Abstract: A device for establishing an environment of a required fluid inside a length of pipe, comprising two pipe-engaging members adapted to engage the interior surface of the pipe at respective positions spaced therealong, and means for introducing said fluid into the interior of the pipe between said engaging members, each pipe-engaging member comprising a casing for contacting the pipe interior surface and containing an inflatable element; wherein the casing of each engaging member includes at least a portion of stretchable material for enabling expansion and contraction of the casing in a direction radially of the pipe, for engaging a range of internal pipe sizes.