robjul
Chemical
- Nov 6, 2007
- 24
Happy New Year to my colleagues!
I was given an assignment to calculate the pressure drop on a 10"ND pipeline where 600MT/hr of refrigerated Propane (-42deg. C) would be discharge from an LPG cargo vessel (via 2,000 KM of submarine pipeline) at the Jetty then, goes 45deg upwards diagonally then horizontally onshore for 500m long up to several "bullet type" storage tanks. I assumed the storage tank temperature would finally be in equilibrium with an ambient temperature of 25deg. C. Discharge static elevation is 25m.
I don't know what condition to use (to based on -42deg. C or 25deg. C) for my pressure drop calculation since I am aware that, with the lenght of the pipeline, Propane will pick-up heat and therefore, cannot assume an isothermal condition. I am thinking of a weighted averaging calculation where an isothermal condition can be assumed for every kilometer or every 100m of pipe lenght then, add the individual pressure drops to get the total. This is of course a tedious calculation but is this a right approach?
Please share if you have any sample calculation or spreadsheet. Actually, my boss prefers a manual calculation because he was used to it during his 1970's schooling and then, I have to countercheck it with an online spreadsheet. I actually had done some manual calculation using Crane's Technical Paper 410 but my counterchecked with an online spreadsheet yielded with an answer 10 times greater than the manual calculation! Hence, obviously as per my engineering "feel", the manual calculation is wrong and can't find the error even with further reviews and checks of the input data and calculations.
My online spreadsheet calculation yielded an acceptable pressure drop but failed on velocity. The criteria I used for a 10"ND line and above is: Allowable velocity = 3.0 - 4.6m/s whilst Allowable max. delta P = 0.45 bar/100m. Are these criteria correct which was just given to me by a colleague.
I had done so many pressure drop calculations in the past but it looks like calculations involving LPG mix, propane & butane is a bit complicated as its density varies along the lenght of a long pipeline.
Indeed, many thanks for the help/assistance.
I was given an assignment to calculate the pressure drop on a 10"ND pipeline where 600MT/hr of refrigerated Propane (-42deg. C) would be discharge from an LPG cargo vessel (via 2,000 KM of submarine pipeline) at the Jetty then, goes 45deg upwards diagonally then horizontally onshore for 500m long up to several "bullet type" storage tanks. I assumed the storage tank temperature would finally be in equilibrium with an ambient temperature of 25deg. C. Discharge static elevation is 25m.
I don't know what condition to use (to based on -42deg. C or 25deg. C) for my pressure drop calculation since I am aware that, with the lenght of the pipeline, Propane will pick-up heat and therefore, cannot assume an isothermal condition. I am thinking of a weighted averaging calculation where an isothermal condition can be assumed for every kilometer or every 100m of pipe lenght then, add the individual pressure drops to get the total. This is of course a tedious calculation but is this a right approach?
Please share if you have any sample calculation or spreadsheet. Actually, my boss prefers a manual calculation because he was used to it during his 1970's schooling and then, I have to countercheck it with an online spreadsheet. I actually had done some manual calculation using Crane's Technical Paper 410 but my counterchecked with an online spreadsheet yielded with an answer 10 times greater than the manual calculation! Hence, obviously as per my engineering "feel", the manual calculation is wrong and can't find the error even with further reviews and checks of the input data and calculations.
My online spreadsheet calculation yielded an acceptable pressure drop but failed on velocity. The criteria I used for a 10"ND line and above is: Allowable velocity = 3.0 - 4.6m/s whilst Allowable max. delta P = 0.45 bar/100m. Are these criteria correct which was just given to me by a colleague.
I had done so many pressure drop calculations in the past but it looks like calculations involving LPG mix, propane & butane is a bit complicated as its density varies along the lenght of a long pipeline.
Indeed, many thanks for the help/assistance.