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『Medical Gas Flow Meter: Clinical Thorpe Tube and Dial Selector Systems』Related information(v cone flow meter|rotary gas meter|gallon meter|gear meter|metal tube rotameter|glass tube rotameter|nutating disk meter|transit time ultrasonic flow meter|wedge flow meter|pd meters|hydraulic flow meter|ultrasonic water flow meter|water flow meter|air flow meter|magnetic water flow meter|oxygen flow meter|gas flow meter|argon flow meter|air velocity meter|gasoline flow meter|fuel flow meter|ultrasonic water meter|digital water meter|nitrogen flow meter|solid flow meter|Oxygen tank flow meter|digital water flow meter|diesel fuel flow meter|steam flow meter|02 flow meter|compressed air flow meter|oil flow meter|liquid flow meter)
Medical Gas Flow Meter: Clinical Thorpe Tube and Dial Selector Systems
Thorpe tube flow meters use a tapered tube and float to visually indicate flow rates of medical gases like oxygen and nitrous oxide. Dial selector flow meters set fixed flow steps via an indexed control, reducing adjustment errors in busy wards. Silver Automation Instruments provides thermal mass flow meters and pressure transmitters for precise medical gas pipeline monitoring and calibration.
Thorpe Tube Flow Meter Working Principle
A Thorpe tube flow meter consists of a vertical tapered glass or clear plastic tube and a lightweight float. Gas enters at the bottom, lifts the float, and the flow rate is read at the center of the float against a scale. Typical scales read directly in LPM (liters per minute). Common ranges include 0-3 LPM for neonates, 0-8 LPM for pediatrics, and 0-15 LPM for adults. Accuracy is usually plus minus 5% of full scale. These meters need a stable inlet pressure, often 50 PSI, regulated upstream. The tube is protected by a polycarbonate shield to prevent breakage in crowded clinical areas.
Dial Selector Flow Meter Design
A dial selector replaces the variable area tube with a multi-port valve. Each click on the dial opens a calibrated orifice. Flow steps are preset, for example 0.5, 1, 2, 3, 4, 5, 8, 10, 15 LPM. This design avoids parallax error and speeds up setting. In practice, nurses prefer dials when dealing with multiple patients because they reduce miscounts. Dial selector systems are common on wall outlets in hospitals in Southeast Asia and the Middle East. They require less cleaning compared to Thorpe tubes that can accumulate dust inside the shield. Because the dial clicks into discrete positions, flow adjustments remain repeatable even when the operator wears gloves.
Key Specifications to Check Before Ordering
Always confirm the gas type: oxygen, medical air, carbon dioxide, nitrous oxide, or vacuum. Each gas has a specific connector standard. Outlets may follow DISS (Diameter Index Safety System), NIST (Non-Interchangeable Screw Thread), or quick-connect. Check the flow range and number of steps for dial selectors. Inlet pressure and temperature are critical, especially in countries like Saudi Arabia and Nigeria where clinic room temperatures reach 40 degree C. Specify inlet thread size, typically 1/4 inch NPT or BSP. Some applications need a 4-20 mA output for remote monitoring. Our thermal mass flow meters offer 4-20 mA HART, RS485, and a local display for medical gas headers. Do not forget to state the required O-ring material if the device will see high humidity or sterilization agents.
Silver Instruments for Gas Flow Monitoring
Silver Automation Instruments does not produce clinical Thorpe tubes directly. However, we supply the core sensing technology behind many medical gas systems. Our inline thermal mass flow meters measure oxygen, air, an
Common Installation Pitfalls
One common mistake is connecting a Thorpe tube to unregulated high pressure. A 200 bar cylinder needs a regulator set to 3-4 bar before the flow meter. Another issue is using an oxygen flow meter for medical air. The internal calibration differs because of gas density. If you swap gases without recalibration, the displayed flow can be off by up to 20 percent. We have seen this on customer sites many times. A maintenance team in Jakarta unknowingly installed an oxygen Thorpe tube on an air line and only noticed the error when patient complaints increased. Here is the thing: even small leaks at the inlet fitting will cause a floating float to bounce, giving false low readings.
Frequently Asked Questions
How do I clean a Thorpe tube flow meter?
Remove the polycarbonate shield, extract the float and tube. Clean with a mild detergent solution. Do not use alcohol or solvents. Replace the O-ring if dry. Silver does not sell cleaning kits, but we can recommend local suppliers.
Can I use one flow meter for multiple gases?
No, each gas needs a dedicated flow meter because the density and viscosity affect calibration. Some dial selectors have interchangeable gas-specific scales, but you must recalibrate. We suggest using a separate device per gas type.
What output signals are available for remote monitoring?
Our thermal mass flow meters provide 4-20 mA analog output, pulse, and RS485 Modbus. You can connect them to a central nursing station PLC or digital chart recorder. We also supply paperless recorders for historical data logging.
Do you supply flow meters with NIST or DISS fittings?
We can offer process connections with BSP or NPT threads. For medical-specific connectors, we can provide adapters upon request. Please specify the standard in your enquiry.
What is the delivery time for 10 units of thermal mass flow meter?
Standard delivery is 2 to 3 weeks from our Nanjing factory. For urgent orders, we can expedite to 5 working days. Contact us with quantity and gas type.
Send us your gas type, pressure (bar), temperature (degree C), pipe size (DN or inch), and flow range (LPM). Email [email protected], call +86-135-1213-1526, WhatsApp 86-135-12131526, WeChat +86 13512131526. Silver Automation Instruments, Nanjing, China.