Which Olympus thickness gauge to choose: 27MG, 38DL, 39DL, 45MG or 72DL

Why compare the models

The Olympus thickness gauge catalogue holds several instruments with similar names. In practice the difference is not brand prestige but the task: pipe corrosion, coatings, thin layers, plastics or laboratory precision.

Below is a working matrix for reliability and QC teams in Kazakhstan: CHP plants, refineries, mines, metals plants and service contractors.

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The short answer

Task	Instrument
Basic corrosion rounds on pipes and vessels	27MG
Universal field corrosion inspection	38DL PLUS or 39DL PLUS
Corrosion plus THRU-COAT coatings, flexible options	45MG
Multi-layer coatings, high speed, thin layers	72DL PLUS
Plastic, glass, non-ferromagnetic walls	Magna-Mike 8600

If you need one primary instrument for the site with a digital datalogger and fast minimum-thickness scanning — look at the 39DL PLUS. If the budget is tight and the task is only "remaining wall thickness" — the 27MG.

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27MG — the entry point to corrosion monitoring

The 27MG is a light one-handed gauge for internally corroded pipes and parts. Minimal settings, a dual-element probe, a clear display.

Choose it if:

• you need a simple instrument for operators on rounds;
• the task is remaining metal thickness from one side;
• there is no requirement for Wi-Fi, large files or complex modes.

Do not choose it if: you need coatings, precision single-element work, a high scanning rate or wireless data export.

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38DL PLUS and 39DL PLUS — the field standard

The 38DL PLUS was the workhorse for years: dual/single element, wide range, memory, IP65.

The 39DL PLUS is the current flagship of the same class: corrosion and precision, scanning at up to 60 Hz update rate, Wi-Fi / Bluetooth / USB / microSD, THRU-COAT and echo-to-echo.

Practical rule:

• renewing the fleet or writing a new tender → 39DL PLUS;
• already have trained personnel and a 38DL fleet → add 39DL units without scrapping the old instruments immediately.

Both cover pipes, vessels, tanks and casings — the typical assets at power and oil and gas sites.

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45MG — when options and coatings matter

The 45MG is often chosen as a flexible platform: base measurements plus software options for the task, including THRU-COAT for measuring through paint without stripping it (with compatible probes, for example the D7906-SM).

Choose it if:

• the site has both corrosion and coating inspection;
• you want to grow functionality through options rather than replace the whole instrument.

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72DL PLUS — speed and multi-layer work

The 72DL PLUS is for tasks where an ordinary field gauge is not enough: high frequencies, thin minimums, display of several coating layers, work closer to laboratory pace on the production floor.

Choose it if:

• you have multi-layer coatings and need accurate layer control;
• you need a high-speed process on the line or in QC.

For "just measure the pipe wall on a round", the 72DL is usually overkill.

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Magna-Mike 8600 — not ultrasound

The Magna-Mike 8600 measures thickness using the Hall effect: the probe on one side, a magnetic ball / disc / wire on the other. That is a different physical principle.

It suits plastics, glass, some composites and non-ferromagnetic thin-wall parts — where an ultrasonic gauge is awkward or gives an ambiguous signal.

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How to choose in five questions

1. Metal with access from one side? → ultrasonic gauge (27/38/39/45/72).
2. Only remaining wall needed? → 27MG or 39DL.
3. Need coatings without stripping paint? → 45MG / 39DL with THRU-COAT.
4. Need multi-layer and thin minimums? → 72DL PLUS.
5. Plastic / glass / thin non-ferromagnetic material? → Magna-Mike.

After choosing the instrument, do not forget probes and calibration blocks — the NDT catalogue has transducers D790, D791, M112 and step wedges.

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What to put in the request

For most industrial sites in Kazakhstan the working starter kit is:

1. 39DL PLUS (or the 45MG if coatings are the priority)
2. A dual-element probe for pipes
3. Couplant and a step wedge
4. If required — a separate Magna-Mike for plastics and packaging

The full thickness gauge catalogue is in the NDT / thickness gauging section. Selection for your site and operator training are available via the Olympus page or KEG TRK contacts.