Application of the hottest differential pressure f

2022-07-23
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Application of differential pressure flowmeter below 30% of full scale

many process personnel on site may understand that the standard throttling device is not suitable for use at 30% of full scale, and the range ratio is appropriate, that is, 3:1. If it is too large, it will seriously affect the accuracy. Although many differential pressure flow meters can achieve a large range ratio, such as V-cone flow meters, which are widely used now, can achieve 13:1, while wedge-shaped flow meters, which are good at measuring dirty media, can achieve 15:1. These products directly make up for the small measurement range ratio of standard throttling devices. So why is there such a small flow when the throttling device measures the field flow? After studying its principle, it is not difficult to find that this is mainly determined by the flow calculation formula of the throttling device. Here is a detailed introduction to the reason:

in flow measurement, the national standard stipulates that the applicable flow ratio of the throttling device is 30% (that is, the maximum flow: the minimum flow =3:1). Here, because the differential pressure is proportional to the square of the flow, the accuracy cannot be guaranteed when the flow ratio is less than 30%, NCM materials generally include ncm111, ncm424, ncm442, ncm523, ncm622, ncm811, etc. in addition, the falling ball impact tester is applicable to the impact strength test of plastic, ceramic, acrylic, glass, lens, 5 gold and other products. When the flow rate is lower than 30%, the Reynolds number is often lower than the limit Reynolds number, and the flow coefficient α Is not constant, resulting in inaccurate flow measurement

how to deal with this situation

1. First, negotiate with the process personnel to reduce the maximum flow. If the Reynolds number is large enough, it can be solved by changing the orifice or differential pressure

2 Use other differential pressure flow meters. If the on-site operating parameters cannot be changed and the flow range is large, we can choose V-cone flow meters with the increase of eccentric moment. V-cone flow meters are widely used at present. Their main characteristics are: high precision, large range, small pressure loss, and the storage function of experimental curves and experimental data to save energy. For on-site corrosive media, Wedge flowmeter can be selected. Main features: low lower limit of Reynolds number, wide application range and good stability

3. For on-site large-diameter measurement, in terms of economy and installation, plug-in differential pressure flowmeter can be selected, such as Annubar averaging tube flowmeter, plug-in double venturi flowmeter, plug-in V-cone Flowmeter, etc. these instruments have absolute advantages in measuring large-diameter. First of all, they have low cost, simple installation, and more importantly, they can ensure the on-site measurement effect

no matter which type of flowmeter has its limitations, we should use other methods to make up for its shortcomings. The company will make persistent efforts to achieve greater breakthroughs. (end)

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