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Biodiesel Flow Meter DN50 and Glycerin Separation Flow Line Metrics
Quick Answer
Quick Answer: For biodiesel glycerin separation lines, a DN50 flow meter must handle real viscosities from 50 to 500 cP and process temperatures between 40 and 80 °C. Silver Instruments recommends an oval gear flow meter with PTFE gears or a direct mass Coriolis meter to get repeatable volume and mass flow data. Typical flow range on a DN50 separation line sits between 0.5 and 10 m³/h. Send us your pressure, temperature, pipe size, and flow range to receive a same-day price.
Why Glycerin Separation Flow Measurement Is Not Simple
Glycerin is not a single-phase fluid with constant properties. In a biodiesel plant, the glycerol stream leaving the separator carries methanol, water, soap traces, and residual catalyst. The viscosity shifts with temperature and phase purity. A DN50 pipe at 40 °C can see glycerin at 400 cP; the same pipe at 80 °C drops to 80 cP. Standard flow meters like turbine or vortex meters drift badly under these viscosity swings. Many engineers learn this the hard way during commissioning.
Flow meter selection for this line is not about picking a DN50 device and hoping for the best. You need a meter that is immune to viscosity changes or one that physically displaces a known volume per revolution. That is why positive displacement and Coriolis meters dominate this application in Southeast Asian biodiesel plants. We have seen customers in Indonesia and Thailand replace ultrasonic clamp-on meters after just six months because the signal attenuation through viscous glycerin was too unpredictable.
Recommended Flow Meter for DN50 Glycerin Lines
Silver Instruments supplies two field-proven options for glycerin separation flow lines. The first is our oval gear flow meter, built with 316L body and PTFE gears. It outputs one pulse per discrete volume, so viscosity does not change the K-factor. You get volumetric flow directly, plus a 4-20 mA signal and optional HART communication. For a DN50 line, we typically set the flow range from 1 to 10 m³/h. The meter head can handle up to 130 °C and 40 bar, so it fits most biodiesel separation skids without extra cooling.
The second option is a Coriolis mass flow meter, which is useful when you need both mass flow (kg/h) and density to track glycerin purity on the fly. A DN50 Coriolis meter from Silver Instruments gives you direct mass flow accuracy better than 0.2% of reading, even when the fluid changes from 80% glycerol to 95% glycerol. The wetted parts are 316L stainless steel, and the transmitter supports Modbus RTU and 4-20 mA HART. This meter removes the need for separate density sampling because it reports live density in kg/m³.
Here is the thing: many plant managers want a cheap turbine meter. We advise against it for glycerin separation. A turbine meter in viscous service under-reads by 8 to 15% once glycerin cools down. You end up with missing inventory and report errors. Pay the capital cost once for the right meter instead of explaining mass balance gaps every month.
Key Installation Metrics and Setup Tips for DN50
Your DN50 flow meter needs a straight run, but positive displacement and Coriolis meters are far less sensitive than DP devices. For an oval gear meter, we recommend 5D upstream and 2D downstream of clear pipe. The meter body must be full of liquid at all times, so install it in a low point of the separation line with a small back-pressure valve if needed. Glycerin tends to form a sticky film,
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Temperature compensation matters. Silver Instruments oval gear meters can be ordered with an integrated PT100 sensor. The transmitter uses the temperature input to correct volume to a standard temperature (usually 15 °C) for inventory reporting. On a DN50 line, a 30 °C shift in glycerin temperature changes the volume by about 2 to 3%, enough to create a noticeable billing error between the biodiesel plant and the glycerin refiner.
Process connections are usually DIN PN16 or ANSI 150 flanges. If the separation line is located in an ATEX Zone 1 area, we supply meters with Ex ia or Ex d certification. A biodiesel plant in Vietnam ordered five DN50 oval gear meters from us last year with ATEX Zone 1 and IP67 rating because their entire transesterification building was classified.
A Real-World Example from a Biodiesel Plant
Last year a customer in Malaysia asked us for help. Their glycerin separation line used a vortex flow meter on a DN50 pipe. At 45 °C the glycerin viscosity was around 280 cP, and the meter showed 4.2 m³/h. After we installed a Silver Instruments oval gear meter, the true flow was 4.9 m³/h. The vortex meter had been under-reading by 16%, and the plant was losing 700 liters of crude glycerin per day that went unaccounted. Once they reconciled the numbers, they ordered three more meters for their other separation trains. This is not an isolated case. We see it in the Philippines, in Peru, and in Jordan.
How to Request a Quote
We do not send generic pricing because every glycerin line has different pressure, temperature, and hazardous area requirements. Send us your process data and we will return a quotation within one business day. The information we need: operating pressure in bar, minimum and maximum temperature in °C, DN (pipe size), flow range in m³/h or kg/h, and the hazardous area class if applicable. Use the contact form on flow-meter.com.au or email our process engineering team directly. Tell us you need a flow meter for biodiesel glycerin separation and we will recommend the correct model and wetted material.
FAQ
What flow meter technology works best for raw glycerin separation? Positive displacement meters (oval gear) and Coriolis mass flow meters are the most reliable. They are not affected by the wide viscosity changes that ruin turbine or vortex readings.
Can I use a magnetic flow meter on a DN50 glycerin line? No. Glycerin has very low electrical conductivity, typically below 5 µS/cm. Magnetic flow meters need a minimum of 5 to 20 µS/cm to function. They will give zero or erratic readings on this application.
What is the typical pressure drop across an oval gear meter in glycerin service? For a DN50 meter flowing 8 m³/h of glycerin at 300 cP, expect about 0.4 bar pressure drop. As viscosity drops at higher temperature, the pressure drop falls further.
Does Silver Instruments offer ATEX-certified flow meters for biodiesel plants? Yes. We supply oval gear and Coriolis meters with Ex ia IIC T4 or Ex d certification. Specify the zone and gas group when you request a quote.
How do I get a price for a DN50 glycerin flow meter? Send us your pressure, temperature, pipe size, and flow range. We will return a quote with technical datasheet and delivery lead time usually within 24 hours.