Reinforcement Pads 4

[rockeo]

Why do we use reinforcement pads whenever there is an opening of a particular size in the vessel? Is it due to stresses induced due to cutting and welding?

 

[TGS4]

It is due to the stresses caused by the lack of material (the material removed) at the opening. It had nothing to do with the process of creating the opening.

 

[rockeo]

But we are connecting a closed pipe at the end that will also contain the pressure. Stresses are produced due to the application of forces. By creating a hole we are not increasing any force that would act on the shell. The reinforcement seems illogical to me. I just can't get the concept behind it.

 

[RVAmeche]

Assuming it's a pressure vessel, there's internal pressure from the process that's creating stress in the entire vessel. If it's liquid filled there's thermal expansion of the fluid inside or a hundred other things that could cause stress.

 

[FormerAIS]

The size of the opening must be replaced in some way. With small fittings, the thickness of the coupling/pipe and the size of the weld suffice to meet this requirement. As the opening increases in size, the material must be replaced somehow. Reinforcement pads fit the bill perfectly, though having a large weld or an extremely thick coupling/pipe could also work. The internal pressure is a direct contributor to this calculation.

The stresses being contained is the purpose behind why reinforcing pads are used. Stress is increased and applied via pressure/temperature in this case.



Quality is not an act, it is a habit - Aristotle

 

[geesamand]

Adding any pipe to a shell increases stresses there. It's caused by the change in stiffness (the pipe is stiffer than the shell alone). Generally speaking, unless the entire shell is already excessively thick, a repad is required to restore its strength.

For a real-world example, have a look at an iPhone charger cord. It's a soft flexible cord that connects to a rigid connector. There is a strain relief in that design between the actual cord and the plastic connector. (The iPhone charger cord is actually *not* a good design because it still pinches on the soft cord and consistently breaks apart). But a repad is a strain relief in every sense.

 

[MrBTU]

A repad is not always required. See Fig UG-37.1. The missing material can be replaced in a number of ways - area available in shell, nozzle wall, inward and outward, weld fillet inward and outward.

 

[TGS4]

I just can't get the concept behind it.

Perhaps it is time for you to do a little research on your own. Much has been written about this topic in the peer-reviewed literature over the last 80+ years. Please do a little research on your own. After you have done so, feel free to return to this forum with specific questions about specific research papers. We will expect you to refer to the research that you have performed on your own (seriously - I expect something akin to a bibliography) before answering additional questions. And no, I am not going to provide you with the list of papers to read. You are an engineer who would have learned how to do that in school.

This website is eng-tips, not eng-spoonfeeding.

 

[r6155]

I agree with TGS4

Regards

 

[rockeo]

Thanks for your replies guys! I got the concept.