Thickness gauging, flaw detector or PAUT: which NDT tool you need

Three different questions — three classes of instrument

On site people often ask for "Olympus ultrasound" while meaning completely different tasks:

1. How much metal is left? → thickness gauging
2. Is there a crack / lack of penetration / inclusion? → a classic UT flaw detector
3. Do I need a defect map across a weld or complex geometry? → PAUT / TFM (OmniScan)

The confusion is expensive: either defects are missed, or PAUT is bought "just in case" without a procedure or an operator.

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Thickness gauging — remaining wall and corrosion

A thickness gauge (39DL PLUS, 38DL, 45MG and others) answers one question: what is the wall thickness here and now.

Typical assets: pipes, vessels, tanks, casings, corrosion and erosion zones.

Suitable if:

• access is from one side only;
• the defect is wall loss, not an oriented crack in a weld;
• you need a walkdown route and a log of minimum readings.

It does not replace a flaw detector where the goal is weld inspection to a UT procedure.

More detail on models — in "Which Olympus thickness gauge to choose".

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EPOCH — classic flaw detection

The EPOCH 650 and EPOCH 6LT are portable UT flaw detectors for finding and sizing discontinuities: welds, parent metal, standard insonification schemes.

Choose EPOCH if:

• you have (or will have) a UT procedure and qualified personnel;
• you need A-scan, DAC/TCG, work with wedges and different frequencies;
• the object is welded joints, forgings, castings (within your scope).

The EPOCH is not meant to be a "fast thickness gauge for rounds" — for corrosion routes the 39DL/38DL is far more efficient.

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OmniScan — PAUT and advanced UT

The OmniScan X3 / X4 is for when you need phased array, encoded scanning, TFM/PCI and a fuller picture of the inspection zone.

Justified if:

• critical welds, complex geometry, a requirement for C-scan or volumetric documentation;
• you have trained PAUT operators and an agreed method;
• the inspection volume pays back the cost of the platform and scanners.

PAUT without a method and training becomes an expensive black box. For some tasks a good EPOCH is enough.

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BondMaster — a separate branch: bonded and honeycomb structures

The BondMaster 600 is not about pipe wall thickness. It inspects adhesive bonds and composite honeycomb (pitch-catch, resonance, MIA). For aviation and composite repair it is its own loop; it does not compete directly with thickness gauging or PAUT.

For screening impact damage in laminates there is a separate simple instrument, the 35RDC.

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The link with vibration and ESA

Bently Nevada, Artesis and SDT systems answer: the machine is behaving abnormally. Olympus answers: there is (or is not) a specific defect in the metal, the weld or the cavity.

A practical scheme for a mine or CHP plant:

1. PdM flags a machine as needing attention.
2. Thickness gauging / RVI / UT confirm or clear the structural risk.
3. The repair decision rests on both loops.

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Mini decision algorithm

1. Need wall thickness? → thickness gauge.
2. Need weld inspection to UT? → EPOCH (plus a procedure).
3. Need a map / PAUT / TFM on critical welds? → OmniScan.
4. Need composites / bonds? → BondMaster / 35RDC.
5. Need to see inside a cavity? → IPLEX (a separate RVI class).

The method catalogue is in the non-destructive testing section. Help with configuration is on the Olympus page and via KEG TRK.