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

[paulazanor]

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

 

[prex]

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 , where you can take [α]_f[Δ]T=[Δ]V/V and [α]_v[Δ]T=0. There you'll find also the compressibility of water.

prex
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[chicopee]

You are missing one closing parenthesis in your formula.

 

[paulazanor]

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)