In the Canadian oil sands industry, the bitumen-containing sand is mixed with water, and the resultant slurry is transported through pipelines. Due to the abrasive nature of solid particles in the slurry (slurry can contain solid particles up to five inches in size), pipeline wear has been a major issue. Due to excellent abrasion and corrosion resistance, the use of non-metallic pipe components, such as rubber hoses and elastomer-lined steel pipes, has increased. To achieve long wear life, thick elastomeric liner of 1-2 inches has been used in non-metallic pipes. Wear monitoring of pipeline is critical in asset integrity management; however, there are limited technologies available for non-metallic pipes. For example, embedded continuity wire system has been popularly used for rubber hoses, where copper wires are spirally wound to cover the entire rubber hose and embedded inside the liner at certain liner depths. As liner wear progresses, the embedded wire is exposed to coarse particles in the slurry, then the wire breaks with further progress in liner wear leading to loss of electric continuity. Therefore, if no electric current is detected through an embedded wire, it can be assumed the liner is worn out beyond the liner depth where the specific wire is embedded. However, this technology cannot tell the exact location of liner wear. Also, this technology can provide “go/no go” type of information only; once a wire is broken in one location, the entire wear monitoring capability is lost. In addition, the sensor system using continuity wires tends to break down often during handling and installation.
Radio frequency identification (RFID) is an automatic identification and data collection technology utilizing programmable tags. RFID technology has been used mainly for tracking and tracing purposes; however, Syncrude Canada Ltd. developed a novel wear monitoring concept by using RFID tags. RFID tags, which are programed with individual ID and location information, are embedded at different axial and circumferential locations inside the liner of non-metallic pipes. If a tag can be scanned, the specific location where the tag is embedded can be assumed intact. If a tag cannot be scanned, the specific location where the tag is embedded can be assumed to have been worn out. Therefore, the exact wear location can be identified by checking existence or absence of the embedded tags. Tags can also be embedded at different liner depths at the same location, and by tracking the tags along the liner thickness, progressive wear monitoring can be achieved. Figure 1 describes the progressive wear monitoring concept, where three tags are embedded at three different liner depths (T1 at 25% liner depth, T2 at 50%, and T3 at 75%). If all tags are detected, it can be assumed the liner wear did not progress up to 25% liner depth. If only T2 and T3 tags are detected, it can be assumed the liner wear progressed between 25% - 50% liner depth, and so on. Wear monitoring of rubber hoses can be done by external or internal scanning since RFID signal can penetrate through rubbers and fabrics. However, RFID signal cannot penetrate through steel pipes, so wear monitoring of lined pipes can be done only by internal scanning (e.g. use of smart pigs). Syncrude Canada Ltd. was awarded a Canadian patent on this technology (CA 2922137).
Rubber hoses were targeted for the development of external wear monitoring technology using RFID tags. RFID tags are categorized into two: active and passive. Passive tags, although they have shorter read range compared to active tags, are much smaller in size and more suitable to be embedded into rubber hoses. Therefore, passive RFID tags were selected. The following two uncertainties were identified. Manufacturing of rubber hoses requires a curing process, which is typically done at high temperature and pressure in an autoclave. The first concern was possible damage to the embedded tags during the hose manufacturing process. Slurry hoses being used in Canadian oil sands are thick-walled (in the range of 4 -7 inches depending on hose size, pressure rating, etc.) and significant signal attenuation was expected while RFID signal travels through the thick wall of rubber hoses. The second concern was lack of signal from external scanning as the result of signal attenuation. To rectify those concerns, prototype rubber hoses were manufactured and dipole-style ultrahigh frequency (a band from 860 MHz to 960 MHz) RFID tags were embedded in the hose. Tags could be read via internal scanning, suggesting tags were not damaged during the manufacturing process. However, the embedded tags couldn’t be read via external scanning, which was partially due to serious signal attenuation while traveling through the thick-walled rubber hose. It was also found that carbon black, a filler being added to rubber compound, detuned the RFID signal. Dr. Patrick King from TROI suggested adjusting the length of the antenna to optimize the reading distance specifically for the environment surrounding the embedded tags. RFID tags with different antenna lengths were embedded into a prototype rubber hose and their reading distances were measured. As a result, an optimum tag design could be determined. When scanned from the outside of the test hose, the modified tags produced the reading distance of one foot or more. The tag and the prototype rubber hose in use are shown in Figure 2.
To evaluate field performance of the RFID wear monitoring system, a total of 96 tags were embedded into a commercial rubber hose of 30 NPS, 42 ft. length, at eight locations along the length (A1 - A8), four locations around the circumference (12, 3, 6, and 9 o’clock positions), and three locations through the liner depth (25%, 50%, and 75%). All tags could be read during baseline scanning, which was conducted before hose installation, indicating the embedded tags were not damaged during hose manufacturing. The commercial rubber hose came with thicker wall (5 -7 in.) than the prototype hoses in the previous study, resulting in shorter reading distance of approximately 6 in. The test hose was installed nin a S-shape configuration in a tailings line, as shown in Figure 3, and all the embedded tags could be scanned, suggesting tags were not damaged after significant bending during installation. Successful in-service RFID scanning demonstrated reliable wear monitoring of rubber hoses could be done by using the developed RFID technology. Further development is on-going in collaboration with National Research Council (NRC) in Vancouver, BC for the development of remote RFID wear monitoring system (Figure 4). This novel technology is expected to resolve the previous issue of limited wear monitoring capability of non-metallic pipes, contributing to improved asset integrity management through enhanced monitoring capability of the liner wear.
This article was originally published in
MTI CONNECT 2021, Issue 1.
Related: See the
Emerging Technology Track at the MTI Global Solutions Symposium, March 1-3, 2022 for a presentation on this subject.