Vibration Monitoring of Hot Bitumen Storage Tank

The owner had concerns about the stresses induced in the various tank and piping components during the periodic vibrations experienced by the storage tank system. The objective of the investigation was to establish whether or not the integrity of the tank/piping systems was at risk of failure due either to excessive loading or to fatigue failure. Long term operating parameters were to be defined for process control purposes.

Vibration instruments were installed to monitor the tank and its associated piping during steam injection and the subsequent collapse of vapour bubbles. Five biaxial velocity sensor packages were installed at five stations on the outer surfaces of the tank wall, nozzle, heater piping and concrete support base. A further thirteen wieldable strain gauges designed for long-term applications were installed using capacitance discharge spot microtacking techniques.

The signal conditioning from both the velocity sensors and strain gauges was done using a Terrascience ST41 system. The conditioned signals were then acquired by a Weir-Jones Group Automeasure™ data acquisition system; a parallel stream of data was transmitted approximately 500m as current loop signals to a control room.

Weir-Jones was able to certify that the peak stresses from the current cyclic loading levels was below the threshold of concern and failure of the components was unlikely as a result of these stresses. However, Weir-Jones was told that previously much higher loads were applied to the system and Weir-Jones was also able to confirm that the greater peak stresses previously induced likely exceeded the recommended endurance limits and if continued could have led to catastrophic fatigue failures of the components.