{"id":49862,"date":"2020-05-27T09:52:30","date_gmt":"2020-05-27T04:22:30","guid":{"rendered":"https:\/\/ye1o34zhk8.onrocket.site\/?p=49862"},"modified":"2023-11-02T13:13:35","modified_gmt":"2023-11-02T07:43:35","slug":"orifice-flowmeter-rangeability","status":"publish","type":"post","link":"https:\/\/instrumentationtools.com\/orifice-flowmeter-rangeability\/","title":{"rendered":"Orifice Flowmeter Rangeability"},"content":{"rendered":"\n

Orifice<\/a>, combined with differential pressure transmitter<\/a>, is the most used flow measurement device in oil & gas plants because of its low cost and its ease of installation and maintenance.<\/p>\n\n\n\n

Flowmeter Rangeability<\/h2>\n\n\n\n

However, the orifice only allows 3:1 rangeability to maintain accuracy. This means, if one wants to measure a maximum flow of 10 MMscfd, then the minimum flow measurement that could be measured is only 3.3 MMscfd.<\/p>\n\n\n\n

According to the Bernoulli principle<\/a>, the relationship between the flow and pressure drop of fluid passing through an orifice is given by the following formulae:<\/p>\n\n\n

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\"Orifice<\/figure>\n<\/div>\n\n\n

Q = Volumetric flowrate
dP = Measured pressure drop \u03c1 = Density
Ao = Cross-sectional orifice area
Cf = Constant<\/p>\n\n\n\n

Hence, flow value could be obtained by measuring pressure drop<\/a> and the relationship between them is a square root<\/a>.<\/p>\n\n\n\n

Let\u2019s say the orifice is intended for flow measurement of 0-10 MMscfd which is represented by 0-100 inH2O pressure drop (as shown below the curve)<\/p>\n\n\n

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\"Differential<\/figure>\n<\/div>\n\n\n

At a maximum flow of 10 MMscfd, a change of 1% of full flow (0.1 MMscfd) to 9.9 MMscfd will be represented by a change of 2% of DP (from 100 inH2O to 98.01 in H2O).<\/p>\n\n\n\n

The following table summarizes the value of flow, its corresponding pressure drop, and its dP change in percentage of full scale for a 1% change of full flow at the specified flow.<\/p>\n\n\n\n

The less flow to be measured, the more sensitivity suffers.<\/p>\n\n\n

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\"Orifice<\/figure>\n<\/div>\n\n\n

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