Current position > News detail
『Krohne Variable Area Flow Meter Calibration: H250 Metal Tube Rotameter Setup and Limits』Related information(clamp on meter|electromagnetic meter|venturi meterrotameter|orifice meter|ultrasonic flow meter|mass flow meter|coriolis mass flow meter|coriolis flow meter|magnetic flow meter|magmeter flow meter|magflow flow meter|mag meter flow meter|electromagnetic flow meter|vortex flow meter|turbine flow meter|thermal mass flow meter|thermal flow meter|rotameter flow meter)
Krohne Variable Area Flow Meter Calibration H250 Metal Tube Rotameter Setup and Limits
Quick Answer: Krohne H250 metal tube rotameter calibration depends on fluid density, viscosity, flow range, and vertical installation. Set the 4-20 mA output after you check the float at zero and full flow. Standard limits include media temperature up to 200 °C, pressure based on flange rating, and viscosity usually below 50 cP for reliable readings.
Why Calibration Data Matters for the H250
The H250 is a metal tube variable area flow meter. A float moves inside a tapered metal tube. The float position is proportional to flow. But the float also responds to fluid density and viscosity.
Factory calibration is done with one reference fluid. If your process fluid is not the same, the indicated flow shifts. That shift is not a small issue. A seafood processing plant in Vietnam ran brine at 1.15 kg/L density. The H250 was calibrated for water. The error reached 6 percent until the plant sent us the brine density for a new scale.
You should always provide the exact fluid name, density, viscosity, and operating temperature when you order or recertify an H250.
Step by Step Setup on Site
Install the H250 in a vertical pipe. The flow direction must be from bottom to top. A tilt of more than 1 degree can add error because the float may touch the tube wall.
Before you connect power, check the mechanical zero. No flow means the float rests at the bottom stop. On the H250 scale, the needle or magnet follower should read zero. If not, adjust the indicator linkage or check the float position.
Connect the 4-20 mA HART output. Most H250 M40 models have menu-driven setup. Set the flow unit, range, damping time, and low flow cut off. Damping values between 2 and 10 seconds work well for most liquid lines. Gas lines may need 1 to 3 seconds to catch fast changes.
After setup, run a wet calibration. Use the actual process fluid or a substitute with the same density and viscosity. Compare the H250 output with a reference flow meter or a calibrated vessel. Adjust the span only after the zero is stable.
H250 Calibration Limits You Need to Know
The H250 is not a universal meter. Standard models often handle media temperatures from -25 °C to +200 °C. High temperature versions can go higher, but you must specify that at order stage.
Pressure limits depend on the flange rating. Common versions are PN16, PN40, ANSI 150, or ANSI 300. Never use the calibration from a PN16 meter on a PN40 process without checking the float and tube material.
Viscosity is a bigger limit than most engineers expect. Above 50 cP, the float response becomes non-linear. At 100 cP or higher, the standard H250 scale may be off by more than 5 percent unless a special float or viscosity correction is applied.
Flow range limits are fixed by cone size and float material. A DN15 H250 with a standard float may cover 2.5 L/h to 250 L/h for water. A
_600x400.jpg)
Do not use the H250 on abrasive slurries. Solid particles wear the float and the metal tube. For those services, choose a different principle or add filtration.
Calibration Sheet and Factory Data Review
Every H250 ships with a calibration certificate. Check the serial number, float code, reference fluid, density, viscosity, and the full scale flow rate. If the certificate reference fluid does not match your process fluid, the meter needs a new scale or a correction factor.
Many teams skip this part. Last year a paint manufacturer in Thailand complained about a 10 percent error on solvent flow. The H250 certificate showed water calibration at 20 °C. The actual solvent had a density of 0.82 kg/L and viscosity of 3 cP. The float rose higher than the scale for water. The problem was fixed with a new density-specific scale.
Order a recertification only if you can send the unit to a bench with traceable reference meters. Field recertification usually covers only the 4-20 mA trim, not the float scale.
Silver Instruments Compatible Options and Calibration Support
Silver Automation Instruments supplies metal tube rotameters compatible with the Krohne H250 footprint. We provide factory calibration certificates, 4-20 mA HART output, limit switches, and PT100 options for liquids, gases, and steam.
We often help customers in Southeast Asia, Oceania, Latin America, Africa, and the Middle East replace aging H250 meters or add new lines. Ask us for a calibration sheet with your actual fluid name, density, viscosity, and flow range. We will confirm the scale before shipping.
Send us your pressure in bar, temperature in °C, pipe size in DN, and flow range. Tel: +86-25-68650347. Whatsapp: +86-25-52155837. WeChat: +86 15365082610.
FAQ
Can the H250 be calibrated on site?
Yes. You can trim the 4-20 mA zero and span on site. Full float scale calibration needs a bench and traceable reference meters.
What is the standard accuracy of a Krohne H250?
Typical accuracy is 1.6 percent of full scale for liquids and 2.5 percent for gases. Check the specific float and calibration certificate.
Does viscosity affect the H250 calibration?
Yes. Viscosity above 50 cP changes the float response. Use actual viscosity data for any new scale.
Can I use an H250 for gas and liquid with the same calibration?
No. Gas density and expansion behavior are different. Use separate scales or order a H250 with dual scales from the factory.
What pipe size and flow range should I send for a quote?
Send pipe DN, fluid name, density, viscosity, operating pressure, temperature, minimum flow, and maximum flow. We will select the right meter and float.