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Medium range Ultrasonic inspection technique for detecting micro-biologically induced corrosion in automatic fire sprinkler systems

Final Report Summary - SPRINKTEST (Medium range Ultrasonic inspection technique for detecting micro-biologically induced corrosion in automatic fire sprinkler systems)

Executive Summary:
Fire sprinkler systems installed in domestic and commercial environments can be seriously undermined by corrosion. Conventional visual pipework inspection to check for such corrosion is extremely time consuming and often involves the removal of pipe sections for evaluation. Moreover, the pipes are often enclosed and difficult to access for close viewing.

The SprinkTest portable inspection system uses ultrasonic guided waves to inspect up to 6m of pipework from a single inspection location. It delivers substantial time and cost savings, and provides an effective means of inspecting hard to access pipes.

The SprinkTest system comprises an inspection collar (with up to 16 transducer modules), an ultrasonic pulser-receiver unit and an Android tablet installed with automatic defect detection software.

Project Context and Objectives:
The installation of sprinklers can result in substantial reductions in insurance premiums and so insurance companies are becoming increasingly interested in their proper installation and function. For example, the British Automatic Fire Sprinkler Association has abundant evidence about the effectiveness of their members’ technology in reducing loss of life and property in office, residential, retail, storage, public venue buildings and in special sites such as ships, control rooms and hospitals.

The proper functioning of fire sprinkler systems can be catastrophically undermined by corrosion. The water in the system pipes is stagnant and, if inhibitors are inactive, then this can give rise to microbiological induced corrosion (MIC), which leads to leaks. This corrosion is localised and is not evident in close visual inspection until the leak starts. Moreover the pipes are often enclosed and difficult to access for close viewing. MIC may occur in both dry and wet sprinkler systems.

Long range ultrasonic testing (LRUT) has been developed for screening long lengths of pipe (up to 100m from one test location) for corrosion, especially in otherwise inaccessible areas. It has been used to a limited extent on the feeder pipes and risers in sprinkler systems. However, the sprinkler pipe lengths are too short (typically <6m) and the defects too small in comparison with the ultrasonic wavelengths for current LRUT systems. Moreover the numerous features such as pipe elbows and branches, makes interpretation of ultrasound echo-signals difficult.

The main objective of the SprinkTest project was to develop a guided wave fire sprinkler pipework inspection system, which uses the Synthetic Aperture Focusing Technique (SAFT) to achieve enhanced defect resolution for medium range inspection, an adjustable transducer collar that can be adapted to fit commonly used pipe sizes, and low-power electronics to enable hand-held portability.

Project Results:
The developed medium range inspection technique for sprinkler pipework exploits guided waves and modified SAFT processing algorithms. The most important parameters influencing the performance of the technique were identified, investigated and possible errors assessed. It was shown that the most important parameters are ultrasonic velocity, pipe diameter and parasitic delay time (used by the reconstruction algorithm). Using modelled and experimental data it was shown that correct selection of parameters enables positioning of pipe features/defects with the required accuracy. It was also shown that in order to achieve the required lateral resolution, helical waves need to be exploited. It was demonstrated via numerical modelling that correct transducer placement is crucial for accurate measurements.

Experiments performed using the three most commonly employed coated sprinkler pipes (red oxide primer, hot-dipped galvanized and powder coated pipes) showed that the pipe coating has an insignificant effect on the results obtained (limited ultrasonic signal attenuation observed).

A variety of transducer types and transducer arrays were analysed in order to identify the most appropriate transducer design and transducer configuration for the inspection of sprinkler pipework. Piezoelectric transducers were selected for the SprinkTest system as they were shown to transmit the most reliable axisymmetric waves, with the highest signal-to-noise ratio.

An adjustable two-ring transducer mounting mechanism (collar), based on magnetic coupling was developed. It was shown to be compatible with the required range of pipe diameters and to provide the necessary information to determine the exact location of features/defects in the pipe segment under inspection.

A modular, compact, light-weight pulser-receiver unit was designed, manufactured and validated. A series of performance tests were used to demonstrate that the unit can generate and process the ultrasonic guided waves necessary for reliable sprinkler system inspection. The pulser-receiver unit was validated in terms of the type of transducers supported, number of transmit and receive channels, transmit frequency, transmit voltage, receive circuit resolution, receive sampling rate, battery specification, unit dimensions and weight.

Several areas were investigated to overcome the limitations of the computing resources available on a tablet PC (Android platform); including data acquisition, pre-processing filters (smoothing, de-noising) and the steps involved with implementing the SAFT inspection algorithm. A specific data parsing and packaging methodology to overcome the limited computational resources was designed. The developed multi-thread file segmentation procedure was the central part of this methodology.

The software development strategy focused on the design and implementation of an extensible, high-performance, responsive graphical user interface (GUI). The GUI was realised via user-friendly interface components and the powerful multi-threading tools of the Android platform and the Java Dalvik operating system. These specific features provide high-levels of reusability and extensibility and have made the application extremely portable. Special care was taken to design modular software with low execution times, tailored to the memory and processing speed constraints imposed by a tablet PC, and to provide an intuitive presentation of the inspection results.

