In essence probably not, but it depends what you're trying to do.
By European spec, I assume you mean an PN rated flange. A direct replacement is not physically possible as the design of the two types of flanges is not the same and they don't match. you can sometimes use a flange adaptor where a plate with a hole in it has two different sets of stud bolts welded to the different sides, but they look terrible and the strength of them is often questionable.
However, if you replace an entire flange set or flanges and valve, this can be accomplished providing that the design pressure of the system is equal or lower to your now new flange rating. Eg if a design pressure is 16 barg or less, you could replace a class 150 flange set with a PN 16 rated flange set. You might need to use the next rating up which is higher than the ANSI class rating to do this.
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