If you have a stainless steel (shell) heat exchanger and you need saddles with a "wear plate" (the plate between the shell and the saddle itself), should the "wear plate" be stainless steel even though the saddles themselves are carbon steel?

Or putting it another way....should the "wear plate" be the same material as the shell?.....even if the saddles themselves can be carbon steel.

Thanks in advance for any advice given

Fernandez

All the external attachment directly welded to pressure parts have to be of same material as of pressure part material.

So wear plate shall be of SS even though saddles are of CS.

Don't think it is written in code any where but followed widely.

Sanjeev

Hi Fernandez,

If you have a procedure for the combination of these materials, there is no restriction as far as the Code is concerned. However, when something is not forbidden, it doesn´t mean automatically that it´s reasonable. As always the Code assumes that you know how to design your vessel.

Besides, different types of material always stand for a lot of other "problems" like different thermal expansion, corrosion, etc. which you have to consider. Maybe you do not "have to" as Sanjeev has mentioned so strictly, but it´s strongly recommended.

Michael

onething I would like to add more regarding the wear plate, it is also strongly recommended that wear plate should not be thicker than the shell. It is a recommendation of Henery H.Bednar.


Nasir