My application involves pumping a chemical fluid using bladed pumps mounted on the end of long (2-3 feet) flexible shafts. The bladed end is not supported in a bearing. The entire pump is also flexibly mounted and can move around several mm's during normal operation. If you put your hand on the outlet pipe you can sometimes feel a pulsing fluid flow. This is undesirable since the pulsing fluid causes instability in the downstream process. This pulsing is generally caused by dirty or damaged blades. I have tried measuring vibration but the excessive movement of the entire pump/motor structure tends to mask everything. I would like to attach some device to the outlet pipe that could detect these pulses and provide a warning of the presence of pulsing fluid. Any ideas?

Janno,

I am surprised that you cannot measure blade-rate pulsation (# blades X shaft speed) with vibration spectrum analysis. If the blades are like a propeller, then measure in the axial or thrust direction.

PCB Piezotronics has ICP-type dynamic pressure sensors that would work well for this application, if temperature is below 250-F. Charge-type sensors are needed for higher temperatures.

Walt

Janno,
Why not put in an electronic pressure transmitter and feed it's electrical output to an oscilloscope to observe the time waveform (TWF) and/or to a frequency analyser to observe frequency spectrum (FFT)? This should reveal a lot regarding dynamic pressure performance!