Independent technical reference. Not affiliated with, endorsed by, or a distributor for Liquid Controls or any manufacturer. Names are used only to describe a recognised meter technology.
"LC" and the M-series designations (M5, M7, M10, M15, M25, M30, M40, M60) are shorthand across the petroleum industry for rotary positive-displacement meters used in fuel, oil and LPG custody transfer. This page describes how that family of meters works and where each size fits.
Rotary PD, Sized by Model Number
The M-series is a classic rotary positive-displacement design: rotors sweep a fixed volume per revolution inside a precision chamber, and a register or pulse output totalises the count. The model number broadly tracks capacity and line size — smaller numbers for smaller lines and lower flow, larger numbers for bulk loading. A rough guide:
| Model | Typical line size | Typical duty |
|---|---|---|
| M5 / M7 | 1.5–2 inch (DN40–50) | Delivery trucks, transfer |
| M10 / M15 | 2–3 inch (DN50–80) | Mid-flow transfer, dispensing |
| M25 / M30 | 3–4 inch (DN80–100) | Bulk transfer |
| M40 / M60 | 4 inch+ (DN100+) | Depot and rack loading |
Built for Custody Transfer
What distinguishes meters in this class is the accessory ecosystem around the measuring element: mechanical registers, electronic preset controllers, ticket printers, air/vapour eliminators, strainers and temperature-volume compensators. Together they form a metering system designed to meet legal-for-trade requirements such as OIML R117 and the API MPMS, where repeatability and provability are as important as raw accuracy. Our calibration page covers how such systems are proved.
Fuel-Friendly by Design
Like all PD meters, the M-series performs best on clean, lubricating fluids and needs protection from solids and vapour. The fluid's own viscosity seals the internal clearances, keeping accuracy in the ±0.2–0.5% of reading range across a wide turndown — ideal for diesel, gasoline, aviation fuel, lubricating oils and LPG. Specific reference pages here include the M10 and the M40 4-inch DN100.
Related Reading
Compare with Tokico rotary fuel meters, or step back to the positive-displacement principle and the full technology comparison.