iicorr Ltd

The Field Signature Method	FSM-IT
FSM Features	Buried
The FSM Corrosion Monitoring Tool	FSM G4 System Overview
Subsea	Typical Problem - Weld Root Corrosion
Topside	Typical Problem - Pitting

The Field Signature Method

A non-intrusive method for monitoring internal corrosion, erosion and cracks in piping systems
Based on electrical field mapping of the object
High sensitivity and accuracy compared to alternative methods
Measures metal loss on the actual pipe section
May provide substantial cost savings due to improved corrosion control and reduced inspection cost

FSM Features

Sensitivity ( 1 ppt for General Corrosion, OnLine Systems)
Detects changes in the actual pipe wall
Provides information on corrosion mechanism
Monitors relatively large area and different geometry e.g. welds
Non Intrusive - does not affect pipe integrity
There are a number of variants of the FSM system allowing for installation in differing environments.

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The FSM Corrosion Monitoring Tool

The field proven FSM (Field Signature Method) technique detects metal loss, cracking, pitting or grooving due to corrosion by detecting small changes in the way current flows through a metallic structure.

Sensing pins or electrodes are distributed in an array over the monitored area to detect changes in the electrical field pattern. The voltage measurements are compared to a set of initial reference measurements. Typical distance between the pins is 2-3 times wall thickness.

The system presents graphical plots indicating the severity and location of pits and cracks, and calculates actual corrosion trends and rates. Both sensitivity and repeatability are typically better than 0.1% of remaining wall thickness for online systems.

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Subsea

The FSM subsea monitoring system typically comprises a spool piece with ROV retrievable electronics and optional battery. The length of the spool piece is typically 6-8 m, depending on outer diameter. The most common protection is rubberisation, but pipe-in-pipe design is available for high temperature applications. Communication is through cable (via subsea control system) or through hydroacoustics. Power supply through cable or by means of long-life battery.

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Topside

A normal installation consists of the instrumented pipe section with current feeding arrangements, sensing pins with wires and reference plate, temperature sensors, and the protective cover. Data acquisition unit with power and communication, ranging from stand-alone versions with battery, on-board storage and manual data retrieval, to large online systems monitoring several FSM units simultaneously. MultiTrend, a Windows-based data retrieval and presentation package.

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FSM-IT

This system allows multiple sensing pin locations to be monitored with one portable instrument. Ideal for monitoring pipe work in downstream processing. The high temperature version is capable of operating on pipe work up to 500 ° C (930 ° F).

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Buried

FSM systems can be installed on buried pipes utilising a special protective cover and be either of the online or the FSM-IT specification.

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FSM G4 System Overview as per Subsea and Topside Systems

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Typical Problem - Weld Root Corrosion

The image below shows a typical example of severe weld root corrosion. The 3D plots are taken from tests demonstrating FSM capabilities of monitoring weld root corrosion.


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FSM Principle across a Weld

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Typical Problem - Pitting

	The graph is an example of how FSM shows pitting as well as uniform corrosion. This gives the ability to quantify size and depth as well as location of the pit.
(click to enlarge)
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