CrMo vessel external attachment with full penetration 1

[lilili]

API 934A/C/E require that all welded joints including non-pressure to the vessel body should have full penetration joint design. I have seen many horizontal vessels/heat exchangers having saddles designed with wear plate, which is fillet welded to the vessel shell. Is this acceptable, or a good practice?

Thank you.

 

[metengr]

If a nonpressure part attachment carries less than 10% of the membrane stress in service, fillet welds should be acceptable. If you have load (in excess of 10% of the membrane stress) being transferred from the attachment to the shell, partial or full penetration welds are desirable.

 

[MJCronin]

I believe that there may be a rule mix-up.

Horizontal vessels with wear pads are commonly designed to ASME VIII, where fillet welds are permitted

API Recommended Practice 934 series was developed specifically for heavy wall fabrications of low Chrome Molly materials.

The 934 series are quite recent

-MJC

 

[SnTMan]

Fillet welded support pads are more than common, regardless of the service or metallurgy. Just vent it with a pipe tap hole.

Regards,

Mike

 

[gr2vessels]

The most cautious and correct answer is as usual from metengr. I am having some reservations over the assumption that API 934 was somehow incorrectly restricting all the welds to be full penetration. The equipment designed in accordance with API 934 is not suppose to have reo pads, saddle wrappers or any other attachment fillet welded to the shell or heads. That's the intent of the standard. However, the same equipment can be designed safely in accordance with other pressure vessel code, which allows other type of connections, without compromising the safety and integrity of the equipment. Perhaps lilili shoud review again the nameplates of those exchangers or vessels having fillet welded attachments to establish if they were designed to API 934 or another PV code.
Cheers,
gr2vessels

 

[SnTMan]

If it really were heavy wall, a pad might be unnecessary, the support webs and so forth could be full pen welded.

The pad is not really a wear plate (in the sense of a shell sitting on concrete supports) if it is welded to the shell.

The answer, as always, it depends....

Regards

Mike

 

[Duwe6]

Also API is "Guideline & Recommendations". Use ASME Sect VIII Div. 1. It is a "Code", and has 'force of law' in most USA juristictions. It is also much, much more 'mature' and time-tested.

In general. API doesn't address true pressurevessels well, and ASME has been addressing pressurevessels since before 1920.