Table of Contents
- Introduction
- What Is a Portable Eddy Current Flaw Detector?
- Key Features to Look For
- Where Portable Detectors Are Used
- Portable vs Benchtop and Automated Systems
- How to Choose the Right Portable Detector
- Who Makes Portable Eddy Current Flaw Detectors?
- Conclusion
- FAQs
Introduction
Portable eddy current flaw detectors can conduct NDT directly at the component, and are useful for field, maintenance and in-service NDT. These handheld battery-powered instruments require minimal set up, as opposed to benchtop or rack mounted or automated systems, and can be carried to the inspection site.
Portable detectors trade some throughput for mobility, for a look at the fixed-scanner and robotic side of ECT, see our full guide to automated inspection systems.
→ Read: Automated and Robotic Eddy Current Testing Systems in Modern NDT
What Is a Portable Eddy Current Flaw Detector?
The portable eddy current flaw detector is a battery-operated, handheld NDT instrument designed for inspecting the surface and near surface discontinuities in conductive materials in the field and in-service. Unlike benchtop or automated systems, it includes signal generation, receiving and processing, display and probe connection all within a mobile package.
The big plus of its mobility. Inspectors are allowed to take the instrument directly to the aircraft, welds, large structures, remote components or some other location where transporting the part to a fixed inspection station would be impractical.
Key Features to Look For
When selecting a portable detector, it should be done based on the inspection application, and not the specification sheet. The following features have a direct impact on inspection capability, usability and documentation.
Frequency Range
The frequency has an impact on the depth and nature of the eddy current interaction with the material. In general, higher frequencies are effective for surface defects, and lower frequencies are effective for appropriate subsurface applications.
A broad frequency range is useful but only if coupled with probes and inspection procedures that are useful.
Single- and Dual-Frequency Operation
Many routine inspections will require single-frequency operation. Dual-frequency can benefit in distinguishing defect signals from interference from fasteners, geometry, conductivity variations, or lift-off.
Frequency mixing may help interpret the signal in applications where signals can be confusing, such as for the inspection of multilayer aerospace structures.
Probe Compatibility
The detector should be able to accommodate the probes needed for the inspection. They can be either pencil, surface, differential, absolute, bolt-hole, rotating or special probes, depending on the application.
Compatibility is also a crucial factor with connectors. Choosing a detector that matches an existing detector inventory will lower equipment costs and help make training easy.
Eddy Current Array Capability
The multiple coils of Eddy current array (ECA) can scan a larger area than a standard single-coil probe. Advanced portable instruments can present the array results in the form of a C-scan which allows the inspector to visualize the location and extent of the indication.
This capability of an array is valuable, especially where inspection coverage and speed are critical, but is more expensive and complex. It should therefore be chosen as per the actual inspection needs.
Display and Signal Visualization
The patterns, amplitude, phase and other characteristics of the signals can only be correctly evaluated by a clear display. A bright, high resolution screen is particularly helpful for outdoor or (variable-light) inspections.
The portable instruments offer a variety of display modes, freeze functions, reference traces and adjustable signal views. These features can simplify calibration and interpretation of indications in the field.
Battery Life
The battery-powered system enables inspections to be carried out when mains power is not available. For field teams, having strong enough batteries to be able to cover an entire inspection shift might be more useful than having some extra bells and whistles that eat the battery life.
Removable or spare batteries come in handy especially at off-site locations with limited charging options.
Weight and Ergonomics
Portable detectors can be kept in the air for hours, carried up and down mountains, or used in restricted spaces. Low weight, easy controls, hand straps, and one-handed operation can minimize fatigue and make operation easier.
A major factor of this difference is height in aircraft, rope-access, or elevated inspections.
Environmental Protection
Field equipment may be subject to dust, humidity, temperature fluctuations, impact, and accidental drops. It is therefore appropriate to look for rugged, IP rated and operating temperature ranges.
