EFFECT OF LONG HOLDING TIME ON SA-516 70N DISH END NOMALIZING

[staticmh]

Hi Folk! Good Day!

This is regarding the 2:1 Ellipsoidal dish EFE & end heat treatment, dish end nominal thickness is 20mm and material is SA-516 Gr. 70 N.

As per the code clause UCS-79 (d) is applicable, which states “if dish end formed with cold forming and determined the extreme fiber elongation(EFE) higher than 5% then heat treatment shall be performed as per UCS-56 temperature & holding time”

But over and above, client specification of SHELL DEP is also applicable, which states that “in case of dish end cold formed and determined the EFE higher than 5% then NORMILIZING shall be performed with following temperature (850 to 960 deg C)”

As per UCS-56:

Dish end Nominal thickness = 20mm
Holding minimum Temperature shall be = 595 Deg C.
Holding minimum time duration = 1 Hr / 25mm
Holding minimum time duration per mm = 2.4 minute / mm

Now as per Nominal thickness holding time = 20 x 2.4 => = 48 minute.



As per Shell DEP:

Holding Temperature shall be = 850 to 960 Deg C
Holding minimum time duration = Need to specify, as SHELL DEP is silent on Holding time.

Question no-1 : Whether Holding time for normalizing shall be followed as per UCS-56 or as per material test report (MTC)?

If we see on material test report, it is calling for 1.75 minute / mm and if we calculate as per MTR then it shall be 1.75 x 20 = 35minute.

Question no-2 : Please advice material specialized person & vessel design engineers on above clarification. that what can be the effect on original material properties due to higher holding time considering for normalizing.

 

[r6155]

What is the actual % fiber elongation?

I suggest to use the MTR. No problem with higher holding time.

Regards

 

[staticmh]

@r6155

Its higher than 5%.

What will happen if we maintained higher time than MTR?

 

[r6155]

@ staticmh
Waste time and money.

Regards

 

[SnTMan]

staticmh, you will want to make sure your material meets specified mechanical properties. You should be pulling the mechanicals anyway. See UG-85, UCS-85 and related references.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[GD2]

Staticmh,
Every specification/standard have its own twists and turns and you will notice some variances. Usually, in a project, Customer/project specification will govern. In your case, it's shell DEP. My advice is the following:
1. Raise a Technical RFI(Request for Information) to the Client stating that Normalizing for the ellipsoidal dish head is required and what is missing.
2. Recommend UCS-56 holding time.
3. Get it approved.
In this way, you are covered and is following the Client's rule.

GDD
Canada