Butterfly valves with a monoflange body have a concentrically positioned flange with through holes. The flange would not allow a double dead-end service at fully rated pressure, but can be used for the one-sided shut-off of pipelines at lower pressure rates, to permit dis mantling one side of the pipeline. The flange does not extend over the regular body length of thevalve, so the short bodies, by which butterfly valves are characterised, are maintained.