Effect of Heating on Base metal 1

[Momo1988]

Hello for all,

We a problem in a pressure vessel and we solved it but i am afraid that our solution may harm the base metal of the shell.

So we have a vessel with SA 516 Gr 70 material which I.D diamter is 3000 mm thk 20 and after fabricating the shell the ELL.HEAD arrived by error with I.D 3040 so we have some suggestion one of them as follow

We have heated by flame the edge of the ELL.HEAD from outside till its I.D have reached 3000!

Is these dangerous on the base metal, we have tested the hardness and make lamentation which values are in range.

 

[0707]

This is not a good practice because the seam weld will be tensioned you have to make replicas on the HAZ to see if there are changes in the metalographic structure.

luis

 

[SnTMan]

We have heated by flame the edge of the ELL.HEAD from outside till its I.D have reached 3000!

MohamedAFatah, you care to explain more fully how you accomplished this?

Regards,

Mike

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

 

No, no no, do not attempt this. Extreme localized stress including bending, not hardness, is not how this sin is assessed and immediately condemned.

0707,
HAZ structure is not the issue with this. Strain/stress cannot be observed through a microscope.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[r6155]

I hope this PV is installed at least 100 km from my house !!!

Regards

 

[0707]

ironic you are the expert let us know!

luis

 

[r6155]

Any photo?

Regards

 

Do the thermal expansion calcs and tell us how much 'preheat' is necessary to bring the two circles into alignment.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[r6155]

I would never accept this situation. This manufacturer is disqualified for me. He doesn't know how to work.
Always expect to receive the head and then roll the cylindrical shell, unless a certified dimensional check is received in advance.

Regards

 

[Jay_]

I find it weird,
We rarely use hot forming in the fabrication of any vessel, it’s just not good practice especially if it’s not needed.
We usually start by fabricating the head and then rolling the cylindrical shell based on the measured circumference of the head.
Now one thing you could have done is to make the straight flange longer by cold forming using the machine to decrease the diameter. Some machines can’t do that since they do have limit in the straight flange dimensions, and then do some heat treatment if required.
I can’t really say what can happen in the future with your vessel, but it’s just not good practice.

Detailing is a hobby,

 

[Momo1988]

Dear all;

Many thanks for your replys i am thinking about all what you say, the head is already rejected and until the vendor bring another head we just make some trials to solve the problem but after your opinions beside many other opinion the solution will be cancelled by using a new ELL HEAD.

But on the rejected head which we heated how can we observe any damage or change on the mechanical properties based up on what we done ?

Tension test , bending test , mechanical properties?

 

[Trestala]

Probably fabricate a conical section or a forged ring with 1/3 taper to insert in between the two.
But I would reject that proposal if I were the Client.

 

[Jay_]

The mechanical properties surely have been altered.
And you will certainly observe a change in the bending behavior.
However since it’s rejected, there is no harm in doing some tests and compare with one that wasn’t heated.
And please share your result.

Detailing is a hobby,

 

[david339933]

Always expect to receive the head and then roll the cylindrical shell, unless a certified dimensional check is received in advance.

Couldn't agree more....roll the shell before you get the heads is a gamble not worth taking.

 

[SnTMan]

In the shell & tube industry heads are routinely ordered out before the cylinders are rolled. It pretty much always works. An early design decision is available head dimension & thickness. Cylinder design diameter then may be selected appropriately. It helps to have trusted vendors

Momo1988, you've made the correct decision. Still I'm curious: Can you explain how you reduced the head ID by heating it?

Regards,

Mike

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

 

[Don56]

SA-516-70 heads are routinely formed hot and cold. Hot formed heads require testing the mechanical properties on the same heat/slab coupons to verify the material meets specification.
How was the original head formed?
What temperature did you heat it to, to modify the diameter?
If you reworked it without using a flanging machine you most likely have turned the straight flange into a cone.

 

[gtaw]

What temperature scale are you using. 3000 degree F would have melted the head.

Best regards - Al