ABSTRACT
Elbow taps are easy to implement because most piping configurations already contain elbows in which taps can be located. Accumulation of extraneous material in the differential pressure connections can plug the elbow taps. As with other head-type primary flow measurement devices, the differential pressure developed by a given flow is precisely repeatable. Taps in long radius pipe or tube bends do not develop sufficient differential pressure for good flow measurement at low flow velocities. The upstream piping is a factor in the installation of elbow taps. Tap hole diameter should not exceed Gࢠof the pipe diameter. Threaded elbows with the flow section larger than the pipe develop less differential pressure and thereby increase the error. When selecting an elbow for flow measurement purposes, it is preferable to pick one that is located between two horizontal pipe sections. As the differential pressure instrument is piped to these taps, this piping will not be self-draining.
