Pipeline Basics

[Jriad]

What is the relationship between pressure and velocity in a pipeline if any? Is the only reason for high pressures in gas pipelines to compensate for pressure drops?

Thanks,

 

[zdas04]

One is the inverse square of the other. Sure, but there may be other reasons.

David

 

[Montemayor]

There is a definite relationship between pressure and velocity in a pipeline. It is called Specific Volume - which is the inverse value of the density of the gas at the flow temperature and pressure.

It should be obvious that, for a given fixed mass flow, as the flow pressure increases, the specific volume decreases and the resulting velocity decreases as well. Conversely, as the pressure decreases, the specific volume increases and so does the gas velocity. The latter effect is exactly what happens in a gas transport P/L. As the compressed gas travels downstream, it suffers pressure drop due to flow resistance and friction. Consequently, its velocity starts to increase as the pressure drops along its route.

High pressure is employed in P/Ls not only for allowing for pressure drop. It also adopts to the economic justifications for the P/L since the incentive is to transport as economically as possible. This has to do with the max. allowable pressure for the given pipe diameter and schedule.

 

[Ashereng]

In a general sense, you can say that high pressure is primarily for pressure loss. If high pressure is not needed, most P/L operator would chose to go lower pressure, to save money.

High pressure costs money - not just in the compressor (gas) and pumps (liquid), but piping, fittings, valving, etc.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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