To avoid increasing shell thickness due to nozzle load 1

[mechengineer]

Whenever the calculated stresses based on the nozzle loads in specification exceed the allowable stresses, the actual nozzle loadings to be provide for re-checking. If increase the whole shell thickness due to the nozzles load, the user/client approval for acceptance is required.
In principle, a user would not allow to increase the whole shell thickness due to the nozzle load that you can identify by the fact that the shell thickness somewhere is thicker, somewhere is smaller. An user shall assess and balance the cost if reduce the piping load from piping side (like add piping support…..) to avoid piping engineer throw the problem to PV manufacturer and increase the cost for the pressure vessel due to the nozzle load. EPC may not be care for such case if it does not exceed the project budget.

 

[SnTMan]

In some classes of work it can make sense to, if necessary, increase shell thickness a small amount to meet client nozzle loads and get on with life, rather than spend days or weeks negotiating fictitious nozzle loads with a client who may have little or no incentive to do so. In my experience.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[mechengineer]

That's true. But I feel uncomfortable for such design using an assumed load to waste a material as a design engineer.

 

[Venkatachalam Ponnusamy]

Use Insert Plate instead of RF pads to over-come the nozzle load issues, in that case you no need to increase the shell thickness.

 

[SnTMan]

Venkatachalam Ponnusamy, people tend to consider that an expensive fix, partly due to the extra welding involved. Depends a lot on the class of work.

mechengineer, a lot of this work is, "hold your nose and do it"

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[DriveMeNuts]

Tell the project manager that it will create a three-month fabrication delay, to make the shell thicker. Then it will become the piping teams problem.
When pipe loading exceeds 30% of the nozzles stress capacity, it typically means a shoddy piping design with excessive loading.

 

[goutam_freelance]

You can discuss with the piping designer how he calculated the load. It is possible that he has considered the nozzle connection as fully rigid anchor giving rise to increased thermal load. In this case you can estimate a nozzle stiffness and suggest to the piping designer, consideration of which may reduce the piping load.

 

[r6155]

When designing pressure vessels, it is quite important to know the loads exerted on the nozzle by the connecting pipe
work. However the piping reactions computed by the piping structural analysis are often not available at the vessel
design stage. To overcome this problem, the pressure vessel must be exclusively designed for the internal design
pressure, after which the permissible external loads for the nozzle- vessel intersection as well as for the nozzle-piping
connection (flange) can be calculated. In this way the load limits and load capacity of the nozzle can be determined and
are available at an early stage to the piping designer (pipe stress analyst). Successively it is the responsibility of the
piping designer to ensure that the piping reactions are kept within the permissible load limits of the pressure vessel
nozzle. The advantage of this approach is that the imposed loads does not necessitate thickening of the pressureretaining
shell of the vessel nor require additional reinforcing pads around the nozzle neck. Moreover it should be noted
that by increasing the vessel shell thickness or adding a reinforcing pad, the nozzle becomes more rigid and therefore a
better approximation to a fixed point or anchor thus effectively eliminating the advantage of any nozzle flexibility. This
approach avoids remedial work of pressure vessels and/or pipework at late stages of a project, which for sure has
negative impact on project costs and schedule.

Regards

 

[KevinNZ]

Note to piping designers. Don't sit on you hands waiting for the pressure vessel designers to tell you the allowable nozzle loads. Get in first with your pipe loads then be prepared to negotiate.