In a Nutshell:
Scaling within a pipeline usually occurs due to high levels of minerals like calcium carbonate or barium sulfate. While slight scaling might be considered beneficial because the inside surface of the pipe is coated with harmless materials acting as a barrier to corrosion, thick scale can result in a low flow rate and increased pressure, ultimately resulting in production losses. With our ploughing cleaning tool, we are able to claw into and remove thick scale buildup in the pipeline. In this case, ROSEN experts from our Asia Pacific region were able to restore the flow rate of the asset completely and prepare the pipeline for the following inspection in a single run.
This case study shows the value of choosing the right solution when it comes to the cleanliness of a pipeline and the need for adequate cleaning programs prior to in-line inspection activities. Cleaning and maintenance work can dramatically increase the efficiency of a pipeline, but it can also have dramatic effects on the success of other integrity activities.
Figure 1 – Examples of thick mineral scaling
Thick scaling within a pipe is typically made up of minerals such as barium sulfate or calcium carbonate and drastically influences the throughput of an asset. For example, an uneven deposit of only 5% can cause a loss of throughput of around 35%, or it could mean a required increase of pressure to maintain constant flow of around 140% (see Figure 2).
Moreover, thick scaling can also create an environment for aggressive under-deposit corrosion and can lead to blocked pipelines or clogged instruments. To avoid production losses and pipeline downtime, it is important to take the necessary precautions and to invest in proactive cleaning programs. Standard cleaning programs might not be able to fully remove large buildup or uneven deposits, as the cleaning pigs might get damaged or even become stuck in the pipeline.
Figure 2 – The importance of cleaning demonstrated in a 12" pipeline
BREAKING THE BARRIER
In this case, ROSEN was contracted to carry out a descaling project for a customer on Borneo Island, Malaysia. The onshore pipeline was 5 km long and had not been previously inspected by ROSEN experts.
Prior to the cleaning campaign, the customer had been closely observing the flow rate of the pipeline through monitoring software and noticed a reduced flow rate of 0.8 m/s to 1 m/s instead of 2 m/s, resulting in production losses of more than 50%.
Pressure trending showed that the differential pressure (DP) increased over a certain period of time, meaning there was definitely a restriction in the pipeline limiting the flow. The client was not aware of the extent of scale restricting the asset and therefore ran a standard cleaning program in an attempt to help increase the flow rate. In this case, however, thick scale was blocking the pipeline, reducing the flow rate and thus decreasing production. This led to the standard cleaning pig becoming stuck in the pipeline. The customer was monitoring the whole process and scanned the identified pipeline section to exactly locate and extract the tool that got stuck due to the scaling problem.
It then became clear that standard cleaning would not suffice in this case and that the debris was too severe for standard cleaning tools. Therefore, the operator contacted ROSEN asking for an aggressive cleaning solution to remove the scale. After additionally reviewing the pigging history of the respective asset, our experts diagnosed the severity of the scaling and realized that a comprehensive cleaning program was required. In order to guarantee correct data during the planned inspection run and to avoid tool damage due to the scaling while at the same time minimizing the risk of damaging the pipeline, we suggested a tailor-made progressive cleaning program that included our innovative ploughing tool.
PROPOSED CLEANING PROGRAM
The dedicated ROSEN team in our Asia Pacific region thus suggested the execution of an aggressive cleaning and progressive descaling program. The project was executed during an eight-day shutdown window and involved gradual pig aggressiveness introduced into the pipeline from the start until the end, using chemical soaking and water pumping to prevent the pig from getting stuck due to massive scale accumulation from pigging activities.
The pipeline was sectioned into two parts, one covering the first 1.1 km of the asset and the second one covering the rest of the 5-km asset, which will be cleaned at a later point. For the first section, we carried out a total of 23 cleaning runs, starting with foam and light wire brush foam tools, followed by a heavy wire brush foam pig and bi-directional tools with spider nose and gauge plate. Ultimately, the team ran a heavy duty ploughing and descaling pig to loosen up the heavy scale as well as a bulldozer/dewaxing tool to push the debris out the pipeline.
Figure 3 – Pull unit with attached ploughing addition
PLOUGHING THROUGH THE PIPELINE
The ROSEN Ploughing Tool is a very aggressive cleaning tool dedicated to breaking up hard scale. The plough elements are more aggressive against hard scale than our standard aggressive cleaning elements, including descaling cups, lamella sheets and pencil-type ring brushes. The ploughing tool should be part of a progressive cleaning campaign followed by a recommended bulldozer cleaning tool for removing the loosened debris.
The blades on the heavy scraper ploughs are adjustable to different diameters (in a small range). Thus, the tool can handle small internal diameter changes in a certain range with adapted aggressiveness. To avoid damage to the inner pipe wall, the material of the ploughs has to be softer than the pipeline material. ROSEN is flexible enough to respond to every pipeline material requirement and able to manufacture the ploughs out of different materials. The operation range of the tool is approximately 292 mm to 308 mm, covering a wide range of applications.
Figure 4 – The blades on the heavy scraper ploughs of the tool can be adjusted with washers and by tightening the nuts; the operation range is approx. 292 mm to 308 mm
With the future of the asset and optimal output in mind, we assured the client that our ploughing tool would not damage the pipe wall. We opted for mechanical removal as the best option in this case, as it is proven, economical and environmentally safe. Upon completion of the cleaning program with our ploughing tool, the customer was looking at a deposit-free asset and was able to return to a velocity of 2 m/s, up from an initial 0.8 m/s to 1.0 m/s before the cleaning campaign.
Figure 5 – Inside of the pipeline, including thick scaling, prior to the cleaning run (left) and after the cleaning campaign (right)
During the initial phase of the project, our team was able to clean the first kilometer of the 5-km asset, which contained thick scaling. In a second phase, which will be carried out at a later time, we will run a second cleaning program for the remaining 4 km of the pipeline in which we are expecting mineral scale. Therefore, the cleaning program will be even more aggressive than for the first section of the pipeline.
Removing the thick scale during the initial cleaning run with our aggressive ploughing tool enabled the customer to return to an increased production flow. Additionally, they were able to avoid additional descaling runs and follow up directly with operational or maintenance pigging. By using the right cleaning program, they were able to optimize the flow of the pipeline, ultimately resulting in increased production. By using our ploughing tool and therefore a highly efficient cleaning campaign, we were also able to minimize the downtime of the asset. Had a regular bi-directional tool been used in this case, it would have easily taken an additional week of intense cleaning to finish the project.
Although the solutions in this particular case all seemed to focus on the operational aspects of the inspection, the ultimate goal is always to collect the highest-quality data possible in order to gain insights into an asset’s integrity status, which was achieved. Looking back on the project, we can say that the importance of cleaning programs and the correct choice of measurement technology are vital. Not only can regular pipeline cleaning prepare a pipeline for upcoming in-line inspections, thus preventing failed inspection runs, it also can dramatically increase the performance of an asset.