We are having a small rig at our R&D lab where we are testing the newly developed drag reducing additive. The rig is a closed circuit. It starts with suction diesel vessel, downstream screw pump and around 30 m pipe segment (the pipe segment is divided into straight length, semi circles, circles etc) and finally ends in the suction vessel. There are four differential pressure gauges installed at different sections of this pipe segment. The maximum pressure drop across the entire pipe segment is estimated to be approximately 0.23 bar and the minimum pressure drop across the straight pipe segment is expected to be around 0.08 bar.
The problem we are facing is the reading in these differential pressure gauges always fluctuating. The ranges of the four differential pressure gauges are as mentioned below:
1) 0 - 3.5 bar
2) 0 - 7 bar
3) 0 -7 bar
4) 0 - 10 bar.
We have checked and corrected all the leaks, also the pump downstream pressure and flow is also constant still there is fluctuations in reading of the differential pressure gauges. One reason we we are guessing could be the range of differential pressure gauges is significantly higher than the to be measured dp. Is our reasoning correct?
Request you to please help with your suggestions.