Cement should typically flow freely if aerated correctly and free of moisture.  Aerated Cement should be flowing at 74 lbs. / cuft.  The rate of flow will be determined by the diameter of the butterfly valve or cement screw.  Following are typical flow rates;
Cement Butterfly Valve Gravity Rate (Typical)
8” – 144 TPH
10” – 226 TPH
12” – 325 TPH
14” – 443 TPH

Cement Screw Rate (Typical)
8” – 80 TPH
10” – 115 TPH
12” – 200 TPH

Flyash and Slag will flow slower because aerated Flyash should be flowing at 45 lbs. / cuft and slag should be flowing at 60 lbs. / cuft. If Cement / Flyash / Slag is not flowing, please check the following;

1. Confirm all of the aeration pads are receiving 9 psi of dry air.
2. Empty Cement silo and confirm the cone section does not have build up or is plugged.
3. Confirm the butterfly valve is opening up vertical and closing horizontal.
4. Confirm the emergency jam gate is not closed.
5. Confirm the Cement screw flites are a continual spiral.

Special note – Recently we have found some Flyash to remain suspended in the cone section of a silo when the butterfly valve is open.  This is typically caused by the Flyash weight falling below 42lbs. / cuft. Changing the style of the aeration blower might correct the problem.