What are the methods of measuring liquidity?

Two methods are currently commonly used:

(1) Standard funnel method (refer to GB1482 or ISO4490)

Weigh (50±0.1)g powder sample, plug the small hole of the funnel, pour the powder sample into the funnel, open the small hole, and time with a stopwatch (accuracy 0.2s) until the powder sample runs out and the timer stops. The standard funnel is usually calibrated by a standard sample, and the standard fluidity value is (40±0.5s)/50g.

(2) Comprehensive characteristic measuring instrument

The Carr fluidity index can be measured, which comprehensively evaluates the angle of repose, collapse angle, particle size, bulk density and cohesion, and obtains a representative value, which is used as a criterion for powder fluidity. The range of liquidity index is 0~100. The relationship between liquidity and liquidity index is shown in Table 11:

Table 11 The relationship between liquidity and liquidity index