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Krohne Flow Meter Calibration Frequency: Standard Wet-Proving Benches vs On-Site Field Verifications
Quick Answer: Krohne flow meter calibration should match the meter function. Custody transfer and revenue meters need wet-proving bench calibration every 12 months. Process control meters can use on-site field verification every 3 to 6 months plus a bench calibration every 2 to 3 years. Field verification is fast and cheap. Wet-proving gives traceable accuracy.
Standard Wet-Proving Bench Calibration: What It Actually Is
A wet-proving bench uses a master meter or gravimetric tank. Water or oil flows through the meter at controlled temperature and pressure. The bench compares total pulses or mass against a reference standard. This method removes most installation effects. Uncertainty is low, often 0.05 percent or better for electromagnetic and Coriolis meters.
Most engineers skip this part in smaller plants because the meter must be removed. That means pipe spool removal, seals, lifting, and transport. A chemical plant in Vietnam spent two days per year sending a Krohne DN80 electromagnetic flow meter to a calibration lab. The downtime cost was less than the billing error they found in batch dosing.
On-Site Field Verification: What It Covers
Field verification does not remove the meter. A technician checks the coil resistance, electrode contact, excitation current, and liner condition. For Coriolis meters, the verifier checks drive gain, pickoff voltage, and sensor symmetry. The result is a health report. It is not a traceable calibration.
In practice, field verification catches drift and deposit buildup. A wastewater plant in Mexico found a 2.1 percent zero shift on a DN200 electromagnetic flow meter. The shift came from electrode coating after six months of activated sludge service. The meter did not fail. But the reading was wrong enough to affect chemical dosing.
Calibration Frequency by Industry and Meter Type
No single frequency fits every plant. Water and wastewater plants with low value effluent can run field verification every 6 months and bench calibration every 24 months. Oil and gas custody transfer meters often need bench calibration every 12 months. Marine fuel meters in Singapore and Fujairah follow the same interval because bunker disputes carry high financial risk.
For chemical and food plants, batch accuracy affects product quality. A dairy plant in Australia uses Coriolis meters for milk and cream. They run a bench calibration every 18 months. Between bench runs they test zero stability once per week. This interval came from internal quality audit data, not from a generic manual.
Temperature and vibration accelerate drift. A flow meter near a steam boiler or a piston pump needs shorter intervals than a cold water line in a stable basement.
Why Bench Calibration Wins for Accuracy and Traceability
Wet-proving gives a certificate with reference standards and numbers. This matters for ISO 9001 audits, pharmaceutical batches, and export documentation. A bench calibrat
We have seen customer sites where a Krohne meter passed field verification but failed bench calibration. The cause was liner swelling. Field verification did not detect the small cross-sectional change. Bench calibration caught a 1.4 percent deviation at maximum flow.
Why Field Verification Wins for Uptime and Cost
Field verification takes 30 to 60 minutes per meter. The meter stays in the pipe. No hot work permit, no lifting, no transport. For a water treatment plant with 60 flow meters, annual bench calibration would shut down large sections of pipe. Field verification lets the plant schedule checks during normal rounds.
But field verification is not a replacement. It is a screening tool. Use field verification for trending. Use wet-proving for proof.
How Silver Instruments Handles Calibration and Replacement
Silver Automation Instruments supplies electromagnetic, Coriolis, ultrasonic, vortex, oval gear, and thermal mass flow meters. Many clients ask us about Krohne calibration because they think the only path is sending the meter back to the original manufacturer. That path is slow. We provide bench calibration against traceable reference standards for common line sizes from DN15 to DN300. We also support field verification with portable equipment for electromagnetic and Coriolis meters in Southeast Asia, the Middle East, and Australia.
If you need a replacement instead of a repair, we can match the flow range, process connection, liner material, and output signal. Send us your pressure in bar, temperature in deg C, pipe size DN, and flow range. Contact Silver Instruments at Tel +86 25 68650347, Whatsapp +86 25 52155837, or WeChat +86 15365082610.
FAQ
How often should a Krohne flow meter be calibrated? For custody transfer or billing, run a wet-proving bench calibration every 12 months. For process control, run bench calibration every 24 months and field verification every 6 months.
What is the difference between wet-proving and field verification? Wet-proving compares the meter against a traceable reference standard on a bench. Field verification checks electronics and sensor health without removing the meter.
Can field verification replace a bench calibration? No. Field verification does not provide traceable accuracy numbers. Use it for trending and condition monitoring.
Which meter types need wet-proving most often? Custody transfer Coriolis, positive displacement, and electromagnetic meters in oil and gas or marine fuel need annual bench calibration. Thermal mass meters in clean gas can go 2 years if the gas is dry and stable.
Can Silver Instruments calibrate a Krohne meter? Yes for common DN15 to DN300 electromagnetic, Coriolis, vortex, and ultrasonic meters. Contact us with your meter model, line size, and current reading error.