Is Impact testing required for ASTM A105 special forging?

[fizzy]

Hi guys,

I'm working on a carbon steel vessel with MDMT of -24degree C, the shell material is ASTM A516 Gr70 and the forgings/flanges are A105. I understand ASME B16.5 flanges are excepted from impact testing up to -29degree C. I've got a heavy neck forging of 152.4mm thk welded into the 35mm thk plate. I've carried out a preliminary calc as per UCS-66 which is indicating it being excepted.

Can someone throw more light or ref me to the relevant section.

tr (required thickness of forging neck) = 4.961mm
tn (norminal thickness of forging neck) = 152.4mm
E (joint efficiency) = 0.85
C (corrosion allowance) = 0

Many Thanks in advance.

Fizzy

 

[SnTMan]

fizzy, hard to say without more detailed information. What is the joint configuration? Are you exempting per UCS-66(b)?

Just based on nominal thickness, the plate itself is good for only +8C.

Regards,

Mike

 

[vesselfab]

If you are just concerned about the forging....use 350-lf2 and forget it.

 

[jharris3]

Fizzy,

Assuming: 1 - joint config similar to that shown in Fig. UCS-66.3(a or g).
2 - you are using a long weld neck type forging (Fig. UCS-66(c)(4))

Then the governing thickness would be the plate= 35mm.

Your design would need to include some kind of reduction based on UCS-66(b) in order to reduce the MDMT of the joint because the plate doesn't pass without it. (Or you normalize the shell plate and you move to a curve D where everything is fine)

I think that the B16.5 flanges are allowed the lower MDMT because of the process used to make them, geometry, and mostly experience that those flanges will work to -29 C. the reference to their exemption is UCS-66(c)(1)for flanges &(4) for "long weld neck flanges"

But it seems like you have chosen a flange that meets your requirements so I am a bit confused about what kind of information you are looking for.

What is the required thickness of the shell?
Why did you choose such a large forging for the nozzle?

Did you use the flow chart shown in Fig UCS-66.2?

Remember you are evaluating a welded assembly not simply the forging.

The bolting on the flange has to be rated for the MDMT as well.

james

 

[fizzy]

Many Thanks for your input guys,

The plate will be normalised so i'm guessing curve D excempts it. The joint config is similar to Fig UCS-66.3g. I'm thinking excempting it with UCS-66(b)(3) since the ratio is smaller than 0.35.

The vessel is being repaired with the addition of a very large nozzle which requires further nozzle reinforcement hence the heavy neck configuration.

As per jharris3 comment on ASME B16.5 flanges, my case a special forging but-welded unto the flange, does this require further consideration as i have used Fig UCS-66.3(c) and UCS-66(b)(3) in excempting it as well. I don't know if i'm right in doing that.

Does this look right?

Cheers,
Fizzy.

 

[jharris3]

Ok, that is much more clear.

Yes, you need to evaluate the flange and the hub as a welded assembly, choosing the correct governing thickness of the joint. Should be simple though because the governing thickness is going to be the thickness at the weld between the two not necessarily 152 mm.

Having said that...vesselfab's comment above also applies because the material they are referencing is rated for low temperatures. This would let you take the exemption for the flange and the hub would be simple to rate for your needs.

-jharris3