Use of the technology is particularly relevant to outdoor infrastructure and oil & gas applications and power plants, marine applications and remote inspections.
Data storage and reporting
Digital storage enables the settings, signals, measurements and results of inspections to be stored for future review. This is useful for situations where there is a need for traceability and reporting in inspection.
High-end equipment can also include PC connectivity, wireless transfer and reporting software, and encoded scan data.
Encoders and Scanning
Manual scanning is adequate for many local inspections. The value of encoder support is realised when the inspector requires the inspection information to be related to an exact physical location.
Repeatability may be enhanced by encoded scanning and indications can be assessed by either mapped inspection information or C-scan images.
Conductivity and Coating Thickness Measurement
Some portable instruments have both flaw detecting and conductivity and non-conductive coating thickness measurement capabilities.
Material verification, alloy identification and evaluation of some heat-treatments may be accomplished with the use of conductivity testing. These functions must be considered as application-specific functions instead of being considered as standard functions of all the flaws detectors.
For a deeper look at how array probes generate C-scan coverage compared to single-coil scanning, see our full breakdown of eddy current array technology.
→ Read: Types of Eddy Current Testing
Where Portable Detectors Are Used
Aircraft Skin and Fastener-Hole Inspection
One of the primary applications of the portable eddy current inspection is to be used in aerospace. Inspectors can view aircraft skins, fastener locations and bolt holes without having to remove components from the aircraft.
Portability lets the detector be carried directly to an aircraft on the ramp or in a hangar. Low-frequency methods can also be used to support the inspection of multilayer structures with suitable techniques.
Weld Toe and Surface Inspection
Portable detectors can be used to check weld toes, heat affected zones, accessible surfaces for defects that affect the surface of the weld.
The ability to move the instrument to large structures or to high welds removes the need to move parts to a fixed inspection location.
Bolt-Hole Inspection
Fatigue critical areas are critical holes, especially in aircraft structures. Hole surfaces can be examined for appropriate discontinuities using portable detectors and appropriate probes or scanners without extensive disassembly.
In-Service Spot Checks
Maintenance teams may only need to look into a specific area and not be in constant surveillance. Handheld detectors can be carried directly to the suspected area and then immediately examined.
This makes portable ECT beneficial for troubleshooting, maintenance shutdowns and for specific condition evaluations.
Conductivity / Coating Verification
If the instrument is capable of these functions, inspectors may also conduct a conductivity or coating test while performing a flaw detection test. This can help to decrease the number of instruments used in the field.
Remote and Mains-Free Locations
Fixed equipment for pipeline inspection, bridge inspection, wind turbine inspection, marine structure inspection, and large industrial facilities can be tricky to use.
The detector operates from batteries and will therefore be able to be taken to remote areas and work without reliance on electricity supplies.
Portable vs Benchtop and Automated Systems
Portable systems are strongest where access, mobility, and deployment speed matter. Benchtop and automated systems generally perform better where throughput, repeatability, positional control, and standardized digital records are priorities.
How to Choose the Right Portable Detector
Start With the Material and Defect
Define material, type of expected defect, depth of defect, component geometry, and location of inspection. Various frequencies and probes may be needed for surface cracks, subsurface flaws, material verification and conductivity measurements.
Match the Detector to Your Probes
Inspect and determine what probes are available and what probes are needed for the new inspection. Before ordering, check electrical and connector compatibility.
A large probe stock can be a seemingly affordable detector that ends up being quite expensive.
Decide Whether You Need Array Inspection
ECA capability can be very useful for large inspection areas or when a detailed coverage is needed for a specific application. Conventional probes might be less complicated and cheaper when used for local crack detection.
Consider Data and Reporting Requirements
Decide whether it is necessary to carry out only real-time indication assessments or permanent digital records need to be created.
Data storage, encoded scanning, traceability and reporting software can be important safety critical or highly regulated inspection selection criteria.
Match the Environment and Operator
Think about the location and who will be using the instrument. Rugged construction and bright display might be needed for outdoor inspections, and lightweight equipment would be ideal for rope-access work.
