I want to select material for baffl 5

[ENGRANIA]

I want to select material for baffles cheaper than sa-387 for effluent reactor cooler.
Material of shell sa-204 gr.B
Material if tubes sa-213 TP 304
TEMP. For tube side 430°c
Temp for shell side 410°c

 

[r6155]

Use SA 240 TP304

Regards

 

[ENGRANIA]

But the temperature limit for sa-240 don't govern the design temp for cooler

 

[Krausen]

rb6155 is correct. Match your baffle metallurgy to your tube metallurgy. You'll thank yourself later after 10 years of service.

 

[EdStainless]

Unless the tubes are sacrificial use the same alloy for the baffle.

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P.E. Metallurgy, consulting work welcomed

 

[Christine74]

You'll have to discuss this with a metallurgist but unless there is some special concern there's really no need to make the baffles from any higher grade material than the shell material since both components are exposed to the same fluid at the same temperature. More often than not alloy tube material is specified due to the corrosivity of the tube-side fluid, not the shell-side fluid.

In your case the shell is SA-204 Grade B which is a C-0.5Mo which is not commonly used these days (typically 1.25Cr-0.5Mo material is used as a replacement).


-Christine

 

[MJCronin]

I agree with Christine ...but, like all similar postings, I suspect that there is more to the story

But how is it that you feel that you can use low chrome molly "SA-204 Grade B" for the shell material at 430C (~800F) ??

Is this a new or an "old vessel that must be reused", as per the demands of your hostile boss ?

Please explain... What are the rest of the details you have not told us ?

I believe that, under current PV Codes, you are beyond the allowable temperature range for this material..

I assume that A387 Gr 11 or Gr 22 would be a suitable replacement ... and NO mild carbon steel plate is not suitable !!!

MJCronin
Sr. Process Engineer

 

[r6155]

See API RP 571 2020 Damage Mechanisms Affecting Fixed Equipment in the Refining Industry

Galvanic corrosion can occur in any unit where different metals are coupled in a conductive fluid. Heat exchangers are susceptible if the tube material is different from the tubesheet and/or baffles,

Regards

 

[ENGRANIA]

Dear MJCronin,
Idon't know what do you mean with third world posting!!!!!
i have posted a thread with a certain enquiry .if you need more details, you can ask about it without any sarcasm.
This was an old effluent reactor cooler and the design was from an european manufacturer. We want to take it offline to replace the bundle with a new one.
Now all what i need to find a suitable material cheaper than sa-387 which is commonly used for these conditions for baffles.

 

[Krausen]

r6155 is again correct. Dissimilar metals in contact on shellside btw tubes & baffles, along with your shellside fluid electrolyte, will cause galvanic corrosion long term. I've replaced a number of bundles where the higher metallurgy tubes held up, but the lower metallurgy baffles corroded away from shellside galvanic corrosion, compromising the bundle integrity. Vendors will often go with the lower metallurgy baffles to save money, it's imperative of the engineer to require higher metallurgy baffles (matching the tubes) to eliminate this common error in design.

 

[Christine74]

Assuming the galvanic corrosion concern is real (does high-temperature hydrocarbon effluent normally have electrolytes?), are you saying that you would rather have the shell acting as the anode than the baffles?

The shell is a pressure boundary. Galvanic corrosion on the shell would be very localized so difficult to monitor while the equipment is in service. Maybe non-metallic baffles are worth considering here but I don't know of any non-metallic materials that can be used at that high of a temperature.


-Christine

 

[r6155]

We don't have any more information on this HX: Fixed Tubesheet, U-Bundle, Diameter, Pressure, .........etc.
The baffles SS are not in contact with the CS shell.

Regards

 

[Christine74]

Obviously you've never seen an actual heat exchanger before. Tube bundles do not levitate in the shell. Most or all of the baffles would make direct contact with the bottom of the shell cylinder.

And all of the information you're requesting (Fixed Tubesheet, U-Bundle, Diameter, Pressure, etc.) is irrelevant to the OP's question about the baffle material.


-Christine

 

[SnTMan]

Without going into a lot of unnecessary detail I'd like to point out that CS or low alloy baffles are used with stainless tubes all the time. Depends on the process...

Regards,

Mike

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

 

[SnTMan]

To the OP: I doubt that stainless baffles would be any cheaper than lo-chrome. CS might work, might not. Don't go too cheap on the baffles...

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

 

[ENGRANIA]

i don't want to select too cheap material, i have some doubt that sa-240 tp 304 is suitable for this temp. and hydrogen service as for effluent reactor cooler.

 

[SnTMan]

ENGRANIA, SA-516-70 permitted to 1000F, SA-204-B permitted to 1000F, SA-387-11 permitted to 1200F, S-240-304 permitted to 1500F, per Sec II, Part D.

Your baffles are not subjected to any particular stress, they even need not be Code material.

I'd be most concerned about corrosion. SA-516 might work and could be made thicker than TEMA mins, but SA-387 is likely more corrosion resistant. Not at all familiar with your process.

EDIT: Do you know what the existing baffles are? I'd match them as closely as possible.

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

 

[georgeverghese]

Shellside Cross flow baffles are not pressure retaining components, so why A387? Why not SS304, or something galvanically close to SS304?

And what about the tie rods then?

 

[Krausen]

And what about the tie rods then?

Same concept - metal up on the tie rods & tie rod nuts too

 

[EdStainless]

I made a living selling SS HX tubes, mostly replacements.
A fair amount of the work was replacing tubes that failed by fatigue in CS baffles.
The combination of erosion, corrosion, and wear would open the holes up to the point that the tubes started slapping against each other.
It is hard to tell when this will happen as I have seen it even in high purity applications.


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P.E. Metallurgy, consulting work welcomed