FSM is a non-intrusive monitoring technique based on a patented principle, developed for the purpose of detection and monitoring of both general and localization corrosion, erosion and cracking In steel and metal structures, piping systems and vessels. The System requires virtually no maintenance nor replacement of consumables. The service life of an FSM System equals that of the pipe itself.

FSM is commercially available for a variety of applications, such as laboratory research, corrosion monitoring in oil and gas flowlines (e g. buried pipelines) and the first FSM Subsea systems were installed and started monitoring the second half of 1994.

This paper describes the principles of FSM, typical subsea applications and various options of system solutions. Examples of experience from field installations are presented, and technical solutions and advantages of FSM subsea discussed. A new generation hydroacoustic telemetry link integrated with the system provides for online communication with the top-side data collection system. Results from performance tests and from more than one year installation In the North Sea will be presented

FSM Subsea has a sensitivity better than 1/1000 of the actual wall thickness, and will therefore give early warnings ~f corrosion rates Increase, allowing correctiver actions before corrosion damage takes place FSM is a tool for optimized inhibitor control, and can justify a reduced frequency of intelligent pig surveys The availability of FSM may accordingly contribute to the acceptance of carbon steel pipelines/flowlines as an alternative to expensive, corrosion resistant materials


Corrosion monitoring and inspection is commonly done in the industry for various purposes:

  • inspection of wall thickness and cracking of pipework for safety and maintenance planning

  • monitoring for control of corrosion mitigation programs, e.g. injection of corrosion inhibitors

  • research, e.g. inhibitor testing and materials evaluation.

Commonly corrosion monitoring has been carried out utilizing various intrusive corrosion probes. Such techniques provide high sensitivity and accordingly early information. However, the validity of the information may often be questioned, since the methods use foreign samples or electrodes inserted into the pipe. The methods also have theoretical limitations and practical disadvantages such as requirements for space for retrieval operations, possible complications during retrieval services and possible leaks along the probe.

Inspection is normally based on various NDT techniques and on the use of intelligent pigs for assessment of pipeline corrosion along its entire length. Such inspection is costly, and the sensitivity is low compared to the corrosion monitoring techniques. Hence, inspection has a limited value for corrosion control and mitigation.

The FSM method was developed and patented by Center for Industrial Research (SI) in 1985186 (1). CorrOcean has acquired all rights from SI for worldwide commercial exploitation of the FSM technique, which is now used for a wide range of industrial monitoring applications.

The FSM technology has earlier been presented in various papers and articles, and more information about the technical principles behind the FSM can be found in references (2, 3, 4).

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