UCS-66 1

[soykraken]

The first, sorry but my english language is bad.
Hi, i need help.
My client say me that the vessel material (A-105 and A-106 Gr. B must have impact test.
I have two flanges W.N. DN 14" welded to a central tube DN 14" Sch. 20.
The design temperature is -40ºF/248ºF
The UCS-66 say me that i need impact test ?
Thank yu very much.

 

[TomBarsh]

UCS-66(c) will exempt the standard B16.5 flanges to -20° F. Exemption from impact testing to colder MDMT can be made using Fig UCS-66.1. How much colder you can go with the flanges will depend on the "coincident ratio" defined in Fig UCS-66.2, down to a -55° F per UCS-66(b)(1)(b). If the coincident ratio is less than 0.35 then you can rate the flanges to -155° F! Of course, you will have to provide suitable low temp bolting as well. But in these latter cases maybe it's better to get the better grade flange material intended for low temp service.

You find the coincident ratio for B16.5 flanges as the ratio (flange rating at design temperature) / (flange rating at MDMT).

A similar procedure can be followed for the pipe. It will receive an MDMT rating as cold as -40° F for pressure up to about 540 psi.

 

[TomBarsh]

hey, how'd he do that, you ask?

well, let's see. The 14" sch 20 gets basic rating per Curve B of -20° F. The coincident ratio is
= treqd(at MDMT) * E(star) / (min thk - corr)
= 0.218295 (reqd thk based 540 psi and S at ambient temp) * (1) / ((0.312 wall * 0.875) - (0 corr))
= 0.8

Fig UCS-66.1 gives about a 20° F reduction for coinc ratio = 0.8.

So, -20° F rating - (20° F reduction) = -40° F.

 

[soykraken]

Sorry friend but i don´t understand.
Is neccesary the impact testing ?

 

[TomBarsh]

I'm sorry, but it would not be appropriate for me to give you a 'yes' or 'no' answer without having the full particulars of your design. I am happy to help you with the rules of UCS-66, but you must make the final decision.

 

[soykraken]

Ohh, sorry friend.
I don't know more that this data.
The dimension is 14" and the thickness is sch.20.
The design temperature is -40ºF/248ºF
My single client says to me that the material must to fulfill with UCS-66.
Thanks friend.

 

[stanweld]

The requirements for impact testing are based on design; stress induced due to pressure and temperature. If your design conditions provide for sufficient excess thickness less corrosion allowance, impact testing will not be required. If not, impact testing will be required. Not knowing the pressure or the corrosion allowance but based on the thin nozzle materials specified, I would guess that impact testing would be required.