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Gear Oil Flow Meter DN150: Rugged Demands for Rolling Mill Process Lines
Quick Answer
The Silver Instruments oval gear flow meter DN150 handles gear oil up to 25,000 cP at 200 °C and 40 bar. It outputs 4-20 mA with HART and resists pipe vibration in steel rolling mills. Typical accuracy is ±0.5 % across 40 to 400 m³/h, and the meter needs no upstream straight pipe run.
What Kills a Gear Oil Flow Meter in Steel Plants
Rolling mill gearboxes run on ISO VG 320 or VG 460 lubricating oil. The oil film protects bearing journals and pinion stands under extreme load. Flow meters sit on the supply line to each mill stand. In a hot strip mill in Indonesia, the oil gallery temperature reaches 115 °C on a normal shift. A turbine meter with a plastic pickoff will seize within weeks. Oval gear meters survive because the measuring chamber is a simple pair of hardened steel rotors.
Most engineers skip this part. It is not just the temperature. Fine metal wear particles from the back-up roll chocks travel in the oil. A 100-micron chip will stop a coriolis meter tube or jam a turbine rotor. An oval gear flow meter with a 100-mesh Y-strainer upstream and a 0.3 mm clearance between rotor and housing lets those particles pass without damage. We learned this on a site in Vietnam where the strainer clogged too fast. The solution was a tandem filter with a differential pressure switch, not a tighter meter.
How Silver Instruments Builds the DN150 Oval Gear Meter
The DN150 body is ductile iron with ENP coating for corrosion resistance. The oval gear pair sits on tungsten carbide bushings and stainless steel shafts. This is not a light meter. It weighs 98 kg and has a flange rating of PN40. The maximum working pressure is 40 bar at 100 °C, derated to 32 bar at 200 °C. The meter is available with an integrated PT100 temperature sensor that outputs via a 4-20 mA loop. The flow computer can then output mass flow in kg/h using density compensation.
Because the meter is positive displacement, the output is inherently linear. The pulse output resolution is 0.6 litres per pulse. Connect it to a PLC counter module and you get a direct volume total. No K-factor linearization. We have supplied this setup to a gear oil blending station in Turkey where the customer needed to batch 1600 litres into 200-litre drums. The batch controller stops the pump at the target volume with ±2 litre repeatability.
One Installation That Taught Us About Vibration
Last year a steel rerolling mill in the Philippines asked us why their DN150 meter drifted after six months. The bearing journals of the oval gears showed asymmetric wear. The root cause was not the oil. The meter was bolted directly to a reciprocating pump skid without pulsation dampeners. Pressure spikes of 15 bar peak-to-peak hammered the gears on each stroke. We replaced the meter and added a dampener with a 2-litre nitrogen-charged bladder accumulator upstream. The new meter has been running for 14 months with zero drift. So the lesson: mount the DN150 meter on a r
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Output Signals and Remote Monitoring
The standard transmitter on the DN150 meter delivers 4-20 mA HART with a local LCD display. Because HART superimposes digital data on the analog loop, you can read instantaneous flow rate, totalized volume, and diagnostic alarms from a DCS or a HART multiplexer. For remote tank farm monitoring in the Middle East, we often add RS485 Modbus RTU output. The meter then talks directly to a radio telemetry unit. One field in the Modbus map gives you the oil temperature if the PT100 option is installed. You can set a high-temperature alarm at 130 °C and trigger a cooling water valve without extra hardware.
Frequently Asked Questions
Q: Can the DN150 meter handle oil with visible metal flakes from the gearbox?
A: It can if you install a 100-mesh Y-strainer 1.5 metres before the meter inlet. The oval gear clearances are 0.3 mm. Particles smaller than that pass through. The strainer catches the larger chips. Inspect and clean the strainer element once a week during the first month. After that the metal debris load usually drops.
Q: What is the pressure drop at 300 m³/h for ISO VG 460 at 60 °C?
A: Less than 0.9 bar. The meter interior has a smooth, swept path. The oval gears rotate at only 290 RPM at 300 m³/h. Because the rotation speed is low, the viscous shear loss stays low.
Q: Do I need straight pipe runs upstream and downstream?
A: No. Positive displacement meters do not require velocity profile conditioning. You can install the DN150 meter immediately after a 90-degree elbow or a Y-strainer. The only requirement is to isolate the meter from pipe expansion forces and heavy vibration.
Q: Is the meter certified for an explosive atmosphere in a hot rolling mill oil cellar?
A: Yes. The DN150 oval gear meter can be supplied with ATEX Zone 1 certification (Ex d IIC T3 or T4 depending on the oil temperature). The pulse preamplifier is potted in a flameproof enclosure. Inquire with your zone classification and gas group and we specify the correct certificate.
Q: How often do the gears or bearings need replacement?
A: With clean gear oil below 200 °C, the tungsten carbide bushings typically last 8 to 10 years on continuous operation. The gears themselves will outlast the bearings. We recommend a factory recalibration every 24 months. Send the meter back to our service centre. We clean, inspect, replace seals, and issue a new calibration certificate traceable to ISO 17025.
Get a Quotation for Your Rolling Mill Oil Line
Send us your pressure in bar, oil temperature in °C, pipe size (DN), and flow range in m³/h or L/min. We will recommend the correct DN150 gear oil flow meter model and include the PT100 option if needed. Our email is [email protected]. For a faster response, include a photo of the existing meter nameplate. Most quotes are returned within 4 hours during business days.
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