Where are S.G. or M.W. measurements generally used? 1

The density, specific gravity or molecular weight apply to nearly all vapor or liquid calculations for flow meters, control valves or related pressure drop calculations. Some are assumed constant for basic calculations and others are measured. The variable hydrogen composition within a propylene mixture (perhaps liquid) may be desirable. In general the online explosion-proof properties of the measurement are important for any such field instruments. Propylene may be more important in petrochemical plants than some refineries.

For a gas - SG and MW are the same - its just a conversion factor. SG is MW/29 - so same-same

Best regards

Morten

For an ideal gas, but that was hardly the question. Probably the answer for Robin is whereever it is safe to do so.

For any gas!

SG=MW/29 - no matter what condition you have - its a reference.

Best regards

Morten

ok - it may be 28.9 - but that wont change that its a reference. Probably made by some non-chemist

Best regards

Robinhud,

I don't know what company you are working for and what is your job function.But is very surprising that you are asking some one out side your company to tell you where and how your company products are being used in the industry.Stop relying on others too much and start thinking yourself.

Density (and viscosity) are also used as quality control parameters.
Molecular weight is a measure of quality used in various reactions such as polymerisation.
Taken together density and viscosity can provide information on the parafinic content (the viscosity gravity constant, ASTM D2501 - 91(2005)) and together they can also be used to derived a measure of molecular weight. everal ASSTM standardss for this and a paper here: ASTM and ISA are good sources of information on the use of various measurements.
Try a search within there publications.

JMW

JWM - thanks for the links - D&V are my fleid. The ASTM D2501 and MW from D&V are new ones on me and I'll check these out.

Pumpsonly, its only since learning of compressor surge control that I discovered how MW can be useful for control. I'm unfamiliar with refineries and hence asking the experts for other similar applications.