The accurate and reliable indices of heat and coal consumption rate are the foundamental basis for measures in energy-saving and consumption-reducing

as well as in enhancing the equipment availability of thermal power units

whereas the main flow rate is a most crucial pamameter for calculating the said indices.At present

the uncertainty of flow rate measuring facilities in domestic power plants is very high

it is difficult to satisty the requirements of performance test for energy-saving and consumption-reducing of the units.The throat-tap nozzle with low β value is a high accurate flow rate measuring facility recomended in 《ASME Performance Test Code》

in order to ensure the lower uncertainty of said nozzle

the varification method of said nozzle and correct evaluation of the varified data are most critical.