Projects: inspection technologies

Production testing

A company manufacturing wind turbine blades from a mixture of plastic and wood composites was having difficulties in production testing these large structures for delaminations and voids. Cambridge Applied Physics carried out a series of investigations on tap testing techniques, resulting in a design for a small hand-held transducer system. CAP manufactured and supplied the units to the production testing team, allowing several blades to be tested simultaneously, rapidly and accurately.

Fixed structures

Cambridge Applied Physics has developed a novel method for monitoring the structural health of jackets (cross-braced tubular steel structures that support oil platforms in the North Sea and elsewhere). Based on structural acoustics, the method uses a sparse array of fixed transducers to monitor an entire structure. With funding from the UK Health & Safety Executive (HSE), the system has been proved on a laboratory scale model.

Pipeline integrity

Gas Distribution Pipeline Advanced Pressure Testing
Pressure testing new gas mains has been made vastly quicker and more accurate by the incorporation of an acoustic temperature measurement system researched and designed by Cambridge Applied Physics. Gas mains can now be tested before they are buried, and the effects of temperature variation can be removed from the results (with an accuracy of 1 milliKelvin). Built by Advantica, the system is in regular service with Transco.

Pipe Bedding Condition Assessment
Buried pipelines can be damaged if the supporting material is washed from under them, or if they are laid across a sill of hard material and the surrounding soft material subsequently subsides. CAP carried out a feasibility study which showed that measurements of the cut-on frequencies, damping, and mode shapes of pipe vibration modes can be used to characterise both the condition of the pipe wall and the surrounding bedding material.

Ultrasonic Water Mains Condition Measurement
The UK has thousands of miles of water mains, made of materials ranging from cement, through cast iron, to modern plastics. The water companies need to be able to assess the state of these pipes in situ, rapidly and economically. CAP has developed a range of ultrasonic transducer arrays for measuring water pipe size and wall thickness, and detecting corrosion, cracks, leaks, joints, valves, linings and other features. The arrays are battery-powered and miniaturised, designed to be carried inside instrument packages that can pass through kilometres of water pipe while information is continuously recorded. They are currently on trial with a major water company.

Advanced pressure tester

The Advanced Pressure Tester is a system for testing new-laid gas pipes for leaks before the trench is backfilled. Using an acoustic system developed by CAP for Advantica, the APT measures the average temperature of the gas in a pipe during pressure testing. The effects of temperature on gas pressure can then be allowed for so that leaks can be detected via the extremely small decay in gas pressure over time that a typical leak produces. The measurement is made from one end of the gas pipe and is entirely non invasive.

The APT was developed for Advantica PLC.

Leak radar

Almost all existing technologies for finding leaks in water mains use the sound radiated from the leak to home in on it (including the magic carpet). This can sometimes lead to other sources of sound (such as flow obstructions in pipes, or part-open valves) being misidentified as leaks, leading to wasteful excavations. It also means that leaks which do not produce detectable levels of sound cannot be located.

The leak radar uses a completely different principle of detection. It is a radio-frequency interferometer, which works by transmitting a low power radio-frequency (UHF) signal directly into the ground. The signal is reflected off the water issuing from the leak and returns to the antenna, where it is amplified and passed to a sensitive interferometer system. This effectively ignores any signal whose character does not change with time. If there is a leak, the signal reflected from it varies rapidly; the interferometer recognises the signal, which is then amplified, processed, and displayed to show its strength and character.

The system can be used either to confirm possible leaks located by other means, or to locate leaks which are known to exist but cannot be located by acoustic detectors.

Development is in abeyance awaiting hardware improvements.

Magic carpet

The Magic Carpet is a ground-acoustic sensor array used to detect leaks in buried pipes. Primarily designed for the water industry, it is able to detect leaks of any fluid from a pressurised pipeline, including liquid hydrocarbons.

 

The Urchin

The Urchin autonomous leak detector is a 2-inch diameter, wireless device for detecting leaks in water mains. Inserted into a main through any standard fitting, it moves with the water flow, recording the positions of any leaks that it passes.

The Urchin was developed for AES Ltd.