Why Positive Displacement Flowmeters?

Positive Displacement Flowmeters are chosen when accuracy is non-negotiable and process conditions are unforgiving. Unlike velocity-based technologies, a positive displacement flowmeter measures fluid by physically capturing and transferring a known volume within its measurement chamber. Among all variants, oscillating piston designs have consistently proven superior in real industrial service.

While oval gear, screw, vane, and nutating disc meters all belong to the positive displacement meter family, they suffer from wear, sensitivity, and complexity.

Oscillating piston Positive Displacement Flowmeters simplify the mechanism to a single moving element, delivering repeatable accuracy across extreme viscosity ranges, high pressures, and even hygienic applications. This makes them one of the most versatile positive displacement meter technologies available today.

Core Information

Oscillating piston Positive Displacement Flowmeters incorporate precision engineered measurement chamber and rotor assemblies.

Core Configuration

  • Precision machined measuring chamber with defined geometry
  • Single oscillating piston as the only moving element

  • Electronic transducer

  • Electronic transmitter with industrial outputs

This configuration allows the same oscillating piston positive displacement meter principle to be adapted across industries without compromising accuracy.

  • Precision measurement – Accuracy options 0.5%, 0.2%, 0.1%
  • Outstanding repeatability – Better than 0.02%
  • The only positive displacement flowmeters with built-in strainer design
  • 316L body and PEEK polymer rotor construction
  • Double case design for bulk metering
  • Optional nickel superalloy construction
  • Electronic transmitters with HART/FF/Profibus/Modbus outputs
  • Measures viscous media upto 300,000 cPs
  • ATEX/IECEx/UKEx approvals
  • Weights and measures certified for custody transfer
  • OIML R117 in progress
  • True volumetric measurement
  • No metal-to-metal contact
  • No straight runs of pipe required
  • Operates on pulsating flow and turbulent flow
  • Little to no maintenance

  • Unique design with built-in strainer

  • Superior low-flow performance upto 1 LPH

  • Stable accuracy over long service life

  • Reliable operation under fluctuating conditions

  • Suitable for hygienic and sanitary service

  • Pressure compliance options upto 650 bar

Applications

Oil and Gas

  • Liquid hydrocarbon oils
  • Lubes
  • Aviation fuel
  • Ethanol

Fuel Oils

  • Heavy oils
  • LSHS
  • Furnace Oils
  • Light Diesel Oil

Petrochemical measurement

  • Distillation
  • Intermediates

  • Acids

  • Corrosive chemicals

Pharmaceutical and Life Sciences

  • Demineralized water measurement
  • Organic solvents

Utilities

  • Condensate water
  • Boiler feed water
  • Oil flowmeters

Distilleries

  • Technical Alcohol
  • Rectified spirits
  • Extra Neutral Alcohol

Flow Chemistry

  • Acids and alkalis
  • Catalysts

Power Plants

  • Lubricant Oil
  • Diesel

Why Oscillating Piston Beats Other Positive Displacement Meters

Parameter Oscillating Piston Oval Gear Screw Vane Nutating Disc
Moving parts Single element Two gears Multiple screws Rotor + vanes Disc + linkage
Low-flow accuracy Excellent Poor Poor Fair Fair
Wear rate Very low High High High Medium
Pressure capability Up to 800 bar Limited Limited Low Low

Oscillating Piston Advantage

  • One moving part only
  • Controlled clearances
  • Consistent volumetric capture
  • Lower friction losses
  • Longer service intervals

Related Products

Series 6600 – Oscillating Piston Flowmeters

  • 66X0 Product Catalogue

  • Instruction Manual

  • Application notes

Series 6610 – Oscillating Piston Flowmeters

  • Catalogue

  • Instruction Manual

FAQ’s

What is a Positive Displacement Flowmeter?

A Positive Displacement Flowmeter measures flow by trapping a fixed volume of fluid and counting how many times that volume is transferred through the meter. This method provides direct volumetric measurement, making positive displacement flowmeters highly accurate and reliable, especially for viscous fluids, low flow rates, and applications where fluid properties vary significantly.

Positive displacement flowmeters are primarily designed for liquids. While some specialized designs can measure gases, oscillating piston positive displacement flowmeters are best suited for liquid applications. Gases tend to compress, which affects volumetric accuracy. For gas measurement, technologies specifically designed to account for compressibility are generally preferred.

Maintenance requirements are relatively low, especially for oscillating piston designs. Periodic inspection for wear, seal condition, and cleanliness is usually sufficient. Since oscillating piston positive displacement flowmeters have only one moving part, they experience less mechanical wear compared to multi-part designs, resulting in longer service intervals and stable accuracy.

Yes, oscillating piston Positive Displacement Flowmeters can be engineered for high-pressure service. With reinforced housings and appropriate sealing, they can operate reliably at pressures up to 750–800 bar. This makes them suitable for hydraulic systems, test rigs, and high-pressure industrial processes.

Positive Displacement Flowmeters are widely used in oil and gas industry, custody transfer, oil and fuel measurement, chemical dosing, lubrication systems, pharmaceutical processing, food and beverage production, and high-pressure industrial applications. Their ability to measure viscous fluids accurately and maintain long-term stability makes them a preferred choice across many industries.