Specifying Specific Specific Gravity
Specifying Specific Specific Gravity
(OP)
I am a recent graduate.
I am sizing some PSVs for a natural gas compressor station.
On the spec sheets the vendor gave me it asks for Oper. Sp. Gr.
Since HYSYS is not giving me a SG in the properties tab (other than the petroleum SG(60/60) which I am not sure what this is.
The MW of the gas is 20.78. So in other work I have been doing, I have reported the SG to be 0.72, (20.78/28.85).
However I am confused about the wording Oper. Sp. Gr.
Does this mean that I take the mass density of the gas at operating conditions (120F, 1200psig)
and divide it by the mass density of air at 120F, 1200psig.
If so the SG would be 0.91.
Any help is much appreciated.
Thank you.
I am sizing some PSVs for a natural gas compressor station.
On the spec sheets the vendor gave me it asks for Oper. Sp. Gr.
Since HYSYS is not giving me a SG in the properties tab (other than the petroleum SG(60/60) which I am not sure what this is.
The MW of the gas is 20.78. So in other work I have been doing, I have reported the SG to be 0.72, (20.78/28.85).
However I am confused about the wording Oper. Sp. Gr.
Does this mean that I take the mass density of the gas at operating conditions (120F, 1200psig)
and divide it by the mass density of air at 120F, 1200psig.
If so the SG would be 0.91.
Any help is much appreciated.
Thank you.





RE: Specifying Specific Specific Gravity
if you have doubts call the vendor asking to explain
RE: Specifying Specific Specific Gravity
If you are not sure what HYSYS is giving you - you need to ask youself the question "Am I competent to use HYSYS?" If you are not sure of the outputs from HYSYS then ask someone who does in your Company. Remember GIGO is the acronym!!!
RE: Specifying Specific Specific Gravity
In any case I would ask the vendor for clarifying this input data as well as stating the reference conditions (0 degC, 15degC, 20 degC, 1bar, 1atm, etc. etc.).
Dejan IVANOVIC
Process Engineer, MSChE