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Air Flow Meter LPM: Medical Gas Thorpe Tube Volumetric Visual Scales
Quick Answer
A Thorpe tube air flow meter with LPM volumetric visual scales gives direct gas flow reading in liters per minute. The scale is printed on the tube so a nurse, engineer, or technician can read flow without corrections. Silver Automation Instruments supplies these variable area flow meters with NPT, BSP, and custom scale options for medical gas distribution and OEM replacement.
What Is a Thorpe Tube Flow Meter for Medical Gas
A Thorpe tube flow meter is a vertical variable area flow meter. The glass or polycarbonate tube has a tapered bore. Gas enters at the bottom and pushes a float or ball up the tube. The float position lines up with a direct reading scale in LPM. Medical gas versions use a clear tube and a printed scale for oxygen, air, nitrous oxide, or carbon dioxide. The outlet can be open or hose barbed. In most designs the valve is located on the outlet side. That valve position protects the tube from pressure shock when the unit is switched on.
LPM Ranges and Volumetric Visual Scales
Most replacement Thorpe tube air flow meters cover 0 to 1 LPM, 0 to 2 LPM, 0 to 5 LPM, 0 to 10 LPM, or 0 to 15 LPM. Some laboratory purge panels use 0 to 30 LPM or 0 to 50 LPM. The scale is volumetric at normal pressure and temperature. A direct reading scale removes the need for correction charts. Accuracy depends on gas viscosity and inlet pressure. For oxygen at 50 psi or about 3.4 bar, a typical full scale accuracy is 3 percent to 5 percent. Always confirm the scale gas because a flow meter calibrated for air will not read correctly on carbon dioxide.
Gas Types, Wetted Parts, and Calibration
We see oxygen, medical air, nitrous oxide, carbon dioxide, and nitrogen in gas therapy and laboratory lines. Each gas has a different density and viscosity. A direct reading LPM scale must match the operating gas. Silver Instruments provides single gas scales and dual gas scales. The wetted parts can be 316L stainless steel, PTFE, polycarbonate, or borosilicate glass. Medical gas service requires clean parts and no oil residue. Ask about degreased cleaning before shipment if the flow meter will be used for oxygen. Here is the thing. Small dirt in an oxygen line is a serious safety issue. We clean and pack each tube carefully.
Connection Types and Mounting Options in Different Countries
Thorpe tube flow meters connect to a gas source in a few ways. Common industrial threads include 1/8 inch NPT, 1/4 inch NPT, G1/4, and R1/4. Some medical wall terminal units in Australia, New Zealand, Saudi Arabia, Vietnam, and the Philippines use different quick connect fittings. In practice, most replacement buyers send us a photo of the old flow meter and the inle
How to Order a Thorpe Tube Air Flow Meter Without Guesswork
The fastest way to get a quote is to send four data points. Describe the gas or gas mixture. Give the flow range in LPM. Give the inlet pressure in bar or psi. Give the connection thread or terminal type. Also state whether the outlet is open or barbed. But most engineers skip this part and then find the scale is wrong for the gas. We have seen this on customer sites many times. A small detail like a 0 to 5 LPM scale for CO2 instead of air changes the reading by more than 20 percent.
Common Applications Beyond Medical Gas
The same LPM visual scale flow meter is used in laboratory purge lines, oxygen concentrator test benches, biogas monitoring, food packaging gas flush lines, and laser gas brazing. In these jobs the flow meter is not always called a medical device. The flow meter is called a variable area flow meter. Silver Instruments is an industrial flow meter supplier for OEM and distribution users. You get a clean accurate tube at a practical price without long lead times typical of some medical brand replacements. Last year a laboratory gas panel builder in Vietnam asked us for 120 units with 0 to 5 LPM air scales and G1/4 threads. We shipped in four weeks.
FAQ
What does LPM mean on a Thorpe tube flow meter?
LPM means liters per minute. The scale shows volumetric flow at normal conditions. The float position gives direct reading in LPM.
Can I use a medical gas Thorpe tube flow meter for oxygen and air?
You can if the unit has a dual scale or if the scale is calibrated for the gas you are using. Do not assume air and oxygen scales are the same. Oxygen has a different density than air. Send the gas type before ordering.
What inlet pressure does a Thorpe tube flow meter need?
Most medical gas systems supply 50 psi or about 3.4 bar. You can order units for lower or higher pressure ranges. Tell us the pressure and we will check the float and tube combination.
Do you supply replacement Thorpe tube flow meters for OEM equipment?
Yes. Silver Instruments supplies replacement flow meters with custom scales for OEM users in Southeast Asia, Oceania, Latin America, and the Middle East. Send the old unit photo and your target LPM range.
How do I get a price and delivery time?
Send your gas type, flow range in LPM, inlet thread, outlet type, and quantity to Silver Instruments. Call +86-25-68650347 or message WhatsApp +86-25-52155837. For WeChat use +86 15365082610.