Pressure surge or water hammer simulations are performed to evaluate a safe design or operation of oil transfer systems. The speed of sound of the transferred fluid plays a key role within pressure surge simulations. Unlike for steel pipe systems, the speed of sound in hoses is not easily determined. In industry, a value of 450 m/s is frequently used for hoses, but this value is often used independent of conveyed fluid, pressure or the type of hose. For that reason, a project was performed that aimed to experimentally reaffirm existing speed of sound data and to extend its usable range by including tests at several static pressure levels.
Speed of sound measurements were performed on two 20”, 12 meter long, water-filled oil offloading hoses. The speed of sound was determined by the initiation of pressure waves in the hoses, while performing pressure measurements on either side of the hose. These experiments were performed at different static pressures up to 18 bar(a).
The measured values depend on the applied method to determine the speed of sound. For both applied methods, the speed of sound is higher than the classically assumed 450 m/s. The method that is considered best applicable for the purpose of the experiments, the speed of sound is significantly higher and can reach values up to 1100 m/s. The consequence of this is that the results from pressure surge studies in which 450 m/s was used, are not conservative.