Ultramonit: A New Concept for Monitoring Using Ultrasonics

Recent developments in the fields of electronics, computer systems and communication technology have enabled the use of many new concepts within inspection and monitoring. ULTRAMONIT is one such example where we try to extend the use of ultrasonic measurements in terms of accuracy and what we can measure. In this concept, an array of ultrasonic sensors is placed permanently onto the pipe. The location of these sensors will typically be in a field joint directly at, or close to a weld, and the objective will be to monitor for corrosion attacks and cracks. Permanently installed sensors are advantageous as exact position, orientation and acoustic coupling are maintained between surveys. Compared to conventional ultrasonic inspection, this means significantly improved possibilities for high-resolution trend analysis of the data. Under good conditions, UT wall-thickness can be measured with a resolution in the order of 0.01 mm. Using fixed sensors; such very high resolution could be made available for monitoring purposes. Two versions of this system are developed, one for use on subsea pipelines, and one for use topside or on land facilities. ULTRAMONIT Subsea is implemented as an instrumented pipeline clamp, where the required electronics and sensors are placed and protected in a rugged steel structure. Reliability has been a key objective for this concept, and has been addressed by keeping the permanently installed electronics as simple as possible, while making the more complicated parts of the instrumentation accessible in an ROV carried unit. This ROV is used for interrogation with the sensors by use of a specially developed inductive coupler, which provides power, analog signal for the ultrasonic transducers, and digital communication for the signal multiplexer. This unit is controlled digitally and the number of channels is only limited by signal degradation due to total spanned length of analog cable, as the channel count gets very high. Our prototype has 48 channels in one row of sensors around the circumference of a 10” pipe, but both HW and SW is ready for any practical number of channels. ULTRAMONIT Subsea will be lab-tested at the Statoil R&D center in Trondheim, and a topside/land facilities version of this same system is being installed on a 12” pipe at the Ka˚rsto̸ gas processing plant. Both tests will commence in December 2003, and continue through 2004. Results from these tests will be presented at the conference.