Advanced NDT
Pulsed eddy current (PEC) testing
Corrosion under insulation is hard to find because the insulation hides it, and stripping insulation everywhere to look is expensive. Pulsed eddy current measures the average wall thickness of carbon and low-alloy steel through insulation, weather cladding, coatings and fireproofing, so the insulation stays on and only the areas PEC flags need to be opened up.
How PEC works
The probe sends a pulse of magnetic field into the steel and measures how the induced eddy currents decay. The decay depends on the wall thickness under the probe footprint, so comparing readings along a line or grid shows where the wall has thinned relative to the nominal or to unaffected areas.
The reading is an average over the probe footprint, which is typically larger than a pit. PEC is therefore a screening method for general wall loss; localised pitting and the minimum thickness are confirmed with UT or radiography after the insulation is opened.
Where it is used
- Corrosion-under-insulation screening on piping and vessels in a CUI programme.
- Measurement through fireproofing on vessel skirts and structural supports.
- Repeat monitoring at the same grid points to trend wall loss between turnarounds.
- Inspection without removing coatings or scale at elevated temperatures within the probe rating.
Limits to plan for
- Ferromagnetic steels only; stainless and non-ferrous materials need other methods.
- Footprint averaging understates isolated pits.
- Steel weather jacketing, nozzles, supports and flanges affect readings and are recorded as limitations.
How we deliver it
Pulsed eddy current (PEC) is carried out to a written procedure approved for the scope, naming the code and edition, the equipment and calibration, the coverage and the acceptance criteria. The procedure and each technician’s certification are submitted for the client’s review before mobilisation.
Work is planned and supervised by ASNT Level III personnel; our founder holds ASNT NDT Level III in UT, RT, MT, PT and VT. Reports state the coverage achieved and any limitations, so the engineer reading them knows what was examined and what was not, and any reportable finding is raised the same day.
Governing codes and standards
- API RP 583 (corrosion under insulation and fireproofing)
- API 570 and API 510 (inspection programmes the results feed)
- Written procedure with readings verified on known thicknesses of the same material
What you receive
- Grid or line readings with percentage wall loss against reference
- Map of areas recommended for insulation removal and follow-up UT/RT
- Data set for trending at the next inspection
Industries served
- Refining and petrochemical
- Gas processing and LNG
- Power generation
- Offshore production
Frequently asked questions
Can pulsed eddy current find pitting?
PEC averages wall thickness over its footprint, so it is reliable for general wall loss but understates isolated pits. Areas it flags are opened and measured with UT or radiography.
Talk to an inspection engineer
Send the equipment list or drawings, the inspection you need and your timing. Quotes are prepared for each scope and region.
Request a QuoteRequest an inspection quote (RFQ)
Tell us the asset, the method, where it is, the governing code, your dates, the size of the job and the report you need. We reply with questions or a quote. Affordable, accessible, fully customizable — no published pricing.
Or email the same details to info@atlantisndt.com. Mobilisation: North America; confirm your location in your RFQ.
Speak to an ASNT NDT Level III
Atlantis NDT provides ASNT Level III consulting, NDT training to ASNT SNT-TC-1A, inspection management software and independent report validation. Request a free consultation and we will return a tailored quote — affordable, accessible and fully customizable to your programme.