image description Subsea Corrosion Erosion Monitor

Corrosion-Erosion Monitor

The ClampOn DSP Subsea Corrosion-Erosion Monitor (CEM) continually monitors and quantifies changes in wall thickness over a large area of a pipeline. The instrument estimates the rate at which corrosion and/or erosion reduces the thickness of the pipe wall. In this way, it can provide operators with an early warning of potentially catastrophic failures before they occur. The CEM is therefore also an effective tool in helping operators comply with newer regulations regarding the need for condition monitoring. It can be retrofitted to existing structures or installed on new pipelines before they are deployed subsea.


How it works

The ClampOn Subsea CEM measures and monitors wall thickness loss in pipes, plates or other metal structures. The instrument uses Acoustic Guided Lamb Waves (AGLW), a technology that gives an average wall thickness reading for a large section of pipe. Transducer pairs operate in a pitch-catch mode and use the ultrasonic waves to give the average wall thickness between the transducer pairs. The transducers are fixed at pre-determined points on the pipe to monitor the wall thickness loss in sections of the pipe typically up to two meters long.

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Subsea CEM trial installation in Bergen Harbour

There are two different models available, one ROV-installable for existing pipes and structures, and one pre-installable solution that can be installed topside before the structure is submerged. Both models operate in the same way and will give the same results when it comes to reliability and repeatability.

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Subsea CEM Illustration


The Corrosion-Erosion Monitor can be interfaced using Ethernet, RS-485/422/232, acoustic modems or indirectly using battery packs with internal logging and a USB interface. The instrument has a dual Ethernet interface built in, and supports Modbus TCP/IP, OPC UA, FTP, HTTP, NTP and numerous other IP-based industry standard protocols. As a member of SIIS, the Subsea Instrumentation Interface Standards JIP, ClampOn participates in developing the standard for Ethernet-based instrument interfaces subsea (SIIS Level 3), and continuously aligns the interface of the Corrosion-Erosion Monitor with the latest version of the standard. In case Ethernet is not available on the control system side, the subsea CEM also has serial interfaces (RS-485 and RS-232) which support Modbus RTU. Whether the Ethernet or direct serial interfaces are used, the instrument can be managed via a transparent link using the CEM Client application, which supports rich functionality (software updates, historical trending etc.) using user defined Modbus function codes. On locations without wired communication and/or power, the CEM can hand off results via an acoustic link, or store the results in a retrievable battery pack. The acoustic link or battery pack can also communicate configuration updates to the subsea instrument.