How Much Water is Needed to Increase Pipeline Pressure for a Hydro Test?

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Discussion Overview

The discussion revolves around calculating the amount of water needed to increase the pressure in a pipeline during a hydro test. Participants explore various methods and considerations for determining the required water volume, taking into account factors such as pipeline material, pressure changes, and water density.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant calculates the volume of a 2" pipeline that is 6.5 km long and seeks to determine how much additional water is needed to achieve a pressure of 10 barg.
  • Another participant mentions that tables exist which provide the density of water at different pressures, suggesting that the difference in pressures can help calculate the additional water required at constant volume.
  • A follow-up question asks for the source of these density tables.
  • A suggestion is made to search online for "water density table" or similar terms to find the necessary information.
  • Another approach is introduced, referencing the bulk compressibility of water as a factor in the calculations, with a specific value provided.

Areas of Agreement / Disagreement

Participants express different methods for calculating the required water volume, indicating that there is no consensus on a single approach. The discussion includes multiple perspectives on how to account for pressure changes and material properties.

Contextual Notes

Participants acknowledge that factors such as pipeline expansion under pressure and temperature variations may influence the calculations, but these are not fully resolved within the discussion.

G Neilson
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I am trying to figure if there is a calculation for working out how much water I would have to pump into a system to increase the pressure.

For example, I have a pipeline which is 2" and 6.5 km long. I worked the volume out using πr² × height so π×0.0254m²×6500m which is 13.17m³.

How do I now determine how much more water I require to increase the pressure to 10 barg?

I know the material of the pipeline matters but I am just looking for a ballpark not exact accuracy. I also know that temperature matters but for this case let's say the temperature remains constant again this is because I require a ballpark figure.

It is for a hydro test (pressure test) of the pipe. we are taking it up to 150% of its design pressure which is 414 barg so 621barg
 
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There are tables giving the density of water at different pressures. The difference between the two pressures allows to figure out how much water has to be added at constant volume. If your pipeline expands under pressure, this could be the dominant effect, then you have to know how much it expands.
 
mfb said:
There are tables giving the density of water at different pressures. The difference between the two pressures allows to figure out how much water has to be added at constant volume. If your pipeline expands under pressure, this could be the dominant effect, then you have to know how much it expands.

Do you know where can i Find these tables?
 
Google "water density table", "water density table pressure" or related things?
 
Another approach is to use the bulk compressibility of water, which is on the order of 5 x 10-4/MPa.

Chet
 

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