Wastewater flow measurement now possible underall conditions

The successful measurement of low flows in partially full pipes and open channels has never been easily accomplished. Problems have ranged from questionable theory to real maintenance issues encompassing fouled sensors, sediment and plugging. The “point velocity” and “line velocity” theories that imply a velocity measured on the fluid surface or near the pipe wall can be substituted for the average velocity throughout the cross-section of the pipe have always been significantly challenged. In addition, flow sensors that sit in the invert of the pipe or hang from the top have made installation difficult, while providing a place for rags and other debris to accumulate. The accuracy of these single technology flowmeters are only consistent within a specific or prescribed range of conditions. If conditions change, the stated accuracy ratings are no longer valid.

A new solution…. Accuron Hybrid Technology Cartridge Meters, available in the UK from Bell Flow Systems, who will be exhibiting at WWEM on stands 22 and 23,combine two distinct technologies in order to achieve maximum efficiency for monitoring of such flow under all conditions.

The Cartridge Meter is the first open channel flowmeter to utilise hybrid technology. The new technology combines a stainless steel trapezoidal flume and Teflon level sensor combinationfor low flow applications with the highly accurate and non-foulingtransit-time chordal velocity method for high flow applications. This new hybrid technology system allows for precise and highly accurate flow measurement during extremely low flows, high flows, flood events, reverse flows, stagnation and non-uniform hydraulic profiles.

During periodsof minimal flow (Zero to 1/3pipe diameter), The Accuronmeasures flow within its’ lowoperating range by utilizing thehighly efficient combination ofa trapezoidal flume and ultrasoniclevel sensor. Calibrated accuracy is ±3-5% of actual rateat a turndown: 60:1

During periodsof maximum flow (1/3 to fullpipe diameter). The Accuronmeasures flow within its highoperating range by utilizing anextremely accurate area-velocitysystem that combines an ultrasoniclevel sensor with a pair oftransit-time velocity sensors.

The Accuron Cartridge Meter comes with the assurance that each critical component will remain perfectly aligned during its installation plus operate free from the ongoing costs of repetitive maintenance.Transit-time chordal measurement is the most viable technique for predicting average velocity. It provides for detection of chordal velocity across the entire path of the fluid being measured.

Accuracy and cost efficiency is guaranteed by providing the end user with a pre-engineered field ready system designed for "out of the box" installation as opposed to the traditional solution. A single cartridge, pre-sized for its specific application, arrives at the job site as a fully integrated unit, requiring only 30 minutes for installation. Every component is factory precision aligned, calibrated and programmed in strict accordance to customer supplied operating specifications.
 

Engineering and plant personnel may now specify an extremely reliable and cost efficient system to monitor and measure flow in a single assembly. The Accuron Cartridge Meter shifts the responsibility of installed accuracy from the field to the factory. The added labour and expense of field programming, precise sensor alignment and costly flume installation is totally eliminated.

Prior to field shipment, each Accuron cartridge Meter is NIST traceable tested, calibrated and certified at the factory’s Flow Metrology Laboratory under the identical size and flow conditions specified for its ultimate application.

The risk and expense associated with repetitive confined space entry due to fouled submerged sensor problems is eliminated by using an “above the flow stream” submersible Teflon level sensor. The trapezoidal flume’sflat straight through bottom permits the flume to pass debris quite readily and reduces the problem of sediment build-up up-stream of the flume and the cartridge’s transit time velocity sensors are designed to prevent the accumulation of rags, branches and similar debris from interfering with the performance of the transducers.