A benchmark is organised to quantify the variability relative to structure dynamics
computations. The chosen demonstrator is a pump in service in thermal central units, which
is an engineered system with not well-known parameters, considered in its work
environment. The blind modal characterisation of the separate pump components shows a
5%–12% variability on eigenfrequency values and a less than 15% frequency error in
comparison with experimental values. The numerical-experimental MAC numbers reach 0.7 at
the maximum, even after updating. An example of modal results on the pump assembly fixed
is presented, which shows a larger discrepancy with measurement values, essentially due to
the modelling of the interfaces and boundary condition, and to the possible simplification
of the main components F.E. models to reduce their size. Though a significant frequency
error, the first overall modes are correctly identified. If this tendency can be confirmed
from all the participants’ results, the conclusion to be drawn is that, if the predictive
capability of F.E. models to represent the dynamical behaviour of sub-structures is
satisfactory, the one relative to structures that are built-up of several components does
not allow their confident use. Additional information issued from measurements is needed
to improve their accuracy.