Welded Thermowell and ASME B31.3 1

[Fran67]

Hello everybody,

I work on a piping system, designed according to ASME B31.3, and I want to install a welded thermowell on a run pipe.
Do you know what is required by the B31.3 code for the design in this case?
Is there a specific chapter to use, or can I calculate the connection like a "branch connection"?

Thank you

F67

 

[LittleInch]

I would just make sure your thermowell is correctly rated, but in essence is similar to aweldolet.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Rputvin]

I can't remember which B31 code I was working to, but I ended up needing the ASME PTC 19.3 TW, 2016 is current edition. It's a fairly straightforward code with calculations and examples to check vibration, resonance, presure, and a bunch of other factors for thermowells in flow.

https://www.asme.org/codes-standards/find-codes-standards/ptc-19-3-tw-thermowells

 

[davefitz]

As I recall, the failure at the Monju LMFBR reactor occurred at a thermowell that used a partial penetration weld, experienced the initial crack ( at the weld edge) due to the thermal stress, and the crack extended to failure due to fluidelastic vibrations. A full penetration weld may have prevented the failure, but modeling using FEM and calcualting the fluideleastic properties would also have assisted in the correct design.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

[MJCronin]

Because may have asked this question before, this White Paper, by EMERSON may help you ...

It is clear and very well written. It also provides background information on the MONJU failure ...

https://www.emerson.com/documents/a...hermowell-calculations-rosemount-en-89838.pdf

Let us know if this meets your needs ...

MJCronin
Sr. Process Engineer

 

[XL83NL]

See para 306.6. That actual section may currently be under ballot for a new revision though.

Huub
- You never get what you expect, you only get what you inspect.

 

[hacksaw]

The Monju case led to the recognition of thermowell resonance occurring at half the predicted resonance condition of that outlined in the current version of PTC 19.3TW, for supercritical Reynolds numbers.

Some firms offer designs supercritical shedding dynamics, but are not suited for all processes, and require accounting for the altered force coefficients used in the calculations. The new designs experience elevated drag forcing and require addressing resonance conditions due to turbulence of pulsating flow conditions.

Thermowell connections are governed by the piping codes regarding small bore connections (Weld-O-Lets, Soc-O-Lets, flanged,, etc.

Consult you piping design rules regarding the connections for your project.

 

[hacksaw]

The following may provide a degree of insight to the failure associated with the Monju Incident

 

[hacksaw]

With Attachment

 

[hacksaw]

Perhaps with a successful attachment

The figure identifies the crack location.

 

[hacksaw]

As a foot not to the Monju incident, the current PTC 19.3 (2016) does account for the failure, and were it in use at the time failure would have been avoided.