Increase pipe schedule - influence on pump ?
Increase pipe schedule - influence on pump ?
(OP)
Hi
We have some corrosion problem in my acid piping and I would like to increase the pipe schedule from SCH 10 to SCH 40 for 3'' and 6'' diameter (SS316L).
I want to know if the increase in pressure drop (lowering the ID) will affect my pump (total Head). Is it significant ?
How can I confirm if I can do the change for a 700 ft long corroded piping line? Do I have to calculate all my system and simulate the modification ? It should exist a table of something to see if there is a significant influence. I don't even think that SCH was original on the design...
Thanks for you input
Cedric
We have some corrosion problem in my acid piping and I would like to increase the pipe schedule from SCH 10 to SCH 40 for 3'' and 6'' diameter (SS316L).
I want to know if the increase in pressure drop (lowering the ID) will affect my pump (total Head). Is it significant ?
How can I confirm if I can do the change for a 700 ft long corroded piping line? Do I have to calculate all my system and simulate the modification ? It should exist a table of something to see if there is a significant influence. I don't even think that SCH was original on the design...
Thanks for you input
Cedric





RE: Increase pipe schedule - influence on pump ?
<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying " Damn that was fun!" - Unknown>>
RE: Increase pipe schedule - influence on pump ?
For example: new diameter .9 times original, new pressure drop 1.23 times original pressure drop.
Ted
RE: Increase pipe schedule - influence on pump ?
It is a 1000 ft line in the aire with difficulty of access. I want to make the calculations only if necessary.
RE: Increase pipe schedule - influence on pump ?
I do not understand your last post
<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying " Damn that was fun!" - Unknown>>
RE: Increase pipe schedule - influence on pump ?
ie, known friction loss in pipe A = ( dia A / dia B)^5
RE: Increase pipe schedule - influence on pump ?
<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying " Damn that was fun!" - Unknown>>
RE: Increase pipe schedule - influence on pump ?
Ted
RE: Increase pipe schedule - influence on pump ?
However, increasing the schedule of piping connected to a pump will adversely affect mechanical loads imposed on the pump.
Edward L. Klein
Pipe Stress Engineer
Houston, Texas
"All the world is a Spring"
All opinions expressed here are my own and not my company's.
RE: Increase pipe schedule - influence on pump ?
RE: Increase pipe schedule - influence on pump ?
"If stupidity got us into this mess, then why can't it get us out?" - Will Rogers (1879-1935) ***************
http://virtualpipeline.spaces.live.com/
RE: Increase pipe schedule - influence on pump ?
Further, lowering the friction loss which was the original post by increasing pipe dia. will also have the effect of lowering discharge pressure.
Don't have time to check the relative thrusts -- increased dia./ lower pressure / smaller dia./ higher pressure, too busy playing builder renovating my apartment.
RE: Increase pipe schedule - influence on pump ?
I'm not going to check it here either, primarily because nobody asked about it.
"If stupidity got us into this mess, then why can't it get us out?" - Will Rogers (1879-1935) ***************
http://virtualpipeline.spaces.live.com/
RE: Increase pipe schedule - influence on pump ?
RE: Increase pipe schedule - influence on pump ?
[;sigma]t = dT * α * E
F = σ * x-sect Area
and imparts compressive stress on the pipe when temperature is increased.
****************************
Pressure stress in the axial direction Sa = Poisson's ratio (v = around 0.25) * pressure (or hoop) stress,
Sa = v * PD/2/t, which acts to shorten the pipe length or cause an axial tensile stress, if the pipe is restrained in the axial direction. So it tends to reduce the axial thermal stress, if that stress was caused by the usual increasing temperature.
If hoop stress is limited to say, yield stress / 2, pressure stress = 0.25 * YS/2, or 0.125 * YS
Steel pipe thermal stress is about 0.000006/Fº * E * dT, or
0.000006 * 30,000,000 = 180 psi/Fº
Take a 6" discharge pipe change from sch 10 to 40, dT=50 Fº
disch pressure 700 psig. Axial pressure stress reduces to less than 1/2 with the heavier WT, but axial thermal stress increases by 2 from 26 Kips to 54 Kips with the x-s area, if fully axial restrained. Since pressure stress, when restrained, is tension any compressive thermal stresses are reduced. The net effect to the above being that the 6" sch 40 net axial load is almost 3 times the axial load of a 6" sch 10, in a fully restrained case, holding discharge pressure equal in both cases. However, if he doubled the discharge pressure, the increased axial tension would reduce the compressive thermal load in the sch 40 such that the net axial compressive load becomes only 2 x that of the sch 10. Hopefully when the discharge pressure is reduced, the pipe cools off.
The most critical stresses can be generated in cold piping, where axial tension from both thermal and pressure cases add together and total shear stress is increased. The only good thing about that is that net axial tension does not buckle pipe.
Thermal stress * x-sect area is the largest component of change.
"If stupidity got us into this mess, then why can't it get us out?" - Will Rogers (1879-1935) ***************
http://virtualpipeline.spaces.live.com/
RE: Increase pipe schedule - influence on pump ?
"If stupidity got us into this mess, then why can't it get us out?" - Will Rogers (1879-1935) ***************
http://virtualpipeline.spaces.live.com/