API 934 C Preheat requirement
API 934 C Preheat requirement
(OP)
Hello all,
We have a vessel with Shell material of SA-387-12 CL2 and shell thickness of 105mm.This vessel needs to follow the API 934-C requirements.
API 934-C para 7.3.1 (Preheat) mandates that "All base metal should be preheat to a minimum of 300 def F during rolling.
Out vessel supplier is asking waiver to this requirement.
My question is how difficult is it to meet this requirement?
Regards,
Mechmania
We have a vessel with Shell material of SA-387-12 CL2 and shell thickness of 105mm.This vessel needs to follow the API 934-C requirements.
API 934-C para 7.3.1 (Preheat) mandates that "All base metal should be preheat to a minimum of 300 def F during rolling.
Out vessel supplier is asking waiver to this requirement.
My question is how difficult is it to meet this requirement?
Regards,
Mechmania





RE: API 934 C Preheat requirement
RE: API 934 C Preheat requirement
Are you defining prior to rolling of the shell course or prior to welding? If prior to welding, see metengr.
If rolling the shell course or prior to welding, understand what "should" means. Should is a recommendation; shall is a mandate.
RE: API 934 C Preheat requirement
As to whether or not it's necessary is another matter, but I can say we're rolling 387-22 in 2.375" thickness to a ~ a 50" radius at ambient temperature. So the necessity for preheat is a function of material type/ grade / condition, thickness and final radius. There are of course other factors that play into the situation such as the type of rolling equipment available, pre-bend etc.
RE: API 934 C Preheat requirement
However, I must confess when I reviewed the OP, I focused on preheat for welding and not forming. If it is for forming, it makes no sense.
RE: API 934 C Preheat requirement
And yes the Standard says “SHOULD” so it’s more of a recommendation than mandate.
The supplier is suggesting following in lieu of Pre heat before rolling.
1) UT (Grid wise 9" x 9") and MT (100%) examination after rolling (from inside).
2) Hardness check with grid length of 9 inches from inside.
Does these alternate adequate provides the properties ensured by pre heating?
Supplier wants waiver siting the difficulty in accommodating this pre heat (before rolling)requirement in actual fabrication procedure.
What if we do not get adequate properties with pre heat waiver? What is possible fix than?
Should we enforce this suggested requirements or alternate suggested by supplier would be okay?
Thanks
Mechamania
RE: API 934 C Preheat requirement
I see no reason to perform the UT and hardness prior to rolling simply because the preheat recommendation is being waived. In this case, 300 deg F is too low a temperature and will provide little benefit in terms of roll forming. I would waive the 300 deg F preheat for rolling if it cannot be done using a furnace to heat the entire plate thickness.
RE: API 934 C Preheat requirement
Thanks for quick response.
Grid UT, MT(100%) and Hardness check will be performed after rolling to make sure there are no defects.
So as i understand from your suggestion that 300 deg F would not do much and its okay to allow them to cold roll the shell followed by above mentioned check(Grid UT,MT and hardness Check)?
Thanks.
RE: API 934 C Preheat requirement
RE: API 934 C Preheat requirement
RE: API 934 C Preheat requirement
These posts have been very helpfull to us since we are dealing with something very similar but in grades 11 and 22.
It seems that our client is in agreement to void preheating before rolling. However, it is not the same for thermal cutting, we believe that preheating has been achieved during cutting operations and we are having very smooth profiles and PT/MT are being applied to all edges.
Your comments are highly appreciated.
Regards,
RE: API 934 C Preheat requirement
Preheat for thermal gouging or cutting process is entirely different, and I agree with your client for not voiding the preheat for thermal cutting processes for air hardenable materials. Yes, surface NDT of base material after heat affected material has been removed is prudent for detection of cracks.
RE: API 934 C Preheat requirement
Thank you for your prompt reply; I am refering to cutting prior to rolling with pieces flat on the cutting machine, we cut and bevel in a single operation with CNC Machine, after preheating, welding, DHT complete vessel will be PWHT.
Is it still required a preheat before cutting? plates are 26 and 50 mm thk.
Thanks,
RE: API 934 C Preheat requirement