In this project, velocity profiles were measured in a diaphragm valve using an ultrasonic velocity profiling (UVP) technique. A non-Newtonian CMC model fluid was tested in this highly complex geometry and velocity profiles were measured at four different positions at the centre (contraction) of a specially manufactured 50% open diaphragm valve. The coordinates of the complex geometry and velocity magnitudes were analysed and compared to the bulk flow rate measured using an electromagnetic flow meter. Two different ultrasonic transducers (standard and delay line) were used and results were compared in order to assess velocity data close to wall interfaces as well as the accuracy and magnitude of measured velocities. The difference between calculated and measured flow rates was 32% when using the standard ultrasonic transducers. The error difference decreased to 18% when delay line transducers were introduced to the measurements. The velocity data obtained in the diaphragm valve showed a significant improvement close to the wall interfaces when using the delay line transducers. The main limitation when using delay line transducers is that beam refraction can significantly complicate measurements in a highly complex geometry such as a diaphragm valve. A new delay line transducer with no beam refraction could provide a solution. The introduction of delay line transducers showed that UVP can be used as a powerful tool for detailed flow behaviour measurements in complex geometries.