What causes fluctuations in the inlet throat differential pressure of air compressors?

The installation location of the instrument measurement points, inaccurate instrument readings, pipeline layout, and unstable suction can all have an impact.

The throat pressure difference actually measures the flow rate of the air compressor; if the flow rate of the air compressor fluctuates, then the throat pressure difference will also fluctuate.

The throat difference of an air compressor indicates the flow rate. To determine whether fluctuations in this throat difference are caused by actual changes in air volume, it is necessary to consider the outlet pressure of the compressor; generally, these fluctuations should not be too large. The fluctuations in throat difference seem to be related to the surge point

Excluding temperature and atmospheric pressure, it is the change in throat difference caused by changes in the air separation load (air volume)~~

The pressure difference in the throat is actually achieved by using the inlet pipe or casing of the air compressor to create a venturi-shaped or nozzle-shaped structure; it can be regarded as a throttling device, and the resulting pressure difference can be approximated as that of a throttling flow meter. Since atmospheric pressure changes very little, and air temperature fluctuations are also limited, the differential pressure is generally taken as the square root value to be used as the flow rate input for controlling surge in compressors. Currently, the new compressor design by MAN includes an inlet air thermometer to compensate for air flow. Based on my experience, regarding fluctuations in the pressure difference in the throat, assuming that there are no issues with the instruments themselves, if the exhaust pressure and flow rate remain relatively stable and the system is not in a surge condition, it’s necessary to check the intermediate coolers, especially the first two stages of cooling. It’s possible that fouling in these coolers has blocked some of the air passages, thereby causing surge between the compressor stages. It would be useful to check the energy consumption and the cooling efficiency of the compressor as evidence. In the past, our unit encountered a similar situation: a leak in the primary cooler caused scaling to form in the air passages of the cooler, thereby blocking those passages. The performance issues include high energy consumption, a slight increase in primary vibration, large fluctuations in inlet differential pressure, and poor cooling efficiency.