Density Calculation from specific gravity

[Beginner - Inspector]

I want to calculate the density of crude and Kero Product , the Specific gravity is given at T & P, whether I have to multiply it with 1000kg /m3 (density of water @4 degree Celcius) or I have to find the density of water at that particular temperature and pressure and then multiply with SG.

PLEASE ADVISE !!!

 

[pierreick]

Hi,
To determine liquid density from specific gravity, you multiply the specific gravity (relative to water) by the density of water at the same temperature and pressure
Pierre

 

[Beginner - Inspector]

Hi,
To determine liquid density from specific gravity, you multiply the specific gravity (relative to water) by the density of water at the same temperature and pressure
Pierre

If my liquid sg=0.766 at 244 degree C & pressure = 8.63kg/cm2, what will be its density(liquid) ?

 

[Beginner - Inspector]

If my liquid sg=0.766 at 244 degree C & pressure = 8.63kg/cm2, what will be its density(liquid) ?
whether I have to multiply it by 1000kg/m3 xSG ?

i.e 0.766 x 1000kg/cm3 = 766 kg/m3=density of fluid

 

[pierreick]

I don't understand your question. your reference fluid is vapor at T,P
If you take your data sheet: 147 C, 8.3 kg/cm2 g the density of water is 920 kg/m3 so density of the liquid is 0.76 *920 = 699 kg/m3
Pierre

 

[LittleInch]

View attachment 6639

I want to calculate the density of crude and Kero Product , the Specific gravity is given at T & P, whether I have to multiply it with 1000kg /m3 (density of water @4 degree Celcius) or I have to find the density of water at that particular temperature and pressure and then multiply with SG.

PLEASE ADVISE !!!

I think you're over thinking this.

To me this is just reporting the specific gravity, I.e. relative to water at 4C seems to be the definition. The T and P bit just refered to the SG at that products temperature and pressure. I do not agree with Pierre in this instance. The crude and kero are both liquid at those temp and pressure. You don't change water density to match the product.

Would have actually been easier to write it in kg/m3.....

It makes no sense to keep changing the reference point for SG. I have never ever seen anyone correct the density of water when converting SG into density in kg/m3.

If you look up kerosene density vs temp you get about 760 kg/m3 at 150C

So I believe your calculation in post no 4 is correct.

 

[Beginner - Inspector]

If my liquid sg=0.766 at 244 degree C & pressure = 8.63kg/cm2, what will be density of water i am suppose to consider

 

[LittleInch]

1000 kg/m3, like you said in post no 4.

Your data sheet says SG 0.766 at 147C. Where did 244C suddenly come from. Stop confusing things.

This is from the NPL which is the UK national laboratory. They will know.

What is the difference between density and specific gravity?

Both are used to describe mass and to compare substances

www.npl.co.uk

 

[Beginner - Inspector]

I don't understand your question. your reference fluid is vapor at T,P
If you take your data sheet: 147 C, 8.3 kg/cm2 g the density of water is 920 kg/m3 so density of the liquid is 0.76 *920 = 699 kg/m3
Pierre

If my liquid sg=0.766 at 244 degree C & pressure = 8.63kg/cm2, what will be density of water i am suppose to consider. It will be vapour at 244 C

 

[Beginner - Inspector]

1000 kg/m3, like you said in post no 4.

Your data sheet says SG 0.766 at 147C. Where did 244C suddenly come from. Stop confusing things.

This is from the NPL which is the UK national laboratory. They will know.

What is the difference between density and specific gravity?

Both are used to describe mass and to compare substances

www.npl.co.uk

1000 kg/m3, like you said in post no 4.

Your data sheet says SG 0.766 at 147C. Where did 244C suddenly come from. Stop confusing things.

This is from the NPL which is the UK national laboratory. They will know.

What is the difference between density and specific gravity?

Both are used to describe mass and to compare substances

www.npl.co.uk

244 C is Another case . my intension is not confuse you. please

 

[LittleInch]

If my liquid sg=0.766 at 244 degree C & pressure = 8.63kg/cm2, what will be density of water i am suppose to consider. It will be vapour at 244 C

That's why the response is incorrect. SG does not change the reference density.

 

[Snickster]

My understanding is when you refer to specific gravity it is always relative to water SG = 1.0 at density of 62.4 pounds per cubic foot (1000 kg/m3) density at standard conditions (14.7 psia at 60 F) in US customary units no matter what pressure and temperature of your fluid is.

So at 15 C and atmospheric pressure standard conditions your SG = .844 x 1000 = 844 kg/m3

At 147 C and 8.3 kg/cm3 your SG = 0.76 X 1000 = 760 kg/m3

In other words the SG is not the density of the fluid at P&T divided by the density of water at the same P&T - it is the density of your fluid at P&T always divided by the density of water at standard conditions = 1000 kg/m3.

 

[LittleInch]

My understanding is when you refer to specific gravity it is always relative to water SG = 1.0 at density of 62.4 pounds per cubic foot (1000 kg/m3) density at standard conditions (14.7 psia at 60 F) in US customary units no matter what pressure and temperature of your fluid is.

So at 15 C and atmospheric pressure standard conditions your SG = .844 x 1000 = 844 kg/m3

At 147 C and 8.3 kg/cm3 your SG = 0.76 X 1000 = 760 kg/m3

In other words the SG is not the density of the fluid at P&T divided by the density of water at the same P&T - it is the density of your fluid at P&T always divided by the density of water at standard conditions = 1000 kg/m3.

It looks like it's actually water at 4C.

15 C and atmospheric pressure 101300 is standard conditions for gas.

 

[pierreick]

Hi,
I could be wrong if I refer to the link underneath:

What is Difference Between Liquid, Vapor, and Gas? | THINKTANK

In general, a vapour phase consists of a phase with two different substances at room temperature, whereas a gas phase consists of a single substance at a defined thermodynamic range, at room temperature.

cncontrolvalve.com

This is weird .
Pierre

 

[shvet]

@Inspector
Do not believe them, only the original designer knows what the referenced water temperature (RWT) is as industry standards require the both temperatures to be specified.

ASTM E1547-2017

specific gravity - the ratio of the mass of a unit volume of a material at a stated temperature to the mass of the same volume of a gas-free distilled water at a stated temperature
Specific gravity x/y °C
where:
x = temperature of the material (<units>), and
y = temperature of the water (<unis>)

ASTM D1298-2017

3.1.7 relative density (specific gravity), n - the ratio of the mass of a given volume of liquid at a specific temperature to the mass of an equal volume of pure water at the same or different temperature. Both reference temperatures shall be explicity stated.
3.1.7.1 Discussion - Common referenece temperature include 60/60 °F, 20/20 °C, 20/4 °C. The historic deprecated term specific gravity may still be found.

So your datasheet is a kind of in-house and you should find&ask an original designer or conduct a study. The actual RWT can be any as it is site&case specific both.
Given the SG@60°F (15°C) and assuming that RWT is 60°C per ASTM above you can convert SG to density@60°F, next extrapolate density@60°F to the operating temperature (OT) with a reasonable accuracy, next devide the density@OT°C on the water density at different referenced temperatures (4°C, 15°C, 150°C etc.), e.g. see API TDB A6. The result matching with the datasheet will reveal the designer logic. There is no a magic, just routine calculations.

I would bet on the RWT 15°C.