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Building upon our range of Parshall flume accessories, Openchannelflow manufacturers a range of accessories to customize our Montana flumes

These accessories cover a wide range of installation, site, and monitoring conditions, but keep in mind that we always have the capability to customize our products to your specific needs.

For applications where below grade flow monitoring is required, Openchannelflow offers fiberglass Packaged Metering Manholes.


End Connections

End Adapter

inlet end adapter with pipe stub on fiberglass Openchannelflow Montana FlumeEnd connections for Montana flumes revolve around the inlet end adapter.  An end adapter is a rectangular structure that attach to the inlet of a Montana flume that allow flow to be transitioned into the flume in a controlled manner.  

End adapters can be provided with pipe stubs, flanges, or caulking collars to connect to piping.  Additionally, end adapters can be left with the ends open if necessary.  

End adapters are also convenient locations to mount other accessories that otherwise would not fit in the Montana flume itself.

Staged Manhole Transitions

Taking our standard Parshall end adapter, a curved is molded into the piece so that the flume can now be directly connected to a manhole wall – eliminating the need to either form a transition or have a pipe connection to the flume.  Staged transitions are available for select sizes of Montana flumes and manhole diameters.  Contact Openchannelflow for additional details.

Wing Wall Transitions

Wing walls are radius plates that are attached to the inlet of a Montana flume to direct flow into flume from a wider channel.  

Wing walls can be factory attached or shipped loosed for field installation as required.

Montana flume wing walls should always be of the radius type.  Research has shown that flat 45º inlet wing walls can adversely affect flow in the converging section of the flume.


Flow Conditioning

Energy Absorber

An energy absorber is structure placed in the inlet end adapter that breaks up energetic flows from inlet pipes.  Flow entering the flume hits the energy absorber, is slowed, and then flows around absorber and into the flume.

Energy absorbers develop turbulence and non-uniform velocity profiles and should always be used in conjunction with flow straighteners.  Also, energy absorbers should not be used on flows containing high solids as these will collect on the absorber plate.

Finally, the splashing turbulence generated by an energy absorber may require that a cover be placed over it.

Flow Straightener

Flow straighteners (usually used in sets of two or more) installed upstream of the flume serve to break up the incoming flow pattern and force it into parallel lines as it enters the flume.  

Like energy absorbers, flow straighteners should not be used on flow containing large solids.  They should also not be used on flows with floating debris.

Perforated Plate

Another approach to conditioning flows in small Montana flumes is the perforated plate.  Used in a series of two or more, perforated plates slow and then straighten flow before it enters the flume.

Flow / Level Accessories

Bubbler Tubes

A bubbler tube is a stainless steel assembly used in conjunction with a bubbler flow meter that's mounted in a cavity molded into the sidewall of a flume.  The tube extends down to the floor of the flume and is secured in place by two nuts in the top flange of the flume.  

Rigid and recessed from the main flow stream, a bubbler tube allows the operator to connect the usual vinyl / Teflon tubing from their bubbler flow meter to the flume.

Staff / Head / Level Gauge

staff gauge on a fiberglass Openchannelflow Montana flumeEssentially a ruler attached or molded into the side of a flume that allows for a quick visual measurement of the level.  

With black numbers / gradation printed onto a high visibility yellow-green background, Openchannelflow staff gauges are designed to be easily read from a distance.  

The standard staff gauge is dual scale with centimeters, 1/10-foot, and 1/100-foot increments.  Staff gauges are also available with custom level and flow scales.

Stilling Well

stilling well on a galvanized steel Montana flumeA stilling well is a chamber (round or rectangular) off to the side of a flume where flow measurement or parameter monitoring can be conducted.  Isolated from the main flow of the flume, the level in a stilling well is quite – with surface waves and turbulence eliminated.  

Stilling wells can be attached to the side of the flume or they can be remote from it (detached) and are available in a range of sizes – from 6-inches [15.24 cm] and up.

The connection between the flume and the stilling well is usually a 2-inch [5.08 cm] connection, although larger / smaller connections are available.

The floor of a stilling well is usually recessed below that of the flume so that there is always standing water in the stilling well at all times – even when there is no flow in the flume itself.  This body of water can help to keep parameter probes wetted.

Stilling wells are not for use on sanitary flows (clogging) or flows with high solids contents (sedimentation).  Periodic flushing / maintenance may be required.

Ultrasonic Transducer Bracket

An adjustable stainless steel bracket designed to hold ultrasonic transducers (and their separate temperature sensors) above a flume or stilling well.  Transducers up to 1-inch [2.54 cm] can be accommodated with the standard bracket – with custom sensor holders available for larger sensors.

Openchannelflow ultrasonic transducer brackets have multiple degrees of freedom and can be mounted in horizontal or vertical positions and on uneven surfaces.

Parameter Monitoring Accessories

Probe Holder

A stainless steel assembly recessed into the sidewall of a flume that allows a parameter probe to be held rigidly in place.  The probe holder is secured to the top flange of the flume with two nuts, while the probe is held by two stainless steel spring clips welded to the assembly..  

Probe holders are preferable to probe wells in applications where sedimentation may occur.  Probe holders are not, however, recommended in applications where ragging solids are present.

Probe Well

probe well on a fiberglass Montana flumeA probe well is a small diameter tube molded on the outside of a flume that allows a parameter probe to be slid into it without the need to unbolt / mount the probe (like a probe holder).  

Simpler and cheaper than a probe holder, a probe well is essentially a smaller version of a stilling well – with all of its advantages and disadvantages.

Sampler Tube

Similar to a bubbler tube, a sampler tube is a rigid stainless steel assembly that can be mounted in a cavity molded into the sidewall of a flume.  The tube extended down to the floor of the flume and is secured in place by two nuts in the top flange of the flume.  

Recessed from the main flow stream, a sampler tube allows an operator to sample from the flume with standard suction line.  

Unlike a sampler strainer, a sampler tube has only one opening through which a sample can be drawn.  As a result, should the opening ever be clogged, no sample with is taken.



Flume Covers 

Available in bolt-down, hinged, and fixed configurations flume covers are one way of keeping debris, inflow (and prying hands) out of a flume.  

Covers are available in a variety of materials and can be provided with hinged and fixed observation windows to operator access without the need to remove the cover.  

Nested (Dual Range) Flumes

Flume nesting allows a smaller, lower flow flume to be installed in a larger, higher flow flume.  

Nested flumes are usually used in applications where the flow will trend one way or the other over time (subdivision build out or water conservation), but they can also be used in applications where there is a defined pattern of widely varying flows (resorts).  

Recessed Grating

For installation where foot traffic will be present next to or around a flume, recessed grating may be necessary to ensure operator safety.  Mounted into a recess at the top of the flume, recessed grating is flush with the top of the flume – eliminating any trip hazard while ensuring that the operator cannot accidentally fall into the flume.

Replacement Floors

Replacement floors are a way of correcting flume hydraulics where a flume has been set at the wrong elevation or where downstream conditions have changed and the flume is now submerged.


While ASTM D1941 prescribes standard sidewall heights for Parshall / Montana flumes, there are times when a flume needs to be shorter or taller to meet the needs of an installation. For these cases Openchannelflow offers modified height sidewalls.

Irrigation flumes are the most common use of modified sidewalls (usually half height), although other applications may call for them.  

While not verified by research, extended height sidewalls are one means of obtaining higher maximum flow rates without increasing an installations footprint.