POST FORMING HEAT TREATMENT UCS -79

[212197]

UCS-79 (POST FORMING HEAT TREATMENT) REFERES TO UCS56 FOR HEAT TREATMENT (POST WELD HEAT TREATMENT).
BUT SOME STANDARDS LIKE EIL,INDIA ASK TO CARRY OUT NORMALISING WHEN THICKNESS IS 16 MM.
WHAT WILL HAPPEN WHEN WE CARRY OUT STRESS RELIEVING AS PER UCS-56 (SOAKING TEMPERATURE = 595 DEGREE CEL.) INSTEAD OF NORMALISING? THICKNESS IS 80 MM. MATERIAL IS SA 516 GR 70.

 

[david339933]

80mm thick SA-516-70 must be normalized per the SA-516 specification.

WHAT WILL HAPPEN WHEN WE CARRY OUT STRESS RELIEVING AS PER UCS-56 (SOAKING TEMPERATURE = 595 DEGREE CEL.) INSTEAD OF NORMALISING?

You will satisfy ASME Sec VIII Div. 1 Code rules.

 

[212197]

as per my understanding, SA 516 i.e. plate specification calls for normalizing of plate i.e. raw material. Accordingly my plate is procured as normalized.

Here, my doubt is about post forming heat treatment of dished end.
1) normalized plate is formed to make dished end
2) it requires post forming heat treatment as per UCS 79.
3) The vessels a whole requires stress relieving heat treatment as per UCS-56.
4) I do not want to carry out post forming heat treatment immediately after dished end forming. If post forming heat treatment of dished end is stress relieving & not normalizing then I can avoid one separate heat treatment of dished end as dished end will be heat treated as a complete vessel.
5) if dished end requires normalizing then my dished end will be 2 times heat treated . First (normalizing) as separate dished end & second (stress relieving) as a whole vessel.
6) so my question is what will happen if I carry out stress relieving instead of normalizing to 80 mm formed dished end. This is to avoid separate heat treatment cycle cost.

 

[david339933]

If the entire vessel is to undergo PWHT, there is no need to PFHT the heads. UCS-79 will be satisfied by the one PWHT, when the vessel is complete.
I cannot speak on the other Codes you stated, but UCS-79 directs you to use UCS-56 for heat treatment. Normalizing is not mentioned in the paragraph.

SO: Buy the Normalized plate
Form the head
Weld the head on the vessel
PWHT entire vessel.

UCS-79 = Satisfied.

 

[212197]

I agree that UCS-79 does not specify normalizing as post forming heat treatment.
But as THICKNESS is heavy I am worried that whether there will be any implications of carrying out stress relieving in place of standard practice of carrying out normalizing for 80 mm thick dish.
code also talks about engineering judgement.

 

[david339933]

Standard practice is stress relieving not normalizing. The purpose here is to relieve the stresses induced by the forming process.