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To help you focus on your flow numbers - and not how you got them - Openchannelflow flow offers a range of accessories for our Trapezoidal flumes

While these accessories cover a wide range of installation, site, and monitoring conditions, keep in mind that we always have the ability to customize our products to meet your specific needs.  Just drop us a line and let us know.

For applications where below grade flow monitoring is required, Openchannelflow integrates Trapezoidal Flumes into our fiberglass Packaged Metering Manholes.


End Connections 

End Adapter

end adapter with pipe stub on a fiberglass Openchannelflow Trapezoidal flumeEnd adapters are formed structures that attach to the end of the flume that allow flow to be transitioned into / out of 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 flume itself.

Staged Manhole Transitions

staged end adapter for adapting Trapezoidal flume to round manhole wallStarting with our regular end adapter, a curved is molded into the piece so that the flume can now be directly connected to a manhole wall.  This eliminates the need to either form a transition or have a pipe connection to the flume.  Staged transitions are available for number of flume / manhole diameter combinations. Contact Openchannelflow for additional details.


Flow Conditioning

Energy Absorber

An energy absorber is plate placed in the inlet end adapter of a flume to slow down the energetic flow from an incoming pipe.   Flow enters the end adapter, hits the energy absorber, slows down as it goes around the absorber, and then flows 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 straightener mounted in the inlet end adapter of a Trapezoidal flumeFlow 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

For small Trapezoidal flumes perforated baffle plates can be used to simultaneously slow and straight the flow entering the flume.  Perforated plates are installed upstream of the entrance of the flume and are used in sets of two or more.  The first plate slows down the flow and breaks up the velocity profile, while the second plate straightens out the flow as it enters the flume. 

Flow / Level Accessories

Bubbler Tubes

bubbler tube mounted in Trapezoidal flume

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.

Probe Well

A probe well is a small diameter tube molded on the outside of a flume that allows a submerged pressure transducer to be slid into it without the need to unbolt / mount the probe.  

Staff / Head / Level Gauge

galvanized steel Trapezoidal flume with staff gaugeEssentially a ruler attached or molded into the side of a flume that allows for a quick visual measurement of the level.  Black numbers / gradations are printed onto a high visibility yellow-green background.  

The standard staff gauge is in centimeters, 1/10-foot, and 1/100-foot increments, although level and flow scales are available.  

Openchannelflow Trapezoidal flume staff gauges have been corrected so that indicated head is the VERTICAL head the flume.

Stilling Well

stainless steel Trapezoidal flume with detached stilling wellA 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

ultrasonic transducer bracket mounted over a Trapezoidal flumeAn 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 

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 Trapezoidal 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.  

sampler tube in Openchannelflow fiberglass Trapezoidal 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 

bolt down fiberglass cover over a Trapezoidal flumeAvailable 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.  

In applications were more operator access may be required, sections of a flume cover can be hinged (typically over the point of measurement) while the rest of the cover remains in place.

Flume Enclosure

Large 60ยบ Trapezoidal flume mounted in Openchannelflow fiberglass Redstone EnclosureSmall, Large, and Extra Large 60º Trapezoidal flume flumes can be integrated into our Redstone Equipment Enclosures providing a turn-key flow measurement solution.

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.

Larger flumes may require the use of multiple sections of grating while smaller flumes may have the grating as one continuous piece.

Sectioned Flumes

As a flume gets larger it gets heavier.  This can make it both cumbersome and difficult to transport a flume to a remote site or to install it in a confined space.  For these applications Openchannelflow offers flume sectioning.  Sectioning a flume breaks it down into manageable sections that are later field assembled.