100 bar / 1451 psi sludge cake pipeline
100 bar / 1451 psi sludge cake pipeline
(OP)
I am in the process of speccing a carbon steel sludge cake pipeline for sizes 1/2" thro 4".
Given pressure is 100 barg (1451 psi), corrosion allowance of 0.04" and at ambient temperature (from table A-1 using an allowable stress of 20 ksi for pipe A106 Gr B).
For the 4" pipe, I've selected class 600 for group 1.1 materials from ASME B16.5, but when I do the calc for the wall thickness using ASME B31.3 I find it comes out at t(nom)=0.23" which is schedule 40 pipe.
When I checked this wall thickness against my 'The Piping Guide' (By David Sherwood and Dennis Whistance), I found for 4" schedule 40 pipe they have listed the design pressure as 604 psi. I realise 'the piping guide' bases the design pressure per ASME B31.1 with an allowable stress of 9000 psi, but I just get the feeling that my calculated results are a little too optimistic as I was expecting to find schedule 80 pipe mated to class 600 flanges.
Can anyone set my mind at ease, and agree/disagree that schedule 40 pipe is acceptable.
Given pressure is 100 barg (1451 psi), corrosion allowance of 0.04" and at ambient temperature (from table A-1 using an allowable stress of 20 ksi for pipe A106 Gr B).
For the 4" pipe, I've selected class 600 for group 1.1 materials from ASME B16.5, but when I do the calc for the wall thickness using ASME B31.3 I find it comes out at t(nom)=0.23" which is schedule 40 pipe.
When I checked this wall thickness against my 'The Piping Guide' (By David Sherwood and Dennis Whistance), I found for 4" schedule 40 pipe they have listed the design pressure as 604 psi. I realise 'the piping guide' bases the design pressure per ASME B31.1 with an allowable stress of 9000 psi, but I just get the feeling that my calculated results are a little too optimistic as I was expecting to find schedule 80 pipe mated to class 600 flanges.
Can anyone set my mind at ease, and agree/disagree that schedule 40 pipe is acceptable.





RE: 100 bar / 1451 psi sludge cake pipeline
Your ANSI 600 flanges look a tad marginal for the pressure also. My table shows them good to 102 bar below 38C which is a really skinny safety margin.
I would tend to use ANSI 900 flanges and Sched 80 pipe and sleep really well at night knowing that if the operation is really 120 bar after it gets started I'm not going to hurt anyone.
David
RE: 100 bar / 1451 psi sludge cake pipeline
You used the word pipeline, so B31.8 would apply, but it is your choice.
You need to document your selection in any case for risk management. Sch 80 would be overkill and maybe going to .250 wall would be better. Same with the flange rateing, its your choice. Give that you have what appears to be a "mostly Harmless" (my appologies to Mr. Adams), you could stay with the lower line rating, agian your call.
RE: 100 bar / 1451 psi sludge cake pipeline
Dcasto, when I did a check for pressure of the 4" pipe (P=2tSE/(D-2tSY)) I found a max pressure of 2199 psi (Using D=4.5", t=0.237" mill tolerance not taken into account, S=20ksi, E=1 for A106 Gr B).
There is one unknown - there is no design temperature for the pipe (That is why I originally assumed ambient), I think I may even select class 900 flanges as at 50 deg C the working pressure for class 600 flanges is 100.2 bar.
RE: 100 bar / 1451 psi sludge cake pipeline
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RE: 100 bar / 1451 psi sludge cake pipeline
I have spoken with another engineer on the same project and he has confirmed that the temperature is to be ambient.
Initially I selected the class 600 (ASME B16.5:2003)which states from table 2-1.1 (Pressure-Temperature ratings for Group 1.1 materials) a working pressure of 100.2 bar at a temperature of 50 deg C. As this project is new and a lead mechanical engineer is still to be appointed, I was hoping to confirm my findings on this forum, so when my calcs are checked they will all be in order.
Biginch, can you confirm that 4" sched 40 pipe (0.237" wall thickness) is acceptable? If not then I may have to select from the next shedule up (i.e. Sched 80 - which would be overkill according to Dcasto)
From my original post the corrosion allowance is 0.04".
Thanks
RE: 100 bar / 1451 psi sludge cake pipeline
Since t<D/6 = 4.5/6 = 0.75",
Then use equation 3a,
P = 2 * t * (SE + PY) / D
Including a minimum weld quality factor of 0.85 (use 1 if seamless)
including a mill tolerance of 0.85
using "other material's" Y value of 0.4
using corrosion allowance of 0.04"
using wall thickness of 0.237"
Allowable stress 20000 psi
P = 2 * (0.85*0.237-0.04) * (20000* 0.85 + P * 0.4) / 4.5
starting with a P of 2000 and iterating for a final solution for P, I get 1579 psig
Nearly 10% higher than 1480 psig, the ambient limit for ANSI#600. Short term surge pressures up to the lowest value of either the ANSI#600 1480 psig + 10% = 1628 psig or the pipe's 1579 psig + 10% = 1737, so that's up to 1628 psig will not need any additonal wall thickness.
4.5" OD x 0.237" WT PIPE and ANSI#600 FLANGES at nominal ambient temps works very well for me.
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RE: 100 bar / 1451 psi sludge cake pipeline
In case I'm not on this forum before the holiday season prevails, a big Merry Christmas to all.
RE: 100 bar / 1451 psi sludge cake pipeline
Steve Wagner
RE: 100 bar / 1451 psi sludge cake pipeline
RE: 100 bar / 1451 psi sludge cake pipeline
David
RE: 100 bar / 1451 psi sludge cake pipeline
http://virtualpipeline.spaces.msn.com
RE: 100 bar / 1451 psi sludge cake pipeline
http://virtualpipeline.spaces.msn.com
RE: 100 bar / 1451 psi sludge cake pipeline
As BigInch so eloquently pointed out, it has nothing to do with "designing it so close", it is simply following the code and then whatever dumps out dumps out and then you can decide which standard wall thickness to use or play around with the SMYS and optimize within the box that is defined.
Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website: www.oil-gas-consulting.com
RE: 100 bar / 1451 psi sludge cake pipeline
I've always had a sore spot with one engineer adding this bit of fat, one engineer adding that bit of fat, another painting it gold.. pretty soon you get a golden elephant with three legs and nobody knows what you really have underneath the hood. I also think, if you're using a code, you're never going to get very near a true limiting state if the product stays within the design conditions. Ex. a design pushing the burst limit in this case might be something like an internal pressure of 2 x 0.197 x 35000/ 4.5 /0.9 to get into the plastic range = 3064 psig. If the A106B is actually 42000, as it probably is, it might even be as high as 4085 psig. When accidents happen, its usually when some process variable has gotten out of hand, the cyclic life parameters, or the corrosion allowance was exceeded without replacement of the material, etc., cures for which are meant to be included elsewhere; not in "adjustments" to the piping codes. I'd just bet you that following a code to the letter will very seldom ever, if ever, be the source of a problem. At least I haven't ever found one single incident where I could have pointed to it. Have I been wrong all these years?
http://virtualpipeline.spaces.msn.com
RE: 100 bar / 1451 psi sludge cake pipeline
Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website: www.oil-gas-consulting.com