24/7 pipeline intelligence

Figure 4. When complete the pipeline will supply Bulgaria with low-carbon natural gas.

Figure 5. Kostas Plainos, Mechanical Engineer of AVAX Group, (left) with Haris Bailas of Sigma Bulgaria.

considered among the best and highest quality machines in the industry. We have been very satisfied with the way they have performed for the implementation of this demanding pipeline. We don’t face major breakdowns and the response of the service team is prompt when required. And according to our operators, the machines run smoothly and exhibit no difficulties in movement and pipe lifting. The controllers also have a very good response and are easy to use.”

This is not the first time AVAX has worked with Volvo CE. The company also used Volvo pipelayers in the construction of the high pressure natural gas pipeline between Theodori and the Public Power Corporation’s Plant (PPC) at Megalopolis in South Greece, back in 2014. At the time deemed one of the most challenging pipeline projects in Europe, due to the mountainous terrain, extremely steep slopes and hard rock, it was important that the work for this megaproject was carried out with the utmost safety.

So for this 24 in. and 30 in. pipeline measuring a total length of 158 km, AVAX acquired seven Volvo PL3005Ds, five Volvo PL4608s and the Volvo PL4809. Thanks to the machines’ capability of placing the boom uphill to stabilise the machine on steep slopes, single grousers to provide the right grip and traction, a cab riser for better visiability and easy to control and smooth hydraulics, safety always came first. Volvo CE also chose the project as a final test period for the new PL4809 before its global release in late 2014. The close collaboration between the two partners was further demonstrated by the recommendations and remarks from AVAX which informed the final touches to the PL4809 before it was released to the market.

Now in its latest iteration, the versatile PL4809E pipelayer not only displays stability and safety no matter the conditions, but if required can also be converted into a standard excavator, thereby offering the benefits of two machines in one. While the digging kits for machine conversation were not required for this particular job with AVAX, hydraulics perfectly matched for both pipelaying and digging applications means there is no loss of power in either configuration.

Built on decades of engineering excellence Volvo’s E-Series pipelayers are built to deliver equal measures of productivity and safety – starting with the Volvo cab. From the adjustable air-suspended seat, the operator is in total control of his comfort. The spacious, noise and climate-controlled environment is further enhanced by controls that fall easily to hand. The hydraulically-elevated ROPS-safety certified cab delivers a commanding view of the job site and trench and features the Intelligent Load Management System (LMS), which monitors the load and alerts the operator when the limit is reached, for optimum safety and efficiency.

The sale of the machines for the ICGB project was completed through the Sigma Bulgaria dealership, a member of the Greek multinational group Saracakis, whose team of highly qualified specialists pride themselves on finding the right service and projects for its customers with guaranteed speed and reliability. Haris Bailas, Executive Director at Sigma Bulgaria, says: “As the first project that AVAX has won in the region of Bulgaria, it was important that we at Sigma Bulgaria delivered the best for the job and we are proud to have performed our best efforts to support the Greek company. The support of Volvo CE is invaluable during this process and I consider that all parties are not only committed, but also aligned, in order to perform to the highest possible global standards.”

AVAX Group regularly participates in tender procedures for major projects and is a major contributor to the Greek economy with an acclaimed status in international markets. Furthermore, it is one of the few companies with specialised know-how and experience in mechanical, electrical and plumbing (MEP) works in the Middle East region. The group is also the only Greek construction company certified to implement high pressure large diameter pipeline projects – having successfully delivered 365 km of 48 in. pipeline for the Greek section of the mega pipeline project Trans Adriatic Pipeline Project (TAP) in 2019, as well as delivering 158 km of DESFA’s demanding high pressure natural gas pipeline from Theodori to Megalopolis in South Greece in 2014. Thanks to a strong collaboration across all parties, this latest ICGB project is yet another challenging pipeline project for AVAX that is being completed to the highest possible standards in safety, innovation and environmental issues.

The Fiber Optic Sensing Association (FOSA) discusses how distributed fibre optic sensing technology is advancing safety and efficiency in pipeline operations.

Pipeline integrity is critical for safe and efficient pipeline operation. There are several reasons why a pipeline network needs to be monitored: for example, leak detection, accidental or malicious damage, subsidence and theft. Distributed fibre optic sensing (DFOS) provides the unique ability to monitor in real-time several physical phenomena associated with these threats, such as temperature, strain and vibration. As such, the technology is increasingly being applied in the monitoring of pipeline networks as it overcomes many of the challenges associated with traditional discrete sensors and periodic monitoring and inspection approaches. This article by FOSA reviews the different technologies, their advantages, which applications they are most appropriate for and considerations to take when laying fibre.

Technology background DFOS uses a process whereby an interrogator sends pulses of laser radiation into a fibre and analyses the backscattered radiation. In this process, the term ‘distributed’ means that the signal is generated continuously along the whole optical fibre without the need for discrete sensors. As such, this is an ideal setup for long linear assets such as pipelines. Signals from different locations arrive at the interrogator with different delays, which are directly determined by the distance divided by speed of light inside the fibre. The signal is then sequentially sampled at thousands of locations along the entire monitored route. These signals allow pipeline operators to identify and interpret physical events along the fibre route to determine the condition of the pipe.

