Corrosion Allowance of Plates in Plate Heat exchangers 1

[CoCoE]

Do we need to consider Corrosion allowance for plates in plate heat exchangers if the plate is made of high alloys like Alloy C-276?

I have a service which is coming in contact with 98% H2SO4 and no corrosion allowance is considered although the ISO Corrosion curve shows a corrosion of 0.13 mm/year.

Could anyone please help me out?

Thanks a lot in advance

Coco

 

[moltenmetal]

No substantial corrosion allowance is practical in plate type exchangers.

Take into consideration that the plate metal will be at a temperature determined by exchanger design, so it will be either hotter or colder than the process fluid by an amount determined by where the controlling resistance is selected. That can be used to mitigate corrosion- or might push you to more resistant alloys.

 

[EdStainless]

H2SO4, and your not using alloy 20?
In general you do not use a corrosion allowance with high performance alloys.
This is largely that even if they have some corrosion it is likely to be very localized (such as pitting) so making the material thicker is of no use in extending the life.

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P.E. Metallurgy, Plymouth Tube

 

[cap1a79]

Although C-276 is the highest grades (CS <SS 316L < Alloy 20 < alloy B-2 < C-276, as per API 571, sulfuric acid service), we cannot say that C-276 is free from metal loss corrosion unless you do not find how stable iron sulfate film is naturally formed on C-276. Referring to ISO curve, at the temperature around 90 C, the corrosion rate can be increased up to 0.51 mm/year even if it is below 0.13 mm/year at room temperature. As you mentioned that it is "heat exchanger", I would suggest that service life corrosion (during life time) is within the tolerance of thickness. (Nominal thickness - the thickness required by strength calculation VS service life corrosion)

Lee SiHyoung,
WorleyParsons Oman Engineering,

 

[EdStainless]

Selecting one alloy for sulfuric service is like picking one thing to drink for the rest of your life, there is no correct answer.
Alloy 20 is commonly used because of its versatility.
There is no alloy that is always better in this service.
For various specific conditions depending on the concentration, impurities, and temperature there will likely be better options (C276, 625, 31, A611 or SX or ZeCorr, or even E-Brite).

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P.E. Metallurgy, Plymouth Tube