Standard nozzle and standard sharp orifice plate
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For the same project, the design institute uses steam flow meters for the same medium at a pressure of 1.0 MPa, with a temperature of around 184 degrees Celsius. Some are chosen as standard nozzles, while others are selected as standard sharp-orifice plates. Dear colleagues, what are the advantages and disadvantages of each when used for measuring steam, and what is the difference in price?
The pressure loss of the nozzle is low, and the required length of the straight pipe section downstream is also shorter compared to that of standard orifice plates. Its price is higher than that of orifice plates, but the range of nominal diameters it can handle is smaller than that of standard orifice plates; seemingly, the maximum diameter it can handle is around 500 mm.
As a supplementary point, nozzles have high precision, while orifice plates have relatively lower precision; the precision of nozzles remains unchanged over long periods of use
Compared to the other, the nozzle has higher precision and lower pressure loss ； The accuracy of orifice plates is lower, and of course the price is also lower
The process engineering team has specific requirements regarding the pressure loss associated with flow meters. When selecting a flow meter, standard orifice plates are typically used for calculations first; if the calculated pressure loss is not acceptable, standard nozzles are considered for further calculations. If that still doesn’t work, it’s necessary to verify the data with the process engineering team – it’s possible that the pipe diameter is too small, or that the pressure loss is too low and needs to be increased slightly.
Orifice plates do not require calibration; nozzles have lower precision before calibration compared to orifice plates. The required straight pipe section is longer than that for orifice plates, the pressure loss is lower than that of orifice plates, but higher than that of Venturi tubes.