In our Factory we have a Compressor which rates 660 CFM (Kirloskar Make), which is a VFD Compressor. And next to compressor, we have a Receiver tank. Next to Receiver Tank, we have a Dryer. The Consumption of the Total Plant is around 350-400 CFM. The Flow in the Dryer Outlet was around 400-450 CFM, whereas the flow is uniform for 4 to 5 min. Then the flow drops down to 50-70 CFM and remains in that for 40 Secs. But still all the machines were in the same running State. And after 40 secs, the Flow in the Dryer Outlet was about 400 to 450 CFM. Why this kind of low CFM is happening in the Dryer Outlet?
Does this happen repeatedly, when you turn it on, after a while, etc? If your load is around 50-75% of your compressors output and your operating in VFD, if it happens at start up, perhaps its the PID trying to figure out what it wants to tell your VFD to do. If that's the case, after a while running at your plants normal load, the cfm drop and time in between should taper off.
And your sure the system is plumbed COMP > TANK > DRYER ?