Abstract: A device for measuring in situ, the optical density of a sample in a medium, in which the immersed sample has a main part with a slot at one end. A mobile part can be lodged in this slot. This mobile part has an open chamber which moves with the mobile part into the slot. This open chamber will contain a sample and will be aligned with an optical device in the housing, when moved into the slot. The mobile part and open chamber are, therefore, movable between an open position in which the medium to be studied circulates in the chamber, to a closed position when the mobile part is lodged in the slot whereat the open chamber is isolated from the medium to be studied. Measurement is carried out while the device is in the closed position by measuring the optical density of the isolated medium.

Abstract: The invention provides, at the end of a pipe which extends a valve being part of an exhausting device for pressure-relieving a pressurized fluid, a nozzle which is exactly at the input of a hood, the convergent portion of said nozzle reducing its exit section so as to make it substantially double the maximum passageway section through the valve.

Abstract: The pressure in a high-pressure steam boiler or other pressure fluid tank is occasionally relieved by means of a discharge device having a pressure-relief valve mounted on an ejection conduit opening into a hood connected to a discharge conduit. A break in continuity is provided between this ejection conduit and this hood in order to allow relative movements thereof under thermal expansion; furthermore the ejection conduit opens into the hood through a generally transversely directed nozzle system so that the jet issuing therefrom has a zero or negligible axial velocity component.