Elster IRM-3 DUO Rotary Gas Meter DN100 to DN200

Low-pulsation rotary gas meter for distribution and industrial metering

The Elster IRM-3 DUO is a positive-displacement rotary gas meter from the Honeywell Elster range for sizes DN100 to DN200 (4 in to 8 in). Its distinguishing feature is the DUO measuring principle: two measuring chambers with two phase-shifted pairs of impellers sit in one housing, so the pulsations of the two units cancel each other. Honeywell describes the result as quiet operation without resonance or pulsation, and the same characteristic allows the larger sizes to serve as a master meter on test rigs with a high measuring range.

The meter measures operating volume directly, so its accuracy is largely independent of the installation conditions and it suits compact metering skids that have no straight inlet section. It is approved for custody transfer and is designed for natural gas, filtered non-corrosive gases and 100% hydrogen. Where billing needs standard volume, the meter is paired with an electronic volume conversion device.

Technical specifications

Index heads, pulse outputs and tamper protection

The standard S1D index carries two 8-digit mechanical registers, one for each flow direction; after installation the register that matches the flow direction is used and the other is covered. The IP67 index head can be rotated by 350 degrees without breaking any seal. Two low-frequency reed pulsers and a manipulation contact for detecting external magnetic interference are standard, and the IN-S1x pulser modules plug on without opening the index, so they can be replaced or retrofitted later. For flow computers and EVCs that need a higher resolution, two inductive HF sensors can be factory-fitted, and an absolute encoder option is offered for digital data transfer to the flow computer.

Selecting and installing a DUO rotary meter

Start from the flow range: choose the size whose Qmin and Qmax bracket the real minimum and maximum flows, and note that the high rangeability figures apply to G650 and G1000. Rotary meters need filtered gas, so confirm that an inlet filter is part of the metering skid. The datasheet lists the housing as aluminium with PN16 / Class 150 flanges and a maximum pressure of 20 bar, so higher-pressure transmission duties need a different meter type. Mounting dimensions, bolt circles and weights are given in the datasheet for each size; check them against the existing pipework before ordering a replacement.

Documents and quotation

State the gas and its composition (including hydrogen share), minimum and maximum flow, operating pressure and temperature, flange standard, the index and pulse configuration, the hazardous-area zone and whether a calibration certificate or volume corrector is required. The datasheet edition is dated July 2026.

The attached Honeywell datasheet covers the IRM-3 DUO technical data, index options and dimensions. Seven Star LLC, an independent supplier in Muscat, can quote the meter once the configuration above is known. Related items are listed under Flowmeters, and for ultrasonic metering see the Elster Q.Sonic plus ultrasonic gas flow meter.