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Fisher Scientific Flow Meter Selection: Laboratory Gas Rotameters and Mass Flow Controllers
Quick Answer: For laboratory gas lines, a glass tube rotameter works when you need a simple local display and low pressure drop. A thermal mass flow controller works when your process needs closed loop control, a 4 to 20 mA signal, or totalized gas flow. Send us your pressure (bar), temperature (°C), pipe size (DN), and flow range to get a fixed quote from Silver Automation Instruments.
Fisher Scientific flow meter selection often lists glass tube rotameters and mass flow controllers for laboratory gas service. Silver Automation Instruments supplies industrial equivalents for the same small bore gas lines in Asia, Oceania, Latin America, Africa, and the Middle East. We ship from our factory in China to labs, OEM skids, and distributors.
Here is the thing. A rotameter and a thermal mass flow controller solve different problems. If you pick the wrong one, the meter becomes a maintenance issue instead of a measurement tool. Do not start with a Coriolis meter for a 1 SLPM gas purge. It works, but it adds cost and weight.
Laboratory Gas Rotameters Fit Simple Purge and Bench Lines
A laboratory gas rotameter reads flow from a float position inside a tapered tube. It needs no power supply. It adds very little pressure drop. Typical accuracy is 2 to 5 percent of full scale. For a 0 to 10 SLPM air meter, that means a possible error of 0.2 to 0.5 SLPM at full scale.
Use a glass tube rotameter for manual gas lines, purge lines, and equipment where a local visual check is enough. A 150 mm reference scale unit works for bench experiments. A 65 mm unit works for panel mounting. Add a needle valve on the inlet or outlet to trim flow.
Because gas density changes with pressure, a rotameter reading drifts when backpressure changes. We have supplied DN6 and DN15 metallic variable area meters for lab gas racks in Malaysia and Australia. A vacuum research lab in Perth replaced a broken glass tube with a 0 to 1 SLPM nitrogen rotameter. The float moved at 0.1 SLPM and the lab stopped over purging.
Thermal Mass Flow Controllers Add Control and Repeatability
A thermal mass flow controller for laboratory gas measures heat transfer from a heated sensor. It gives a direct reading in standard litres per minute or standard cubic centimetres per minute. Accuracy is often 1 percent of full scale plus 0.5 percent of reading. Repeatability is much better than a rotameter.
Mass flow controllers also bring signal output. You can get 4 to 20 mA HART, Modbus RTU, or a 0 to 5 V output. Use them for gas blending, reactor feed, calibration rigs, and GC supply lines. A customer in Vietnam replaced a manual rotameter with a CO2 mass flow controller. The unit held setpoint within 0.3 SLPM during a six hour test.
But a mass flow controller costs more than a glass rotameter. So do not size one for a job that only needs a visual check. In practice, most engineers pick a mass flow controller when the gas flow feeds a PLC, a data logger, or a closed loop.
Fisher Scientific Flow Meter Selection Compared to Silver Instruments Options
Fisher Scientific flow meter selection is a useful reference for lab consumables and glass tube hardware. Silver Instruments sells the industrial side of the same measurement loop. We do not sell glass lab consumables. We do sell variable area flow meters, thermal mass flow meters, and mass flow controllers for gas and liquid.
For a gas chromatograph supply line, use a needle valve rotameter with a 0 to 0.5 SLPM range. For a bench reactor that needs a setpoint, use a thermal mass flow controller. For
Ask These Questions Before You Buy
What is the gas type? Air, nitrogen, argon, helium, CO2, and methane have different heat transfer values. A rotameter is gas specific. A mass flow controller can be programmed for multiple gas curves.
What is the flow range? State minimum and maximum in SLPM or SCCM. Do not size for 10 SLPM if your normal use is 0.3 SLPM. Turndown matters on both rotameters and mass flow controllers.
Most engineers skip this part. They state a line size but not the normal flow. That creates a meter that cannot control at low flow.
What pressure and temperature? A glass tube rotameter hates thermal shock and high pressure. A metallic tube meter works up to 10 bar or higher. Most of our thermal mass flow controllers handle 1 to 10 bar gas inlet, with options up to 100 bar.
Do you need a signal? If yes, choose a mass flow controller or a rotameter with a 4 to 20 mA transmitter. This is the question that separates a simple lab meter from an industrial loop device.
We have seen this on customer sites many times. A university lab in Perth bought a 0 to 5 SLPM rotameter for a 0.1 SLPM argon purge. The float barely moved. They changed to a 0 to 1 SLPM unit and the flow became readable.
How to Specify a Laboratory Gas Rotameter or Mass Flow Controller
When you send an inquiry to Silver Automation Instruments, include these details. Gas name or gas mixture. Minimum and maximum flow. Inlet pressure and outlet pressure. Ambient temperature. Pipe or tube size such as 1/8 inch, 1/4 inch, or DN6. Required output signal. Hazardous area classification if any, such as ATEX Zone 1 or Zone 2.
Last year a paint manufacturer in Southeast Asia ordered three thermal mass flow controllers for nitrogen blanketing in solvent storage. The lab gave us inlet pressure of 1.5 bar, temperature of 20 °C, and a range of 0 to 10 SLPM. We calibrated all three units against actual nitrogen.
This allows us to quote a fixed price with freight to Singapore, Bangkok, Lagos, Dubai, or Santiago. We ship small metering skids from our facility in China. Standard lead time is 5 to 10 working days for a calibrated thermal mass flow controller.
Contact Silver Automation Instruments at Tel +86-135-1213-1526, WhatsApp 86-135-12131526, or WeChat +86 13512131526.
FAQ: Laboratory Gas Flow Meter Selection
Q1: Can I use a Fisher Scientific flow meter selection for industrial gas lines?
Yes for reference only. Lab rotameters are often low pressure and small bore. Industrial lines may need a metallic tube rotameter, a thermal mass flow meter, or a differential pressure based system.
Q2: Which is better for nitrogen purge, a rotameter or a mass flow controller?
If you only need a local visual check, a rotameter costs less. If you need a repeatable purge rate or data logging, use a mass flow controller.
Q3: What gas types can Silver Automation Instruments support?
Nitrogen, air, argon, helium, CO2, oxygen, methane, and custom gas mixes. We calibrate each mass flow controller against the actual gas where possible.
Q4: Do you supply ATEX rated gas flow meters?
Yes. We have thermal mass flow meters and variable area meters for ATEX Zone 1 and Zone 2. Inform us of the zone and gas group.
Q5: How do I get a quote for a laboratory mass flow controller?
Send us gas type, flow range, pressure, temperature, tube size, output signal, and quantity. Use Tel +86-135-1213-1526, WhatsApp 86-135-12131526, or WeChat +86 13512131526.
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