One of the problems contractors often face when installing a flume in a concrete manhole is forming the transitions into / out of the flume.  Done poorly and the result is a flume that either experiences turbulence or submergence – both which will seriously compromise the accuracy of the flow measurement.

For medium to larger flumes, usually the only solution for below grade flow monitoring is to use a Packaged Fiberglass Metering Manhole. But for smaller flumes, it can often be a trade-off between ease of installation, cost, and manhole accessibility. 

When a new or existing concrete manhole must be used and standard length end adapters are too long to fit within the structure, Openchannelflow has developed Staged End Adapters that are design to securely fit a flume into the manhole. 

Standard vs Staged End Adapters

Standard Openchannelflow end adapters provide both a rise up into the flume and an extended inlet section to help calm and condition the flow before it enters the flume.  The standard end adapters are also chemically bonded to the flume at both ends to ensure a strong, watertight connection.

The Staged differ from Openchannelflow’s standard end adapters in a number of way:

• Staged end adapters are shorter in length and do not provide as much transitional flow conditioning as standard end adapters
• There is little rise from staged end adapters into the flume
• Staged end adapters are specific to a particular flume style / size and manhole diameter combinations
• Staged end adapters are only available for smaller Parshall, Montana, Cutthroat and Trapezoidal Flumes

Staged End Adapter Construction

When transitioning flow through a flume, the inlet transition is critical.  As such, the inlet staged end adapter is chemically bonded to the flume, while outlet staged end adapter is loosely bolted to the flume.

On site, the installer can unbolt the outlet staged end adapter, move the flume with the inlet staged adapter into place in the manhole, secure the flume to the upstream manhole wall, and then install the outlet staged end adapter. 

By allowing the outlet end staged end adapter to be removed, any deficiencies in the manhole can be addressed at the site without the need to perform a wholesale modification to the flume.  At worst, the outlet staged end adapter can be omitted if necessary to secure the installation.

Elevated Installations

While staged end adapters are intended to bolt to the manhole walls, these bolted connections are not intended to support the flume under operational loads.  When the flume is suspended in the manhole, supports should be placed under the flume at the entrance and exit.  The supports should be perpendicular to the longitudinal axis of the flume (the direction of flow).