Assessment of the SprinkTest system was performed via a series of laboratory and field trials. The SprinkTest system was thoroughly tested in the laboratory; subsequently field trials were conducted on a fully operational sprinkler system. The laboratory experiments were used to establish the performance and capabilities of the system components (pulser-receiver, transducer collar, Android tablet software and the Synthetic Aperture Focusing Technique (SAFT) used for processing the inspection data), prior to trialling the integrated SprinkTest system. A formal operating procedure was created that documents the key knowledge required when conducting an on-site SprinkTest inspection. The field trials were used to assess the performance of SprinkTest system in its intended environment. It was concluded from the trials performed that (1) The SprinkTest system offers a portable, user-friendly, effective method of inspecting sprinkler pipework; (2) The inspection time for a six metre length of sprinkler pipework is approximately ten minutes (3) Under normal circumstances, an operator with minimal training (around half-a-day) can perform standard pipework inspections (4) A more experienced operator can use the advanced options to tailor the system to non-standard applications.

A set of training materials comprising a PowerPoint presentation and a user manual was produced to explain how to correctly install, operate and maintain the SprinkTest system.

Potential Impact:
The SprinkTest project is expected to create significant impact and economic value for the Consortium SMEs through the innovative technology that has been developed in the project for detecting corrosion in sprinkler systems that are now being widely used in public buildings across Europe. The system will be highly beneficial for the sprinkler system maintenance companies and will provide some protection to insurance companies as well. The EC and the consortium SME investment in the project is expected to yield a healthy return on investment (ROI) over the 5 years following commercialisation of the project results.

The wide installation and use of sprinkler systems in areas and facilities with significant fire risks is instructed and supported by recognized organizations, such us the European Fire Sprinkler Network, the British Automatic Fire Sprinkler Association (in the UK) and various national fire sprinkler networks across the countries of the EU. The activities of these organizations have resulted in the wide use and installation of sprinkler systems. The emerging need for the wider acceptance and installation of sprinkler systems has also been fed by horrendous fire incidents across Europe. The retrofitting of sprinkler systems in all German airports was directed after a fire at Düsseldorf airport on 11 April 1996. During that fire 17 people were killed. A fire in an illegal immigrant detention centre at Schiphol airport in the Netherlands on 27 October 2005, killed 11 detainees and led to the retrofitting of sprinklers in all similarly designed prisons in the Netherlands. Since then, major steps towards the recognition of the sprinkler system significance with regards to human safety and fire detection have been made. In Wales, sprinklers are mandatory in all new homes since 2011. Soon, the regulation will extend to almost every building or facility, including care homes, university halls and schools. Scotland is also on the same approach. Nordic countries have also adopted the same philosophy regarding care homes, sheltered housing and high rise flats. The retrofitting of sprinkler systems in these facilities is required or will be required in the near future. The Consortium SMEs will benefit from increased opportunities in the sprinkler system maintenance market through sales of the SprinkTest products and provision of inspection services.

With an established market and a critical need, SprinkTest shows great potential for being a commercial success for Europe. Sprinkler system installation and maintenance is mostly conducted by SMEs that also dominate the inspection equipment and fire hazard prevention market in Europe. The SprinkTest project has resulted in prototypes which with some additional funding can be commercialised and sold by the IP owners, the SMEs in the project.

Innovative sprinkler corrosion inspection technologies such as SprinkTest can also have a significant impact on the whole of Europe. SprinkTest will enhance the safety of European public places by reducing the likelihood of disasters from fire. Therefore, the developed technology will have wider economic and social implications for the entire European community.

A list of the main SprinkTest dissemination activities is included below:

A project website has been created that acts as a point of reference for interested parties (

An article that summaries the SprinkTest project and its anticipated impacts appeared in TWI’s Connect+ magazine (Issue 7 – Oct/Nov 2014).

A conference paper was produced for the Fire Sprinkler International 2014 Conference and Exhibition (London, May 2014). The paper describes the common problems encountered with sprinkler system pipework, current inspection techniques, conventional UT and guided wave testing, development of the SprinkTest system and the preliminary results.

A conference paper was presented at the 6th International Conference on Emerging Technologies in Nondestructive Testing (ET-NDT6) (Brussels, May 2015). The paper describes long-range ultrasonic testing for the detection of defects in fire sprinkler systems, the developed SAFT technique and verification of the technique using modelling and experimental data.

The SprinkTest project and its technological advances were publicised at the poster sessions of the ISH Fair (Frankfurt, March 2015) and the 2015 International Congress in Ultrasonics (Metz, May 2015).

A SprinkTest workshop was held at TWI Ltd (Cambridge, October 2015) during which the prototype system was demonstrated to key fire sprinkler organisations.

List of Websites:

Partner Contacts:-

Coordinating Partner
Matthew Deere
Granta Park
Great Abington
Cambridge CB21 6AL

Other Partner Contacts:-

WLB Ltd (SME Partner)
Contact: Marianna VARI

Contact: Mr Nigel Thorpe (Exploitation Manager)

Baugh & Weedon Ltd (SME Partner)
Contact: Mr Peter Burrows

DVC (SME Partner)
Contact: Mr Marc VERTONGEN

EFSN (End-User SME Partner)
Contact: Mr Alan Brinson

KTU (RTD Partner)

INNORA (RTD Partner)
Contact: Manthos Alifragkos