5 replies to this topic

[CS10]

Hello Everyone,

 

I am working on calculating what is the pressure at the outlet nozzle of the top loading arm to NGL road tanker.

 

I have done the caclulation using HYSYS to determine the pressure at the inlet nozzle (N1) of loading arm. But, I don't know what is the pressure left at loading arm outlet nozzle (N2) connected to the tanker since there is no Isometric drawings to get the data (i.e. length, elevation, fittings)

 

How can I calculate the pressure at outlet nozzle (N2) of the top loading arm?

 

I know the flow rates and the total piping pressure drop until N1 from HYSYS model. Can I calculate the pressure at outlet nozzle (N2)???

 

Please see the loading arm sketch

 

Thanks in advance.

Attached Files

•  Loading Arm Sketch.xlsx   10.97KB   16 downloads

Edited by CS10, 06 November 2017 - 12:08 AM.

[Pilesar]

Where the outlet nozzle of the loading arm meets the road tanker, the pressure will be the same as the road tanker. How can you calculate pressure at N1 without knowing the pressure at N2? Work backwards: recalculate pressure at N1 based on pressure at N2. Location of control valves matter to your calcs. Consider the effect of flashing liquid.

[CS10]

Thanks Pilesar

 

The pressure at N1 is calculated from the Hydraulic model from transfer piping (until N1 connection), the pressure at the end of transfer piping connect to N1, I considered as N1 pressure which is ~4.5 barg.

 

I believe there should be some pressure drop across the loading arm and will reduce the N2 pressure. Can I calculate the N2 pressure (with knowing the N1 pressure and the flow rates)?

[Pilesar]

CS10 asks 'Can I calculate the N2 pressure (with knowing the N1 pressure and the flow rates)?'

Unfortunately, you do not know the pressure at N1 because you calculated it incorrectly. The pressure at N2 is the road tanker pressure. I find I am repeating myself. Maybe someone else can explain it with more clarity. Good luck.

[latexman]

CS10,

 

By studying how the road tanker is filled will determine the pressure in the road tanker (N2).  Is it a closed system?  What is the pressure when filling is started?  What is the pressure when filling has ended?  Is it an open system?  Is the road tanker vented back to the NGL tank?  You must first determine (or obtain data, if existing) the pressure in the road tanker while filling.  That pressure in the road tanker is the resisting, downstream pressure that must be overcome to enable flow of NGL.  Once you know the pressure in the road tanker (N2) and the pressure drop caused by NGL flow, you can calculate pressure at loading arm inlet (N1).  As Pilesar said work backwards, from downstream to upstream.

[CS10]

Thanks PileSar and latexman for your advise

 

My apology for the confusion due to my wrong steps for the calculation. I will try to recalculate the Pressure using backward calculation from N2 to N1.