Archived technical note, republished as independent reference material. Not affiliated with any manufacturer; no product is offered.
A 2-inch (DN50) oval-gear meter is a mid-line workhorse for diesel and oil transfer — compact, rugged, and accurate on viscous fluids. This note covers the oval-gear technology at this size.
Oval-Gear at DN50
At 2 inch, an oval-gear meter comfortably handles diesel transfer and mid-flow dosing at tens of litres per minute. Two meshing rotors carry fixed volumes through the chamber, giving direct positive-displacement measurement with no straight-run requirement and accuracy around ±0.5% of reading, improving as viscosity rises. A built-in digital display typically shows both a batch total and a cumulative total.
Typical Duty
The DN50 size sits between small dispensing meters and large custody-transfer units, which makes it a natural fit for filling equipment, transferring diesel between tanks, and dosing lubricants or additives where a moderate but accurate flow is needed. Because the oval-gear element measures volume mechanically, the same meter reads consistently across a range of fluid temperatures, which matters outdoors where diesel viscosity changes noticeably between a cold morning and a hot afternoon. Where volume must be converted to litres at a reference temperature, an electronic register can apply temperature compensation.
Practical Use
Fit a strainer upstream — oval-gear clearances are unforgiving of grit — and keep the line free of vapour. Size the meter to the actual flow so it runs mid-range, not at its limits, and avoid sudden valve closures that spike the differential pressure across the rotors. Within those rules a DN50 oval-gear meter is a low-maintenance, accurate instrument for fuel and oil transfer that will hold its calibration for a long service life.
For broader mechanical-measurement practice, the American Society of Mechanical Engineers (ASME) publishes useful independent guidance.
Related Reading
See the Macnaught technology overview, the smaller 1-inch DN25 size, and the general oval-gear page.