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Grease Flow Meter: High-Pressure Positive Displacement Tools for Industrial Lubrication
Quick Answer
A grease flow meter based on positive displacement gives the only reliable measurement when you pump thick, high-pressure lubricants. Silver Automation Instruments supplies oval gear and gear-type PD meters that handle pressures up to 400 bar and viscosities beyond 100 000 cP. These meters work accurately with NLGI #2 grease, lithium complex greases, and extreme-pressure industrial lubes in automated lubrication systems.
Most process engineers learn the hard way that turbine meters, Coriolis meters, and ultrasonic meters struggle with pulsating grease flows. The fluid is too thick, the pressure is too high, and the air pockets ruin readings. A positive displacement meter cuts through all that. It physically traps a fixed volume of grease between rotating gears and the housing. The output is a pulse train directly proportional to the volume transferred. No fudge factors. No density compensation needed.
We have seen this on customer sites many times. A grease pump manufacturer in Malaysia replaced their inline turbine meter with an oval gear PD meter. Their discharge pressure was 250 bar at 80 °C. The turbine rotor simply stalled at low flow. Our oval gear meter with PPS gears and 316L housing delivered a steady 4 to 20 mA HART signal from day one. The maintenance team stopped calling us. That is the quiet proof of the right meter.
Why Grease Demands a Positive Displacement Flow Meter
Grease is semi-solid. It does not flow like water or diesel. It channels through pipes. It develops a yield stress that must be overcome before movement starts. A flow meter must not obstruct the flow path, yet it must capture every gram that moves. Positive displacement designs excel here. Oval gear meters and gear flow meters use meshing rotors that sweep the entire cross-section. Every pocket of grease trapped between the gears gets counted. This gives a repeatability of ±0.2 % of rate or better, even when the flow oscillates between 2 L/h and 30 L/h.
Here is the thing, Coriolis mass flow meters can measure grease, but the pressure drop across the tubes becomes a problem above 300 bar. Additionally, Coriolis meters demand a full pipe and zero air entrainment. Grease systems often have tiny air bubbles from the pump packing. A Coriolis meter interprets this as a density shift and alarms. A PD meter simply pushes the bubble through and keeps counting. You lose a fraction of a percent. That is acceptable in almost every lubrication application.
High pressure is the second challenge. Centralized lubrication systems in steel mills run at 200 to 400 bar. Bearing lubrication skids on mining shovels push grease at 300 bar to dozens of points. The meter housing and seals must hold that pressure without extrusion. Silver Instruments builds oval gear meters with a thick-walled all-stainless steel body and FKM or PTFE seals rated up to 400 bar at 150 °C continuous. The same body covers DN6 to DN25 connections, covering flows from 0.5 L/h to 1 200 L/h. That is the sweet spot for most industrial grease skids.
Typical Specifications for a High-Pressure Grease Flow Meter
In practice, the buying conversation always starts with four numbers: pressure in bar, temperature in °C, viscosity range in cP, and flow rate in kg/h or L/h. Below are the typical specifications engineers ask for when they contact Silver Automation Instruments.
Pressure rating: 250 bar standard, 400 bar with reinforced housing
Temperature range: -20 °C to 150 °C (standard), -40 °C to 200 °C (high-temp version)
Viscosity: 20 cP to 1 000 000 cP. NLGI #000 to #2 grease handled without heating
Flow range: 0.5 L/h to 600 L/h typical, up to 2 000 L/h on larger gear meters
Process connections: DN6, DN10, DN15, DN20, DN25 threaded (BSPP, NPT) or flanged
Materials: 316L stainless steel housing, PPS or 440C stainless steel gears
Outputs: Pulse (NPN/PNP), 4-20 mA HART, Modbus RTU over RS485
Certifications: ATEX Zone 1 Ex d ia IIC T4, IP66
Accuracy: ±0.5 % of reading above 20 % of full scale, ±0.2 % on request
Repeatability: ±0.05 %
We recommend the OGF oval gear series for most grease applications. The OGF uses an oval rotor design that provides a clean, high-resolution pulse signal. For extremely high pressures near 400 bar with abrasive greases, the HPG gear flow meter with tungsten carbide bearings extends service life. An engineer from a marine lubricant blending plant in Singapore told us their HPG meter ran for two years without drift, even with graphite-filled wire rope lubricant.
