Heat Exchanger with ASTM B-124

[Peregrino7]

We have an existing heat exchanger built in 1955, with a tubesheet material of ASTM B-124 alloy 5, and we need to rerate this equipment for an increased design pressure. Where can I find the allowable stress (for a metal design temperature of 650°F) in order to evaluate this equipment. This material is not available in ASME Sec.II. Thanks for your help.

G

 

[metengr]

Several questions;
1. Is this an ASME Section VIII, Div 1, U-stamped vessel, and is it registered with the National Board?
2. Does this vessel reside in a Jurisdiction, and does it require an Operating Certificate or periodic inspection by an Authorized Insurance or Inspection Agency?

3. Is the vessel retired and you are interested in returning it to service?

The answers to the three questions above will allow me to provide you with proper direction.

 

[Peregrino7]

Dear Metengr, here the answer to your questions:

1. Actually we do not know what is the original design code for this equipment neather if it is registered with the National Board.
2. No, it does not.
3. No, it is not. It is actually in service but for a shell design pressure of 20.6 Barg, and we are interested in rerate it for an increased shell design pressure up to 25,2 Barg.
If you can help us in this matter, it will be highly appreciated.

G

 

[metengr]

Ok. Look for a nameplate on the side or head of the heat exchanger. If you see a "U" stamped on the shell or head along with the letters NB and a serial number this would indicate it is registered with the NB and is an ASME Code pressure vessel. Where is the object located - in or outside the US?


If you have no shell or head markings. What I would do is perform or sub-contract out a comprehensive engineering evaluation of the heat exchanger. This engineering evaluation would consist of nondestructive testing (NDT) of the shell and head girth welds and/or seam welds, PMI (positive material identification) of the shell and head materials, wall thickness of the shell, tubesheet and tubing. I would also NDT the tubing to assure structural integrity for the up rate in service.

Based on these results, I would use the formulas in Section VIII to verify adequacy of the current design, and with the up rate in design pressure. The alloy 5 allowable stress could be back calculated using the formulas in ASME Section II for determination of allowable stress values. You will need to know the UTS and YS of the material. I would probably recommend a hydrostatic test at 1.5X the new design pressure if the design formulas in Section VIII show acceptable design margin, and make sure you change the safety relief valves for the up rate in pressure.

Since you have no Jurisdiction or 3rd party insurance issues you are on your own.

 

[metengr]

As a follow-up, I reviewed ASTM B-124, which is a Standard Specification for "Copper and Copper Alloy Forging Rod, Bar and Shapes". There is no previous listing or designation for alloy 5. You should obtain a PMI of the tubesheet to confirm alloy composition.