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 ClampOn CEM is based on Acoustic Guided Lamb Waves (AGLW). One of the most important properties of AGLW is the dependence on the velocity of the frequency and the thickness of the structure through which they propagate. Knowing the dispersion curves of various materials enables ClampOn to calculate the wall thickness and observe the change along the signal path. Any change in plate thickness can be detected by the change in the Lamb wave velocity due to the dispersive nature of the modes.

Wall thickness changes of 1% can positively be detected and the system has a repeatability of ±0.04%. The technique is robust and will not break down. The subsea system will be available for pipe OD of 6” (15.2 cm) and greater and wall thicknesses in the range of 4‐35mm (0.158‐1.378 inches).


  • Pre installed
  • ROV installed
  • Fully interfaced
  • Battery powered
  • Internal data storage
  • Wireless communication