Problems with orifice plate flowmeters
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Question: How is the set value ΔP for the differential pressure gauge in a orifice plate flow meter determined? And what determines the range? Dear seniors, I found some information online, but the explanations weren’t detailed enough; I still don’t understand it
Once the material property data and the nominal flow rate are determined, selecting the upper limit of the differential pressure determines the orifice ratio β, which in turn determines the pressure drop ratio. Since the pressure loss of the throttle element at maximum flow rate must not exceed the requirements of the process, the upper limit on the differential pressure cannot be too high. Pressure loss ratio = pressure loss / maximum differential pressure = 1 – β2. For example: Suppose the process requirement is that the pressure loss at the maximum flow rate should not exceed 5 KPA, and you want β to be around 0.6; then the scale differential pressure = 2 * 5/0.64 ≈ 15 KPA ； If you want β to be around 0.4, then the scale differential pressure will be around 2 * 5/0.84 = 12 KPA.
Both △P and the measurement range of the orifice plate flow meter are determined based on the orifice plate design specifications, and the settings must be made in accordance with those specifications.
Is each new orifice plate accompanied by setting parameters?
Normal flow rate x 1.4; maximum flow rate x 1.2. The higher of the two values is taken, and then rounded to an integer.
Pressure loss ratio = pressure loss / maximum differential pressure = 1 – β2. For example: Suppose the process requirement is that the pressure loss at the maximum flow rate should not exceed 5 KPA, and you want β to be around 0.6. In that case, the scale differential pressure will be approximately 2 * 5/0.64 = 15 KPA. Hello, according to your formula, it should be 5/0.64 – why is a multiplication by 2 necessary?
This post was last edited by HEJIYUER on 2020-7-4 20:42. If the scale flow rate/normal flow rate = 1.4, then the scale differential pressure = 2 times the normal differential pressure. X2。 This method is used only for quick estimation, to roughly determine the range of the scale differential pressure. The results obtained from orifice plate calculations must not only comply with ISO standards but also meet the maximum pressure loss requirements specified by the process; neither condition can be ignored. β can be adjusted, but pressure loss is a numerical value; therefore, the pressure loss can be taken into account first when designing the β for the orifice plate.
This post was last edited by hfrs on 2020-7-6 at 11:05. You can just try different software versions – there’s no need to worry too much about it. If we follow what’s written in the books, the upper limit for the differential pressure is equal to 2–2.5 times the pressure loss caused by the orifice plate. However, for some throttling devices, such as venturi tubes, B is sometimes set close to 0.7; in this case, the pressure difference must be much higher than the pressure loss, mainly to reduce the pressure loss.
p is listed in the calculation sheet; you specify the requirements for measuring the process parameters, and the manufacturer carries out the calculations and production based on those specifications. The range of measurement, etc., is also determined by the manufacturer using the process parameters