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To help you focus on your flow numbers - and not how you got them - Openchannelflow flow has developed a wide range of accessories for the H Flumes we manufacture.  

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

For applications where below grade flow monitoring is required, Openchannelflow offers HS and H flumes integrated into fiberglass Packaged Metering Manholes.


End Connections

Approach Section

approach section on a 1-foot H flume manufactured by OpenchannelflowInlet end connections for H flumes usually involve an approach section.   An approach section is nothing more than an upstream extension of the rectangular cross-sectional shape of the inlet of an H flume.

Approach sections are recommended to be 3 to 5 times the maximum anticipated head (Hmax).  As a default they are usually sized to be 3 to 5 times the depth of the H flume.

An approach section is also a convenient location to mount other accessories that otherwise would not fit in the H flume itself.

It's to the approach section that inlet pipe stubs, flanges, caulking collars or other connections are usually made.

While approach sections are not mandatory when connecting an H flume to inlet piping, they are strongly recommended as the straight run of the approach section allows the flow to become less turbulent and assume a more uniform velocity profile before it enters the flume.

Drop Box

outlet drop box - left - on a 0.5-foot H flumeFor an H flume to operate correctly the discharge must freely spill off the end of the flume.  

To connect the flume to downstream piping, a drop box is offered to collect the flow spilling out of the flume and to direct it into the discharge piping. The discharge piping can leave the drop box horizontally or vertically as required.

Inlet Bulkhead

inlet bulkhead with pipe stub on a 0.5-foot fiberglass H flumeAn inlet bulkhead is a flat plate attached to either inlet of an H flume or (more usually) an approach section.  The bulkhead provides an area onto which a pipe stub, flange, or caulking collar can be mounted – allowing the H flume to be connected to upstream piping.

While approach sections are not strictly mandatory when using a bulkhead, they are strongly recommended as the straight run of the approach section allows the flow to develop a more uniform velocity profile before it enters the flume.

Staged Manhole Transitions

Taking our standard H flume approach section, a curved is molded into the inlet 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 0.4 and 0.6-foot HS flume and 0.5 and 0.75-foot H flumes. Contact Openchannelflow for additional details.

Wing Wall Transitions

galvanized steel h flume with inlet wing wallsWing walls are radiused (or flat) plates that are attached to the inlet of an H flume (or its approach section) to direct flow into flume from the channel.

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

Flow Conditioning

Energy Absorber

energy absorber mounted in an H flume approach sectionAn energy absorber is a flat plate placed in an approach section to break up and slow energetic piped flow.

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 - right - downstream of an energy absorber in a H flumeWhen the approaching flow is unbalanced or possess and otherwise poor velocity profile a flow straightener (or set) can be installed in an approach section to force the flow into parallel flow lines.

Flow straighteners are usually used in conjunction with energy absorbers and like energy absorbers they should not be used on flows with large solids or floating debris.

Perforated Plate

removable perforated baffle plates in a fiberglass H flumeAnother method to conditioning flows in small HS / H flumes is the perforated plate.  Like flow straighteners for larger H flumes, perforated plates force the water into parallel flow lines before they enter the flume.

Flow / Level Accessories

Bubbler Tubes

bubbler flow meter tube mounted in a 1-foot H flume

A bubbler tube is a stainless steel assembly used in conjuction 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-level gauge on an Openchannelflow fiberglass H 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.

Probe Well

probe well on an Openchannelflow fiberglass H flumeA 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.  

The probe well is connected to the main flow of the flume through a 1-inch [2.54 cm] or 2-inch [5.08 cm] opening.  To keep the probe wetted, the well usually extends 3-inches [7.62 cm] below the floor of the flume. 

Stilling Well

attached stilling well on a fiberglass h 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

ultrasonic bracket over a stilling well on a H 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 Accessories

Probe Holder

removable probe holder mounted in the sidewall of a H flumeA 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 H 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 

bolt down fiberglass cover over H flumeBolt-down covers are one are one way of keeping debris, inflow (and prying hands) out of the approach section of an H 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.  

Note that the geometry of the H flume is such that covers can only be placed over the approach section.

Flume Enclosure

H flume mounted in an Openchannelflow fiberglass Redstone equipment enclosureFor above grade industrial flow stations, Openchannelflow offers fiberglass enclosures with integrated HS and H flumes.  

0.4 to 1.0-foot HS and 0.5 and 0.75-foot H flumes can be mounted in a Redstone Equipment Enclosure, with the result being a complete turn-key flow measurement package.  

Each HS / H flume enclosure includes:

  • Flume
  • Approach section
  • Outlet drop box
  • Inlet / outlet pipe stubs (or flanges).

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.

Like flume covers, recessed grating is only available for H flume approach sections.