What Is Pulsed Eddy Current (PEC) Testing?
Pulsed Eddy Current (PEC) testing is a cutting-edge non-destructive testing (NDT) technique used primarily for detecting corrosion under insulation (CUI) and wall loss in metallic structures without the need to remove insulation or coatings. This technology emits a pulsed electromagnetic field into the test material, inducing eddy currents whose decay characteristics are measured to assess the thickness and integrity of the metal beneath.
At Welle Inspection, we specialize in PEC testing for industries where downtime is costly and asset accessibility is limited—such as oil & gas, petrochemical plants, power generation, marine, and heavy industries. Our advanced Lyft PEC system, combined with PECA Gen 1 probes, delivers accurate, efficient, and reliable corrosion assessments even in challenging environments.
Understanding Pulsed Eddy Current Testing: Principles and Workflow
How PEC Works: The Science Behind the Technology
PEC testing relies on the principle that when an alternating current pulse is applied to a coil in the probe, it generates a transient magnetic field that penetrates the conductive material beneath insulation or coatings. As the current stops, the steel underneath becomes magnetized and then demagnetizes, inducing eddy currents that flow inside the metal.
The critical factor here is that the eddy currents decay over time, and the rate of decay is directly related to the wall thickness and the presence of corrosion or metal loss. The PEC probe’s sensors measure the strength and decay of these eddy currents, which allows technicians to estimate the remaining wall thickness and detect areas of corrosion without direct contact or surface preparation.
Step-by-Step PEC Inspection Process at Welle Inspection
- Pre-Inspection Planning: Our experts assess the asset’s condition, insulation type, temperature, and access challenges. This helps select the appropriate probe and scanning strategy.
- Probe Deployment: The PECA Gen 1 probe or PEC Array probe is placed on the insulated or fireproofed surface. No removal of insulation or coatings is necessary, saving time and cost.
- Data Acquisition: The Lyft system generates pulsed magnetic fields and collects real-time data on eddy current decay signals, which are visualized as B-scans and C-scans for detailed corrosion mapping.
- Data Analysis & Interpretation: Skilled engineers interpret decay curves with advanced software, distinguishing between wall loss, coating thickness, and insulation effects.
- Reporting & Recommendations: Comprehensive reports with corrosion maps, thickness trends, and risk assessments support informed maintenance decisions.
Why Choose PEC for CUI and CUF Inspection?
Feature | Benefit |
Non-contact | Inspect without removing insulation or fireproofing |
Deep Penetration | Detect corrosion through up to 250mm of insulation |
Rapid Scanning | Large areas covered quickly, especially with PECA |
Accurate Wall Thickness | Effective at detecting uniform and localized wall loss |
In-Service Testing | No need for shutdown, allowing inspections during operation |
Versatile | Suitable for pipes, tanks, vessels, and structural steel |
Safe & Environmentally Friendly | No radiation, no hazardous waste |
Corrosion hidden under insulation or fireproofing is a leading cause of unplanned outages, safety risks, and costly repairs. PEC enables early detection of these hidden threats before catastrophic failure occurs.
Don’t Let Hidden Corrosion Surprise You—Get Tested Now!
Applications: Industries & Assets Where PEC Excels
Oil & Gas and Petrochemical Facilities
- Inspection of sphere legs, skirts, and pipe racks without removal of passive fire protection.
- Corrosion assessment on insulated cryogenic tanks and piping.
- Tank floors coated with fiberglass or other protective layers.
- Pressure vessels and piping systems with complex insulation.
Power Generation Plants
- Monitoring feedwater and condensate piping for wall thinning.
- Inspection of heat recovery steam generator (HRSG) finned tubing.
- Detecting corrosion in coal feed and re-circulating water systems.
Marine and Offshore Platforms
- Surveying offshore platform legs and subsea structures through thick coatings.
- Corrosion mapping on ship hulls and seawall bulkheads.
- Structural steel inspections hidden by fireproofing.
Industrial Manufacturing & Infrastructure
- Inspecting insulated pressure vessels and heat exchangers.
- Bridge pier sheet piling and other infrastructure elements protected by coatings.
- Storage tanks with insulation and cladding layers.
