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LPG Flow Meters & LPG Gas Flow Meters: Explosion-Proof Volumetric Transfer Systems

Quick Answer: Silver Automation Instruments supplies positive displacement oval gear flow meters for liquid LPG transfer, bottling, truck loading, and tanker unloading. These explosion-proof volumetric transfer systems are ATEX Zone 1 or Zone 2 rated, fit DN15 to DN100 lines, and output 4-20 mA HART plus pulse. Send your pressure in bar, temperature in °C, pipe size in DN, and flow range in kg/h for a quote.

This article covers liquid LPG transfer. If you need an LPG gas flow meter for vapor recovery lines or gas phase measurement, the meter type is different. For liquid LPG, a volumetric meter is often the most practical choice because it measures actual volume directly. Many depots in Vietnam, Nigeria, and the Philippines use oval gear flow meters on LPG filling carousels and road tanker loading arms. We also see the same setup in Australia, Chile, and Kenya where LPG distribution skids need repeatable batch totals.

Which LPG Flow Meter Works for Liquid Transfer Skids

Silver Automation Instruments recommends a positive displacement oval gear meter with a 316L stainless steel body and PPS or PEEK internals for most LPG liquid streams. LPG has a viscosity around 0.1 cP to 0.3 cP. That is low. The meter needs bearings and gears that tolerate thin, non-lubricating fluid without excessive slip.

Standard accuracy is 0.5% of reading across the linear range. Repeatability is better than 0.03%. If you need higher precision for custody transfer, a calibrated meter with PT100 compensation can reach 0.2% of reading after in-line proving.

Here is the thing. Flow range should match the loading rate, not just the pipe size. A DN50 oval gear meter often covers 3 to 300 L/min. A DN25 meter covers 1.2 to 120 L/min. A DN80 meter covers 6 to 600 L/min. For small cylinder filling lines, a DN15 meter with 0.6 to 60 L/min range is enough.

Explosion-Proof Ratings and Signal Wiring You Should Specify

LPG loading areas normally fall under hazardous area classification. Specify Ex d IIC T6 or Ex ia IIC T6 depending on your local zone. For Zone 1 areas, use an Ex d housing with stainless steel conduit entries. For Zone 2, the same housing works but you may also consider an Ex e terminal box.

Last year a customer in Oman asked for a DN50 meter with Ex d IIC T6 and 316L body for a 20 t/h LPG filling skid. That combination is common because it covers the flow range and the hazardous area requirement in one meter body.

Output options include a local mechanical totalizer, a pulse output for PLC or batch controller, and 4-20 mA HART for remote flow rate and total. A PT100 sensor can be embedded in the meter body for temperature correction. Many customers in the Middle East also request RS485 Modbus RTU.

Because LPG is flammable, do not use general purpose transmitters with plastic housings. The entire meter body, sensor, and terminal compartment should carry the correct Ex marking for your plant zone.

Installation Notes That Prevent Vapor Lock

LPG can flash if the pressure drop across the meter is too high or if the line temperature is near boiling point. Install a back pressure valve downstream of the meter. Keep the meter full of liquid. Remove air and vapor before startup. Because the meter is a positive displacement device, vapor pockets cause over-registration and noisy flow signals.

Use a strainer upstream. LPG from storage tanks can carry mill scale, pipe thread debris, or valve grease. A 100 mesh stainless steel strainer protects the measuring gears. Clean the strainer during the first week of operation. In practice, most startups find debris in the strainer after 5 to 10 batches.

Seal and Elastomer Selection for LPG Service

Not all O-ring materials survive LPG service. Buna N may swell with propane an