Elster TRZ2 Turbine Gas Meter DN50 to DN150

Custody-transfer turbine gas meter with a replaceable metering cartridge

The Elster TRZ2 is a turbine gas meter from the Honeywell Elster range for nominal sizes DN50 to DN150 (2 in to 6 in). Honeywell describes it as a robust meter for gas distribution, industrial plants and commercial users, with MID approval for fiscal measurement and a record of staying accurate from the first calibration to the end of a long service life.

The patented metering cartridge is the core of the design. A flow conditioner at the inlet straightens the gas, the cross section is then reduced to raise the velocity and the driving force on the turbine wheel, and the wheel runs on ball bearings to keep performance high with little maintenance. Because the cartridge is decoupled from the meter body, ambient changes such as a temperature drop have little effect on the reading, and a cartridge can be exchanged in the field to shorten service time. The wheel revolutions are carried by gears and a magnetic coupling to an 8-digit mechanical counter in a pressure-less index head. For sizes above 6 in the datasheet points to the SM-RI-X, which is available up to 24 in.

Technical specifications

Sizes, measuring ranges and pulse outputs

The datasheet lists eleven combinations of nominal size and meter size. A smaller meter size in the same nominal diameter gives a lower Qmin, so the choice follows the real flow range rather than the pipe size.

Two low-frequency reed outputs are standard and connect to a flow computer or electronic volume corrector; the extra switch reports attempts to disturb the meter with an external magnet. High-frequency outputs are optional for flow computers that need a finer pulse resolution.

Selecting and installing a TRZ2

Start with the lowest and highest gas flow the meter must see, then pick the meter size that brackets both, and check the operating pressure, because Qmin at high pressure is lower than at atmospheric pressure. Filter the gas upstream so particles do not damage the wheel. The compact inlet requirement of 2 DN, independent of flow disturbance for DN80 to DN150, makes the TRZ2 suitable for skids with little straight pipe. Measuring ranges above 1:20 are possible depending on pressure and are agreed with the factory.

Documents and quotation

State the gas, minimum and maximum flow, operating pressure and temperature, nominal size and flange standard, body material, the LF and HF pulse requirement, whether an encoder, thermowell or direct-mounted corrector is needed, and the hazardous-area zone. The datasheet is dated January 2017 and should be checked against the current Honeywell edition when the order is placed.

The attached Honeywell datasheet gives the technical specification, pulse options, pressure-loss data and dimensions of the TRZ2. Seven Star LLC, an independent supplier in Muscat, quotes the meter once the configuration above is known. See further meters under Flowmeters, and for ultrasonic metering the Elster Q.Sonic plus ultrasonic gas flow meter.