Operating Standby case for reboiler

1.I have a vaporizer drum connecting to two reboilers
2.The Bottom tan line of drum and reboiler support(rigid support) location is exactly at the same elevation.
3.Process requirement is to connect the drum and reboiler with single elbow and a valve inbetween. so i have a fitting to fitting connection.
4.With both reboilers at operating condition, nozzle loads for the drum are within the allowable.
5.If reboiler tubes are clogged they close the valve and disconnect the clogged reboiler after cooling (may be 8 hrs), with other reboiler in normal operating condition.For this operating standby case i have more nozzle loads on the drum nozzle (5 time higher than the normal case) due to expansion of the vertical drum
6.Is there any option to accomdate these huge nozzle loads for a period of time for the drum nozzle occasionaly.

Different options I could think of:

1) Use nozzle flexiblities to reduce the loads.

2) Send the loads to vendor for approval.

3) Do a WRC 107/297 type analysis to check for local stresses or use FEA to compute local stresses and check if they are within allowable.

4) Pl. note that for fatigue analysis ( Pl+Pb+Q+F) you will have to properly find out the no. of cycles when such excursions will be there and then apply Miner's rule which will give you some comfort margin.

5) Elastic plastic analysis also can be done but depends on your resources, capabilities , time constraint and project/client aggrement.

Thank you anindya ,


I have used the first three to reduce the nozzle loads.

I want to know whether we can use Hot elastic modulus to reduce the nozzle loads.

Yes.