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Refrigerant Flow Meter for Flammable Gas: Explosion-Proof Architecture for Hydrocarbon Lines
Quick Answer: Measuring liquid propane (R290), isobutane (R600a) or propylene (R1270) demands a meter that eliminates all ignition sources inside the pipe. Silver Instruments supplies fully welded Coriolis mass flow meters with ATEX Zone 1 Ex d or Ex ia certification, no internal elastomers and 4-20 mA HART output. Send us your gas type, pressure in bar, pipe size (DN) and maximum flow in kg/h and we will return a complete explosion-proof quote within one working day.
Why a Standard Meter Fails on a Hydrocarbon Refrigerant Line
Most flow meters are not designed for fluids that turn into a flammable gas the moment a leak occurs. A small seepage past an O-ring on a turbine meter or a cracked sight glass on a variable area meter puts a flammable cloud directly next to an electrical terminal. We saw this at a chiller test stand in Malaysia where a technician swapped in a general-purpose magnetic flow meter for R290 trials. The lining swelled within three days because hydrocarbon refrigerants attack EPDM and NBR aggressively. The meter body lost earth continuity and became a static discharge risk. A properly engineered refrigerant flow meter removes every one of these failure points before they become an incident.
All-Welded Sensor Architecture Removes the Ignition Source
In a Coriolis mass flow meter built for hydrocarbon service, the sensor tubes, manifold and process connections form one continuous all-welded envelope. There are no gaskets, no clamp seals and no dynamic seals exposed to the fluid. Silver Instruments uses dual U-shaped 316L stainless steel tubes with full-penetration orbital welds. The drive coil and pickoff coils sit outside the secondary containment housing. Even if a tube fails under fatigue, the refrigerant stays trapped inside a secondary shell rated to the same pressure as the process line. The housing itself carries an ATEX Ex d flameproof certification with a 40 bar secondary containment rating as standard.
Small Line Sizes and Low Flow: DN6 to DN25 is Where It Counts
Refrigerant charge lines, oil return circuits and vapour injection branches often run at DN10 or DN15. Flow rates can be as low as 0.2 kg/h during part-load operation. A bulky meter with a large dead volume misreads these tiny flows and adds liquid hold-up that complicates ATEX charge limit calculations. Our smallest explosion-proof Coriolis meter covers a 0 to 60 kg/h range on a DN6 connection with a measurement accuracy of ±0.2% of rate. The wetted volume is barely 12 ml. For a 10 kW R290 heat pump on a rooftop in Brisbane, that means you stay below the 150 g charge threshold in EN 378 while still tracking lubricant migration.
Electronics That Stay Safe Without Purging
Many explosion-proof strategies rely on Z-purge or X-purge enclosures, which require a clean, dry instrument air supply. Refrigeration skids installed on a rooftop in Dubai or a fishing vessel in Indonesia rarely have that utility available. Silver Instruments fits the transmitter in a compact Ex d enclosure with an integral 4-20 mA HART output. You wire it like any other two-wire loop device. There is no need for external barriers when you select the Ex ia output option for Zone 0 applications. The local display can be glass-to-glass bonded so the operator reads mass flow, density and temperature without opening the cover in a classified area.
Materials and Connections That Resist R290 and R600a
Hydrocarbon refrigerants are not corrosive in the electrochemical sense but they are aggressive solve
Field Experience From a Paint Plant to a Refrigerated Container Line
Last year a customer in Vietnam approached us after a variable area meter on an R1270 solvent recovery line kept fogging the glass tube. The gas environment inside the enclosure was Zone 1, so the mere presence of a glass tube rated only for Zone 2 put the plant in a non-compliance situation during an insurance audit. We proposed a DN10 all-welded Coriolis meter with Ex d electronics and an IECEx certificate that matched the plant’s existing ATEX dossier. The meter was installed downstream of a plate heat exchanger condensing propylene at 45 °C and 18 bar. Mass flow was 0.6 to 4 kg/h. Because the meter measures density inline, the plant also uses it to detect when inert gas breaks through during purging, a trick most operators skip but that prevents a flammable mixture from entering the recovery tank.
FAQ: Explosion-Proof Refrigerant Flow Meter
Can you supply a meter for liquid R290 charging stations that need ATEX Zone 1?
Yes. Our standard SILVER-CMF series with Ex d enclosure and secondary containment is certified for ATEX Zone 1, IECEx Zone 1 and North American Class I Division 1. We test every meter with helium before shipping and you can request a third-party FAT witness.
What is the smallest flow rate you can measure on a DN6 meter?
With a standard accuracy of ±0.2% of rate, the floor is 0.08 kg/h on liquid hydrocarbons. We have validated this with R600a on a gravimetric rig in our production hall. If you need a lower range, we can supply a 0.1% option with tighter tube geometry.
Does the meter need an external barrier for the Ex ia version?
When you order the 4-20 mA HART Ex ia output, we supply a matching galvanic isolator in the scope. You can also integrate it with Pepperl+Fuchs or MTL barriers that you already have in the cabinet. Just send us the barrier make and model during inquiry.
Can the same meter handle vapour-side flow during defrost on a heat pump?
In practice a Coriolis meter reads both liquid and gas phases, but accuracy drops when the fluid becomes fully gaseous because of density span. We normally recommend installing the meter in the liquid line before the expansion valve. If you must measure low-density vapour, provide the gas density at flowing conditions and we will check whether the driver can sustain oscillation.
How do I get a quote that matches my charge limit calculations?
Send us your refrigerant type (R290, R600a, R1270 or others), maximum allowable charge in grams, pipe size (DN), operating pressure in bar, temperature in °C and flow range in kg/h. Email these numbers to [email protected] or message us on WhatsApp at +86-25-52155837. We will return a dimensional drawing, an explosion-proof certificate copy and a priced offer the same day. You can also reach us by phone at +86-25-68650347 or WeChat: +86 15365082610.