Stress 1

[arvindpandit]

Hii...

In Sec II part D, allowable stress value are given for temperature limit from -30 to 900 deg C. If the design temperature for any Pressure vessel is min. -100 to -40 or below -30 deg C, then how to select/ arrive the allowable stress?

Also, How to decide the material for Pressure Vessel like SA 516 gr 55/60/65/70 or 515 All Grades.
We have our standard practise that for temp. range -39 to 250 degC and thickness less than 25mm, we select SA 516 Gr.60 and t>25mm, SA516 Gr.70. But I dont know what is the reason behind it. Similarly there are list of material based on the temp range. But I want to know the reason.

 

[MJCronin]

Arvin...

Repost this in the proper forum...

MJCronin
Sr. Process Engineer

 

[arvindpandit]

ok....

in simple just explain when we use SA 516 and SA 515 as both have similar Mechanical properties but little different in Chemical properties?

I need proper answer other than written in ASTM A516 and A515 as A515 is use for "intermediate- and higher-temperature service in welded boilers and other pressure vessel".

 

[bimr]

SA 516 has fine grain structure and the SA 515 has coarse grain structure. SA 515 can be used for intermediate to higher temperature purpose (for boilers) and SA516 is used for lower to intermediate temperature purpose (for vessels). The ASME BPV code defines the materials. See the ASTM standard for details keeping in mind your service requirement.

 

[arvindpandit]

ok thnx....

lets have some conditions
Design Temperature= -50 to 60 deg C
Design pressure = 16 Barg
Fluid = Hydrocarbon
Now with these conditions, what will be the MOC of vessel i.e CS or SS?
If it will be CS then what will be the CS material. similarly for SS.

Hope this clears my query.