Heating Coil Bundle Support Conditions

[abuanaselmasry]

I have a heating coil of 3 m length. It is mainly 2 pipes but bended into 8 flows with only 4 ends welded to the cover of the heating coil insertion nozzle.
In order to provide the necessary moment of inertia and to enhance the rigidity of the bundle, I have utilized a longitudinal stiffener with 5 full size baffles. Attached photo is for more clarity.

The question is; what should be the Moment of Inertia to be considered for the cantilever load?
Is it the total bundle Moment of Inertia? i.e the sum of moment of inertia for the support + 4 (the moment of inertia for single pipe + shifting of this moment to the neutral axis of the bundle).
or;
I shall just divide the total load into 4 and check single pipe bending moment on its neutral axis?

There is big difference in the results between the 2 concepts.

Regards,
M.Salaheldin
Static Equipment Mechanical Design Engineer

 

[MJCronin]

I suggest that a cantilever is not the best design.

Are you being forced into a cantilever design by an unreasonable boss or client ?

I have specified several similar tank heaters and I have always supported the far end with a sliding shelf support welded to the inside of the tank. If you extend the longitudinal vertical plate, the support could bear on this

I would use three sliding supports....one at the far end, one midpoint and one a foot or two from the nozzle. The sliding support near the nozzle would help the maintenance insert and align the coil.

I would like to hear the suggestions of others.....

Please complete the thread and inform us of your final solution

Good luck and Best Regards



MJCronin
Sr. Process Engineer

 

[abuanaselmasry]

Thanks for the reply.
The final concept has not been yet finalized. Still waiting for the valuable inputs.

The concept of cantilever is suggested for the easy removal and insertion, and to count for the improper handling during maintenance. However, the option of the sliding support is also one of the options being evaluated.

There is a question regarding the sliding concept. Will the bundle be bolted to the rear support? or it will just rest on it? If not bolted, have you ever before faced vibration/noise problems?


Regards,
M.Salaheldin
Static Equipment Mechanical Design Engineer

 

[abuanaselmasry]

Thanks for the advise. I have utilized your suggestion. But, I didn't bolt it at the end. I have just rest it at 2 supports. one near to center and the other close to exit.

Regards,
M.Salaheldin
Static Equipment Mechanical Design Engineer

 

[EdStainless]

What temperature? Is creep an issue?
If you go with your bayonet bundle can it rest on support/guides in the tank?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[MJCronin]

If this is possible, I also suggest that you consider placing a manway directly above the heater on the roof of the tank.

This will facilitate maintenance and the rare insertion/removal of the bundle. I am envisioning a crane and sling used in maintenance.

Do not bolt the far end or the heater to the tank, allow for thermal expansion.

You will get no vibration or hammering problem if you have a properly sized condensate trap and responsible operating personnel.

What materials are you using to make the heater bundle ?

What is the liquid stored and the desired storage temperature ? What is the temperature of the steam ??

Is this the first bundle you have ever designed ???


MJCronin
Sr. Process Engineer

 

[abuanaselmasry]

Thanks for your concern. I will reply to all questions. I have noted that most of your concerns are related to the thermal and process design. But, I'm working in a manufacturing company. We don't perform the sizing calculations, the process design or material selection. This is the EPC contractor socpe. This coil is part of a vessel that we are manufacturing as per ASME VIII Div. 2.

What temperature? ==> Design 375 °C.

Is creep an issue? ==> Material is not yet decided. For SA-106 B (not recommended solution) this is the start temperature of creep consideration. For SA-355 P11 (most likely will be used), there is no creep.

If this is possible, I also suggest that you consider placing a manway directly above the heater on the roof of the tank. ==> This is a vertical vessel. The hieght is somehow long. However, there is a Manway that is placed almost 180° from the nozzle and above it. The concept of the crane could be utilized using it.

Do not bolt the far end or the heater to the tank, allow for thermal expansion. ==> Yes, I didn't.

You will get no vibration or hammering problem if you have a properly sized condensate trap and responsible operating personnel. ==> Hopefully, this is considered by our Client.

What materials are you using to make the heater bundle ? ==> As replied above. If there is another suggested grade, please advise.

Is this the first bundle you have ever designed ??? We do mechanical design for S/T heat exchangers. So, many bundles I have designed in accordance to TEMA requirements. There are also other spiral heating coils, but it was like a normal piping inside the tank and it was supported inside the tank by mormal pipe supports. The temperatures also were not that much high. Hopefully, I have correctly replied your questions...

Regards,
M.Salaheldin
Static Equipment Mechanical Design Engineer