Before buying a battery, factors to be considered include battery life, environmental protection, controls, training and applicable inspection procedures.
Who Makes Portable Eddy Current Flaw Detectors?
Currently, there are a number of well known NDT manufacturers that supply traditional flaw detectors, conductivity instruments, array capable systems and application specific solutions to the portable eddy current market.
Evident's portable eddy current instruments belong to the NORTEC family, which encompasses applications like flaw detection, conductivity, scanning and dual-frequency inspection.
Eddyfi Technologies provides portable platforms like MIZ-21C that integrate traditional eddy current inspection with advanced array, encoded inspection and C-scan inspection.
Rohmann manufactures ELOTEST portable instruments covering applications such as surface inspection, bore inspection, conductivity, coating measurement, and array inspection.
FOERSTER manufactures mobile eddy current systems such as the crack and hardness testing systems from the family DEFECTOMETER for metallic parts.
ETher NDE supplies portable instruments such as PockET, WeldCheck, PhaseCheck and RailCheck instruments for various applications including rail, tube and weld testing and inspection, as well as aerospace.
Portable detectors, probes, scanners, conductivity systems and accessories are also available from other manufacturers and specialist suppliers. Specifications, configurations and regional availability vary, as does software, so it's important to look at the instrument and probe combination, and not just brand.
Read about portable eddy current flaw detector products and directory of NDT equipment manufacturers for comparison to available products and suppliers.
Compare specific portable eddy current instruments and connect with suppliers directly in our equipment marketplace.
→ Read: NDT Equipment Manufacturers Directory
Conclusion
Mobile eddy current flaw detection systems fit between simple hand held systems and larger benchtop or automatic systems. The main benefit is they can enable electromagnetic inspection to be moved to the component.
Depending on the application, the right detector is demanded. Consider all the following against actual inspection requirements: Frequency range, probe compatibility, array capability, battery life, environmental protection, data storage, and reporting features.
Portability is often a big advantage in aircraft maintenance, weld inspection, examination of bolt holes, checking material, and in-service work at remote locations.
FAQs
What is the normal cost of a portable eddy current flaw detector?
These prices are subject to change depending on the frequency range, probe support, conductivity functions, dual-frequency, array support, software, and scanning hardware. Basic units have a lower cost than systems that use the arrays. Total cost should also include probes, cables, calibration standards, software and service.
What is the difference between flaw detector and conductivity meter?
An eddy current flaw detector is mainly used to detect and assess discontinuities based on electromagnetic response. A conductivity meter is designed to measure electrical conductivity. Some of the more sophisticated portable instruments have both functions, but the procedures and capabilities the device can perform should be confirmed prior to its use.
Can portable eddy current detectors run array probes?
Yes, Some high-end portable detectors have the capability of using eddy current array probes for increased coverage and C-scan imaging. But not all handhelds have array capability. All the detector and the probe, connectors, software, and encoder must be compatible with the inspection to be performed.
What certification is needed to operate a portable eddy current flaw detector?
Requirements vary between countries, employer, industry and inspection standard. Generally, personnel should be suitably trained and qualified in accordance with the NDT certification scheme (e.g., ISO 9712 or a comparable national or employer based certification scheme) in eddy current testing.
How often does a portable eddy current flaw detector need calibration?
Normally, the manufacturer's recommendations, applicable standards and employer procedures dictate calibration intervals. The instrument should also be checked against the appropriate reference standard prior to inspection, and whenever the conditions may have an impact on how the instrument operates. Calibration records must be kept in accordance with the inspection organisation's quality system.
Are portable eddy current flaw detectors suitable for weld inspection?
Yes, Portable detectors and probes are available to examine weld toes, HAZs, and other accessible surfaces for surface-breaking flaws relevant to the weld. The material, geometry, frequency, probe, calibration standard and inspection procedure should be suitable to the weld and defect mechanism.
