How Do You Calculate Variable Water Pressure in Pipes?

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Discussion Overview

The discussion revolves around calculating variable water pressures in pipes, specifically focusing on how to derive a formula that incorporates factors such as inlet pressure, pipe size, configuration, elevation changes, and friction loss. The context includes both theoretical and practical applications related to fluid dynamics in piping systems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant expresses difficulty in finding a basic water pressure formula that accounts for various factors affecting pressure, including inlet PSI, pipe size, and configuration.
  • Another participant mentions having constants for friction loss and gravity but seeks a comprehensive equation to reference for mixing and matching these variables.
  • A participant shares a link to previous posts that may contain relevant formulas, indicating that they are often referenced.
  • There are inquiries about calculating pressure requirements for pumping crude oil over a long distance using specific pipe dimensions and flow rates, with a request for additional information to assist in the calculation.
  • Another participant suggests using the general energy equation for fluid flow to determine the required pressure, contingent on understanding the system layout.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on a specific formula for calculating variable water pressures. Multiple viewpoints and requests for clarification indicate that the discussion remains unresolved.

Contextual Notes

Participants note the need for additional information, such as sketches or detailed system layouts, to accurately apply fluid dynamics principles. There is also mention of dependencies on specific definitions and assumptions related to the calculations.

metroactus
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ive scanned about 200 closely relevant posts to make sure I am not one of those "here we go again" posts, but can find no basic water pressure formula. Specifically I need to calculate variable hypothetical water pressures (with a final conversion to GAUGE pressure) with a known INLET PSI, comparing pipe size, pipe configuration, change in elevation, etc. Short of a hundred bucks for an engineering book, i can't find this exact formula though a lot are close. I have my constants for friction loss, gravity, inlet psi, angled and reduced pipe fittings, but need the equation that ties all these together to constantly reference as i mix and match to achieve the highest psi possible, or at the least, economically feasible.

thanks in advance to accurate replys
 
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metroactus said:
ive scanned about 200 closely relevant posts to make sure I am not one of those "here we go again" posts, but can find no basic water pressure formula. Specifically I need to calculate variable hypothetical water pressures (with a final conversion to GAUGE pressure) with a known INLET PSI, comparing pipe size, pipe configuration, change in elevation, etc. Short of a hundred bucks for an engineering book, i can't find this exact formula though a lot are close. I have my constants for friction loss, gravity, inlet psi, angled and reduced pipe fittings, but need the equation that ties all these together to constantly reference as i mix and match to achieve the highest psi possible, or at the least, economically feasible.

thanks in advance to accurate replys

Here are some formulas complements of Q_Goest a few posts below...

https://www.physicsforums.com/showthread.php?t=211590

CS
 

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Last edited:
Hey, that looks familiar! lol
 
I have a link to your post Q. It comes in handy quite often.
 
To pumping crude oil (0.9 SG) with distance for 72 km on 8" steel pipe with flow rate as 725GPM and my question is how much the pressure (psi) to do this work ?

Please help ?
 
b4123p said:
To pumping crude oil (0.9 SG) with distance for 72 km on 8" steel pipe with flow rate as 725GPM and my question is how much the pressure (psi) to do this work ?

Please help ?

You need to provide more information. A sketch would be helpful. Make sure to note elevation changes, pipe schedule, etc...

You can apply the general energy equation for fluid flow to find the required pressure once you determine the system layout.

CS
 

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