New maintenance in the pipeline

The maintenance of oil and gas infrastructure is critical for safety and performance, but the challenges presented by the conditions and materials ensure that new maintenance efforts are emerging all the time. In any industry, assets deteriorate over time. Equipment wears out. Tools need replacing. And infrastructure requires maintenance. But the matter is particularly pressing in an industry such as the oil and gas industry. Not only are the materials that the business mines a corrosive mixture, but the pipes, platforms and rigs that conduct the mining and transport the mixtures are often in remote locations with extreme environments. As such, regular and effective maintenance to the equipment and infrastructure is absolutely vital to the industry.

“If maintenance isn’t properly undertaken then there would undoubtedly be an increased number of unscheduled breakdowns,” emphasises Grace Baxter, Lead Maintenance Engineer at the Oil and Gas Division of project management and services company AMEC. “You could have plant upsets, and that would greatly reduce product throughput. But more importantly, if you have leaks or escapes of gas then that is a safety issue. So the main focus is ensuring the integrity of equipment is adequate to ensure that you don’t have any conditions on the platform that would be a danger first of all to the personnel and secondly to the equipment and the platform.”

The logistics of working offshore, however, also ensure that maintenance can be an expensive undertaking in this industry. Getting the staff and equipment to an offshore installation, for instance, is one reason that the costs are higher within oil and gas than other sectors. But bolstering these costs are the stringent measures that firms must abide by. “The same problems happen offshore as onshore,” continues Baxter. “Because gas is highly volatile, you have to have a lot of precautions in place. Companies have to undertake technical integrity assurance to ensure that you are not getting to any stage with corrosion that you could have gas escape. That’s where the costs come in – in assuring that you are staying within your operating envelope so that you can operate safely. It doesn’t matter whether it is onshore or offshore. The costs are fairly high but they are essential because it is a safety issue and that is part of the cost of extracting these very valuable fluids.”

Corrosion certainly is an issue of primary concern for the industry. Combining the annual corrosion costs of production, refining, storage, transportation and distribution, the CC Technologies/NACE international cost of corrosion study for oil and gas estimates the figure to be US$24.1 billion annually.

“The cost of corrosion is a waste of resources and investments,” says Neil Thompson, President of NACE International, the professional technical society dedicated to reducing corrosion. “Corrosion is seldom a positive event and the total cost of corrosion in the US, for instance, is 3 percent of the GDP (US$276 billion annually) – a staggering amount. Just as staggering, is that industry experts estimate that at least 30 percent of this cost can be saved by applying current best practice engineering and maintenance to corrosion control.”

Protective coatings

The magnitude of savings of the cost of corrosion is dependent on the technology and mitigation practices applied within any specific industry. But corrosion control and integrity management for pipelines have made significant advances in the past five years. One of the latest trends in pipeline integrity is Direct Assessment techniques. NACE International has taken a lead role by developing standards for practices of external corrosion direct assessment (ECDA), internal corrosion direct assessment (ICDA), and stress corrosion cracking direct assessment (SCCDA). Direct Assessment methodologies are relatively new and their application is not consistent throughout industry even for those for which NACE standards have been released. However, direct assessment methodologies are having a key role in the overall integrity management programs for pipelines along with ILI technologies.

Protective coatings have emerged as a particularly critical tool in the operator’s armament when tackling the problem of corrosion. “Protective coatings are extremely important to most all industries as a primary defense against corrosion,” says Thompson. “In many applications, coating is the only defense against corrosion. In other cases, a corrosion resistant alloy may be coated to impart added protection. In the case of pipelines, corrosion control is obtained by the application of coating and a cathodic protection system, both of which are critical to an effective protection system. Improved coatings have also been developed that have the ability to increase the life of the pipeline through better corrosion control.”

But improvements in other areas are now also providing valuable efforts to keep corrosion under control. “In the pipeline area, better corrosion assessment programmes (ILI improvements and direct assessment methods) have been the most significant developments,” Thompson continues. “In difficult areas, (i.e. multiple pipelines in a right-of-way, pipeline crossings, stray current areas, induced AC from parallel HVAC power lines in the pipeline right-of-way) the use of coupons has been a significant improvement for determining that an acceptable level of CP is applied to the pipeline to meet criterion.

“The oil and gas industry is making progress in many areas of corrosion control. Integrated risk assessment and integrity management programs have greatly increased awareness of critical corrosion problems within the industry. Significant progress can still be made in corrosion monitoring and life prediction modeling for many of the processes involved in the oil and gas industry, especially in the process plants and production areas, as well as pipelines.”

Paraffin wax

Maintenance to pipelines, however, doesn’t begin and end with matters concerning corrosion. There are also performance issues relating to flow to take into consideration. In the current economic climate, operators cannot afford to be inefficient. Every aspect of operations has to come under the spotlight to ensure that it is not running below acceptable standards. And every measure has to be taken to guarantee that these operations, once up to par, will remain that way. However, through the course of normal procedures, operators must accept that the level of efficiency will, from time to time, dip and that steps must be taken to isolate the problem and rectify it.

