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Dosi Flow Meter: Specialized Laboratory Chemical Dosing Micro-Sensor Sizing Guide
Quick Answer: A Dosi flow meter for laboratory chemical dosing needs a micro-sensor sized for flow range, viscosity, wetted material, and tube connection. For most lab loops from 0.5 ml/min to 10 ml/min, Silver Automation Instruments recommends a compact Coriolis mass flow meter or a PTFE oval gear meter. Send us your flow range in ml/min, chemical name, viscosity in cP, pressure in bar, and connection size in mm for a direct sizing reply.
Many lab chemists and process engineers find that standard industrial flow meters are too large for chemical dosing loops. A sensor with a 1 inch body cannot resolve a 2 ml/min feed of sulfuric acid. The result is unstable dosing, poor batch records, and frequent overshoot.
Silver Automation Instruments has supplied small bore flow meters to laboratories and chemical plants across Southeast Asia, Australia, the Middle East, and Latin America. The Dosi class meters we discuss here are not a single product. They are a group of specialized micro-sensors used for additive injection, catalyst feed, reagent dosing, and pilot plant trials.
What a Dosi Flow Meter Means in a Lab Dosing Loop
In Europe and Asia, engineers use the word Dosi as shorthand for dosing or dosage. A Dosi flow meter is not a standard water meter. It is a sensor built for very low flow chemical injection. The meter usually has a micro-bore flow tube, a compact transmitter, and a fast pulse or 4-20 mA HART output.
Laboratory and pilot systems often run from 0.1 ml/min up to 2 L/min. Pipe sizes are small. Common connections are 1/16 inch, 1/8 inch, 3 mm, and 6 mm. Most engineers skip the sensor sizing step and buy a general purpose meter. That causes a mismatch. The meter either drops signal at low flow or creates too much pressure drop.
Micro-Sensor Sizing Parameters That Actually Matter
Here is the thing. Four parameters decide the sensor size for chemical dosing: flow range, viscosity, chemical compatibility, and connection size. Temperature and pressure come next but they matter less for most lab loops.
Flow range is the first input. If you dose a reagent from 0.2 ml/min to 3 ml/min, the meter must be linear in that narrow band. A Coriolis micro flow meter with a 0.5 mm ID tube can measure from 0.05 kg/h to 2 kg/h for liquids with density near water. That is roughly 0.83 ml/min to 33 ml/min. It fits many lab reagent lines.
Viscosity changes the meter selection. An oval gear meter handles 5 cP to 500 cP liquids well. A micro Coriolis mass flow meter can handle 0.5 cP up to 300 cP depending on pressure drop. For viscous polymers or glucose syrup, an oval gear meter with PTFE or PEEK gears tends to be better. In practice, we ask for viscosity in cP on the first sizing call.
Chemical compatibility is the next filter. Many dosing chemicals are aggressive. Hydrochloric acid, sodium hypochlorite, and ferric chloride attack stainless steel. Silver Automation Instruments offers wetted parts in PTFE, PEEK, ceramic, and Hastelloy C. For a low flow acid dosing skid, a PTFE lined oval gear meter or a ceramic tube Coriolis meter usually survives longer.
Connection size is the last hard limit. A 3 mm tube cannot accept a heavy meter body with DN15 flanges. The sensor must fit the tubing, not the other way around. We recommend a 1/8 inch or 3 mm compression fitting for lab dosing loops below 100 ml/min. This detail reduces dead volume and improves response time.
A Simple Sizing Workflow for a Lab Dosing Skid
Most engineers can size a micro-sensor in one afternoon if they collect the right data first. Start with the dosing pump flow range. Look at the minimum and maximum stroke rate. Then write down the chemical name, concentration, density, viscosity, and temperature.
Next, choose a meter type. For flow below 5 ml/min, a micro Coriolis mass flow meter is often the only reliable choice. It measures mass directly and does not need a minimum conductivity. For 20 ml/min to 2 L/min of conductive liquid, a small electromagnetic flow meter with a 1.5 mm or 3 mm ID may work. But many lab chemicals have low conductivity. Check that parameter before you select a mag meter.
Then check pressure drop. A micro-bore Coriolis meter can add 0.2 bar to 0.8 bar of pressure drop at full flow. Small peristaltic pumps often only push 1 bar. If your pump only delivers 0.5 bar, the meter may become the bottleneck. Send us the pump discharge pressure and we will calculate the available pressure for the flow tube.
Finally, decide the output. Most lab PLC systems accept 4-20 mA HART, pulse, or Modbus RTU. We usually recommend 4-20 mA HART for a single loop because it gives flow rate, totalizer, and diagnostics over two wires. The pulse output works well for very low flow totalizing in batch dosing.
