Impact testing 2

[johnick]

ASME UG 20(f) (3)impact testing is not mandatory between -29ºC & 345ºC. Is there an exemption to mandatory test above 345ºC? We have a vessel of design pressure of 2.77MPa & design temp of 350ºC. Material grade for shell & nozzles is ASTM A106B.

 

[API123]

Is the reason for your impact tests to determine the MDMT?

Typically that grade of carbon steel can be used up to 426C, but can be subject to damages such as creep / graphitization /etc. Also you will have a noticeable depreciation in strength at elevated temperature.

What service would this vessel be in?

 

[johnick]

Thanks for reply.
Vessel is a steam distribution header operating at ambient up to 350ºC. Pipe wall thickness is Sch.40 (10.3mm).
Low temperature operation is not a consideration.
I am trying to establish what if any requirements are for operating at this temperature as UG -20 mentions upper limit of 345ºC. for non mandatory impact testing

 

[JoeTank]

johnnick,
It's pretty straight forward at this point. You exceed the temperature limits of UG-20(f) for operation down to -20F (-29C) with out impact testing. Have you reviewed UCS-66 yet? It may also provide a path for impact test exemption as you state that low temp operation is not anticipated.

Joe Tank

 

[johnick]

I have reviewed UCS-65 & 66 but take these to be for low temperature operation. UG-20(f)(3) would seem to put a limit on the temperature range of -29ºC to 345ºC. outside which impacts are required. Our upper design temperature is 350ºC.

 

[teokal]

johnick, is your vessel intented to be used in Europe? If yes, this creates a difference in the aspect of impact test...

 

[johnick]

teokal, vessel is for use in China.

 

[eliebl]

The upper limit of 345 C simply means that the impact test exemption of UG-20(f) cannot be applied. You will need to look at UCS-66 to determine the MDMT below which requires impact testing. If it is steam distribution then MDMT will not likely be an issue. If you get anywhere near the MDMT of the listed pipe you will have ice not steam.

my 2 cents

 

[SnTMan]

johnick, if you are designing to Sec VIII, Div. 1, you (or someone) is REQUIRED to assign the vessel an MDMT. See UG-20. This would be the lowest temperature experienced by the vessel during any operating regime, including startup, shutdown, upsets, etc. Then the need (or lack) for impact testing can be determined per UCS-66 or other Part as applicable.

Regards,

Mike

 

[johnick]

Thanks eliebl & SnTMan for these replies I now understand what I have to do for MDMT for our vessel.
Thanks.