Fluid flow measuring

Claim 1

A device for ensuring the accuracy and reliability of gas flow measurements when said gas contains substantial quantities of entrained particulates, said measurement being taken from a pitot tube with a pressure-sensing means, said pitot tube being disposed in a duct through which said gas flows and having a velocity prressure-sensing tube with at least one orifice facing the upstream direction of flow for measuring velocity pressure, comprising rotation means for interposing a barrier between said orifice and the upstream direction of flow when velocity pressure measurements are not being taken, said rotation means comprising a remotely actuated, external cover rotatable between a first position in which it covers said orifice and a second position in which said orifice is exposed and further including a three-way valve means interconnecting said velocity pressure-sensing tube, pressure-measuring means and a source of pressurized air, said valve means being operable between one position in which said velocity pressure-sensing tube and said source of pressurized air are in fluid communication and fluid communication to said pressure-measuring means is blocked, and a second position in which said velocity pressure-sensing tube and pressure-measuring means are in fluid communication, and fluid communication to the source of pressurized air is blocked.

Claim 2

A device for ensuring the accuracy and reliability of gas flow measurements when said gas contains substantial quantities of entrained particulates, said measurement being taken from a pitot tube with a pressure-sensing means, said pitot tube being disposed in a duct through which said gas flows and having a velocity prressure-sensing tube with at least one orifice facing the upstream direction of flow for measuring velocity pressure, comprising rotation means for interposing a barrier between said orifice and the upstream direction of flow when velocity pressure measurements are not being taken, said rotation means comprising a remotely actuated, external cover rotatable between a first position in which it covers said orifice and a second position in which said orifice is exposed and further including a three-way valve means interconnecting said velocity pressure-sensing tube, pressure-measuring means and a source of pressurized air, said valve means being operable between one position in which said velocity pressure-sensing tube and said source of pressurized air are in fluid communication and fluid communication to said pressure-measuring means is blocked, and a second position in which said velocity pressure-sensing tube and pressure-measuring means are in fluid communication, and fluid communication to the source of pressurized air is blocked.

Claim 6

The device of claims 1 or 4 further including a static pressure sensing tube located in said duct and having at least one downstream facing orifice, and said pressure-measuring means is a differential pressure measuring means which is also in fluid communication with said static pressure sensing tube for measuring a differential pressure between said static pressure-sensing tube and said velocity pressure-sensing tube.