Research at TWI, stimulated by the need of the oil and petrochemical industries for a method to detect corrosion under insulation in pipework, led to the development of the first commercial Long Range Ultrasonic Testing system. LRUT systems and services are now provided to industry by TWI's subsidiary company, Plant Integrity Ltd (Pi).
Pi makes and operates the state-of-the-art Teletest Focus+ system. This is used to inspect pipe in order to detect corrosion and other flaws. It is able to transmit ultrasound many metres (typically 30m) along the pipe in both directions from a 'tool' comprising a 5-ring transducer assembly that is clamped around the pipe by an inflatable collar. It is of particular value for the inspection of pipe that is inaccessible for inspection by conventional methods (insulated, buried, elevated on pipe racks, etc.).
The transducers generate guided ultrasonic waves in the pipe and detect signals reflected from any flaws present. The location of these along the pipe is determined by the time of flight of the ultrasound.
TWI's LRUT Resource
The combined TWI/Pi resource in the field of LRUT comprises some 35 highly skilled engineers and technicians. This makes it one of the largest groups in the world working in this field. TWI's activities concern the development of new applications for LRUT technology, whilst Pi concentrates on enhancements to the Teletest® range of equipment for sale to NDT service providers and inspection companies and on the provision of LRUT services worldwide.
Some recent research projects and achievements in LRUT
- LRUT of pipes in the food industry. In this project sensors were developed that could withstand the harsh environments in heat exchanger piping. It was shown that LRUT could be used to detect not only corrosion but also fouling. The latter capability is of considerable value to the industry, since it enables the maintenance process to be streamlined.
See www.lrutfood.co.uk - Non-invasive monitoring of storage tanks. Corrosion of storage tank floors leading to leakage is a serious problem faced by owners of tank farms. TWI is researching methods of inspecting these from outside the tank using LRUT, thus obviating the expensive alternative of emptying the tank.
See www.timproject.co.uk - SubCTest. This project led to the development of a marinised LRUT system capable of deployment by ROV and aimed at the inspection of offshore structures, submerged pipes and mooring chains.
See www.subctest.com - RiserTest. Steel catenary risers (SCRs) are susceptible to fatigue due to vortex shedding. This project was aimed at satisfying the industry’s need for a method of detecting fatigue cracking. Marinised LRUT sensors were developed capable of operating at pressures up to 200bar, equivalent to a water depth of 2000m. See www.risertest.eu.com
- Permamount. Pi has developed the Permamount system, whereby the Teletest transducer array is permanently positioned on the pipe. The array is interrogated at predetermined intervals, so that developing flaws can be detected. This is one of the many techniques available for continuous Structural Health Monitoring (SHeM), in which TWI is increasingly active.
For more information about TWI's NDT services, please contact us.
