This paper presents an analysis of flashing and non-flashing water flo
ws through a safety relief valve. A set of experiments has been carrie
d out on the CROSBY safety valve and its model. The pressure distribut
ions inside the valve, the inlet and outlet temperatures and the mass-
flow rates (critical or otherwise) have been measured. The characteris
tics of the valve giving the mass-flow rate as a function of the squar
e root of the pressure drop are given. The experimental results are co
mpared with equilibrium and relaxation two-phase flow models. The non-
equilibrium character of fast evaporation and its substantial influenc
e on the two-phase flow behaviour are demonstrated.