Exchanger Tube thickness question

[Bill3752]

I am designing an exchanger, and am wanting to compute the minimum tube thickness. Using the Barlow equation:

tm = PDo/{2(SE+PY)} + C
where P = design pressure
SE = allowable stress = 13,200 psi for A213 tubes @ 450°F
Y = .4 for A213 (304L)

My question is what is good value to use for corrosion/erosion allowance, C? Processing syn gas through tubes at 900 psi. Cooling water on shell side.

Any rules of thumb to use?

 

[0707]

According TEMA code, tubes are not required to have corrosion allowance.

Carbon steel parts of shell, heads and tube sheets vary from 1/16" up to 1/8".


lm

 

[SJones]

You have selected 304L, a corrosion resistant alloy, therefore it would be expected to have an acceptable metal loss from the nominal thickness as computed. Since it is an austenitic stainless steel, it will also have a superior erosion resistance compared to carbon steel and, provided that you are not sending solids through, should give acceptable performance.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[Bill3752]

Thanks for your input. I will proceed with the minimum tube thickness calc assuming no extra allowance is required.
Bill

 

[0707]

Bill3752

If the cooling water has more than 50 ppm of chlorides SS TP304L is not a good material choice.

After determination of the minimum thickness and according the corrosivity of your fluids, shell side and tube side, then you have to chose a “safety” BWG to your tubes according TEMA tables.

lm