Abstract: A process for supplying a flow of nitrogen to a site having flowrate requirements varying between a nominal flowrate and a range situated thereabove comprising: a) passing compressed air into a main line in a separating assembly formed by at least two membrane separation lines mounted in parallel, wherein at least one of the separation lines can be shut off from the main line, the separating assembly having one of the following configurations: a1) when the flowrate requirements are situated at a level of the nominal flowrate, all of the membrane separators of the assembly are in operation, none of the separating lines being shut off; a2) when the flowrate requirements of the site exceed a predetermined flowrate, at least one of the lines of the separating assembly is shut off, keeping at least one separation line and its membrane separator in operation; b) advancing nitrogen gas obtained at the outlet side of each of the membrane separators to a collector connected downstream of the main line; c) evacuating g