I have a customer with a rack-type Hobart bakery oven. It has a flame gun that shoots into a burner chamber then into multiple pipes which form the heat exchanger in the unit. I have visually located a 3" long, very fine crack in one of the multiple pipes after the burner chamber. The oven works but I am sure the crack will only get bigger. The customer wants me to arrange to have the crack welded. Does anybody think this is inadvisable? I'm sure they're going to use it anyway, but wouldn't it be better to at least try to isolate the damage? They do not want to pay for a new heat exchanger or replace the oven.