Pipeline vessel Tensile stress vs Temperature
Pipeline vessel Tensile stress vs Temperature
(OP)
Dear All,
My query is regarding a Vessel made of API 5L Gr. X70,
Wall Thickness is 24 mm
Outer Dia meter is : 40 inch.
During sizing of PSV for this system i found out that the wall temperature is increasing beyond 593 Deg C before the PSV set point .
My doubt is how to relate the Vessel tensile stregnth with the incresed wall temperature. So as to find out if the vessel gets ruptured before the PSV pops up.
Thanks ,
Sahil
My query is regarding a Vessel made of API 5L Gr. X70,
Wall Thickness is 24 mm
Outer Dia meter is : 40 inch.
During sizing of PSV for this system i found out that the wall temperature is increasing beyond 593 Deg C before the PSV set point .
My doubt is how to relate the Vessel tensile stregnth with the incresed wall temperature. So as to find out if the vessel gets ruptured before the PSV pops up.
Thanks ,
Sahil





RE: Pipeline vessel Tensile stress vs Temperature
RE: Pipeline vessel Tensile stress vs Temperature
RE: Pipeline vessel Tensile stress vs Temperature
What design code is it designed to?
This should give you your de rating factors, but it sounds like a fire case?
A few more details please.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Pipeline vessel Tensile stress vs Temperature
I am sorry for the limited information that i provided .
Further , I am sizing a PSV for the Vessel in fire case.
Set point : 100 barg ( The vessel is required to be Design for MAWP of 100 barg)
Op Temp : 20 Deg C
Op Pressure : 30 bar
Now relieving Temperature of the vessel comes as 858 Deg C . Which is quite high than the default wall temperature as per API 521 i.e. 593 Deg C .
My point is , in case of fire, the vessel shall keep on heating up, the inside pressure builts up . At some time the wall temp as well as the inside gas temp shall cross 593 Deg C . But the PSV shall not pop unless the Temp is 858 DEg C ( at that Temp Pressure shall be the set point of PSV)
I want to check if vessel may rupture way before the PSV pop up . Because of weakening of the material due to increase Temp.
That's why i want Tensile stregnth of the vessel vs Temp..
Hope I clarified . and somebody could help me.
Regards,
Sharad
RE: Pipeline vessel Tensile stress vs Temperature
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Pipeline vessel Tensile stress vs Temperature
858C (~1570F) !.... You are in the operating range of superheater tubing in a fossil fired boiler. ! !
Most steels have little or no strength in this range...
I do not believe that your vessel will be under pressure when it reachs these temperatures in a fire.....
What about the contents of this vessel ?
Have you considered that the contents have vaporized, and significantly increased pressure (thereby actuating the relief valve) a long time before the vessel wall reaches 858C ????
I believe that there was an article in Chemical Engineering Magazine (by Wong ??) some years back discussing this type of analysis...
MJCronin
Sr. Process Engineer
Venture Engineering & Construction
www.VentureEngr.com
RE: Pipeline vessel Tensile stress vs Temperature
what you have shown is that at the design pressure you have the vessel will not need a pressure relief because the vessel will have failed well before then.
What you then need to do is work out whether this vessel failing will add to the inferno in a significant way or release poisonous chemicals. If it does you need to find a way to prevent it getting this hot in a fire (bury it, cover it in concrete, deluge it in water etc ) or lower your design pressure so that the PSV does lift n a fire before the vessel melts and ruptures
Past the max design temp of the vessel material it doesn't apply any more and you need to assume failure of your pipe / vessel.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Pipeline vessel Tensile stress vs Temperature
http://www.eng-tips.com/viewthread.cfm?qid=215738
or this one - http://www.eng-tips.com/viewthread.cfm?qid=357254 read down a bit and you'll see that a PSV may not be required if fire is your only relieving case
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way