Greenfuel-CNG Gas Flow Meter, orifice-plate DP metering for N2 & CNG at 1–3 bar.

Why a gas-specific orifice plate matters

Any gas-supply unit that must deliver a measured flow of a particular gas needs a flow element sized for that gas. The Greenfuel-CNG Gas Flow Meter is an N2/CNG Flow Measurement System: the orifice plate is mounted on the flange for whichever gas the flow needs to be measured for. For example, if flow needs to be measured for N2 gas, the orifice plate for N2 is mounted on the flange; if the requirement is CNG, the CNG orifice plate is fitted in its place.

Manufactured by Neometrix Engineering Pvt Ltd, the system pairs this interchangeable orifice-plate arrangement with a Siemens differential pressure transmitter and a panel-mounted Universal DRO indicator, giving a compact, low-maintenance flow readout for gas-supply lines in industrial and test-bench installations.

Working principle — differential pressure across an orifice

Orifice-plate metering works on a well-established principle: restricting the flow area of a pipe with a precisely bored plate creates a differential pressure across that restriction that is related to the flow rate. This is the general method described in ISO 5167 for measurement of fluid flow by means of pressure differential devices. In this system:

• Gas-specific orifice selection: The orifice plate for the required gas — N2 or CNG — is bolted between the flanges in the supply line.
• Pressure drop generation: As gas flows through the bore of the plate, it accelerates and creates a measurable differential pressure between the upstream and downstream tappings.
• DP sensing: The Siemens differential pressure transmitter, mounted on the manifold directly below the tappings, converts this pressure drop into an electrical signal.
• Signal routing: The transmitter signal is wired through the instrumentation enclosure, protected by a 10 Amp MCB on a 230 VAC single-phase supply.
• Flow readout: The Universal DRO indicator on the enclosure door displays the resulting flow value for the operator.

Technical specifications

Outstanding features & advantages, in detail

1. Gas-specific accuracy

Because each gas gets its own correctly sized orifice plate, the system avoids the accuracy compromises of trying to use a single generic flow element across two different gas services.

2. Corrosion-resistant wetted parts

SS 316 construction on the orifice plates and wetted components resists corrosion from both N2 and CNG service over the rated 1–3 bar, 40°C operating envelope.

3. Industrial-grade DP sensing

The Siemens differential pressure transmitter is manifold-mounted directly on the orifice tappings, minimizing impulse line length and keeping the DP signal path short and stable.

4. Simple, direct readout

A panel-mounted Universal DRO indicator gives operators a direct flow reading without requiring a separate DAQ system, though the output can be integrated with plant DAQ where required.

5. Compact, protected enclosure

The 380 x 600 x 210mm painted RAL-7035 enclosure houses the MCB and wiring, keeping the instrumentation protected from the surrounding environment.

6. Low maintenance

With no moving parts in the orifice plate itself, the flow element requires minimal maintenance; periodic inspection of the plate bore and impulse lines is the main upkeep requirement.

System components & their functions

The Greenfuel-CNG Gas Flow Meter consists of the following key components:

• Orifice plate for CNG: SS 316 plate sized for CNG service, rated 1–3 bar / 40°C.
• Orifice plate for N2: SS 316 plate sized for N2 service, rated 1–3 bar / 40°C.
• Siemens differential pressure transmitter: Senses the pressure drop across the orifice plate and converts it to an electrical signal.
• Universal DRO process indicator: Panel-mounted digital display for the resulting flow value, on 230 VAC supply.
• 10 Amp MCB: Protects the indicator and transmitter power circuit.
• Instrumentation enclosure: 380 x 600 x 210mm, painted RAL-7035, housing the wiring and control components.
• Flange & impulse tubing: Bolted split-flange assembly and stainless impulse lines carrying the DP tappings to the transmitter.

Operation & maintenance

Startup / plate selection

• Confirm which gas service — N2 or CNG — the flow measurement is required for.
• Fit the correctly sized orifice plate for that gas on the line flange.
• Switch on the 230 VAC supply and confirm the MCB and DRO indicator power up correctly.
• Open the gas supply and confirm a stable DP reading and corresponding flow value on the DRO.

Shutdown procedure

• Close the gas supply valve before removing power.
• Isolate the 230 VAC supply at the MCB.
• Depressurize the impulse lines before any maintenance on the manifold or transmitter.

Maintenance schedule

• Daily: Check DP reading and flow value for stability, inspect for leaks at the flange and impulse lines.
• Monthly: Inspect the orifice plate bore for wear or deposit build-up, verify enclosure seal.
• Annually: Calibrate the DP transmitter and DRO indicator against a reference standard.

Applications across installations

The Greenfuel-CNG Gas Flow Meter is used wherever a gas-supply unit needs a dependable, gas-specific flow reading. Typical installations include:

• Test-bench gas-supply skids: Measuring N2 or CNG flow delivered to engine, hydraulic, or pneumatic test rigs.
• Industrial gas-handling systems: Monitoring process gas flow in plants that switch between N2 and CNG service.
• Fuel-gas and combustion test setups: Verifying CNG flow delivered to test or calibration rigs.
• N2 purge and blanketing lines: Confirming N2 flow rate during purge or blanketing operations.
• OEM-integrated gas skids: Supplied as a sub-system for custom gas-supply and filling equipment.

Conclusion

The Greenfuel-CNG Gas Flow Meter gives plant and test engineers a straightforward, gas-specific way to measure N2 or CNG flow using an established differential-pressure orifice-plate method, backed by a Siemens transmitter and a simple panel-mounted DRO readout, in a compact and low-maintenance package.