The installation of differential pressure flow meter measuring throttle should comply with the following provisions

1, the throttle device should be installed on the full of measured medium pipeline. 2, either upstream or downstream of the throttle device side should have a certain length of straight pipe. Upstream side of the smallest form of straight pipe and local resistance of upstream side and orifice diameter and pipe diameter ratio ( f l = d / d) The relevant. 一) Orifice, nozzle and venturi nozzle required straight pipe upstream or downstream side of the shortest length hole location b in figure 1) Classic venturi required the upstream side of the shortest straight pipe length are shown in table 6; Downstream straight pipe section, from the throat hole pressure calculation, should be 4 times the diameter of the throat. Table 5 classic asked straight pipe upstream side minimum dome pipes note: (1) the length of the shortest straight pipe are expressed in multiples of process piping diameter D. (2) the upstream side vertical section plane child from the upstream pressure. Pipe material degree. in shall not exceed available in the market of the smooth tube in a degree. in ( About the K/D< 10 - 3) 。 (3) without the value of the bracket is & throughout; Zero additional uncertainty & other; The values of the brackets for & other; 0. 5% of the additional uncertainty & throughout; 。 (4) elbow bend radius equal to or greater than the pipe diameter. (5) is located in the throat for downstream pressure at least 4 times the throat diameter of the pipe or other choke does not affect the measurement uncertainty. 3, such as in horizontal and inclined pipes are installed on the throttle device, take on the hole in the pipe cross section bearing shall meet the following requirements: a) For measuring gas, wet gas, should be an Angle with the vertical centerline & alpha; Within the scope; For dry gas, should be in the center of the horizontal line and half the level below the center line & alpha; Angle range, & alpha; Less than 45 & deg; ； b） When measuring the steam, the horizontal center line; c) When measuring liquid, up and down in a horizontal centerline & alpha; Angle range, when the solid particles in the liquid, above the horizontal centerline. The gas in the liquid, in the horizontal center line below, & alpha; Less than 45 & deg; 。 4, the throttle device should be installed in horizontal pipe runs, can be installed in vertical pipe runs ( Except for eccentric or segmental orifice) , should consider to facilitate installation and maintenance, operation platform should be set up when necessary. When installed in a buried pipeline, should set up well. 5, eccentric orifice plate must be installed in horizontal pipe runs. Measured gas in the liquid, such as orifice and dome point in the process piping and tangent, apply pressure hole located in the horizontal center line of the pipe cross section; Such as measurement of condensate gas or liquid containing solid particles, orifice with round bottom point in the process piping and tangent, take a hole in the pipe at the top or the center line.