Fluid Control Systems Selected product range

253Design of the flow sensor fittingsOrifice selectionThe correct choice of orifice has a decisiveeffect on the function of a flow sensor. Ifcertain values of the flow speed are eitherexceeded or not achieved, the measurementerror increases considerably or the linearbehaviour of the sensor can no longer beguaranteed. If the maximum flow velocityexceeded even further, the transducercould be damaged.Flow rategpm2000010000500020001000500l/min500002000010000500020001000m 3/h50002000100050020010050DN400DN350DN300DN250DN200DN150DN125DN100DN80DN65DN50DN40200500DN32Example of orifice selectionSpecificationThe nominal flow rate should be 10 m 3 /h atan optimal flow velocity of between 2 and3 m/s.SolutionThe intersection of the flow rate and flowvelocity in the chart leads to the appropriateorifice, DN 40.Caution!No liability will be accepted for designerrors.1005020105210.520010050201053220105210.50.20.1DN25DN20DN15DN08DN060.210.50.050.10.30.02Inlet and outlet distancesaccording to EN ISO 5167-10.050.20.010.1 0.2 0.3 0.5 1 2 3 5 10 m/s0.3 0.5 1 2 3 5 10 20 30 fpsFlow velocitySensorsRegulating valve2 x 90° elbow joint3 dimensional2 x 90° elbow joint90° elbow jointor T-pieceExtensionReductionExplanationEN ISO 5167-1 prescribes the straight inletand outlet distances that must be compliedwith when installing fittings in pipe lines inorder to achieve calm flow conditions. Themost important layouts that could lead toturbulence in the flow are shown on the left,together with the associated prescribedminimum inlet and outlet distances. Theseensure calm, problem-free measurementconditions at the measurement point.D = orificeNote:If your measurement conditions do not permit compliance with the inlet and outlet distances,the changed K factors can be determined using the Teach-in function with which many of theBürkert flow measurement units are equipped (see data sheets).Subject to modifications