Flowmeter Problems: Investigating a 12l/min Difference

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SUMMARY

The discussion centers on a significant discrepancy of 12 l/min between two calibrated flowmeters—a sapphire float and a tantium float—used for leak testing in a vacuum system. Despite secure connections and prior calibration, the flow rates do not match, raising questions about potential issues when connecting flowmeters in series. Factors such as pressure drops across the upstream flowmeter and inherent design limitations of the flowmeters may contribute to this difference. The inquiry seeks to understand the underlying causes of this inconsistency.

PREREQUISITES
  • Understanding of flowmeter types, specifically sapphire float and tantium float flowmeters.
  • Knowledge of vacuum systems and their operational principles.
  • Familiarity with calibration processes for flow measurement devices.
  • Awareness of pressure drop effects in fluid dynamics.
NEXT STEPS
  • Investigate the impact of pressure drops on flowmeter accuracy in series configurations.
  • Research best practices for calibrating flowmeters in vacuum applications.
  • Explore troubleshooting techniques for flow discrepancies in fluid systems.
  • Learn about the operational limits and specifications of sapphire and tantium float flowmeters.
USEFUL FOR

Engineers, technicians, and researchers involved in fluid dynamics, vacuum systems, and flow measurement who are troubleshooting flow discrepancies in their equipment.

davidgrant23
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Hi there,

I am currently doing leak testing for a piece of equipment. In order to do so I have a flowmeter at the inlet and outlet (of what is essentially a long cylinder) and have air drawn through by a vacuum pump.

Now, the problem is that even with no obvious signs of leaks the two flows did not match. As a result I connected the two calibrated flowmeters (one sapphire float and a tantium float) together with the vacuum pump and compared the two flowrates. There really shouldn't really be any discernible difference between the two as the connections are very secure. However, there is a difference of 12 l/min between them.

Why would there be such a large difference between the two when they are simply connected in series? They have been calibrated by the vendor previously. Are there any inherent problems if you connect flowmeters in series and compare the two flowrates (such as the pressure drop of the upstream flowmeter)?

Cheers,
Dave
 
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Thanks for the post! Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
 
is it...leaking?
 

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