ESDU 89012 presents the loss data for sudden contractions and expansions, orifice plates, valves (gate, globe, ball and diaphragm) and bends. In each case an equation is given for the two-phase multiplier which, when it is applied as a factor to the single-phase pressure loss calculated at the same mass flow rate, yields the two-phase pressure loss. Data for the single-phase loss are also included and, as in the case of the multipliers, are based on semi-empirical methods. The choice of equation for the multiplier is recommended as a result of correlating predicted pressure loss with a very wide range of experimental measurements drawn from the literature. For each component, that correlation is shown graphically and details are given of the geometry, flow orientation, fluids involved and inlet pressure appropriate to the test results used. The influence of flow regime and pipe orientation is discussed for each component. An approximate iterative method of allowing for flashing is given and is illustrated in one of two worked examples showing practical uses of the prediction methods.