Thin WallThick in Large Diameter
Thin WallThick in Large Diameter
(OP)
Hello every one,I am a new member
As per B31.3 304.1.3, D/t > 100, I am following the procedure outlined in the BPVC-VIII-1, UG28,UG29,UG30 I am trying to determine the minimum wall thickness required under external pressure, and the required stiffening ring. "A" factor that I found falls to the left material/temperature line chart.
the design pressure in my case is 0.7 bar (internal pressure). does it mean that external pressure is just atmospherique pressure?
Anyone who has performed or familiar with such calculation, his/her help would be very appreciated.
NB:
- I made a search in this forum, I didnot find answers to my questions.
Thanks in advance for your help..
Dj
As per B31.3 304.1.3, D/t > 100, I am following the procedure outlined in the BPVC-VIII-1, UG28,UG29,UG30 I am trying to determine the minimum wall thickness required under external pressure, and the required stiffening ring. "A" factor that I found falls to the left material/temperature line chart.
the design pressure in my case is 0.7 bar (internal pressure). does it mean that external pressure is just atmospherique pressure?
Anyone who has performed or familiar with such calculation, his/her help would be very appreciated.
NB:
- I made a search in this forum, I didnot find answers to my questions.
Thanks in advance for your help..
Dj





RE: Thin WallThick in Large Diameter
http://virtualpipeline.spaces.msn.com
RE: Thin WallThick in Large Diameter
I am checking a 66" and 70" pipe under vaccum condition ( design pressure -0.21 barg), internal design pressure is 0.7 barg. to prevent from buckling and ovalization, i am calculating the required minimum thickness under external pressure and the required stiffening rings, using BPVC section VIII div 1, UG28,UG29 and UG30.
My concern is the external pressure, i assume is 0.79 barg, am I correct?
Thanks in advance
Dj
RE: Thin WallThick in Large Diameter
http://virtualpipeline.spaces.msn.com
RE: Thin WallThick in Large Diameter
the design pressure conditions include -0.21 barg then the external design pressure will be 0.21 barg. Am I correct?
Regards
Yani
RE: Thin WallThick in Large Diameter
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RE: Thin WallThick in Large Diameter
The best thing to do is to Reference all pressures to Gauge or Absolute. If pressures involve - gage pressures its even better to convert the references to use ONLY absolute pressures.
Atmospheric is 100 kPaA or 1 BarA (or 0 BarG)
-0.21 BarG = 1.00 BarA -0.21 BarG = 0.79 BarA or 79 kPaA
Using an example of,
Internal Pressure -0.21 kPaG
Absolute = 1 -0.21 = 0.79 BarA = 79 kPaA
External Pressure of 200 kPaG
Absolute External Pressure = 100+200 = 300 kPaA
The Design Pressure should be the maximum pressure differentials between internal and external, thus you could have a maximum case for critical compressive hoop stress and a different maximum critical condition for tensile hoop stress.
Net Design pressure (a differential pressure) =
Internal Pressure - External Pressure
DP = 79 - 300
therefore, Net Design Pressure = -221 kPa
where,
A - sign indicates a net external to internal direction.
(creates compressive hoop stress in the pipe)
A + sign indicates a net internal to external direction
(creates tensile hoop stress in the pipe)
http://virtualpipeline.spaces.msn.com
RE: Thin WallThick in Large Diameter
RE: Thin WallThick in Large Diameter
Kind Regards.
Dj.