Abstract: A valve assembly includes a valve body and, located therein, a valve member which can be moved between a first position, in which the valve is in a first operational mode, and a second position, in which the valve is in a second operational mode. The valve member has a rare earth magnet which, when the valve member is in either one of the two operational modes, causes the valve member to be magnetically biased against movement toward the other operational mode. The valve is provided with a device for generating a magnetic field sufficient for overcoming the magnetic bias in the first or second operational mode, so as to cause the valve member to move to the other of the operational modes.

Abstract: A method for in situ calibration of a flow meter under test installed in a pipe involves positioning a pre-calibrated insertion meter within the bore of the pipe in series with meter and using the output from the insertion meter to calibrate the meter. A calibration system is also described.

Abstract: A 3-phase flow meter comprises a pipeline containing pressure and temperature meters and a meter for measuring the density of the combined flow. A proportion of the flow is diverted through a separator which separates out the gas component from the liquid components. A density meter is provided to measure the density of the combined liquid components. The outputs of the various meters are fed to a processing circuit which outputs the volumes and masses of the three phases.