Determine equivalent vacuum for water depth

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SUMMARY

The discussion focuses on determining the maximum water depth a motor can operate without water ingress by using a vacuum pump to create differential pressure. The maximum vacuum of the pump is specified as 25 inches of Hg, which translates to 337.7 inches of H2O or 28 feet of water. The correlation between vacuum and pressure is essential, and the formula involving the density of mercury (ρg h) is crucial for these calculations. Understanding these relationships allows for accurate assessments of motor capabilities in submerged conditions.

PREREQUISITES
  • Understanding of vacuum pressure measurement (inHg and inH2O)
  • Basic principles of fluid mechanics, specifically hydrostatic pressure
  • Knowledge of the density of fluids, particularly mercury and water
  • Familiarity with vacuum pump specifications and performance metrics
NEXT STEPS
  • Research the relationship between vacuum pressure and water depth using the formula ρg h
  • Explore the specifications and limitations of vacuum pumps, particularly those rated for 25 inches of Hg
  • Investigate the effects of fluid density on pressure calculations in various applications
  • Learn about motor specifications for submerged operation and their correlation with pressure differentials
USEFUL FOR

Engineers, motor designers, and technicians involved in applications requiring submerged motors or vacuum systems will benefit from this discussion.

Jerry Prothro
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Hello, I need to figure out the max water depth a motor will operate without water ingress. The plan is to use a vacuum pump to create differential pressure and correlate that to water depth. My issue is the correlation between the vacuum and pressure. Can someone please provide a formula for determining the equivalent water pressure which the motor can withstand based on the vacuum I can hold? The Max. Vacuum, of the pump is 25 Inches of Hg.

Thanks
 
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I'm pretty sure rho g h will be in there somewhere.
 
Mercury is 13.5 times denser than water , so 25 inHG = 337.7 inH2O = 28 ft of water.
 

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