AN UPDATE ON V-CONE METER WET GAS FLOW METERING RESEARCH

摘要

With the increasing importance of wet gas flow metering to industry, the Differential Pressure (DP) meter wet gas flow correlations are being increasingly utilised. Currently little information exists regarding the applicability of such correlations beyond the limits of the data sets used to create them. In particular little is known about the repeatability of a DP meter with wet gas flows, meter size and liquid property effects on the validity of the DP wet gas correction factors. In 2001 NEL tested a 6" schedule 80, 0.75 Beta Ratio V-Cone meter with a N_(2)/kerosene wet gas flow as part of the UK governments Department of Trade and Industry (DTI) funded Flow Programme. In 2002 McCrometer and NEL jointly presented analysis of this data at the North Sea Flow Measurement Workshop (NSFMW) [1]. The parameters that affected the "over-reading" (i.e. the positive error induced by the presence of liquid with the gas flow) were shown and a wet gas flow correlation was offered. For a known liquid mass flow rate or liquid to gas flow rate ratio the meters gas prediction was to +-2percent with a few outliers. In 2003 McCrometer presented results of repeat tests at NEL and a single wet gas data set from a 4" schedule 80, 0.75 Beta Ratio V-Cone meter tested with natural gas (NG)/decane at CEESI [2]. The V-Cone meter was shown to be repeatable and the results from CEESI were similar to those of NEL. However, in general, the question of what effect meter size and liquid phase properties have on DP meter wet gas over-readings is largely unanswered, even though the applicability of published correlations in different applications is a very relevant industrial issue. This paper shows several V-Cone meter wet gas data sets from four wet gas test loops and compares them, to investigate repeatability, meter size and liquid property effects. The two NEL 6" schedule 80, 0.75 beta ratio N_(2)/kerosene data sets are shown, along with four CEESI 4" schedule 80, 0.75 beta ratio natural gas (NG)/decane data sets, one K-Lab 6" schedule 160, 0.75 beta ratio NG/condensate data set and one CEESI 2" schedule 80, 0.70 beta ratio NG/Stoddard (a hydrocarbon liquid)/water data set. Results show repeatability of the V-Cone meter with wet gas flows, and also allow an examination of the effects of extrapolating the published V-Cone meter wet gas flow correlation for gas to liquid density ratios above and below the limits of the NEL data set used to form the published correlation. (This exercise results in a modification of the originally published V-Cone meter 0.75 beta ratio wet gas correlation at low gas to liquid density ratios.) By comparing the CEESI 2" and 4" meter hydrocarbon liquid data, some initial scaling information can be found; and comparing the water and Stoddard liquid data sets on the 2" meter, some initial liquid property effects can be determined.