Tower Downcomer

[StressPE]

I have a downcomer from a cryo tower to a Al-Brazed heatexchanger. The downcomer as seen in the attachment is 45 ft tall with 9ft LEG. Tower and HE modeled to apply true displacements on the boundary condition. However, The line is working in two different mode ( Temperature) . When I design for the Mode as shown in the attachment, the expansion loop length of 4 ft will let the load in the HE nozzle within acceptable limit . When I design for Mode 2 , I can not find reduce the forces and moments on nozzle to acceptable limit due to high Moment on the HE nozzle . So my case is good for Mode 1 while when the operation wants to switch to Mode 2 then I would have problem . Can anybody help me on this? Please let me know whatever comes to you mind so I can try that .

Regards,

P.S: the reason i put expansion loop there is the tower and part of downcomer is existing and I'm connecting to it

 

[DSB123]

Loop is of insufficient size. You need to locate vertical stop/support below bottom bend. Have you included the wind loading displacement of the tower itself into your analysis - don't forget about it!!!

 

[StressPE]

I already put rest support under the elbow . In EXP load case , this support lifts off. however I don't have any problem regarding code stresses,alt stress etc. . my problem is Mx on the nozzle . Please pay attention to the fact that the tower brings the downcomer down due to low temperature . The Heat Exchanger nozzle is moving up due to contraction of Heat exchanger(so the riser is squeezed more) and the pipe connected into the middle pipe (the one which has spring can) tends to keep the pipe in place so it exert moment on heat exchanger nozzle . As said I can play with loop size to solve the issue in Mode 1 of operation but the design is not good at all in Mode 2 of operation . I wonder if anybody had this case already ? I mean to get answer in 1 Mode of operation while in mode 2 (different temperature profile ) the stresses or loads are not i acceptable ?


I have considered wind load . But I need to solve the EXP load case first .

 

[DSB123]

You need to meet the Code stress limits and equipment loads cor all operational cases - unless you want damage or leakage.