Dear,

My pressure vessel will be installed in sismic zone. So I shall verifie if the thikness can be resist in case of earthquake.

My opinion is to use the Appendix L-2 of the ASME VIII Div 1.

But I have some problem to applie the formula.

First, I have calculated the bending moment due to the earthquake load.

For the longitudinal weld, I have calculated the thikness due to the pressure (P*r/e) + the thikness due to the bending moment. The allowable stress taken into account in this case is the tensile stress of my material given by the code.

My problem is to check the thikness for the circular weld?

I check the tickness due to the internal pressure (P*r/2e). But how can I insert my bending moment in the equation? Shall I use the compression stress for this case?

Please help me

Tanks very much in advance for your reply.

Regards,

Yes ; compressive stress induced by self weight plus bending moment shall be checked for buckling; I understand your vessel is vertical.

More than that the tensile stress in longitudinal direction induced by internal pressure plus stress due to bending moment gets added and to be checked with other stress components if any.

case 1(b) under L-2-1 is for long.stres and hence for circumferential welds.

Is it OK?

With regards

_________________
R.SRINIVASAN
Sr. VICE PRESIDENT
Head, Design and Engineering
PED,ISGEC,
YAMUNANAGAR
HARYANA -135001
INDIA

Dear,

Thanks very much for your help.

Yes my vessel is vertical.

To check the compression stress, can I use the formula of case 2 of the appandix L-2. If I can use her, can you explain me why the thikness due to the pressure is not takken into account?

The earthquake can arrive during exploitation so when the vessel in under pressure?

If I undertstand, the most severe condition is the formula with the thickness due to the bending moment plus the thikness due to the weight?

Thanks in advance.

Ludo

Yes I agree ; assuming that seismic occurs when there is no pressure is conservative for checking the limit on compressive stress.

One has to check all the following:

1. Hoop tensile stress

2. Longitudinal tensile stress (pressure and earthquake)

3. Longitudinal compressive stress -case 2 of L-2 referred by yourself.

One has to check for all the failure modes ; It may happen that allowable compressive stress is higher than the allowable stress s (as given in L-2 itself) ; hence check all possible conditions

_________________
R.SRINIVASAN
Sr. VICE PRESIDENT
Head, Design and Engineering
PED,ISGEC,
YAMUNANAGAR
HARYANA -135001
INDIA