Flow DetectorsHEAD FLOW METERSDallFlowTubeThe dall flow tube, illustrated in Figure 4,Figure 4 Dall Flow Tubehas a higher ratio of pressure developed topressure lost than the venturi flow tube.It is more compact and is commonly usedin large flow applications. The tubeconsists of a short, straight inlet sectionfollowed by an abrupt decrease in theinside diameter of the tube. This section,called the inlet shoulder, is followed bythe converging inlet cone and a divergingexit cone. The two cones are separatedby a slot or gap between the two cones.The low pressure is measured at theslotted throat (area between the twocones). The high pressure is measured atthe upstream edge of the inlet shoulder.The dall flow tube is available in mediumto very large sizes. In the large sizes, thecost is normally less than that of a venturi flow tube. This type of flow tube has a pressure lossof about 5%. Flow rate and pressure drop are related as shown in Equation 4-3.(4-3)VK DPwhere= volumetric flow rateK = constant derived from the mechanical parameters of the primary elementsDP = differential pressureRev. 0 Page 5 IC-04
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business