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This post was last edited by hesonchang214 on 2019-11-24 at 10:16. 1. Reading errors of instruments: Pressure gauges and flow meters are not calibrated before use, resulting in inaccurate readings. The pressure gauge is installed far from both ends of the pressure vessel, and its readings include the pressure losses in the piping; using these readings as the inlet pressure results in a lower inlet pressure and, consequently, a lower water production rate. 2. The inlet water temperature is lower than that specified in the initial design; for every 3°C decrease in inlet water temperature, the water production volume decreases by approximately 10%. 3. Inlet water conductivity (or TDS): The inlet water conductivity (or TDS) is much higher than the designed value. For NaCl solutions, an increase of 1000 ppm in TDS results in an increase in osmotic pressure of approximately 11.4 psi (0.8 bar); at the same inlet water pressure, the water production volume will decrease. 4. At the same inlet pressure, the pressure on the product water side is lower due to backpressure built up on that side, or because the product water pipeline is too small and the delivery distance is long/high, resulting in higher resistance and a decrease in net pressure as well as a reduction in the amount of product water produced. 5. Under normal conditions, for 6-core 8040 membrane elements, the pressure difference between the two sections is approximately 3–4 bar. An unreasonable pipeline design that results in high pressure losses, or incomplete closure of the secondary concentrated water discharge valve, can both lead to a decrease in net pressure, thereby reducing the water production volume. 6. Flux decay of membrane elements: Inadequate storage of wet membrane elements, or the lack of protective measures after these elements are installed in the system, can cause them to dry out, resulting in a significant decrease in flux or even no flux at all, and thus leading to low water production by the system.