Corrosion monitoring of pipes and vessels at power plants and refineries

Why a separate thickness-gauging route

At CHP plants and refineries, vibration and ESA show that a machine is "behaving badly". But a pipe rupture or a thinning vessel is a loss of metal. No accelerometer on a bearing will see it.

A field ultrasonic thickness gauge answers a simple question: what is the remaining wall thickness at the critical points and how does it change from round to round.

Model selection is covered in "Which Olympus thickness gauge to choose". Below is how to build the programme on site.

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What to include in the point register

Typical zones at a power block and a refinery:

• steam and feedwater lines (bends, tees, zones after throttling);
• condensate and drain lines;
• vessels and tanks holding corrosive media;
• sections under insulation (after local removal / per the CUI procedure);
• previously repaired zones and areas with "thin" data-sheet margins.

Do not try to measure everything. Start with 20–40 points where risk and consequences are highest.

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Frequency and the trending rule

A practical scheme for reliability teams:

1. Baseline measurement — record absolute values and a photograph of the point.
2. Scheduled round — quarterly or half-yearly by criticality.
3. Unscheduled — after water hammer, overheating, a leak, or a PdM alert on an adjacent machine.

The alarm is not "one reading below the limit", but a sustained thinning trend or a value below the minimum allowable thickness from the calculation or data sheet.

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Which instrument goes on the route

Level	Instrument	Why
Operator round / contractor	27MG	quick remaining wall
Main CHP/refinery fleet	39DL PLUS or 38DL PLUS	corrosion plus datalogger plus scan speed
Coatings / paint present	45MG / 39DL with THRU-COAT	metal thickness without stripping the paint

For most Kazakhstan sites the working standard today is the 39DL PLUS: fast minimum-finding, wireless export, dual/single element.

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How to tie it to Bently / Artesis / SDT

1. PdM (Bently, Artesis, SDT) flags a machine or circuit as "needing attention".
2. Thickness gauging checks the structure (pipe, vessel, header), not just the machine mechanics.
3. The repair decision rests on both loops: behaviour plus metal.

The difference between methods is covered in "Thickness gauging, EPOCH or PAUT".

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A 30-day implementation checklist

1. Approve the point register and the minimum thicknesses.
2. Buy the gauge plus a dual-element probe, couplant and a step wedge.
3. Train two operators on a single report template.
4. Take the baseline and start a trend table (even Excel is fine to begin with).
5. Build unscheduled measurements into your PdM alert response procedure.

The instrument catalogue is in the thickness gauges section. Route consultation via Olympus / KEG TRK.