304SS flange mated to 3-1/2Ni flange. 1

[PlantMan]

I have a Manway cover that is a 20" 300# blind made of SA-350-LF3 (3-1/2 Ni) steel that needs a new manway cover.

There is a long delivery on a new 3-1/2 Ni manway cover, but I can get a 304SS manway cover off the shelf. The 304SS is acceptable for the cold service. I would have to mate it to the existing 3-1/2 Ni flange that is currently on the manway nozzle.

Before I make the change I want to ensure that there will not be any potential problems. Has anyone ever mated a 304SS blind flange with a 3-1/2 Ni flange?

I would appreciate it if anyone can point out any potential problems.

 

[82253]

This is acceptable by ASME, our company has done it in the pass. Its cheaper alernative as well. The only possible problem is your client not allowing Stainless in the plant area where the tank goes.