Flexim Waste Water Flow Meters with Fiber Glass/GRP Pipes?

There are two aspects to the term <...applicable....>.

1. Whether or not the <...flexim flow meter and...clamped ultrasonic sensors...> will operate on <...GRP/Fiber Glass pipes...> containing <...waste water...>. On the assumption that there is no prior experience locally that can assist, that being the need for a posting in this forum, the only thing to do to find out is to contact these people directly, which will be quickest and easiest by telephone.
2. Whether or not the end Client's standards accept the use of this combination on this service. If it is not shown in the Client's standards or the project specification documents, then the only thing to do to find out is to contact the Client's technical staff directly, which will be quickest and easiest by telephone.

Why ask strangers, when you should have read the installation instructions!

Ultrasonic clamp-on gas flow meters and liquid flowmeters... | FLEXIM

Flexim Ultrasonic Clamp-on Flow Meters

Read the manual!

An issue with any brand clamp-on transit time ultrasonic flowmeter on waste water is the amount of aeration in the pipe and /or suspended solids.'

Transit time technology wants 'liquid only', with zero to very little entrained air/gas and zero or very low amounts of any suspended solids. Any appreciable amount of either will fault a transit time meter. Doppler technology loves suspended solids and I've heard that doppler will make a measurement with air/gas bubbles in the flow stream, but I haven't run into a doppler ultrasonic flow meter that produced a measurement that was better than a flow/no-flow indication.

Might be worth trying one before you buy to make sure it'll make a flow measurement.

When fixing the sensors to the pipe, it is important to assure no air bubbles in the space between the sensor and the pipe surface. The pipes are often rough on the outside, so some sort of bedding compound might be needed. Also, the quality of the pipe wall, voids and inclusions from manufacturing might degrade your signal quality. Different quality sensors will have suitable blanking circuits to discard extraneous target information, especially when you application is relatively small pipes for the design range of the sensor.

The OEM should have application guidelines for non- metallic pipe, as suggested by PWSlack and Lyn. You may not recognize synonyms for FRP Pipe from the manufacturers literature, always a source of confusion especially technical names when not written in your native language.

The technology is feasible and can achieve good repeatability.

The others have already highlighted two main suggestions

Read the manufacturer's instructions to understand the necessary parameters to enter and the configuration to install on the pipe. I Suggest that you mount at 3 and 9 O'clock instead of top and bottom to overcome issues with bubbles travelling in the top of the pipe.

The second is to use the correct gel (and enough of it) on the outside of the pipe so that the signal is not going through air gap.

Finally, check and DOUBLE check the sensor spacing on the pipe as they are usually dependant on pipe diameter, pipe material and wall thickness.

Next, the manufacturer will suggest a length of straight pipe either side of the meter placement to ensure low turbulence flow. Horizontal pipe is best, but if must be on vertical have it in the rising section so that the pipe is always full.

Good luck.