Measurement Equipments

Digital Thickness Meter

See how much metal is left in your receivers and pipework, from the outside, without stopping a thing.

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A handheld ultrasonic thickness meter reading a steel pipe, its probe held against the pipe wall

Product overview

Hidden corrosion, measured from the outside

Our digital thickness meter measures the remaining wall of your air receivers, pipework, dryer towers and other pressure equipment by ultrasonic pulse-echo. The probe sits on the outside surface, sends a short sound pulse into the metal, times the echo from the inner surface and shows the thickness, typically with a resolution of 0.01 mm.

Nothing is cut, drilled or drained, and your system stays pressurised and in service, so a survey of your compressor house needs no production stop.

Condensate corrodes carbon steel from the inside, where it stays invisible until a pinhole leak or a rupture appears. A reading at a fixed location, repeated over the years, turns that hidden process into a measured corrosion rate, the basis for remaining life and your next inspection date.

A handheld ultrasonic thickness meter reading a steel pipe, its probe held against the pipe wall
  • 0.01 mmTypical display resolution
  • About 1 mmTypical thinnest wall measured
  • 5,920 m/sSpeed of sound in carbon steel
  • No shutdownMeasured under pressure, in service

Benefits

Know your walls before they fail

Your compressed air system makes water, and that water collects on exactly the surfaces carbon steel needs to keep dry. Here is what that does, and how the meter keeps it in view.

  • Corrosion you can’t see

    The problem

    A painted receiver can look sound outside while its bottom head has lost half its wall, and an internal examination needs a shutdown.

    How it solves it

    Readings from outside find wall loss at the bottom head of a receiver or the 6 o’clock line of a main, years before a leak or rupture.

  • Safer pressure equipment

    The problem

    A 1 m³ receiver at 10 bar g holds about 1.4 MJ of energy, released in milliseconds if a thinned wall ruptures.

    How it solves it

    Thin receivers and mains are identified before they fail under pressure.

  • Remaining life, calculated

    The problem

    Replace-or-repair decisions made without data rest on guesswork.

    How it solves it

    Two readings at one point give a rate: 6.00 mm at commissioning and 5.20 mm ten years later is 0.08 mm per year, and from it your remaining life and next inspection.

  • No shutdown, nothing cut

    The problem

    Opening equipment for inspection stops production, and many small receivers have only inspection bosses, no manway.

    How it solves it

    The measurement is non-destructive and made while your system stays pressurised and in service.

  • Coatings left intact

    The problem

    Stripping paint to reach bare metal removes the very protection that keeps corrosion off.

    How it solves it

    Echo-echo mode measures through the coating, so your paint stays on.

  • Statutory records

    The problem

    Written schemes of examination, API 510 and API 570 calculations and insurers all ask for thickness data.

    How it solves it

    Data-logging meters store every reading against its location, ready for examination reports and insurance reviews.

Where it’s used

Wherever air is held under pressure

Every receiver, separator, dryer tower and main that carries wet compressed air is a place to measure.

  • Molten metal pouring from a ladle in a foundry

    Compressed air plant in every industry

    Air receivers, separators, filter housings, dryer towers and distribution mains in steel, automotive, textiles, pharmaceuticals and food.

  • Test tubes of coloured chemicals in a laboratory rack

    Oil, gas and petrochemicals

    Instrument air receivers and piping, inspected under API 510 and API 570 alongside process equipment.

  • Electricity pylons and power lines at sunset

    Power generation

    Instrument and service air networks, ash-conveying air lines and control air receivers.

  • A worker pouring concrete over steel reinforcement

    Pneumatic conveying

    Bends in lines conveying cement, fly ash, sand and grain thin by abrasion on the outer radius.

  • Blue plastic bottle caps in a moulded tray

    High-pressure air

    PET blowing lines at 30–40 bar g carry more stored energy, so wall loss matters more.

  • A naval warship at sea

    Shipping and offshore

    Starting air receivers and service air lines working in a salt-laden, humid environment.

Also statutory examination of receivers built to ASME Section VIII Division 1 and IS 2825, nitrogen and oxygen generator vessels, mining and construction air, aftercooler and heat recovery water lines, and checks on second-hand receivers before recertification.

How it works

Send a pulse, time the echo

Sound crosses the steel wall, reflects off its inner surface and comes back. The time it takes, at the known speed of sound in the metal, gives the thickness.

How a digital thickness meter works: a dual-element probe on a film of couplant sends a short ultrasonic pulse into the steel wall; the pulse reflects off the inner surface and returns, and the meter times the round trip to calculate thickness. In echo-echo mode it times the gap between two back-wall echoes, so paint drops out of the reading. Repeat readings at one location give the corrosion rate. 5.20 mm t Δt SteelwallAir underpressure Couplant Dual-elementprobe ≈ 5,920 m/s in steel 10 mm wall: 3.38 µs Paint Corrosion pit6.00 mm → 5.20 mm in ten years0.08 mm per year Thickness meter 12345Ultrasound pulseCouplant gelPaint coatingCondensate

  1. 1. Couple the probeA thin film of gel couplant fills the gap between probe and surface. Without it, an air gap would reflect almost all the sound before it entered the metal.

  2. 2. Send the pulseThe transmitting crystal rings with a short ultrasonic pulse, commonly at 5 MHz for corroded steel, which travels through carbon steel at about 5,920 m/s.

  3. 3. Time the echoThe inner surface reflects the pulse back to the receiving crystal. The meter times the round trip and works out T = v × t ÷ 2: a 10 mm steel wall returns its echo in 3.38 µs.

  4. 4. Read through paintIn echo-echo mode the meter times the gap between the first and second back-wall echoes. Both cross the paint equally, so the coating drops out of the reading.

  5. 5. Track the corrosionRepeat readings at the same marked location give a rate: 6.00 mm at commissioning and 5.20 mm ten years later is 0.08 mm per year. With the code’s required thickness, that gives remaining life and the next inspection date.

Figures for carbon steel, with sound travelling at about 5,920 m/s.

Get the full details

Our brochure covers it in detail, and our questionnaire tells us what we need to recommend the right one for your plant.

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