Liquid Pipeline Pressure drop 1

[SamSnead]

Hi all,

Is there a rule of thumb for the maximum pressure drop in a liquid pipeline (psi/100 ft)? I am used to sizing gas plant piping and haven’t done liquid a whole bunch.

Since liquid is an incompressible fluid, I will expect the pressure drop to not be as significant as experienced in gas pipelines. But, what is the rule of thumb when sizing a liquid pipeline?

Any assistance is greatly appreciated.

Sam

 

[bimr]

Reasonable pipe velocities depend on the application. There is no correct velocity for all applications. Here is a general guideline.

Reasonable Velocities for the Flow of Water through Pipe:

Boiler Feed.............8 to 15 ft/sec
Pump Suction ............4 to 7 ft/sec
General Service.........4 to 10 ft/sec
City.......................to 7 ft/sec
Transmission Pipelines...3 to 5 ft/sec

Go to a basic hydraulics book. Try Cranes Technical Paper 410 as a reference for the above velocities.

http://www.eng-tips.com/viewthread.cfm?qid=111206

http://www.amazon.com/Fluids-Through-Valves-Fittin...

 

[SamSnead]

I am familiar with the velocities. My question is about pressure drop – is there a rule of thumb? 0.1 psi/100 ft? 0.5 psi/100 ft? 1 psi/100 ft?

 

[bimr]

The fluid velocity sets the pressure drop. Liquids pressure drops are more significant than gas pressure drops. For 3-Inch old steel pipe:

4 ft/sec corresponds to 1.8 psi/100 ft pressure drop
7 ft/sec corresponds to 4.9 psi/100 ft pressure drop

 

[Latexman]

About what size line? 1"? 6"? 24"?

5 ft/sec of water will give about:
6 psi/100 ft in 1" pipe
0.6 psi/100 ft in 6" pipe
0.12 psi/100 ft in 24" pipe

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

 

[EmmanuelTop]

See attached "the rules of thumb".

There are no general guidelines on pressure drop - each application is different and requires careful considerations. Different rules apply for gravity lines, pump suction, pump discharge, viscous or non-viscous liquids, etc. Sometimes the process itself requires minimization of pressure drop (e.g. to prevent vaporization of flashing liquid etc.).

See also some of the links below.

http://petroleumcorner.com/line-sizing-criteria-philosophy/

http://www.cheresources.com/invision/topic/16799-line-sizing-criteria-as-per-different-standards/

(you need to be registered in order to download attachments)

Dejan IVANOVIC
Process Engineer, MSChE

 

[EmmanuelTop]

Here is Excel file referenced in the second link - developed by Ajay and available for free download at ChE Resources.

Dejan IVANOVIC
Process Engineer, MSChE

 

[Chemitofreak]

Just for clarification

Pipeline is a long series of Pipes usually of large diameter often underground with few fittings & equipment's mostly Pumps & Valves mainly to control the flow, that are laid with an intention to transport any fluid whether liquid or gas over long distances or cross country.

Piping is a large series & networks of Pipes within the well defined boundaries of the plant/plot with all fittings & equipment's like Pump, Valves, Unions & other Miscellaneous items with an intention to transfer fluid from one facility to another within those boundaries as required

All the aforementioned posts are talking about hydraulics of piping.



Dinesh S SHELATKAR
Process Engineer

 

[LittleInch]

Sam,

Is there a rule of thumb - not really as there are too many variables.

As stated before what you get is a range of generally accepted velocities which you turn into pressure drop. Viscosity and temperature has a big impact on pressure drop in liquids so what is acceptable for say gasoline, might no be for heavy fuel oil.

for long distance pipelines, about 1.8 to 2.2 m/sec has proven to be the most economical between larger pipe, lower pressure drop versus smaller pipe,, higher drop. Pressure drops of about 0.5 to 1.0 bar/km would be good for long pipelines (0.2 to 0.4 psi/100')

Shorter lines the economic velocity increases.

The often quoted maximum velocities of 3m/sec and 4.6 (aka 15 ft/sec) are nothing more than guides or a misreading of e.g. API 14E.

Higher liquid velocities and pressure drops often become subject to things like liquid surge effects (aka water hammer), electrical charge etc

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

Water transmission pipelines typically have a 0.1 psi/100 ft pressure drop.