3 replies to this topic

[applepe]

Hi all, I'm currently confused about this loop (?) that I face while designing my system. So I'm currently tasked to do a hydraulic simulation of a long transmission pipeline. The service is sales gas. I need to deliver 35 MMSCFD of gas. My feed has 500 psig of max pressure and the destination pressure is 750 psig. I developed two option, compressor station at the upstream and compressor station at the downstream.

 

I use pipesim as my tools to do the hydraulic simulation. To use pipesim, you first need to chose the schedule (wall thickness) of your pipeline to do the simulation and after that you'll get the backpresure.  After getting the backpressure, i then can know the op. system of the pipeline and use it as a base to determine my design pressure that will be used for determining the wall thickness. And once i get the wall thickness, i have to re-do the simulation with the new calculated wall thickness, and the backpressure will change too. So it kinda keep me in the loop. I really dont know how to explain this better but im so confused how do i determine the design pressure of a pipeline without getting stuck in a loop like this? Should i just fully rate my pipeline? But then my wall thickness will be too thick and the pressure drop of the pipeline will be bigger too. I read in NORSOK that you can determine the design pressure of compressor using the shut in pressure by adding the maximum suction pressure with 1.3 times the differential pressure and since my system has a compressor too maybe i can use this as a base, but this will lead me in the same loop too.


P.s. as per my last post someone said "my question was not appropriate to be put in this topic and i should move to students forum." guys idk how to tell this i really am a process engineer in a small engineering company and im new. i wish i could ask my supervisor or anyone with more experiences than me but i cant we're all too occupied with our own project. im handling this project alone and i shouldnt be but i dont have any choice.

[Pilesar]

Fully rate the pipeline. Use high design pressure of 1400 psi or greater. This pipe will be in the ground for decades subject to corrosion and the extra thickness is not wasted. This pipeline may be used for other fluids and other conditions in the future. There may be need later for higher pressure or an additional booster station.

[breizh]

Hi,

To add to the discussion:

https://pubs.naruc.o...6E-5DACB1B36C53

 

https://info.citizen...ribution-system

 

design pressure is always much higher than operating pressure. Let say 2 times the operating pressure.

 

Breizh

[Dacs]

You need to do a life cycle cost (LCC) to get the optimum pipeline configuration, considering:

 

1. CAPEX of compressor/pipeline cost

2. OPEX due to compressor energy requirement

 

I developed two option, compressor station at the upstream and compressor station at the downstream.

 

 

First option will potentially require a higher rated pipeline but with (potentially) smaller pipeline size and compressor, due to lower volumetric flow. The 2nd option will be the opposite (potential lower rated pipeline but larger pipeline diameter and compressor).

 

I use pipesim as my tools to do the hydraulic simulation. To use pipesim, you first need to chose the schedule (wall thickness) of your pipeline to do the simulation and after that you'll get the backpresure.  After getting the backpressure, i then can know the op. system of the pipeline and use it as a base to determine my design pressure that will be used for determining the wall thickness. And once i get the wall thickness, i have to re-do the simulation with the new calculated wall thickness, and the backpressure will change too. So it kinda keep me in the loop.

 

 

Don't get too hung up on the wall thickness. Start with the wall thickness that can handle the highest expected pressure rating and do your hydraulics. You can finetune your model as you get a better hold of the hydraulic profile.

 

This is an iterative process. If I were doing this, I'll be presenting multiple options with varying compressor location and pipeline sizes, using LCC as a basis to select the best option.

 

When calculating the design pressure, consider surge condition. As a reasonable estimate, calculate an estimate of expected surge pressure (using Jokouwsky equation) in your pipeline. Then do a proper surge analysis. PipeSIM can do that for you as well.

 

i wish i could ask my supervisor or anyone with more experiences than me but i cant we're all too occupied with our own project. im handling this project alone and i shouldnt be but i dont have any choice.

 

 

Don't bite more than what you can chew. It never hurts to ask for help with your superiors. By the end of the day, they'll be accountable if they sign off your design.