Experiment study on pressure drop of a multistage letdown orifice tube

Multistage orifice tube in a letdown pipe line of nuclear power plant is used to produce high pressure drop at a nominal flow rate. The geometry dimension and the arrangement of each stage orifice are very important to satisfy a high pressure drop operation condition. The experiment method is applied to investigate the pressure drop characteristic for a six stages orifice tube. Comparing the effects of pressure drop regulating approaches through the outlet and inlet of an orifice tube, the test results show that reducing the diameter of orifice in the first stage in the inlet or the sixth stage in the outlet of orifice tube can both increase the pressure drop. However, the regulating through the inlet can enhance the pressure drop characteristic obviously. The caviation index is used to check the geometry of orifice tube and believe that the structure is acceptable and can also avert the cavitation of orifices.