PEC vs Traditional NDT Methods: Strengths and Limitations
Method | Access Needed | Surface Prep | Penetration Depth | Speed | Accuracy | Ideal Use Case |
PEC | No | No | Up to 250mm | Fast | Moderate to High | Corrosion under insulation/fireproofing |
Ultrasonic (UT) | Yes | Yes | Low (requires direct contact) | Slow | Very High | Detailed thickness mapping, weld inspections |
Radiography (RT) | Yes | Yes | Moderate | Slow | High | Flaw detection in welds and components |
Long Range UT (LRUT) | No | No | Long-range | Moderate | Moderate | Long pipe sections, inaccessible areas |
Thermal Imaging | No | No | Surface only | Very Fast | Low to Moderate | Surface temperature anomalies detection |
PEC offers a unique advantage for in-service, insulated assets where removal of insulation is impractical or impossible. While UT provides higher accuracy for thin materials and welds, it requires direct contact and insulation removal, increasing downtime and costs.
Welle Inspection’s PEC & PECA Service Capabilities
At Welle Inspection, we deliver industry-leading PEC and PEC Array inspection services using:
- Eddyfi Lyft™ platform with Gen 1 PECA probes, offering 18-inch wide scanning with high spatial resolution.
- Advanced signal processing software for precise corrosion mapping and data interpretation.
- Certified NDT technicians trained in Advanced Corrosion Technologies and Training (ACTT).
- Capability to inspect through complex insulation types including fiberglass, foam, fireproofing, plastic wraps, aluminum weather jackets, and more.
- Ability to operate on in-service assets with minimal disruption and rapid deployment.
- Detailed, OEM- and insurance-compliant inspection reports including corrosion trend analysis and risk assessments.
Customer Case Study: PEC Inspection on Fireproofed Sphere Legs
Project Overview
A leading petrochemical company engaged Welle Inspection to perform corrosion evaluation on 16 fireproofed sphere legs without removing insulation during a critical turnaround.
Challenges
- Thick passive fireproofing (~60 mm) prevented direct inspection.
- Access limitations and high ambient temperatures.
- Requirement for rapid inspection with minimal process impact.
Solution & Results
- Used PECA Gen 1 probes to scan entire sphere leg surfaces.
- Detected up to 35% wall thinning in three legs, enabling targeted repairs.
- Inspection completed in 2 days, saving over $60,000 in insulation removal costs.
- Provided actionable data leading to maintenance optimization and shutdown avoidance.
Client Testimonial: “Welle’s PEC inspection gave us confidence in our asset integrity while avoiding costly delays and insulation removal.” – Maintenance Manager
Frequently Asked Questions (FAQ)
What is pulsed eddy current testing used for?
PEC detects corrosion and metal loss beneath insulation or coatings, enabling early detection of CUI and CUF without removing protective layers.
How does the PECA probe improve inspection speed?
PECA combines PEC with eddy current array (ECA) technology, enabling wider coverage (up to 18 inches per scan) and better flaw sizing with C-scan imaging.
Can PEC be used on stainless steel or non-ferrous metals?
PEC is primarily effective on carbon steel and low-alloy steel; sensitivity on stainless steel and non-ferrous metals is limited.
Does PEC testing require insulation removal or surface preparation?
No. PEC can scan through insulation, fireproofing, fiberglass, plastic wrap, and aluminum weather jackets without removal or cleaning.
How accurate is PEC for wall loss measurement?
PEC provides moderate to high accuracy for general corrosion and wall loss detection, especially for uniform thinning. For detailed sizing, it is often combined with targeted ultrasonic testing.
Can PEC testing be performed on live assets?
Yes. PEC is designed for in-service inspection, avoiding costly shutdowns and production interruptions.
Call to Action
Partner with Welle Inspection for Reliable PEC Inspection Services
Whether you’re evaluating wall loss, detecting hidden corrosion, or ensuring CUI compliance — Welle’s certified experts, calibrated PEC equipment, and 10+ years of field experience make us your ideal NDT partner.
Book Your PEC Inspection with Welle Today
📚 Further Resources
To gain a more comprehensive understanding of all major NDT techniques—including UT, PT, MT, and RT—we invite you to refer to the attached Comprehensive NDT Technical Report (PDF). This document, prepared by the Welle Inspection team, offers an in-depth overview of principles, applications, and industry standards.