How to Avoid Measurement Errors in Grease Lin_600x400.jpg)
Most engineers skip this part. They place the meter immediately after a pneumatic piston pump and wonder why the reading jumps. A piston pump delivers grease in pulses. The flow accelerates and stops with each stroke. A positive displacement meter handles pulsation better than any other technology, but you still need a pulsation dampener or an accumulator downstream of the pump. A simple diaphragm dampener sized at 10 times the swept volume of the pump piston will smooth the flow enough for a stable 4-20 mA signal. We learned this from a warranty case in Vietnam. The flow reading was oscillating ±30 %. A dampener costing 150 USD solved it.
Air purging is another overlooked step. Fresh grease cartridges or bulk containers trap air during filling. When you connect a new barrel, run the pump for five minutes with the meter outlet uncorked to vent the air. If you skip this, the first 30 cycles will show a flow rate 15 to 20 % higher than the true grease volume. The meter counts the air plus the grease. The operator then adjusts the pump speed based on a false reading, and bearing over-lubrication or under-lubrication follows. We always include a start-up venting procedure in the shipment documentation.
Integration with Automated Lubrication Systems
Grease flow meters rarely work alone. They are part of an SKF, Lincoln, Graco, or custom PLC-controlled lubrication skid. The meter must talk to the controller. Silver Instruments PD meters output a raw frequency signal proportional to flow. A K-factor, typically listed on the calibration certificate as pulses per litre, allows the PLC to totalize the grease volume. A 4-20 mA HART output is more convenient for many systems because it delivers a scaled flow rate and carries diagnostic data. Modbus RTU is popular in Brazil and Middle Eastern oil fields where long cable runs are involved.
A paint manufacturer in Southeast Asia read our old blog about oval gear meters and asked us for a Modbus version. They wanted to log the grease flow to each bearing of a bead mill. The mill runs at 280 °C surface temperature, so the meter needed a high-temperature FKM seal and a stainless steel gear pair. We supplied an OGF-DN10 with RS485 output and a PT100 temperature sensor built into the meter body. The C-sensor on the bearing housing confirmed the lubrication intervals were correct. The bearing replacement interval doubled. That kind of data pays for the meter in a month.
FAQ
Can I measure NLGI #3 grease with an oval gear meter?
Yes, but you must heat the meter or choose a gear meter with a larger clearance. NLGI #3 has a worked penetration below 230. It may not flow into the measuring chamber fast enough at room temperature. Silver Instruments can provide a tracing block or specify a gear set with a 0.2 mm radial clearance for stiff greases. Tell us your grease penetration and pumping temperature, and we will select the right internal geometry.
What is the typical pressure drop across your grease meter?
At 60 L/h of NLGI #2 grease and 25 °C, the pressure drop across an OGF-DN15 meter is approximately 0.8 to 1.2 bar. At 400 bar line pressure, this is negligible. However, at very low temperatures or high flow rates, the pressure drop can rise to 3 bar. We always recommend a differential pressure check before finalizing pipe sizing.
Do you offer ATEX certification for Zone 0?
Our standard ATEX certification covers Zone 1 for gas (Ex d ia IIC T4) and Zone 21 for dust. We do not market a Zone 0-certified grease meter at this moment. If your application demands a Zone 0 instrument, contact our engineering team. We can explore an intrinsically safe barrier solution with a certified barrier and low-power pulse output.
What maintenance does a grease PD meter need?
The only wear items are the bearings and the seals. In clean lubricating greases, the bearings last 3 to 5 years of continuous operation. If your grease contains graphite, MoS₂, or other solid additives, plan to replace the tungsten carbide bearings every 18 to 24 months. The seal kit should be changed during bearing replacement. No internal calibration is needed because the chamber geometry does not change unless the gears get physically damaged.
How do I send a request for quote?
Send your pressure (bar), temperature (°C), pipe size (DN), flow range, grease type, and output signal requirement to [email protected]. We will respond with a datasheet, price, and delivery time within 24 hours. You can also reach us via Tel: +86-25-68650347, Whatsapp: +86-25-52155837, or WeChat: +86 15365082610. Visit our product page at flow-meter.com.au for more technical downloads.