Last year a customer in Vietnam asked us to size a Dosi flow meter for a laboratory scale neutralization process. They were dosing 30 percent sodium hydroxide at 0.5 ml/min to 5 ml/min. The line pressure was 0.3 bar. The connection was a 6 mm PTFE tube. Temperature stayed near 40 degrees Celsius.
The first option we proposed was a micro oval gear meter with PEEK body and PTFE gears. It handled the chemical and the low flow range. The pressure drop at 5 ml/min stayed below 0.05 bar. We supplied a pulse output version so the lab data logger could count each batch. The system ran without signal loss for over eight months.
We have seen similar loops in desalination labs in Saudi Arabia, food additive labs in Brazil, and polymer pilot plants in Australia. The exact model changes with the chemical and flow range, but the sizing process stays the same.
If your lab runs a similar loop, send the chemical name, flow range, temperature, and tube size to Silver Automation Instruments. Tel: +86-135-1213-1526. Whatsapp: 86-135-12131526. WeChat: +86 13512131526.
Micro Flow Meter Types That Work for Dosing
Three flow meter types cover most laboratory chemical dosing jobs. The first is a compact Coriolis mass flow meter. It measures mass directly, handles low flow from 0.05 kg/h, and works with non-conductive chemicals. The second is a small oval gear meter with chemically resistant internals. It fits viscous liquids, solvents, and polymer additives. The third is a thermal mass flow meter for gas dosing lines such as ammonia or carbon dioxide injection.
A standard electromagnetic flow meter can work for conductive liquids from 20 ml/min to 5 L/min. But do not force it into a low flow acid line if the conductivity drops below 50 µS/cm. The signal becomes unstable. Most lab water and many diluted acids stay above that limit, but solvent based streams do not.
For a skid builder in Malaysia dosing chlorine into a water treatment pilot plant, we supplied a small electromagnetic flow meter with a 1.5 mm ID and PTFE liner. The flow range was 30 ml/min to 300 ml/min. The output was 4-20 mA HART. It worked well because the chlorine solution was conductive and the flow stayed inside the linear range.
How to Send a Sizing Request to Silver Instruments
Do not send a general inquiry like I need a flow meter for dosing. The sizing process moves faster when we receive five data points. Flow range in ml/min or µL/min. Chemical name and concentration. Viscosity in cP if available. Pressure in bar. Connection size in mm or inch. Add the required output signal and the power supply voltage if possible.
Send that data to Silver Automation Instruments by Tel: +86-135-1213-1526, Whatsapp: 86-135-12131526, or WeChat: +86 13512131526. We will reply with a recommended meter type, wetted material, connection size, pressure drop estimate, and price range for your region.
Because we ship to Southeast Asia, Oceania, Latin America, Africa, and the Middle East, we can quote in USD, EUR, AUD, or local currency. We also supply ODM labeling for distributors. Our standard lead time for a small bore Coriolis or oval gear meter is 7 to 15 working days depending on the wetted material.
FAQ: Dosi Flow Meter Sizing for Lab Chemical Dosing
What flow range can a Dosi micro flow meter cover? Most compact meters from Silver Automation Instruments cover liquid flow from 0.05 ml/min up to 10 L/min depending on the meter type and line size. For gas dosing, thermal mass meters cover 0.1 ml/min to 100 L/min at standard conditions.
Can a small Coriolis mass flow meter measure sulfuric acid at 2 ml/min? Yes, if the wetted material is Hastelloy C or PTFE and the acid concentration does not exceed the corrosion limit. Sulfuric acid above 90 percent has high viscosity at low temperature. Send the concentration and temperature so we can confirm the pressure drop.
Do I need a display on the meter or is a blind transmitter fine? Most lab skids use a blind transmitter with 4-20 mA HART or pulse output. A local display helps during commissioning. Silver Instruments can supply a compact display head or a remote display for tight panels.
What kind of accuracy is realistic for a lab dose meter? A micro Coriolis mass flow meter can achieve plus or minus 0.2 percent of rate for liquids above 20 percent of full scale. An oval gear meter can achieve plus or minus 0.5 percent of rate for viscous chemicals. The real limit in a dosing loop is often the pump pulsation, not the meter itself.
Which connection size should I choose for a 10 ml/min chemical line? For 10 ml/min or lower, use 1/16 inch or 1/8 inch tube fittings or 3 mm compression fittings. Larger connections add dead volume and slow down the sensor response after each pump stroke.