# Eddy Current Testing of Stainless Tubes: What Buyers Should Ask

Canonical: https://jundapipe.com/en-GB/blog/eddy-current-testing-stainless-steel-tubes

Review eddy current testing scope, reference standards and coverage for stainless tubing, and distinguish equipment capability from batch acceptance.

For eddy current testing of stainless tubes, ask which material, dimensions, procedure, reference standard and acceptance criteria the examination covers. A steel rolling factory’s equipment list is not an inspection report. The useful evidence is a defined examination applied to identified material, with results assessed against the agreed purchase requirements.

Junda publishes a UT/ET dual flaw-detection system in its [testing capabilities](https://jundapipe.com/production-environment). This supports a discussion of inspection scope; it does not establish that every tube is examined by the same procedure or meets an unspecified acceptance level.

## What does ASTM E426 cover?

[ASTM E426-16(2021)](https://store.astm.org/e0426-16r21.html) covers eddy current examination of seamless and welded tubular products made from relatively low-conductivity materials, including austenitic stainless steels and similar alloys. Its scope specifically distinguishes generally nonmagnetic austenitic chromium-nickel steels from magnetic ferritic and martensitic straight-chromium steels.

The public scope gives a diameter range of 0.125–5 in. and a wall range of 0.005–0.250 in. It treats inch-pound values as standard and metric conversions as information. Those are scope values for this edition, not the operating range of Junda’s equipment.

The practice describes encircling-coil or probe-coil techniques. It notes that internal coils and probes exist but their use is not specifically covered. An in-service exchanger inspection using an internal probe should therefore not be assumed to share the same scope as a mill examination.

## Which questions should the inspection plan answer?

| Question                                               | Evidence to request                                           |
| ------------------------------------------------------ | ------------------------------------------------------------- |
| Is the procedure suitable for this alloy and geometry? | Procedure identification and applicability                    |
| How is examination sensitivity established?            | Reference standard details and documented checks              |
| Which material is covered?                             | Heat, lot, size and piece or bundle identification            |
| Are end zones or other regions excluded?               | Coverage statement and agreed disposition                     |
| What determines acceptance?                            | Referenced criteria from the governing specification or order |
| What happens to an indication?                         | Evaluation, segregation and disposition records               |

These are review questions, not an operator’s testing procedure. Technique settings and acceptance levels must come from the qualified procedure and applicable requirements.

## How should “100% tested” be interpreted?

Ask what the percentage describes: pieces, length, surface coverage or another defined quantity. Confirm whether end regions are included and whether the examination occurs before or after final processing. A coverage claim without that basis is difficult to verify.

Require the report to identify the material, procedure, examination date, result and any excluded areas. A calibration or reference-check record supports a particular examination setup; it does not make the product universally defect-free.

## How should ET enter a Junda enquiry?

Provide the alloy, OD, wall, length, product specification, required condition and inspection criteria through the [contact page](https://jundapipe.com/contact). State whether the requirement concerns mill product examination or an installed component. Request a written explanation of the proposed scope and deviations.

For the separate purposes of ET, UT and hydrostatic testing, use the [inspection comparison](https://jundapipe.com/blog/ut-et-hydrostatic-pipe-testing). No one method should be substituted for another solely because the factory owns both machines.