PEC – Pulsed Eddy Current

Corrosion under insulation is possibly the greatest unresolved asset integrity problem in the industry. Adding a subsea environment to that increases the challenge ten-fold. Current methods for measuring wall thickness over insulation (liftoff) without removing it all have severe limitations. TSC Subsea’s exclusive ROV-deployed subsea Eddyfi Lyft® and high-resolution array probes provide a high-performance solution that reinvents pulsed eddy current (PEC). PEC is an advanced electromagnetic inspection technology used in detecting flaws and

corrosion in ferrous materials typically hidden under layers of coating or marine growth; it can be deployed remotely via our NodeScanner™ and MagCrawler™ equipment. TSC Subsea’s Lyft scans through thick insulation such as concrete and polypropylene, which are used to protect subsea pipelines and structures. PEC is also very well suited for the inspection of subsea storage tanks and vessel hulls where the need to remove heavy marine growth is unnecessary.

How it works

A magnetic field is created by an electrical current in the coil of a probe. When the probe is placed on the pipe or structures coating, the field penetrates through all the layers (including sheeting, if present) and stabilizes in the component thickness; then the electrical current in the transmission coil is turned off, causing a sudden drop in the magnetic field. As a result of electromagnetic induction, eddy currents appear in the component wall. The eddy currents diffuse inward and decrease in strength. The decrease in eddy currents is monitored by the PEC probe and used to determine the wall thickness. The thicker the wall, the longer it takes for the eddy currents to decay to zero. PEC is therefore the analysis of transient eddy currents in a conductive component following a sharp electromagnetic transition.