Heat Exchanger Tube Inspection Singapore — IRIS, Eddy Current & Tube-Bundle NDT

What Is Heat Exchanger Tube Inspection?

Heat exchanger tube inspection is the internal non-destructive testing (NDT) of the tube bundle inside a shell-and-tube exchanger, condenser, air cooler or boiler — reading the condition of the metal from inside each individual tube. A probe is fed from the tubesheet face down the bore of the tube, measuring or sensing wall loss, pitting, cracking and other defects along its full length. It is a fundamentally different job from an external drone visual inspection of the exchanger shell: the shell survey looks at the pressure envelope, nozzles, supports and lagging from outside, while tube inspection interrogates the hundreds or thousands of thin-walled tubes that actually do the heat transfer and most often fail first.

The reason tube inspection is a specialised discipline is that no single technique suits every tube. Exchanger tubes are made from copper alloys, admiralty brass, titanium, stainless steel, carbon steel and duplex, and the physics of each NDT method depends on whether the tube is ferromagnetic or not. A competent tube-bundle inspection therefore begins with selecting the right method — or combination of methods — for the material in front of us, then applying it consistently across the whole bundle so the results can be compared tube to tube and turnaround to turnaround.

Because the work is internal, it can only be done with the exchanger opened, isolated and the tubes hydro-jetted clean. That places tube inspection firmly inside the plant turnaround or shutdown window, alongside the other fixed-equipment inspection scopes on the critical path.

Why Tube Integrity Matters

Exchanger tubes are the thinnest-walled pressure components in most process units, and they live in the harshest position — carrying corrosive process fluids or cooling water at temperature, cycle after cycle. They deteriorate through several well-known mechanisms: general and localised corrosion, flow-accelerated erosion at the tube inlets, pitting under deposits, under-deposit corrosion, stress-corrosion cracking in susceptible alloys, and mechanical wear where tubes rub against baffles. Any of these can perforate a tube wall that started only a millimetre or two thick.

When a tube leaks, the consequences reach well beyond the exchanger. Cross-contamination between the shell and tube sides can push cooling water into a hydrocarbon stream or vice versa, upsetting downstream units and corroding other equipment. A single failed tube in a critical service can force an unplanned shutdown of an entire train — the exact outcome a turnaround is meant to prevent for the next run length. On Jurong Island's refineries and petrochemical plants, where units are expected to run four to six years between turnarounds, knowing the true condition of every bundle is central to setting a defensible run length.

The practical question a turnaround team must answer is simple to state and hard to answer without data: which tubes are fit to run, which must be plugged now, and is the bundle close enough to end-of-life that it should be retubed or replaced? Tube-bundle NDT exists to convert a wall of unknown tubes into a graded, evidence-backed answer to that question.

Tube NDT Methods — and When We Use Each

The value of a tube inspection lies in matching the method to the tube. We select from the established family of internal NDT techniques and, where speed and accuracy pull in different directions, combine them in a sampling strategy.

In practice a bundle is often screened quickly with the appropriate electromagnetic method (ECT for non-ferrous, RFT/NFT/MFL for ferromagnetic) to find where the damage is concentrated, then IRIS is applied on a targeted sample and on any suspect tubes to put a quantitative wall-thickness number against the indications. This sampling strategy balances coverage against the slower, more precise IRIS scan, and keeps the inspection inside the turnaround window without sacrificing confidence in the plug/retube call.

What We Inspect For

Every tube is assessed against the damage mechanisms that actually take exchanger tubes out of service, and each indication is located to a specific tube on the tubesheet.

Where Tube Inspection Fits

Tube-bundle NDT applies to the full population of tubed equipment on a process site: shell-and-tube heat exchangers, overhead and surface condensers, fin-fan air coolers, and fire-tube and water-tube boilers. On Jurong Island refineries and petrochemical plants these run in cooling-water, hydrocarbon, amine, sour-water and steam services, each with its own dominant damage mechanism that steers the method choice.

The work is scheduled into the plant turnaround because the exchanger has to be isolated, opened and the tubes cleaned before any probe can pass. Sequencing matters: because the plug-versus-retube outcome drives long-lead spares and re-tube labour, tube inspection is planned early in the shutdown so the reliability team has answers while the bundle is still accessible. It pairs naturally with the external drone exchanger inspection of the shell and with the wider oil and gas inspection and industrial inspection scopes we deliver across a unit.

Standards We Work To

Tube-bundle NDT is governed by recognised codes and industry practice, and we plan and report our work to align with them. Ultrasonic and eddy current examination follow ASME Boiler and Pressure Vessel Code, Section V, which sets out the requirements for those methods. IRIS ultrasonic tube examination is described in ASTM E2096. The condition assessment sits within the pressure-vessel and heat-exchanger inspection framework of API 510 and the inspection practices of API 572, while eddy-current tubing practice for condensers and heat exchangers draws on established EPRI guidance. Acceptance and plugging criteria are always agreed with your inspection or fixed-equipment engineer before we start, so the grading reflects your fitness-for-service basis for the equipment.

Why Choose SG Drone Inspections

We deliver tube-bundle NDT as part of a full turnaround inspection capability, so the tube data lands in the same coordinated package as the rest of your exchanger and unit scope.

Frequently Asked Questions