BUILDING UP A PIPELINE'S ARMOUR

GlobalData puts the length of global trunk/transmission pipelines at almost 1.25 million miles (2 million km). These pipelines conduit the world’s crude oil, petroleum, natural gas and natural gas liquids from source to refineries, ports, distribution outlets and homes. They are costly to construct, monitor and maintain, and failure can be catastrophic: putting lives, the environment, reputations and revenues at risk. This makes protecting them critical.

Pipeline failure is caused by a number of factors. Corrosion is among the top three. If the pipeline is exposed, a rockshield wrap can lower the risk significantly.

THE COST OF FAILURE
• Pipeline failure can have a huge impact. Since the materials being conveyed are highly flammable, the risk of a fire or an explosion is very high. This can have a direct negative impact on the immediate environment in which the pipeline is located, threatening worker safety and the health of nearby human settlements. In addition, toxic spills can enter groundwater and smoke can affect air quality, increasing the reach of pollution and contamination.

• A 2019 FracTracker analysis of fossil fuel pipeline incidents in the US over a nine-year period lists more than 5500 total incidents causing almost 600 injuries, more than 125 fatalities, 800 fires and 300 explosions, and more than US$4 billion in damages. Almost 30 000 had to be evacuated.

It notes that:
• Hazardous liquids pipelines cause the majority of incidents (64%) and damages (also 64%).

• Newer pipelines less than 10 years old have more incidents than any other age group.

• The causes of these tragedies include equipment failure, operator error, and corrosion.

The US Department of Transport’s Pipeline and Hazardous Materials Safety Administration (PHMSA) Pipeline Incidents report (2000 - 2019) indicates 658 incidents in total in 2019, costing over US$316 million (down from US$2.5 billion in 2018). Of the 658 incidents, almost a quarter were the result of corrosion, over 10% were from excavation damage, and a bumper 43.2% resulted from equipment/weld/material failure.

Another, broader study looking at significant pipeline failures across the UK, US, EU and China in the period 2006 to 2015 also puts corrosion among the top causes. It lists illegal tapping or external interference (up to 50% of failures in these geographies), manufacturing and construction defects (~30% and higher), and corrosion (up to 25%) as the main factors for failure.

The oil and gas industry is highly focused on minimising and eliminating such incidents. Proper corrosion protection can make a significant difference. What can go wrong?

CORROSION AND RISK
Pipelines differ in size and physical make-up depending on the application (i.e. what is being transported) and what part of the refining or delivery process it completes. Gathering lines (up to approximately 11 in. or 30 cm in diameter) usually move product short distances from source to refineries. Feeder lines move the product from processing facilities to transmission lines and distribution lines. Of these, transmission pipelines are longest, often crossing international borders; and largest, reaching up to 1 m in diameter. Maintenance on these pipelines is thus vital to ensure the supply of critical products, to maintain supply chain performance, to prevent disasters, and prevent loss of revenue.

HOW CAN PIPELINES BE PROTECTED FROM CORROSION?
Most transmission lines today are made of carbon steel. Mechanical failure (leaks) can result from improper construction and operations, equipment or material failure and – our focus in this article – corrosion. Recognising this, most countries have put in place regulations that require that the pipes be coated inside and outside to protect against corrosion. Exterior coatings can vary but the most common are fusion-bonded epoxy or polyethylene heat-shrink sleeves. These coatings provide the primary barrier against any corrosive materials that the pipeline might be exposed to in the field, and work together with cathodic protection (CP) to provide a longer lasting barrier.

CP is used in old and new pipelines, preventing corrosion from starting or progressing. CP uses direct electrical current to counteract the normal external corrosion that occurs on metal due to soil and moisture conditions. This is especially useful where a pipeline is buried underground or submerged in water. However, in some instances, pipelines will run above ground. When they do, CP does not work; the coating becomes the primary source of external protection.

As impacts from rocks or other external factors – such as vandalism, being struck by a vehicle or a natural event such as lightning or heavy flooding – can compromise these coatings, exposing the bare metal to corrosion, further protection is required.

The risk is not inconsequential. Transmission pipelines travel hundreds and sometimes thousands of miles, traversing a multitude of geographical settings – from mountainous areas to flat clayey soils. As the main installation method for pipelines is ‘open pit’ – i.e. excavate, place and cover – ease and cost of installation depends on the geography.

To protect the longevity of pipelines, operators are at pains to prevent leaks during installation. The most common failure during installation occurs through improper bedding and placement of the pipeline – for example, construction near the pipeline or improper backfilling that can cause angular rocks to compromise the coating. The risk increases depending on the ground that the pipeline is being installed in, and the exposure of the pipeline to common factors of failure.

ADDING A ROCKSHIELD
Engineers and operators have a number of solutions to prevent these incidents from happening. One solution to protect a pipeline during installation is to implement a rockshield on the outside of the pipe. A rockshield is a physical barrier, typically comprised of a tough polyethylene material that can be wrapped around the pipeline. It protects the pipe and its coating during installation against any angular rocks, and through the lifetime of the pipe from mechanical impacts. A good rockshield will do this without inhibiting cathodic protection.

In addition to puncture resistance, an important characteristic of these products is their ability to absorb the energy of an impact, preventing it from being transferred to and over the pipeline.

Solmax has gone to great lengths to develop a rockshield solution that meets these requirements. The RockArmourTM PRO helps minimise the number of pipeline incidents and prolong the life of pipelines all over the world. The company has also developed RockArmourTM GRID and GRID PLUS versions that comprise a proprietary polyethylene-based formulation extruded grid material, and a gridded material with an additional polypropylene nonwoven geotextile laminated material for additional protection.
Installation of rockshield, especially on long and large pipes, can be labour intensive. Solmax has also gone a step further, adding significant ease and cost efficiency to the company’s solution through the addition of an innovative installation system.

WHAT DOES IT LOOK LIKE?
RockArmourTM PRO is a perforated low-density polyethylene wrap that delivers high puncture resistance, impact resistance and tear strength thanks to specially formulated polyethylene polymers. It protects coated pipes from damage from stones during backfill operations, and it allows cathodic protection current to flow, protecting against damage on the coated pipe surface.

The installation of RockArmour PRO is quicker thanks to embedded tightening straps and longer roll lengths, which are manufactured to meet project needs. This rockshield is installed using a material roller implement (a lowering cradle) that is mounted on an excavator. It can also be manually un-rolled, which helps when equipment access is limited. It is secured using 400 lb (~180 kg) tensile strength ties integrated every 3 ft. The ties are installed at Solmax’s site before shipping, allowing for maximum efficiency in the field during installation – it only requires a four person crew, allowing contactors to save as much as 75% in labour costs, and maintain or exceed the run rate required to stay ahead in the field. This combination means more miles of pipeline that take less time to install, and costs less.

For pipeline operators, rockshields are not ‘a nice to have’. Given the impact of corrosion and potential cost of failure, it is an integral part of pipeline design and risk management in areas where the geography calls for it.

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Original Article Published in World Pipelines:
http://publications.worldpipelines.com/flip/world-pipelines/2020/October/otwp10.html#42