The invention relates to a method for measuring and controlling a fluid flow in a pipe system for liquid transport, such as oil flow during buoy loading, wherein there in each end of a the pipe system is spliced in a sensor (1) consisting of a pipe section (2) with a reinforced rubber bellows (3) positioned as a restriction within the transport pipe. The rubber bellows (3) is forced radially outward when there is oil flowing through the transport pipe, and compresses a gas filled volume in a pressure vessel (4) via a pipe connection (4B) in communication with an annulus (5), and a pressure transmitter (6A/B) gives signals to a control system (7). The sensor (1) on the platform and the tanker vessel measures relative changes in the liquid flow between the two measuring points, as the measurements from the tanker vessel is received via a telemetry system, and the signals from the two measuring points are compared continuously by the control system on the platform, which triggers an alarm and shuts down the loading process automatically at deviation in the measurement on the tanker vessel compared to the reference measurement on the platform.