Technologies and Approaches for The Inspection of Non-Piggable Pipelines
Not all pipelines can be inspected using the pigging method. The amount of design modifications and planning will depend on that specific pipeline. To this end, other technologies and approaches must be followed. As a firm with extensive experience in piggable and non-piggable pipelines, we make use of the most relevant approach for the particular situation in accordance with industry specifications and client requirements. Below is a brief discussion about the methods used for the inspection of non-piggable pipelines.
Non-Piggable Projects
Non-piggable projects include hydrocarbon, product distribution, and offshore pipelines. Inspection through the use of pigging is not possible on certain lines because of the mechanical layout of some lines and operational conditions.
Mechanical Layout Factors That Make Pipelines Non-Piggable Include:
- Dimensions of the line, such as changes in diameter and wall thickness.
- Presence of bend restrictions, such as back-to-back and mitre bends.
- Tee design, such as a non-barred tee.
- Valves that block the pigging.
- Positions of the features that can cause the pig to stall.
- No access to a point of entrance of the launcher, or no retrieving point for the receiver.
Operational Conditions That Can Hamper Inspection
Lines can also be non-piggable because of operational conditions, such as ones related to the temperature, product, pressure, or fluid velocity.
Inspection Technologies for Non-Piggable Lines
The two main technologies used when the lines cannot be inspected through the pigging method are that of Magnetic Flux Leakage (MFL) and the Ultrasonic (UT).
MFL Technology
The MFL technology is insensitive to smooth corrosion. The method is effective for detecting defects near or in the area of the welds. The technology makes it possible to perform data analysis for small defects. The technology can work when the line has high wall thickness. A disadvantage of the technology is that calibration and magnetisation errors can occur.
UT Technology – Guided Wave
The method is well-suited for pinhole detection. It works where the wall thickness is smaller than 5 mm, but multiple BW and liquid are required. A drawback of the technology is that it is sensitive to the tilting of the probes, as is required with bends in the line. It also requires more cleaning than with MFL.
Free-Swimming, Self-Propelled, and Intelligent Technologies
We can use internal tools, such as intelligent free swimming tools. Tethered UT tools, such as the pneumatic-, wheel-driven, and pull-through types are widely used.
The crawler types have advantages, such as the results being available online and safe operations because of the cable winch system. These units are self-propelled and do not require flow. However, the speed of inspection is slow, while limited lengths can be inspected. The equipment is heavy, and the line must be out of service for inspection to take place.
The semi-swimming piglet also enables online result viewing. These tools offer bi-directional operation. The simplified construction makes it possible to inspect many non-piggable lines. However, liquid product flow is required, and the speed of inspection is low. The length of inspection is also limited, and less coverage is possible in bends.
The latest technology developments have made it possible to use robotics for the inspection of non-piggable lines.
We make use of the most appropriate technology for the particular inspection project to ensure accuracy in results. Get in touch for more information on our inspection services of piggable and non-piggable pipelines using a range of technologies, including intelligent and self-propelling tools.
