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HELP WITH HOW TO CALCULATE THE THEORITICAL VALUES FOR PLOTTING THE PRESURE VOLUME PLOT FOR HYDROTEST

HELP WITH HOW TO CALCULATE THE THEORITICAL VALUES FOR PLOTTING THE PRESURE VOLUME PLOT FOR HYDROTEST

HELP WITH HOW TO CALCULATE THE THEORITICAL VALUES FOR PLOTTING THE PRESURE VOLUME PLOT FOR HYDROTEST

(OP)
Gents,

Am preparing for a hydrotesting job.
I need a formular to determine values for pressure and volume i.e for plotting theoritical DV/DP, which will then be used to compare with the field values to determine volume of entrained air in the pipeline during the hydrotest.

Having a bit of a challenge in the application this formular

DV/DP = V*[ (D/(E*t)(1-V2) +C]

Where V = Volume (gallons)
D = OD inches
t= wall thickness inches
V poisson ratio of steel pipe = 0.3
C =Compressibility of test media (inch3/inch3/psi)

Dont know what THE VALUE OF COMPRESSIBILITY OF WATER in Inch3/inch3/psi

Will appreciate any advise or alternative way around this .

many thanks


RE: HELP WITH HOW TO CALCULATE THE THEORITICAL VALUES FOR PLOTTING THE PRESURE VOLUME PLOT FOR HYDROTEST

I suppose that the V in front of the formula is volume, not Poisson. Also the Poisson's ratio does not have its place in this formula, but its influence is, as always, quite small.
See FAQ378-1339: Pressure increase due to thermal expansion of a trapped liquid , where you can take αfΔTV/V and αvΔT=0. There you'll find also the compressibility of water.

prex
http://www.xcalcs.com : Online engineering calculations
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RE: HELP WITH HOW TO CALCULATE THE THEORITICAL VALUES FOR PLOTTING THE PRESURE VOLUME PLOT FOR HYDROTEST

You are missing one closing parenthesis in your formula.

RE: HELP WITH HOW TO CALCULATE THE THEORITICAL VALUES FOR PLOTTING THE PRESURE VOLUME PLOT FOR HYDROTEST

(OP)
Hello Prex (Structural) and Chicopee, I thank you all for responding.

There are two V s in this formular. First one is Volume (big V) second one is supposed to be small v squared for poisson ratio. i wrote that as V2.

Also there is a clossing parenthesis missing. The correct representation is as shown below. Sorry for the mix up.


DV/DP = V * [ (D/(E*t)(1 - v squared)) +C]
Where V = Volume (gallons)
D = OD inches
t= wall thickness in inches
v= poisson ratio of steel pipe = 0.3
C =Compressibility of test media (inch3/inch3/psi) (inch3 = cubic inch)

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