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Small Flow Meter: Miniature Microfluidic Sensors for Chemical Dosing
Quick Answer: For chemical dosing flows from 0.01 kg/h to 10 kg/h, a miniature microfluidic flow meter with PTFE or 316L wetted parts and a 4-20 mA HART output will cover most dosing skids. Silver Automation Instruments supplies the SCF-03 series in DN2, DN4, DN6, and DN15 with accuracy better than 0.5 percent of rate. Send us your flow range, chemical name, viscosity in cP, pressure in bar, temperature in °C, and tube size for a specific quote.
What Counts as a Small Flow Meter in Dosing
In chemical dosing, small flow often means less than 10 kg/h. Many dosing pumps run between 0.05 L/h and 5 L/h. That is below the reliable range of ordinary inline flow meters. A small flow meter for this job needs a small internal volume, low pressure drop, and a turndown of at least 100 to 1. Pipe sizes are usually DN2, DN4, DN6, or DN15 on a skid header. The sensor body matters more than the line size. We have supplied micro flow sensors to a water treatment plant in Vietnam that doses sodium hypochlorite at 2.5 L/h. The operator wanted pulse output so the PLC could confirm every dose cycle.
Sensor Types for Miniature Microfluidic Dosing
Not every flow meter works in the microfluidic range. A turbine meter may stop turning below 0.5 L/h. An electromagnetic meter needs conductivity. That is a problem with deionized water, glycol, and many solvents. Conductivity below 5 µS/cm will not produce a stable signal on a standard electromagnetic meter. For these fluids, we recommend a thermal mass meter or a micro Coriolis meter. A micro Coriolis sensor from Silver Automation Instruments reports mass flow, density, and temperature. That helps when a chemical is blended by mass instead of volume. For viscous polymers above 200 cP, an oval gear meter with matching clearance can give repeatable batch totals. In practice, polymer dosing systems in Southeast Asia often run between 100 cP and 600 cP depending on room temperature.
Fluid Compatibility and Wetted Parts
The first question we ask is chemical name and concentration. Sodium hypochlorite, sulfuric acid, caustic soda, citric acid, and antiscalant all attack different materials. PTFE and PFA wetted parts work for aggressive chemicals. 316L stainless steel is common for solvents and fuel additives. Hastelloy C is better for hydrochloric acid or chlorinated brines. A desalination plant in Saudi Arabia requested a small flow meter for antiscalant injection at 0.8 L/h. The fluid was alkaline and required PTFE lining. Another customer in Australia uses a miniature sensor for dairy sanitizer dosing at 4 L/h. The sensor body is 316L with EPDM seals. We do not guess seal compatibility. Send us the chemical safety data sheet or the main active ingredient.
Outputs That Reduce Dosing Errors
Most engineering contractors ask for 4-20 mA HART. That signal connects to a PLC, DCS, or a paperless recorder. HART is useful for remote diagnostics and for reading totalizer data without opening the panel. Here is the thing. Pulse output is the part many people forget. A pulse output gives each measured volume as a counted pulse. That lets the control system confirm a dose was delivered. Without pulse output, the system only knows the valve or pump was told to run. We have seen this on customer sites many times. A dosing pump can lose prime and the flow meter is the only device that catches it. For ATEX Zone 1 installations, specify an intrinsically safe output. Silver Aut
Pressure, Temperature, and Viscosity Effects
Pressure affects gas flow far more than liquid flow. Chemical dosing is usually liquid, so pressure is mostly a material rating issue. Temperature changes viscosity and sensor stability. A polymer makedown unit in Mexico shifts from 50 cP in warm weather to 600 cP in cool weather. A small flow meter with temperature compensation will hold its calibration better. The PT100 element on a Coriolis sensor reports tube temperature, and the transmitter can correct for density and viscosity drift. Outdoor skids in the Middle East can reach 50 °C. Skids in Northern China can drop to minus 20 °C. Tell us the minimum and maximum ambient temperature. This matters for the display, the transmitter, and the seal material.
Installation Notes We Give to Dosing Skid Builders
Install the small flow meter downstream of the dosing pump. That sees the actual discharge pressure and reduces pulsation errors. Use a straight run only if the sensor type needs it. Many microfluidic sensors are positive displacement or Coriolis and do not need long upstream lengths. Do not mount the meter at the highest point of a line that can trap air. For pulsating pumps, add a small damper or use a sensor with fast signal processing. Most engineers skip this part on small skids and then see unstable readings at low flow. Keep the tube ID matched to the meter. A DN4 meter on a DN10 hose creates expansion and bubbles. Bubbles are a common cause of false totals in chemical dosing.
How to Request a Quote
Send us the process data instead of a long email. We need flow range in kg/h or L/h, chemical name, viscosity in cP, pressure in bar, temperature in °C, pipe size in DN, and output signal. Also tell us if the area is safe or hazardous. A typical quote lists the sensor model, wetted material, connection size, output, power supply, and accuracy. Contact Silver Automation Instruments at Tel: +86-25-68650347, Whatsapp: +86-25-52155837, or WeChat: +86 15365082610. Mention the SCF-03 small flow meter series when you ask for pricing.
FAQ: Small Flow Meter for Chemical Dosing
What is the smallest flow rate you can measure? The SCF-03 series can measure from 0.01 kg/h to 10 kg/h depending on the sensor type and fluid. For stable low flow, a micro Coriolis or oval gear sensor is better than a turbine.
Can these meters handle corrosive chemicals? Yes. Wetted parts can be PTFE, PFA, 316L stainless steel, or Hastelloy C. The chemical name and concentration decide the material.
Do I need a flow meter on a dosing pump suction line? Usually no. The discharge line gives a more stable reading and catches pump prime loss. Some applications measure suction to verify chemical supply.
What output signal should I choose for a dosing skid? Use 4-20 mA HART for the main control signal and pulse output for totalizing. Add RS485 Modbus if you want digital integration with a PLC or paperless recorder.
Can these sensors work in ATEX Zone 1? Yes. Silver Automation Instruments can supply Ex ia versions for hazardous areas. Specify the gas group and temperature class with your quote request.
For a small flow meter quote, contact Silver Automation Instruments at Tel: +86-25-68650347, Whatsapp: +86-25-52155837, or WeChat: +86 15365082610. Send your flow range, pressure, temperature, and pipe size.