We run several small sewage plants and due to regulatory compliance we are required to record outflow/discharges into the creek. We have Mc Crometer turbine meters installed for many years, but they are requiring replacement/rebuilding about every other year, my guess from the atmospheric conditions at times and low flow leading to build up. I was hoping someone might have a recommendation of a better flow meter we could use to register flow in these conditions. Outflow piping is 3".

 

Could you build a v-notch and measure level instead? It is quite precise for low flow. I know we use in wastewater for small village to do the recording.

 

The process fluid is dirty, slightly corrosive and sticky. There is chances of accumulation of matters at low flow in the pipeline. It is recommended to use non-contact type flow meter such as ultrasonic flow meter of different configurations depending on cost benefits and ease of installation. We had used in such applications and is purely maintenance free.

 

I am checking with our inspector to see if the ultrasonic is an acceptable solution. That makes the most sense based on our conditions and effluent we're trying to record. Thanks for the suggestion.

 

I have zero experience with in-line ultrasonic transit time flow meters, but lots of experience with clamp-on, external transit time flow meters.

Transit time technology loves clean liquid, and will fault or fail on bubbles or suspended solids (which doppler flow meters love).

Clamp-on meters in general want and the interior of the pipe to be clean and smooth, corrosion and scaling will degrade signal strength dramatically for clamp-on transit time.

The stated conditions: dirty fluid, corrosive and sticky do not fit well for clamp-on transit time. Plastic pipe can help avoid corrosion (depending) and smooth plastic has some resistance to sticky stuff adhering to the walls, but dirty fluid with suspended solids is a no-no for transit time.

The little experience I had with so-called clamp-on doppler transducers was a disaster. The inaccuracy was gross to the point of scarcely being suitable as a flow switch, to say nothing of a continuous flow meter Be wary of clamp-on claims of useable doppler technology.

 

Apart from redesigning your treatment process, your current flow measurement is the most cost effective

 

For low-flow sewage applications, the two most common choices are:

1. Non-full pipe electromagnetic flow meters: These are a good option if the flow is relatively clean and you can ensure the sensor is always submerged during measurement.
2. Doppler ultrasonic flow meters: These are often more suitable for wastewater with some solids or air bubbles, as they can track particles in the flow.

The best choice really depends on your specific pipe size, the presence of solids, and the required accuracy. Could you share more details about your application for a more precise recommendation?