Acoustic Emission Tank Floor Testing Singapore — In-Service Floor Corrosion Screening

What Is Acoustic Emission Tank Floor Testing?

Acoustic emission (AE) testing is a passive, in-service technique for screening the floor of an aboveground storage tank without taking it out of service. Where most inspection methods send energy into a component and read what comes back, AE does the opposite: it simply listens. When a floor plate corrodes actively, or when product weeps through a developing leak path, the material releases tiny bursts of high-frequency stress-wave energy. An array of sensors clamped around the outside of the tank shell picks up those emissions, and the pattern, location and intensity of the activity tell an analyst whether the floor is deteriorating — all while the tank remains full of product and running normally.

That distinction is the whole point of AE. Corrosion of a tank floor is invisible from the outside and unreachable from the inside without emptying the tank. AE gets around the problem entirely by detecting the damage process as it happens rather than trying to see or measure the damage after the fact. It is a listening test, and because the tank keeps working throughout, it fits into an operating facility with almost no disruption. It is one of the few condition assessments that can be made on a live storage tank without a shutdown.

It is important to be clear about what AE is and is not. It is a screening and grading method — it establishes whether a floor is corroding actively and how urgent the situation is. It is not a thickness-mapping method: it does not measure remaining wall thickness or draw a corrosion map. That quantification comes later, and only for the tanks AE flags as worth opening.

The Core Value: Screening Without a Shutdown

Taking a large storage tank out of service is one of the most expensive and disruptive things an operator can do. The tank must be emptied of product, cleaned, isolated, gas-freed and made safe for entry before anyone can inspect the floor internally. Product has to be stored elsewhere or the terminal loses capacity, sludge disposal carries a cost, and the tank can be off-line for weeks. Doing all of that on a tank whose floor turns out to be perfectly sound is money and downtime spent for no integrity benefit.

Acoustic emission exists to prevent exactly that waste. By grading whether a floor shows active corrosion or leakage while the tank stays full, AE answers the single most valuable planning question an operator has: does this tank actually need to be opened yet? A quiet floor with little emission activity gives evidence to safely defer an internal inspection; a noisy, actively corroding floor justifies scheduling one. In other words, AE turns a fixed, calendar-driven inspection plan into a risk-prioritised one, so that shutdown effort is directed at the tanks that need it and withheld from the ones that do not.

For a terminal or refinery running a whole tank farm, that prioritisation is where the value lands. Instead of opening tanks in rotation and hoping the schedule matches reality, an operator can screen the population, rank the tanks by measured corrosion activity, and build a shutdown scope around genuine need. AE is best understood as an inspection-planning and cost-avoidance tool, not a repair or measurement tool.

How Acoustic Emission Testing Works

An AE test on a tank floor follows a defined, disciplined sequence. A ring of sensors is mounted around the tank shell, typically at low level, spaced so that the array can cover the whole floor and estimate roughly where activity is coming from. The tank is then put through a controlled quiet or settling period: product movement, filling, mixing and other operational noise are stopped or stabilised so that the mechanical and electrical background does not mask the genuine corrosion and leak signals. Once conditions are quiet, a defined monitoring period runs and the AE data is recorded continuously.

During analysis, the recorded emissions are filtered to separate real corrosion and leak activity from spurious noise, and the surviving activity is assessed for rate, energy and distribution across the floor. The floor is then graded — commonly into activity categories that rank it from little or no significant activity through to high activity warranting prompt follow-up. Methodologies of the TANKPAC type formalise this grading so that results are repeatable and comparable between tanks and over time.

The output is a graded assessment, not a thickness map. It says, in effect, "this floor is in category X, here is roughly where the activity concentrates, and here is our recommendation on whether and how soon to open it." That grading is what feeds directly into the inspection plan.

What AE Screening Detects

AE is tuned to the active processes that degrade a tank floor from within, rather than to static geometry. It is most useful for the following.

How AE Fits the Wider Tank-Integrity Toolkit

Acoustic emission is one stage of a coherent tank-integrity programme, and it works best when its role is kept distinct from the methods that follow it. AE is the in-service screen: it answers "do I need to open this tank?" without a shutdown. It does not locate metal loss to the plate, and it does not measure remaining thickness — deliberately, because that is not its job.

When AE grades a floor as actively corroding and the tank is scheduled out of service, the next stage takes over. Magnetic flux leakage (MFL) floor scanning maps the extent and severity of metal loss across every floor plate, showing exactly where the corrosion is and how bad it is. Ultrasonic thickness testing then quantifies remaining wall thickness at the shell and at points of interest, turning the MFL map into hard numbers an engineer can assess against retirement limits. The three methods form a logical chain: AE prioritises, MFL locates, and UT measures.

Presenting them together avoids the confusion of treating AE as a competitor to MFL or UT. It is not — it sits upstream of them. A well-run programme uses AE to decide which tanks to open, then uses MFL and shell UT inside the opened tank to locate and quantify what AE could only flag. For operators in the oil and gas sector, that sequence is the difference between a fixed inspection cost and a targeted, evidence-led one.

Standards and Methodology

AE floor screening sits within a well-established framework. API 653, the industry standard for aboveground storage tank inspection, repair, alteration and reconstruction, provides the context in which a screening result is used to inform inspection intervals and the decision to open a tank. Recognised AE practice of the TANKPAC type defines how the test is set up, run and graded so that results are repeatable and comparable across a tank population. The general principles of acoustic emission examination are codified in ASME Boiler and Pressure Vessel Code, Section V, Articles 11 and 12, which cover AE methods and instrumentation.

Citing these standards is not decoration — it is what makes an AE result defensible. A graded floor assessment carries weight in an integrity file precisely because it was produced under a recognised methodology and feeds an API 653 inspection strategy rather than sitting on its own.

Why Choose SG Drone Inspections

We provide industrial inspection across Singapore's tank terminals and process facilities, with acoustic emission floor screening positioned as the front end of a complete tank-integrity offering.

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