The problem of paraffin wax solids in pipelines and risers is an ongoing challenge to operators, and they can have a significant effect on oil production if not dealt with. Wax deposition in the pipeline can cause increased pipeline pressure drop resulting in reduced throughput and therefore leading to reduced revenue. In more extreme cases the pipeline can plug, thus halting production and leading to a huge loss of earnings especially at recent oil prices

But, as a result of increasing understanding of the problems of wax deposits, there are now successful preventative solutions, including chemical treatment and hot oiling. But most commonly, the problem is solved through ‘pigging’.
“Pigging has been around for many years now and has been the traditional approach to pipeline cleaning and handling problems with debris accumulation in the line,” explains Dr Aidan O’Donoghue. Technical Adviser at the Pigging Products & Services Association. “It is a very important tool in the pipeline Flow Assurance toolbox. The main driver for using pigs compared with other techniques is generally cost and the fact that most pipelines are set up to be piggable today. This makes the use of pigs a routine part of pipeline maintenance and operation.”

Cleaning pigs are launched and received in order to keep the pipeline running at its optimal efficiency. As pipelines are the most cost effective method of transporting fluid, and as such, they must be maintained. But they also pose a threat to safety and the environment and as such, the line integrity must be checked on an ongoing basis. One way of doing this is to use an intelligent pig.

There are different types of intelligent pig: Magnetic Flux Leakage tools which assess defects in the line by measuring flux leakage as a result of saturating the pipewall using very strong magnets; ultrasonic tools which use ultrasound to assess the thickness of the pipewall or remaining wall; and crack detection tools based on a variety of technologies.

“In addition, it is possible to fit smart devices to cleaning type pigs to assess certain features in the line,” says O’Donoghue. “Such devices include data loggers to measure certain parameters that can then be analysed to provide a picture of the line. Calliper tools can be used to check for dents in the pipeline. Pipeline out of straightness can be assessed using geometry tools. Once the major threats to the pipeline integrity are understood, a series of such tools can be sent to ascertain the current health of the line and allow prediction of future life.”

High frequency pigging

In general, pigging is the cost-effective option for most pipelines given the necessary launch and receive facilities and due to the general low cost of a pig. However, there are times when a considerable investment is required in terms of CAPEX and OPEX. “Offshore flowlines may require round trip pigging to wells or the installation of subsea launchers for instance,” highlights O’Donoghue. “In this case then considerable investment in subsea equipment and possible additional pipelines is required to allow pigging to be possible. With subsea launching or pigging from normally unmanned platforms, then cost is incurred in order to launch the pigs. For high frequency pigging, this may make pigging unfeasible and therefore other methods employed. In this case, some cost-benefit analysis is required.”

Pipeline pigging continues to evolve however, ensuring that it the technology is increasingly workable in any scenario. Some of the latest developments include:
• The ability to pig and inspect so called unpiggable pipelines. These lines could be dual diameter, have difficult to negotiate bends or lack launch and receive facilities. More and more of these lines are now been pigged with regulation changes forcing the pace. This has aided in safeguarding older pipelines;
• A better understanding of how pigs work in the pipeline to avoid problems such as stuck pigs, inefficient pig runs and general problems when running the tools. More thought and understanding is being put into the tools and their operation;
• Increasing ability to provide information on the status of the pipeline through improved inspection pigging (higher resolution and accuracy) and smart pigs using data loggers.

“In general, the problems that the operators face are being met to allow the efficiency of the pipeline to be maintained and the integrity to be assessed and verified,” adds O’Donoghue.

“There have been vast changes in how maintenance is approached over the years,” says Baxter. “It used to be reactive maintenance for instance – you fix it, you wait for it to breakdown and then fix it again. But now there is a much more planned maintenance regime, where you fix it before it breaks so that you are not getting any surprises.” Baxter speaks from experience. Her firm, AMEC, has worked to provide planned preventative maintenance, repair and replacement of mechanical and electrical services for over two decades, to enhance owner value, reduce maintenance and operating costs and ensure optimum performance.

Sea change
AMEC’s shift in emphasis reflects the changing approach to maintenance. “We moved to what I would call an ‘improved precision’-type maintenance where we do analysis, and things like total productive maintenance, root cause failure analysis and risk-based inspections. We also improve skills of the people doing the maintenance. One of our current projects involves employing technicians and operations people and we are in the process of teaching local people how to do these jobs. They have the skills and the knowledge from the classroom but we are training them up on the platform in how to maintain and operate the platform safely. Then, eventually we will move out, a gradual withdrawal as we increase their capabilities and their competences. They will then have the competency to recognise problems themselves and predict what will happen and cure them before they become an unsafe condition.”

Indeed, there has been a sea change in the entire industry’s approach to maintenance in recent decades. Certainly the leapfrogs in technological development have played a critical role in the life expectancy of infrastructures and the safety of equipment. The emergence of the latest coating technologies and pigging equipment and their subsequent impact on performance are a case in point.

However, there has also been a more fundamental change, a shift in mindset. The industry is now looking to pre-empt problems, and negate any costly shutdowns or performance dips altogether. Technologies are increasingly developed to flag up any potential problems rather than react once they occur. And maintenance support strategies are increasingly focusing on how the most fundamental tools – the workers – can also be finely tuned to identify and rectify such problems. All of these developments point to a safer and more efficient industry for the future.

“We have probably a better trained workforce than we have ever had before and better tools, more tools designed specifically for the types of jobs that we are doing, which have grown and improved over the years,” concludes Baxter. “We are in a better place now than we ever have been.”

Boxout:

Corrosion costs

For oil and gas the annual corrosion costs can be broken down as:

Production US$1.4 billion
Refining US$3.7 billion
Storage (AST & UST) US$7.0 billion
Transportation (Natural Gas and Liquid) US$7.0 billion
Distribution (Natural Gas) US$5.0 billon

Source: NACE