Fluid dymanics basics ball valve full open vs. half open

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SUMMARY

The discussion centers on the fluid dynamics of ball valves, specifically comparing full open and half open configurations under different pressure conditions. A ball valve fully open at 100 psi allows maximum flow area, while a half-open valve at 200 psi introduces significant restrictions and turbulence. Calculations indicate that a half-open ball valve can reduce effective flow area to approximately 39% of that of a fully open valve, leading to increased turbulence and potential flow issues.

PREREQUISITES
  • Understanding of fluid dynamics principles
  • Familiarity with ball valve mechanics
  • Knowledge of pressure effects on flow rates
  • Experience with flow area calculations
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  • Research the impact of turbulence on fluid flow in piping systems
  • Learn about ball valve sizing and selection criteria
  • Study flow area calculations for various valve types
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Engineers, fluid dynamics specialists, and anyone involved in the design and operation of fluid systems using ball valves will benefit from this discussion.

Mick McCormick
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is there any difference and why ? I have a ball valve with 100 psi jet fuel on one side and atmosphere on the other end ? Is there any difference if o have 100 psi and the valve all the way open vs. say 200 psi and only half way open . Please explain ?
 
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I think there will be a significant difference... for starters, a half-open ball valve has 2 restrictive points (each side of the ball), and depending on the ratio of the size of the ball compared to the size of the hole through it, half-open may only be 30% of the area... This will also introduce a LOT of turbulence
 
I just realized I still have an old Excel calculation I developed to determine to of flow area vs ball valve opening angle; and, taking a quick look at he graph curve of that calculation shows that at 1/2 (45°) open the flow area on each ball end is 39% of the full open area of a full bore ball valve. In addition, there will also be the extreme turbulence issue stated by Rx7man.
 
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