head pressure oil versus water in psi

[kynnhoj]

Hello, I'm in need of a head pressure factor for 1' of water versus 1' of oil (say, 30 weight viscosity) . I have found a factor of .43 psi for 1' of water and oil is less dense than water so I know the figure should be less than .43 psi. Any help on this matter would be appreciated. I don't have a specific gravity on the oil either although I suspect it is around .90 (1.0 for water)Thanks, John

 

[CarlB]

PSI/ft for water = 62.4 pcf/144 sq. in = 0.433

If s.g. is 0.9, the PSI/ft = 0.433 x 0.9 = 0.39

 

[zdas04]

You can convert API gravity to Specific Gravity (relative to water) by

SG = 141.5 / (131.5+APIGravity)

so 30 degree API crude would be

SG = 141.5 / (131.5 + 30) = 0.876

Which makes the hydrostatic gradient:

Gradient = 0.43 * 0.876 = 0.377 psi/ft

Now what I don't know is if SAE 30 weight is similar to the API 30 degree crude (I typed the above before I realized that you had asked about 30 weight, not API grades and thought it might be useful to leave it).

David

 

[BigInch]

SAE 30,
SG=0.912

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[Artisi]

Pressure in PSI = head in feet x sp gr / 2.31

using SG 0.912

1 x 0.912 / 2.31 = 0.398 psi

 

[25362]

It all depends on the accuracy required. When speaking of density of liquids ([ρ]) it would be better to state the temperature. For oils these are:

[ρ] = [ρ]_re^k(T-T_r)​

where
[ρ]_r, kg/m³, is the density at the reference temperature T_r, [K]
k is an exponent of temperature-density dependence (typically = 0.001/K)

A grade 50 base oil could also have a density of 888.7 kg/m³ at 10^oC, while that for water would be 999.2 kg/m³ resulting in a ratio of 0.8894.

The ratio at 60^oC, would be 0.8787.

 

[BigInch]

Vale. I knew somebody would say that. I always give SG and APIº values to std temp, unless noted otherwise. (60ºF)

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com