Loose flange - Forged ring over formed ring 1

[GD_P]

Hello community,

We are designing pressure vessel as per ASME Sec VIII Div 1 with below details:
Pressure: 12 bar
Temp: 180 deg C
Service: Non lethal

Now the body flange of the vessel (slip on type loose flange) is proposed as SA 516 Gr. 70 formed into ring since the MOC is Carbon Steel. And it is clear that, this is not prohibited as per code. It is clear & we must have to perform PWHT, 100% RT of the weld.

But the client is insisting to use Forged ring instead of formed ring from plate.

Have any one experience the same situation.

What was & could be the reason for it?
(Off course we should ask client, but before contacting we should be prepared)

Also if we compare forging vs formed ring,
what should be the aspects of the comparison?
Off course delivery is one of the important,
apart from this what else should be compared, considering forging is made up of SA-105 & Ring as mentioned above.

Could the allowable stress be a factor? I think it should not be the, since both spec are different and the raw product for forging & other is rolling may not be same. So that we can conclude that certain process (forging / rolling) improve allow stresses over the other.

Meanwhile we are trying to figure out what made the client to insist forged ring.

Any help will be greatly appreciated.
Thank you in advance & sorry for the lengthy post.


GD_P

 

[SnTMan]

GD_P, since you have not stated Code of construction, if any, the following is kind of general:

For a loose flange you can form a ring from plate and, as you said, full-penetration weld, x-ray and PWHT the weld seam. You can, depending on diameter, simply burn a ring from plate.

You can, as your client asks, buy a ring forging. This ring will roll-forged from a small pierced blank at red-hot temperature.

There is likely to be no difference in allowable stresses between the two at least at moderate temps, up to 500 F or so. The forging will be the superior material over the plate especially due to the lack of any laminations that may be present in plate. It is entirely possible that it also is the less expensive option considering the labor involved in making the ring from plate.

Ring forgings are very common and pretty much universal for hubbed flanges. I personally would not look forward to the task of trying to convince a client who "insists" on a forging to accept a plate flange.

Regards,

Mike


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