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Glass Tube Flow Meter: Industrial Variable Area Visual Tapered Rotameters
Quick Answer: A glass tube flow meter is a variable area rotameter with a transparent tapered glass tube. It measures liquid or gas flow from 0.2 L/h up to 100 m3/h for pipe sizes from DN15 to DN80. Silver Automation Instruments supplies these meters with 4-20 mA HART output, alarm switches, and local display options for industrial water, chemicals, air, and fuel gas lines.
What Is a Glass Tube Flow Meter
A glass tube flow meter belongs to the variable area flow meter family. Engineers also call it a tapered rotameter. The meter body has a vertical glass tube with a slightly wider bore at the top. A float sits inside the tube. Process fluid enters from the bottom and pushes the float upward. The float reaches a stable height when flow force balances float weight. You read the flow rate on a scale printed on the glass tube.
Most glass tube flow meters work for clean liquids, gases, and air. They do not need external power for basic local indication. The lack of external power works well in remote dosing skids and simple wash line monitoring.
Industrial Applications We See on Customer Sites
We sell many glass tube rotameters to Southeast Asia, the Middle East, Oceania, Latin America, and Africa. A typical customer is a water treatment plant in Vietnam that monitors sodium hypochlorite dosing. Another is a paint manufacturer in Thailand that checks solvent flow to a mixing tank. One customer in Chile uses a DN25 glass tube flow meter for a nitrogen purge line on a wine bottling system.
Common industries include oil and gas, chemical plants, food and beverage, marine, and waste water. The meter is not ideal for dirty slurry, high viscosity fluids above 50 cP, or liquids with large solids. For those cases we recommend an electromagnetic flow meter or an oval gear flow meter.
Key Technical Parameters for Selection
To get the right glass tube flow meter, send us these details first.
Pipe size and connection. DN15, DN20, DN25, DN32, DN40, DN50, DN65, and DN80 are common. Threaded BSP or NPT connections work for small sizes. Flange connections work for DN40 and above.
Flow range. Specify minimum and maximum flow in L/h, m3/h, kg/h, or scfm. For water a DN25 meter may cover 100 to 1000 L/h. For air a DN25 meter may cover 1 to 10 Nm3/h. The scale is specific to fluid type and density.
Fluid type and operating conditions. List pressure in bar, temperature in Celsius, and chemical compatibility. Standard borosilicate glass handles up to 100 degrees Celsius and 10 bar depending on size. Many customers choose stainless steel 316 floats for water and Hastelloy C floats for aggressive chemicals.
Output signal. Basic models have local reading only. If you need remote data, choose 4-20 mA HART output. Alarm switches can trigger a PLC or a warning lamp at high or low flow. We can add a transmitter module without changing the process connection size.
Silver Automation Instruments Glass Tube Flow Meter Range
We supply industrial variable area glass tube flow meters in several configurations.
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Standard borosilicate glass tube rotameter. Good for water, air, and mild chemicals. Threaded or flanged ends. Local scale in L/h or m3/h. Prices start from 80 USD for small DN15 threaded models in quantities.
Glass tube flow meter with 4-20 mA HART output. Includes a magnetic position sensor and an integrated transmitter. This model suits a central control room or a remote skid in a seawater desalination plant. You can connect it to a PLC or a paperless recorder.
Glass tube flow meter with alarm switches. Two adjustable set points. One set point often controls a dosing pump. The other opens a bypass valve. We have seen this on cooling water lines in the Middle East.
We also offer panel mount glass tube flow meters for gas analyzers and laboratory test benches.
Installation and Maintenance Notes
Install the glass tube flow meter vertically. A tilted meter changes float travel and gives wrong readings. Use isolation valves and a bypass line if you cannot stop flow during cleaning. For dirty fluids add a Y strainer upstream. Clean the glass tube with mild detergent and a soft brush. Do not use abrasive pads or strong acid cleaning agents without checking the tube material.
Frequently Asked Questions
Q: Can a glass tube flow meter measure gas and liquid with the same tube?
No. The scale is fluid specific. A gas scale and a liquid scale use different float shapes, tube tapers, and calibration. Always tell us the fluid type when you order.
Q: What is the maximum pressure for a glass tube flow meter?
Standard borosilicate glass tube meters handle up to 10 bar at room temperature. At higher temperatures the pressure rating drops. For high pressure gas lines we often recommend a metal tube variable area flow meter.
Q: Can I get an output signal from a glass tube flow meter?
Yes. Add a 4-20 mA HART transmitter or alarm switches to the meter body. This gives you remote flow rate and high or low flow alarms. The basic local reading model has no electrical power requirement.
Q: Which industries use glass tube flow meters most?
Water and waste water plants use them for chemical dosing. Food and beverage plants use them for clean utility water and nitrogen. Chemical plants use them for solvent and additive flows. Oil and gas sites use them for purge air and sample lines.
Q: How do I choose the right float material?
Choose stainless steel 316 for most water and air applications. Choose PTFE coated float for mild acids. Choose Hastelloy C for strong acids and seawater. Tell us the chemical name and concentration and we will confirm the float and tube material.
To request a quote, send us your pressure in bar, temperature in Celsius, pipe size in DN, process fluid, and flow range. Our application engineers will reply within 24 hours with a model and price. You can reach Silver Automation Instruments by telephone at +86-135-1213-1526, by Whatsapp at 86-135-12131526, or by WeChat at +86 13512131526. We ship glass tube flow meters from our Nanjing factory to industrial users in Southeast Asia, Oceania, Latin America, Africa, and the Middle East.