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Biodiesel Flow Meter DN15: Chemical Catalyst Dosing Pipeline Rules
Quick Answer: For dosing aggressive catalysts like sodium methoxide or potassium methoxide through a DN15 line, an oval gear flow meter with PTFE internals or a small Coriolis mass meter provides repeatability within ±0.5%. Always install a 60-mesh strainer upstream, use 316L piping, and keep the meter body flooded to prevent drying and crystallization. Silver Instruments supplies pre-configured DN15 dosing flow meters with 4-20 mA HART and ATEX Zone 1 approvals for biodiesel plants across Southeast Asia, Oceania, and Latin America.
A biodiesel plant mixes a catalyst into oil to drive the transesterification reaction. Typical catalyst dose rates sit between 0.5% and 1.5% of the oil mass. On a small production skid with a DN15 pipe, the flow rate often lands between 5 and 60 liters per hour. That is a low flow range where many flow meter technologies drift or struggle with high viscosity. Most engineers skip pressure drops across a 15mm pipe, but a meter with small internal passages clogs fast if the operator forgets to flush methanol through after a batch. We have seen this on customer sites in Vietnam and the Philippines many times.
Oval gear flow meters work well for clean viscous chemicals. The pair of oval rotors displaces a known volume per revolution, so viscosity changes cause almost no drift. For DN15, Silver Instruments offers the OG-I-15 model with 316L body, PTFE gears, and PT100 temperature compensation built in. It handles fluids up to 300 cP and operating temperatures to 80°C. The output is pulse or 4-20 mA HART, which integrates directly into a PLC on the dosing skid. In practice, if the catalyst contains solid precipitates or salt crystals, you must install a Y-type strainer with 60 mesh screen just before the meter. Otherwise the rotors jam. Another solid option is a micro Coriolis mass flow meter. It measures mass directly, ignores viscosity and density swings, and tolerates entrained air better than an oval gear meter. A DN15 Coriolis meter from Silver Instruments can read 0 to 100 kg/h with ±0.2% reading accuracy. The Coriolis costs more but cuts rework because you can skip the strainer and stop worrying about catalyst degradation causing density shifts.
Proper pipeline design prevents meter failure and measurement drift. Run the dosing pump on the discharge side of the meter in most cases, so the meter operates under slightly positive pressure. Never install the flow meter on the suction side of a diaphragm pump because pulsation destroys repeatability and accelerates internal wear. If you cannot avoid pulsation, add a pulsation damper. The pipe should be 316L stainless steel with welded or compression fittings. Avoid brass or carbon steel; methoxide catalysts corrode them fast. Keep the meter fully flooded at all times. Install a check valve downstream to stop backflow when the pump stops. For oval gear meters, no straight run is required, which saves space on a compact dosing skid. Coriolis meters also need no flow conditioning. However, you must install a small relief valve if the line can heat up and cause thermal expansion. Methanol trapped in a closed pipe section can build enough pressure to crack the meter housing. Silver Instruments recommends a pressure limit of 40 bar for the DN15 meter body.
Most chemi
Last year a biodiesel start-up in Indonesia installed a standard gear meter without a strainer for sodium methoxide dosing. After three weeks, crystal deposits locked the rotors and the PLC lost flow signal. We replaced the unit with a Silver Instruments OG-I-15 fitted with an 80-mesh inline filter and PTFE rotors. The system has run 14 months without service. Another customer in Thailand switched to a DN15 Coriolis meter for catalyst ratio control because his lab found that catalyst concentration drifted due to methanol evaporation. The Coriolis mass flow output allowed real-time adjustment. Both plants now record catalyst consumption per batch with 4-20 mA HART data logged to the control room.
Send us your catalyst type, flow range in L/h, operating temperature in °C, pipe size (DN15 is standard but we also cover DN10 and DN20), and hazardous zone classification. We will recommend a meter with the right wetted materials and certifications for your dosing pipeline. See the OG-I oval gear flow meter datasheet or the CMF-DN15 Coriolis options on our website.
Can an oval gear flow meter handle potassium methoxide which is more viscous?
Yes, potassium methoxide typically sits around 80 to 150 cP. The OG-I series with PTFE gears works fine up to 300 cP. Provide exact viscosity at operating temperature, and we set the clearance to avoid excessive pressure drop.
What output signal do I need for catalyst dosing control?
Most dosing skids use 4-20 mA with HART to carry flow and diagnostic data on one pair of wires. Pulse output is also common if the PLC counts pulses for totalized dosing. Silver Instruments meters can output both simultaneously.
Why does my flow meter reading drift after a few days?
Common causes: partial clogging from catalyst crystals, air pocket trapped inside the body, or temperature swings that change viscosity and shift oval gear slip. Install a finer strainer, bleed the vent port, and use a meter with PT100 compensation.
Do I need ATEX certification for a biodiesel pilot plant in Australia?
Australian legislation follows AS/NZS 60079 standards. If the catalyst dosing area contains a flammable atmosphere, you need a certified meter. Silver Instruments supplies IECEx-certified meters accepted in Australia, and we help you complete the compliance paperwork.
How quickly can you ship a DN15 chemical dosing flow meter to Malaysia?
We stock OG-I-15 meters with standard PPS or PTFE internals in our Australia warehouse. Shipment to Kuala Lumpur or Port Klang takes 3 to 5 business days via DHL. Custom wetted material builds ship in 2 weeks.
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