Corrosion Mapping for High Temperature Onstream Piping Circuits

Wide coverage, limited access, and high temperatures make process piping circuit inspection difficult and unreliable without shutdown or isolation to cool.

The extensive piping running throughout petrochemical process units and power generation plants can present a challenge for close monitoring of corrosion or defects due to high surface temperatures. Where access is feasible, NDT technicians will typically perform spot readings with high duty cycles, making quick measurements to avoid measurement drift and with frequent calibration which may impact inspection quality. Working in this high temperature environment creates potential safety concerns due to exposure to the high surface temperatures. Engineers responsible for risk-based inspection programs may not receive a comprehensive picture of the high temperature piping circuit condition with this manual assessment, but taking the asset offline is also counterproductive and imparts delays.

An ultrasonic scanner with high-temperature transducers provides in-service corrosion mapping of onstream assets running continuously up to 200 degrees Celsius (392 degrees Fahrenheit).

Automated Ultrasonic Testing (AUT) has proven to be an effective method for corrosion mapping, and inspection and continuous monitoring of piping with onstream circuits at temperature is now possible with a remotely operated scanner integrating Ultrasonic Testing (UT) technology from Ionix Advanced Technologies. This pairing helps produce high-resolution thickness measurements or weld inspection data and removes the need for prior or additional screening, shutdown, or outages.

The RMS 2 remote-controlled ultrasonic corrosion mapping solution by Eddyfi Technologies features an extended umbilical and robust components capable of operating on surfaces with temperatures up to 200 degrees Celsius (392 degrees Fahrenheit) continuously, removing operators from these hazardous areas. The remote-access NDT scanner has a range of probe holders that support high-temperature dual element and time-of-flight-diffraction transducers by Ionix who are experts in challenging environment ultrasonics. The HotSense UT technology can continuously scan surface temperatures up to 350 degrees Celsius (667 degrees Fahrenheit) without duty cycling or cooling. It maintains accurate calibration that allows the probes to reach equilibrium with the asset surface temperature, without measurement drift from heating and cooling gradients.

An in-service onstream piping circuit inspection was conducted using an RMS 2 with Ionix HS582i 5 MHz, dual element probes integrated by a dedicated heat resistant probe holder. The pipe was 250-millimeter (10-inch) nominal pipe size diameter, schedule 40 hot service A106B steel, with a nominal thickness of 9.3 millimeters (0.36 inches) and surface temperature of 200 degrees Celsius (392 degrees Fahrenheit) recorded by an infrared thermometer. A HS582i was connected to a Mantis™ and standardized on two steps of a reference block at ambient temperature before being placed in contact with the pipe, allowing heat equilibrium (approximately 60 seconds). The probe zero was adjusted to compensate for the increased temperature and the velocity was corrected according to ISO 16809 by 0.8 meters (2.6 feet) per second, per degree Celsius.

Using high-temperature pumpable couplant, the RMS 2 successfully collected high-quality C-scan data for an easily understood corrosion map of the pipe circumference. This was achieved by rasterizing 450 millimeters (17 inches) axially and capturing A-scans in 1-millimeter (0.03-inch) steps in each axis covering the circumference. A time corrected gain was employed, and the time-of-flight was determined by gating echoes at maximum peak amplitude to mitigate the effects of increased scatter and attenuation at the elevated temperatures that may reduce reliability of zero crossing measurements.

Several scans were conducted over a three-hour period with the RMS 2 on the surface a maximum duration of 30 minutes. It is recommended to allow the system to cool down for five minutes between each 30-minute interval.

With the RMS 2 and Ionix HotSense transducers, technicians can safely and completely map corrosion of in-service, onstream piping circuits and provide engineers with a comprehensive, real-time dataset to make reliable recommendations. Eddyfi Technologies offers a range of advanced NDT solutions to help stakeholders in the energy sector maximize production efficiencies, lower risk and stay Beyond Current. Contact us to learn more.