Pulsed Eddy Current (PEC) and other advanced eddy current inspection techniques are ideal tools for detecting corrosion under insulation (CUI) and fireproofing (CUF).
Advanced eddy current inspection technology can help detect hidden corrosion before it becomes a potentially expensive and hazardous problem. MISTRAS utilized Pulsed Eddy Current (PEC) and PEC Array (PECA) inspection services for tanks, spheres, piping systems, and other assets.
Pulsed Eddy Current (PEC) Inspection Services
During pulsed eddy current (PEC) inspection, a probe induces eddy currents in a component, and the probe measures wall thickness by tracking the amount of time it takes the eddy currents to decay. The thicker the wall, the longer it takes for the eddy currents to decay to zero. PEC can be applied to in-service assets, and can detect damages through insulation and fireproofing, so it is an effective tool for corrosion-under-insulation (CUI) and flow-accelerated corrosion (FAC) assessments.
Small amounts of water can accelerate corrosion if faulty seals or inadequate construction allow it to penetrate the interface between metal and insulation or fireproofing materials in steel. Passive fire protection and insulation can hide signs of degradation, and if left undetected, corrosion can then cause the failure of steel support structures, piping systems, or vessels.
After performing a detailed visual inspection to look for signs of degradation, MISTRAS technicians will apply PEC technology to measure the wall thickness of the metal behind the fireproofing or insulation. PEC probes placed on the wall in question apply an electric charge to generate eddy currents in the steel, allowing probes to estimate wall loss based on measurements of the induced magnetic field.
PEC obtains a measure of the wall thickness by taking an average reading over the probe’s footprint (the roughly circular area where eddy currents flow). This makes it ideal for measuring general wall loss.
Using the PEC inspection technique offers a variety of benefits, including:
- No interference with production. PEC technology can be applied in-service, so there is no need to empty storage spheres.
- No need to remove the passive fire protection. PEC technology can measure through up to 250 mm of material including the reinforcement mesh.
- Performed in service during plant operation
- Accessibility issues are minimized as it can be used by rope access operators
PEC can be used to detect CUI and corrosion under fireproofing (CUF) in a wide variety of assets, including:
Petrochemical Plants & Refineries
- Sphere Legs
- Insulated Cryogenic Tanks and Piping
- Tank Floors with Fiberglass Coatings
- Pressure Vessels
- Skirts
Power Generation
- Feedwater & Condensate Piping
- Drain Piping
- Coal Feed Piping
- Feedwater Heater Shells
- Re-Circulating Water Piping
- HRSG Finned Tubing
Marine Applications
- Offshore Platform Legs
- Ship Hulls
- Seawall Bulkheads
- Bridge Pier Sheet Piling
- Fireproofed Structural Beams
Pulsed Eddy Current Array (PECA) Services
MISTRAS Pulsed Eddy Current (PEC) Array services combine the advanced inspection capabilities of PEC with the speed of eddy current array (ECA) technology. Our combined PEC and ECA services enable fast, accurate, and in-service inspections for CUI/CUF in pipes, vessels, sphere legs, and more.
Combined PEC & ECA Technologies
In pulsed eddy current inspection, an electric current is introduced in a probe’s transmitter coil, which magnetizes the steel beneath the probe. The current is then switched off and, as a result, the steel demagnetizes. This generates eddy currents in the steel, which diffuse inwards from the steel surface and decay in strength as they propagate, which is detected by a set of receiver coils in the PEC probe.
ECA technology offers the ability to electronically drive multiple eddy current sensors placed side-by-side in the same probe assembly. When ECA data is multiplexed, the individual eddy current coils are excited at different times, allowing the system to excite all of the coils in the probe without ever exciting any two adjacent coils at the same time (avoiding mutual inductance between the individual sensors).
ECA enables larger coverage in a single probe pass while maintaining a high resolution, and improves flaw detection and sizing with C-scan imaging.
PEC Array Applications
PEC Array is able to conduct inspections through:
- Insulation
- Fireproofing
- Fiberglass
- Plastic Wrap
- Concrete
- Non-Ferrous Metals
- Stainless Steel
- Aluminum Weather Jackets
Benefits of PEC Array
- Scans through insulation & fireproofing
- Covers 18 inches in a single pass
- Inspects 100% of the wall thickness
- Provides relative wall thickness measurements
- Does not require surface preparation
- Assets can remain in-service during inspections
