods?
Corroded, leaking pipelines on the ocean floor are not a viable
option for owners or the environment. Coating the IFJs provides
the most mitigation for the money.
Preventing corrosion from the inside out
Designing a pipeline to endure a lifetime means employing
corrosion prevention techniques that do more than meet the
minimum standards; the pipeline should have built-in measures,
such as corrosion prevention coatings, that prevent corrosion or
greatly mitigate it. Built-in prevention does not exclude future
inspection and monitoring; corrosion prevention coatings do
however add many benefits such as:
)) Maintain product purity.
)) Increase pipeline longevity.
)) Reduce internal corrosion.
)) Reduce pipeline flow friction, which minimises pressure drop.
)) Reduce pipe wall thickness requirements.
)) Diminish or eliminate pipeline leaks.
)) Protect the environment from leaks, ruptures or spills.
These benefits are inherent to the parent coating of
pipelines, but when also applied to the internal field joint, they
create seamless, defect-free protection from internal corrosion.
These benefits also address the gravity of internal corrosion
consequences: deepwater pipelines need defect-free, continuous
internal coatings to complement the expensive and complicated
methods of monitoring and inspection.
Customised equipment for best practice
The sheer number of welds and impact on the marine
environment with a project of this size is enough to warrant
specialised equipment and testing. The complexity of keeping
equipment running efficiently while performing also warranted

2. exceptional design. While the customised equipment may seem
excessive at the outset, the long-term OPEX savings, protected
public and marine environment demonstrate that every detail is
essential.
Offshore, there are electronic challenges: the robotic
equipment uses telemetry and it had to be robust enough to
transmit not only through external welding-generated electrical
noise, but also through a massive internal laser welding lineup
clamp. Altogether, 60 printed circuit boards and 11 microprocessor
boards were onboard each set of robotic equipment.
There are also mechanical challenges unique to offshore
work: CRTS engineers designed offshore-rated lifting frames for
all of its robotic equipment, which included equipment baskets
and compressor frames. The frames were designed in Tulsa and
fabricated and load tested in our Abqaiq, Saudi Arabia location.
Six sets of equipment were made, each set consisting of a crawler,
battery cart, cleaner, vacuum and liquid coater. In total, with more
than 100 45Ah batteries on each set of equipment, nearly US$1 million
was spent on batteries alone.
Moving heavy pipe safely and efficiently is a safety concern on
a laybarge. CRTS designed pipe rotators that were used to rotate
the 36 in. pipe with a 1 5/8 in. wall. Each pipe piece was 80 ft long
and was covered with 4 - 6 in. of concrete coating. These massive
rotators had a lifting capacity of 50 t and were used to rotate the
pipe during the preblasting process, which collects and recycles
the abrasive blasting media.
Besides building coating equipment for the IFJs, CRTS
perfected a recovery system in case any equipment rolled to the
bottom of the S-bend. Although CRTS has coated thousands of
offshore IFJs with no mishaps, the customer was adamant that a
recovery system be in place, a safety practice approved by CRTS.
A few simple mechanical components were added to the crawler
features, such as a delatching mechanism for the 10 000 lb of
equipment. CRTS also designed a safety winch as a fail-safe for
retrieving runaway equipment. As expected, it was never used.
Preparing the IFJ for coating
One of the main benefits of remotely controlled robotic
equipment is that it identifies uncoatable (corrosion inviting)
welds at the beginning of the corrosion prevention process. The
wireless video system identified weld imperfections at the root
pass, which made correcting them much simpler than finding
them after all the welding passes had been completed. The visual
inspection of the welding root pass is a valuable tool, regardless
of whether the pipe is coated or not (CRTS has performed this
function for clad steel). Cutting out pipe is one of the most
expensive activities on a lay barge, especially if the faulty section
is not found until after the pipe has been internally coated and is
about to enter the stinger.
Preventing corrosion by applying coatings is easy; preparing
the pipe surface for coating takes stringent effort. Since each
weld is a potential source of corrosion due to its protrusion
into the flow stream, before the pipe was welded together,
handheld abrasive blasting equipment was used to create a
surface roughness on the cutback area that met the coating
manufacturer’s standard.
Once the surface roughness was measured and approved,
the pipe was loaded onto the ready rack, then entered the first
station, the bead stall. After this pipe was welded to another pipe,
the cleaner and vacuum robots worked in tandem to provide the
foundation of seamless internal corrosion prevention: superior
surface preparation.
Figure 1. This train of equipment cleaned and coated nearly
13 000 internal field joints on a Middle East offshore project.
Figure 2. Factory-coated pipe strengthened with coated
internal field joints enters the Arabian Gulf.
Figure 3. CRTS field technicians use telemetry to communicate
with its robotic equipment while it is inside the pipe. This
wireless communication includes receiving video and
equipment parameters data from the equipment cameras.
World Pipelines / REPRINTED FROM AUGUST 2015

3. The robotic cleaner uses a high speed cleaning wheel
to remove weld slag and other impurities generated by the
welding process. The cleaner applied abrasive to the IFJ and then
vacuumed and recycled the abrasive for use on the next IFJ. A
visual inspection using an onboard camera ensured the proper
level of cleanliness was achieved and no debris remained. The IFJ
surface was then ready to receive the protective coating.
Coating the IFJ
CRTS’ coaters are the heart of internal corrosion prevention and
one of the most complex machines that CRTS designs and builds.
Years of design and testing have culminated in machinery that
uses various coating heads to precisely apply both FBE and liquid
coatings on offshore and onshore projects. For this project, the
customer chose SP 9888, a two-part liquid epoxy, to protect the
nearly 13 000 submerged IFJs. The plural component liquid coater
has infinite ratio adjustment with its range, allowing its use with
many different types of materials. The coating operator set the
pump speeds and oscillation distances to accommodate the pipe’s
cutback lengths. This, along with its independent heat controls
for the material components, allowed for mixing and application
conditions as recommended by the coating manufacturer.
The liquid coater was also outfitted with wireless telemetry
and video to allow remote operations. These features enabled the
operator to remotely send the liquid coater to each IFJ for coating.
The camera lets the operator view the weld to ensure it’s coatable
(no abrasive or welding residue); line up to the weld; trigger and
observe the actual coating sequence. Another feature of the
onboard camera is that it allows for instant visual inspection
of the IFJ. Inspecting the coated IFJ at this stage meant that if a
coated weld had any visual defects, it could be repaired before
any product entered the pipe. CRTS also has a fusion-bond epoxy
coater for FBE projects.
Conclusion
CRTS applies its robotic technology to address the high cost of
monitoring, repairing and rehabilitating pipelines by using a simple
process of cleaning, coating and inspecting internal field joints and,
if requested, the internal length of the pipeline. This foundation of
internal corrosion prevention attempts to benefit the pipe owner,
the public and the environment by addressing corrosion before it
has a chance to form and wreak havoc on assets.
This seamless corrosion prevention system works alongside
factory-coated pipe to meet PHMSA’s goal of reducing “the
occurrence of defects that can lead to corrosion-induced failures.”1
While this PHMSA report focuses mainly on US transportation
pipelines, it is a goal worthy of any pipeline project.
Part of the reduction goal on CRTS’ part is designing and
building equipment that works efficiently with the project’s
geographical and other challenges. For this particular customer,
the additional preventive measures will result in lowered OPEX
and repairs over a lengthy lifetime of production.
Reference
1. Fact Sheet: Internal Corrosion. Retrieved from: http://primis.phmsa.dot.gov/comm/
FactSheets/FSInternalCorrosion.htm
REPRINTED FROM AUGUST 2015 / World Pipelines