Anyone getting reliable numbers from a clamp-on ultrasonic on 8–12 inch black steel with 30% glycol? I’m selecting a portable unit to validate design flows during commissioning so we can tune VFDs and catch bottlenecks without hot taps — considering Fuji Portaflow vs Dynasonics TFX-5000; what’s worked for you and how much straight-run did you need?
On a 10" black steel loop with 30% glycol, the TFX‑5000 gave me steady numbers within about 3% once we had about 15D upstream and 5D downstream and ran dual‑path — before that it was jumpy, . Key step: don’t trust presets; use a thickness gauge and manually enter actual ID and the sound speed for “30% glycol” at your operating temp. Fuji Portaflow was fine under 8", but on 12" it drifted unless we wrapped the transducers and re‑zeroed — how much straight run can you get at your test points?
Quick example: on a 12" black steel run during commissioning, our Fuji Portaflow got within a couple percent only after we checked the glycol mix with a refractometer and “entered velocity manually” with the current fluid temp instead of using the preset. Paint under the clamps skewed it before we hit bare metal, so plan on a quick scuff. You going V or Z path on those 8–12" lines?
I only got reliable readings after I measured the actual wall thickness with a UT gauge and entered the true temp/velocity — guessing schedule is like measuring with mittens on. Do the pump‑off ‘zero’ and avoid the seam; a cleaned patch with silicone grease couples better than gel when it’s cold. @jbarnes58, did you check the SNR/quality index before trusting dual‑path?
But on a 10-inch chilled loop, readings stopped wandering once we wrapped the clamps with pipe insulation so the couplant and pipe temp stabilized; that got us about ±2–3% at about 8D/4D using the low‑freq heads. @a_williams91 is right on keeping things steady — do you have a quiet spool that long available?
On 8–12 in black steel with 30% glycol, use a Z‑path with 1 MHz transducers on a vertical run; that’s what finally gave me a solid lock and about 2% error with about 12D/5D. Heads‑up: TFX‑5000 is a fixed unit — for portable, go Dynasonics DXN or Fuji Portaflow; I slightly prefer Fuji for the glycol tables. @dgreen237 is right on wall thickness; do you have a vertical section you can clamp on?
If you’re sticking with “30% glycol”, make sure the meter uses the correct sound velocity at your test temp — don’t leave it on water. Between Fuji Portaflow and Dynasonics, I’d take the Fuji for a true portable; TFX‑5000 is fixed‑mount (DXN is the Dynasonics portable). Clean a bare strip on the black steel and slightly toe‑in the transducers until signal quality peaks — it’s made the difference for me on large pipe.
Had the best results once we bled the loop hard to kill microbubbles; transit‑time hates foam and magnetite more than glycol. For “validate design flows during commissioning,” I’d go Fuji portable with 0.5 MHz blocks, dual‑V on a vertical, do a quick pump‑off zero, then lock the gain and 10 s averaging — I see about 2% without taps. Can you get a short shutdown to zero and confirm OD/wall with a thickness gauge? https://www.fujielectric.com/products/flow/environment/ultrasonic/portaflow/.