There are typically three scattering processes that provide measurements of temperature, strain and vibration (dynamic strain or sound) as shown in Table 1.

Raman scattering is widely used in distributed temperature sensing (DTS). DTS uses a simple optical filter scheme to measure the amplitudes of anti-Stokes and Stokes components and then calculates temperature profiles from their ratio.

Brillouin scattering is widely used in distributed strain sensing (DSS), mostly related to ground movements and its effects to infrastructure. Brillouin scattering creates a peak of energy at a characteristic frequency proportional to the amount of strain or temperature imposed. Since peak frequencies have some cross-sensitivity regarding temperature and strain, additional information like peak amplitude or frequency shifts from different types of fibres could be required to separate both quantities in applications where both are significantly varying.

Distributed acoustic sensing (DAS) is commonly based on coherent Rayleigh scattering. Interference of Rayleigh scattered light from multiple scattering centres within the fibre leads to a speckle-like pattern that depends on the phase difference between the superposing light waves. This pattern is characteristic of the fibre itself but is modulated dynamically by the local environment. Repeating the process quickly enough permits acoustic information to be resolved. The amplitude of the signal is sufficient for sensitive detection of events with a

broad acoustic spectrum like walking, digging and tunnelling while use of the phase component allows quantitative acoustic measurements, precise frequency analysis as well as dynamic strain and temperature monitoring.

Applications of DFOS at pipelines Different DFOS technologies such as DAS, DSS and DTS have numerous fields of use and applications at pipelines, including condition monitoring, structural health and monitoring for third party interference (TPI) (see Table 2, Figure 1). The DFOS methods have many benefits compared with traditional monitoring technologies, being reliable, safe, secure, economical and scalable. DFOS therefore provides an attractive alternative providing 24/7 continuous monitoring over long distances of approximately 100 km from a single location. Multiple applications can be served by a single interrogator which can provide measurements of thousands of locations (Figure 1). As such, it is extremely cost-effective.

Further advantages arise from the fact that DFOS requires no electricity to operate along the monitored asset. Power supply is only needed at the interrogator locations, e.g. every 50 to 100 km, which makes monitoring at remote sites much more feasible. The absence of electric energy eliminates the risk of ignition of explosive fluids, which also helps to improve safety. In addition, fibre-optics are inherently immune to electromagnetic interference, thus providing reliable and accurate monitoring. This significantly reduces the rate of nuisance alarms.

DFOS can use existing telecom fibres, which makes installation easy at locations where fibres are already present. Once fibre has been installed, it lasts for dozens of years, and interrogators can simply be upgraded in line with future monitoring needs without replacing the sensor.

Localisation capabilities of DFOS are superior to most other technologies used in pipeline monitoring. Signals are sampled with meter resolution, and events like leaks, intrusion, theft of ground movements are precisely localised within a few metres.

Examples of DFOS at pipelines Leak detection is one major application of DFOS for pipelines. Multiple thermal, strain and acoustic detection modes, such as orifice noise (OFN), negative pressure wave (NPW), ground heave and liquid impingement (Figure 2) can be employed for detecting leaks. They provide superior sensitivity compared with traditional technologies such as computational pipeline monitoring (CPM) based systems, which makes DFOS suitable for many different types of pipes and products in gas, liquid or mixed phases. Significant efforts have been made over the years to verify the leak detection capability of DFOS systems. Ultimately, the real test is the detection of leak on an active pipeline. Real leaks are thankfully quite rare but the evidence is emerging to show DFOS is proven in the field. A couple of years ago, an operator reported a leak alert on their system. This leak was confirmed as genuine and had occurred on one of the pipes around a pump facility. Post-analysis revealed that the alert had been raised as the result of OFN and strain detections. Monitoring for TPI is another important application. In one case, an oil company was aware of a pipeline theft problem on a refined product line. Using their existing mass balance system, the thefts were observed with a regular pattern in the middle of the night, but the system was unable to detect the exact location. The company installed a DFOS monitoring system and on the first night, the DFOS system alerted the pipeline operator – through the detection of NPW and OFN – to repeated activity on the pipeline. The DFOS system was able to identify the location to within 10 m and the company was able to put measures in place to stop the theft. Heat trace monitoring is another successful use for DFOS on pipelines. For example, pipelines transporting sulfur require heating to ensure that the sulfur remains in liquid form. A skin effect heating system is commonly used and requires continuous temperature monitoring to maintain and protect the pipelines, vessels, and instrumentation. Fibre can be embedded within the pipe

Figure 1. Schematic representation of the multiple fields of use at pipelines that can be covered by a DFOS system.

Figure 2. Detection modes of DFOS for pipeline leak detection.

22 World Pipelines / OCTOBER 2021