Previous in Forum: api 650   Next in Forum: Mechanical
Close
Close
Close
14 comments
Rate Comments: Nested
Guru
Engineering Fields - Mechanical Engineering - New Member India - Member - New Member

Join Date: Aug 2008
Location: City of destiny, INDIA
Posts: 775
Good Answers: 67

Pressure Drop in Piping

08/29/2012 12:37 AM

A 1 km long 20" CS pipe carries oxygen at 17 bar. It has few valves tee and bends in route. I want to calculate pressure drop. I tried from books and net but it mostly deals with liquid. Can someone help, how to calculate for different flow rates?

Thanks in advance

Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#1

Re: Pressure drop in piping

08/29/2012 12:46 AM
Register to Reply
Guru
Engineering Fields - Mechanical Engineering - New Member India - Member - New Member

Join Date: Aug 2008
Location: City of destiny, INDIA
Posts: 775
Good Answers: 67
#6
In reply to #1

Re: Pressure drop in piping

08/29/2012 10:59 AM

Thanks lyn, I also had seen this. But it is only for compressed air, not for oxygen. I could see see another calculator, but it require viscosity of gas. I got viscosity too, but at atmospheric pressure.

Register to Reply
Guru

Join Date: Jul 2005
Location: Stoke-on-Trent, UK
Posts: 4496
Good Answers: 137
#8
In reply to #6

Re: Pressure drop in piping

08/29/2012 12:01 PM

I can't imagine it being much different for oxygen, either the viscosity or the pressure drop.

Out of curiosity I compared that formula with the way I normally do it using Fanning friction factor etc. Using air at flow 11300 m3/h to give actual velocity ~ 10m/s, Fanning gives ΔP ~ 0.3 bar, but the formula gives ~ 0.16 bar. Unless I've dropped a cod.

__________________
Give masochists a fair crack of the whip
Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32175
Good Answers: 839
#2

Re: Pressure drop in piping

08/29/2012 3:20 AM

What on earth is a carbon steel pipe doing carrying oxygen?

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru

Join Date: Jul 2005
Location: Stoke-on-Trent, UK
Posts: 4496
Good Answers: 137
#3
In reply to #2

Re: Pressure drop in piping

08/29/2012 4:37 AM

Is that a problem, if the oxygen is dry? (just asking) Aren't oxygen cylinders made of carbon steel?

__________________
Give masochists a fair crack of the whip
Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32175
Good Answers: 839
#4
In reply to #3

Re: Pressure drop in piping

08/29/2012 7:18 AM

And the use of this oxygen?

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru

Join Date: Jul 2005
Location: Stoke-on-Trent, UK
Posts: 4496
Good Answers: 137
#5
In reply to #4

Re: Pressure drop in piping

08/29/2012 8:13 AM

I don't know, he hasn't said. What's the significance?

It seems like a lot of oxygen, maybe steel-making?

__________________
Give masochists a fair crack of the whip
Register to Reply
Guru
Engineering Fields - Mechanical Engineering - New Member India - Member - New Member

Join Date: Aug 2008
Location: City of destiny, INDIA
Posts: 775
Good Answers: 67
#7
In reply to #2

Re: Pressure drop in piping

08/29/2012 11:02 AM

Yes, carbon steel can be used very well for dry oxygen. The only limitation is velocity, normally below 10 m/s.

Register to Reply
Power-User

Join Date: Oct 2009
Location: Central Midwest
Posts: 455
Good Answers: 38
#9
In reply to #2

Re: Pressure drop in piping

08/29/2012 12:29 PM

I agree with Slacker..... carbon steel is a poor choice of material for an oxygen system and is banned by some codes. There are safety issues here

This must be a homework problem.

This is also a huge system. What is the use for this tremendous amount of oxygen ?

Multiple steel mills perhaps ?

__________________
We have met the enemy....and he is us. POGO
Register to Reply
Guru

Join Date: Jun 2010
Posts: 1296
Good Answers: 104
#10

Re: Pressure Drop in Piping

08/29/2012 8:24 PM

Using a simplified method from the Gas Processors Suppliers Association Engineering Data Book (a very good reference, by the way), and using the good ole English units I've waited 40 years for the metric system to replace 'any day', here goes (I had to convert one way, you'll have to convert back the other):

1 km = 3,280 ft 20" pipe, you didn't say, but I'll assume S/80

17 bar ≈ 350 psia Temperature, you didn't say, but I've assumed 80°F

Mol. Wt = 32 Z (Compressibility), I didn't feel like looking up or calculating, so I used 1.0

gives a Density = 1.38 lb/ft3

You didn't give flow rate, so I did 50,000 lb/hr, 100,000 lb/hr, and 300,000 lb/hr

@50,000 lb/hr, ΔP = 0.129 psi

@100,000 lb/hr, ΔP = 0.516 psi

@300,000 lb/hr, ΔP = 4.64 psi (dang, that's a lot of O2, and still not much ΔP)

This method assumes fully turbulent flow, which, with your conditions, you have by the time the flow is high enough to give significant pressure drop. Therefore, you can correct it by considering that the ΔP is inversely proportional to the density and directly proportional to the square of the flow rate.

By the way, there are carbon steel oxygen pipelines around Houston, TX from separation plants to refineries/chemical plants. I was told that they have stainless steel sections periodically for 'fire breaks'.

Register to Reply
Participant

Join Date: Jul 2012
Posts: 4
#11

Re: Pressure Drop in Piping

08/30/2012 3:05 AM

if you need to fix the pressure drop, you can install a big tank in the end of the pipe for all type of air and gas.

Register to Reply
Guru

Join Date: Dec 2006
Location: Hop around Toronto, New York & Karachi
Posts: 1876
Good Answers: 19
#12

Re: Pressure Drop in Piping

08/30/2012 6:27 AM

http://www.thermexcel.com/english/program/gasus1.htm

http://softwaretopic.informer.com/pipe-sizing-formula-for-oxygen-gas/

http://www.scribd.com/doc/81023942/68/Table-2-12-Selection-Chart-for-Oxygen-Manifolds

__________________
I not only use all the brains that I have, but all that I can borrow. Woodrow Wilson
Register to Reply
Guru

Join Date: Nov 2007
Posts: 519
Good Answers: 11
#13

Re: Pressure Drop in Piping

08/30/2012 9:31 AM

Get a copy of Crane TP-410. You'll have to read the equation description because they offer 3 or 4 equations for this.

You've run into a problem where you use both metric and english units? What are you working with?

Register to Reply
Guru
Engineering Fields - Mechanical Engineering - New Member India - Member - New Member

Join Date: Aug 2008
Location: City of destiny, INDIA
Posts: 775
Good Answers: 67
#14

Re: Pressure Drop in Piping

09/03/2012 10:24 AM

Thanks all. Now I got an on line calculator for pipes, fittings and valves. only we need to feed pressure, temp, density and viscosity.

Register to Reply
Register to Reply 14 comments
Copy to Clipboard

Users who posted comments:

bigg (1); cingold (1); Codemaster (3); ducon (1); HBR thechnique (1); lyn (1); MJCronin (1); pritam (3); PWSlack (2)

Previous in Forum: api 650   Next in Forum: Mechanical

Advertisement