Flow Detectors
HEAD FLOW METERS
Summary
Head flow meters operate on the principle of placing a restriction in the line to cause a pressure
drop. The differential pressure which is caused by the head is measured and converted to a flow
measurement. The basic construction of various types of head flow detectors is summarized
below.
Head Flow Meter Construction Summary
Orifice plates
Flat plates 1/16 to 1/4 in. thick
Mounted between a pair of flanges
Installed in a straight run of smooth pipe to avoid disturbance of flow patterns
due to fittings and valves
Venturi tube
Converging conical inlet, a cylindrical throat, and a diverging recovery cone
No projections into the fluid, no sharp corners, and no sudden changes in contour
Dall flow tube
Consists of a short, straight inlet section followed by an abrupt decrease in the
inside diameter of the tube
Inlet shoulder followed by the converging inlet cone and a diverging exit cone
Two cones separated by a slot or gap between the two cones
Pitot tube
Consists of a tube with an opening at the end
Small hole in the end positioned so that it faces the flowing fluid
Rev. 0
Page 7
IC-04
