Abstract: A compact flow prover for calibrating continuous flowmeters includes a measuring housing comprising a main cylinder having a substantially uniform inside diameter and inlet and downstream sections having inside diameters greater than the main cylinder. The compact flow prover is provided with a displacer movably disposed within the housing having seals which form a fluid barrier while the displacer is disposed within the main cylinder. Inlet and downstream section guide means are provided to maintain the displacer in axial alignment with the main cylinder while the displacer is disposed within either of these sections, assuring smooth exit and entry. The displacer is provided with seals which are circumferentially compressed when the displacer enters the main cylinder and may be statically or dynamically monitored for integrity without an external pressure source.

Abstract: In a flow rate control apparatus, pressure of a primary, or controlled, liquid is reduced without application of shear forces thereto. Each of first and second piston and cylinder assemblies has a first port on one side of the piston and a second port on the other side. A secondary fluid path between the two second ports contains a controlling fluid directed through a pressure reducing valve. The rate of flow of the primary fluid from the discharge cylinder is controlled by the rate of flow of the secondary fluid through the pressure reducing valve. A four way valve couples the controlled liquid at relatively high pressure through the first port in a first cylinder, and the controlled liquid is discharged at relatively low pressure from the first port in the second cylinder. The first and second pistons are rigidly connected to assure synchronized motion and accurate metering of the controlled liquid and to provide for driving of both pistons in response to input pressure of the controlled liquid.