Pressure Drop per Unit Length
Pressure Drop per Unit Length
(OP)
Hi guys. I got one small question. What does the quantity pressure drop per unit length mean (bar/100m, for example) and what is it for? Thanks a lot!
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Pressure Drop per Unit Length
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RE: Pressure Drop per Unit Length
RE: Pressure Drop per Unit Length
Good luck,
Latexman
RE: Pressure Drop per Unit Length
@Artisi: Yes, I am referring to pressure drop for fluid thru a pipeline.
@Latexman: I'm sorry but from what I see in the hydraulic calculation results, this value is a lot higher than the "plain" pressure drop. If I do multiply this pressure drop per unit length to the pipe length, I am not arriving to the total pressure drop of the pipe.
What's its use anyway? I'm just overly curious about the term because we continue to include it in the calculation results. Sure I do understand pressure drop but about the term I'm asking, I do not get its sense at all.
Again, thanks a lot. I've been reading a lot in this site so your names are familiar to me. I'm so glad to get an answer from you guys.
RE: Pressure Drop per Unit Length
The first use is one that I personally use quite often. The number that works for me is on pipes smaller than 16 inch I use 15 psi/mile. On larger pipes I use 5 psi/mile. Both numbers result in acceptable velocities at a wide range of operating pressures. The reason for the lower acceptable velocity in big pipes is the (occasionally invalid) assumption that big lines tend to be dehydrated and the risk of liquids accumulations is lower so slower velocities are effective.
If I have a 500 mile pipeline that starts at 1,000 psig and the minimum acceptable pressure is 600 psig and I'm willing to accept 5 psi/mile then I need a compressor booster station about every 80 miles. If the acceptable pressure drop is 2 psi/mile then I can go 200 miles between stations but the same size pipe can move less gas.
David
RE: Pressure Drop per Unit Length
RE: Pressure Drop per Unit Length
David - it's common practice in the chemical industry to use pressure drop/length for liquids.
Good luck,
Latexman
RE: Pressure Drop per Unit Length
Pipe fittings' resistance can be converted into piping equivalent lengths. See, for example,
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RE: Pressure Drop per Unit Length
Pressure drop/length is a scoping tool. It is far from precise. Adding fittings and equivalent pipe lengths is much like adding micro meter marks on a meter stick. I use it for statements like "going into a compressor station with 100 psig suction I need to be able to live with 250 psig at a well about 10 miles away, what size pipe can do that for the projected volumes (and what compression hp will I need at the well)". It gets me into the design universe and then I do Engineering to decide on pipe sizes, wall thickness, required water removal equipment, etc.
David
RE: Pressure Drop per Unit Length
Good luck,
Latexman
RE: Pressure Drop per Unit Length
"The only liquid I deal with regularly is water from gas wells and the typical level of Engineering in that field is about the same as you'd find on a family farm in the 1850s."
That's still ahead of the technology in our civilization north of the border. We have only recently discovered fire. Accordingly, we often welcome finding water in our gas wells.
Regards,
SNORGY.
RE: Pressure Drop per Unit Length
On the other hand, water systems up there are just as primitive as everywhere else in the world. You can't sell produced water so management doesn't want to spend any money on it. It amazes me how much gas gets shut in because there is no place to take water.
David
RE: Pressure Drop per Unit Length
That said, in a lot of fields and wells, the economics and margins are such that some gas just isn't worth going after.
Regards,
SNORGY.
RE: Pressure Drop per Unit Length
Pressure drop/unit length is the pressure that you loose when any fluid ( gas, fuel oils, water) flow trough a pipe.
This information will be mainly used to acureately size the equipment upstream and down stream of pipes.
upstream equipments could be compressors, pumps.
Down stream equipment will be the burners etc.
so pressure drop is not equal to the line pressure.
but if you add the pressure drop and outlet pressure you should total pressure or the inlet pressure.
hope this explains your question.
RE: Pressure Drop per Unit Length
Have you read the posts in this thread? It is really bad Internet etiquette to read the original question and skip to the end where you post zero information that hasn't been provided in the posts you skipped.
David