Swapping to a VFD on our pit dewatering pump and spot-checking with a handheld turbidity meter cut our floc dosing and kept the polishing pond steady, which sped up bench reclamation by keeping lift surfaces drier and seed-ready. What pump/meter combo has held up for you in cold starts and clay-heavy water?
We’ve had good luck with a Flygt 2640 on a Danfoss VLT AQUA and a YSI ProDSS; the wipeable sensor plus a 60 s soft ramp with 120% torque boost got us through -15°C clay soup without trips. One tweak that helped dosing: enable VFD sleep around 9–10 Hz with restart on a small level rise so you’re not churning fines at low flow — have you tried a sleep band like that, @sadams85?
Running a KSB Amarex KRT on a Schneider Altivar 930 with a 45 s ramp, low carrier (2 kHz), and an hourly “anti‑rag” jog stopped our clay‑cold overcurrent and let us trim coagulant without pond swings. For turbidity spot checks, the LaMotte 2020we has shrugged off freeze‑thaw better than our 2100Q; we keep a sealed 20 NTU standard in the truck and do a 30‑second “warm‑hands” check before readings. If you’re sticking with your combo, set a 28 Hz minimum and enable “flying start” to keep the impeller from cementing overnight.
Same ‘polishing pond steady’ result after moving to a Tsurumi KTZ on a Yaskawa GA500; 50 s S‑curve ramp with flying start and sleep/wake cured cold‑start spikes and let us trim floc. @mark9202 are you letting it sleep at low flow or holding a floor Hz? For spot checks the Lovibond TB350 IR’s been tougher than our old Hach, with a quick daily zero and warming the vial to dodge fogging.