The Insert Style Palmer-Bowlus Flume is designed to be installed in an existing half-pipe or u-channel.  The flume is also used where space is at a premium - as the flume body consists of only the throat of the flume - the point of measurement being upstream of the throat (outside of the flume).  

It is important to note that for the Insert Style, the OD of the flume is line size and not the ID of the flume as is the case with the Permanent Style - the flume is constricted to fit into the line.  Unless the flow tables / equation take this into account, the flume will indicate higher flows than are actually present.

The Insert Style does require that the approach - where the point of measurement is - be field formed.  

No factory integration of measurement or conditioning accessories is possible (as these mount in the approach) and end connections are also not available.

For this flume, note the accumulation of sandy debris upstream.  At low flows / high solids concentrations, upstream sedimentation can occur for Palmer-Bowlus Flumes.