I work in a Canadian Manufactucturing facility that ships to the US, so we are subject to the FDA regulations and requirements. My QA manager has a more intimate knowledge than I do of "Food Grade" and the discussions we have had revolve around "culinary steam". This applies to steam that is to be applied into food directly as part of a cooking process, as opposed to food in indirect contact (thermal vessels).
The requirement states a required filter size (I'm not sure what it is, exactly - by definition, 95% of particles 2 microns and larger must be removed) and that only stainless steel piping be used between the filter and the product.
If this is not your question, my apologies for the waste of time and space.