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Gear Oil Flow Meter 100 L/h: Overcoming Friction in Extreme Pressure Lines
Quick Answer: For 100 L/h gear oil in extreme pressure lines, use a positive displacement oval gear meter with hardened bearings and low friction rotor design. Silver Instruments DN10 or DN15 meters handle up to 400 bar, viscosity from 1 to 1000 cP, and output 4-20 mA HART. This prevents mechanical stall and gives repeatable batches even when line pressure fluctuates.
Most engineers skip the friction part when specifying a gear oil flow meter. But at high pressure, gear oil turns from a lubricant into a drag force. A customer in Vietnam asked us last year why his 80 L/h meter kept locking up at 290 bar. The answer was inside the bearing pair. Standard ball bearings could not cope with the shear.
Why Pressure Magnifies Friction in Gear Oil Lines
Gear oil is thick. At 20 degrees C, an ISO VG 320 oil sits around 800 cP. At 5 bar differential, an oval gear meter turns freely. Raise line pressure to 350 bar and the story changes. The rotor shafts push sideways. The gears press into the chamber walls. The friction moment rises fast. Because the driving torque comes only from the fluid passing through, even a small friction increase can stop the meter.
We have seen this on hydraulic test benches in Indonesia and on marine stern tube lube lines in the Middle East. Once the pressure crosses 250 bar, off the shelf food grade oval gear meters with plain PPS rotors will stall. In practice, you need a meter that was designed for the load, not one adapted from a 16 bar diesel dispenser.
Silver Instruments Oval Gear Meter for 100 L/h High Pressure
The Silver Automation Instruments OGM series covers 100 L/h with a DN10 or DN15 meter body. Here is what makes it work under 400 bar.
Rotor bearings: tungsten carbide journal bearings. These lower the start up torque to below 0.02 Nm. At 400 bar, the friction moment stays within safe limits.
Meter chamber: 316L stainless steel, precision honed to Ra 0.4 micrometer. The oval gears run with a clearance of 15 to 25 micrometers. Even with VG 460 gear oil at 80 degrees C, thermal expansion does not cause rubbing.
Sensor: dual channel hall sensor with PT100 temperature compensation. Output is 4-20 mA HART plus an unscaled pulse. The transmitter is ATEX Zone 1 approved for gas and dust. We preconfigure the span to match your 100 L/h full scale, so the pulse resolution stays at 500 pulses per litre.
A paint manufacturer in South Africa ordered three DN15 oval gear meters set to 0 to 100 L/h for a gear oil dosing skid running at 320 bar. They reported less than 0.3 percent deviation during their six month batch log, and zero mechanical wear after 4,200 hours.
Six Things That Kill Gear Oil Meters at High Pressure
Not every failure is a bearing problem. Here are common traps we see on site.
Solid particles. Always install a 200 mesh Y strainer directly upstream. A single metal chip from a worn pump can score the chamber and spike friction irr
Air slugs. Gear oil systems can trap air after maintenance. A slug of air at 350 bar collapses the cavity and hammers the rotors. We suggest a small air release valve on the high point of the inlet line.
Rapid valve opening. A fast open solenoid valve creates a pressure surge that exceeds the meter rating. Add a soft start valve or orifice plate to limit the dp/dt.
Wire strain. Hard piping that pulls the meter body out of alignment adds side load to the bearings. Use flexible hoses or expansion joints and mount the meter on a rigid bracket.
Fluid degradation. Oxidized gear oil turns acidic and attacks the O ring material. We specify FKM or FFKM seals. Specify your oil type when you order. We select the right compound for you.
How We Pre qualify a 100 L/h Gear Oil Meter for Your Line
Before we quote, we run a simple friction model. Send us your pressure in bar, oil viscosity at operating temperature in cP, temperature in degrees C, pipe size DN, and required flow range in L/h. We check the torque margin and the bearing load. Then we recommend a meter with a provable safety factor.
For a 100 L/h job at 350 bar, typical answer is a DN15 oval gear meter with tungsten carbide bearings and 4-20 mA HART output. Lead time from our China factory is normally 10 to 14 working days by DHL or FedEx. We ship to Australia, Saudi Arabia, Brazil, Nigeria, Vietnam, and anywhere else with full customs documentation.
Send your pressure (bar), temperature (degrees C), pipe size (DN), and flow range to our engineers. We return a datasheet and a fixed price within 24 hours.
Frequently Asked Questions
Can a gear flow meter really handle 100 L/h at 400 bar for years?
Yes. Our DN15 oval gear meters with tungsten carbide bearings have passed endurance tests of 10 million litre cycles at 380 bar with VG 220 gear oil. The wear was under 2 micrometers.
What viscosity range does a high pressure gear oil meter accept?
1 to 1000 centipoise with standard clearance rotors. For viscosities above 1000 cP, we open the clearance to 40 micrometers and derate the maximum pressure to 320 bar.
Is ATEX mandatory for a gear oil metering skid?
If your area is classified Zone 1 or Zone 2, then yes. Our oval gear meter comes with ATEX, IECEx, and North American Class I Div 1 certifications. You receive a certified transmitter and the full conformity package.
What output signal do Silver Instruments meters provide?
Standard is 4-20 mA HART with a configurable pulse output. You can get Modbus RTU on request. The HART signal lets you read flow, totalizer, and meter temperature from one pair of wires.
How do I avoid pressure drop across the meter?
At 100 L/h and 320 bar line pressure, pressure drop across a DN15 oval gear meter is normally below 0.3 bar. Using oversized piping, avoiding tight elbows upstream, and keeping the oil warm at 40 to 60 degrees C keeps the drop low.