Issue link: https://www.e-digitaleditions.com/i/648486
Bulk density testing in practice To illustrate the value of these checks, imagine you're the solid dosage manager at a pharmaceutical manufac- turer who has just received a tote filled with an expensive formulation. All the qualification tests are done, and it's time to make tablets. Because the product is known to be hygroscopic, the qualification process requires you to test the bulk density and conduct other quality checks during production. In the early morning, when the humidity is low, produc- tion is smooth. Over the course of the day, however, the humidity rises and, as scheduled, you perform a quality check using a shear cell. As shown in Figure 2, the powder's unconfined failure strength should be 4.0 kilopascals at a major principal consolidation strength of 9.0 kilopascals, and the bulk density should not exceed 925 kilograms per cubic meter. But the flow function data indicate that the material has gained cohesive strength with the rise in humidity and that bulk density has also increased. Without some intervention, those changes could cause the powder to jam and a cascade of other problems could follow. In this case, the protocol might call for the addition of a flow aid and/or the adjust- ment of the tablet press. In so doing, you continue to make on-spec tablets throughout the day. T&C Reference 1. PFT powder flow tester from Brookfield Ametek, Middleboro, MA. Vinnie Hebert is product manager, powder flow tester, at Brookfield Ametek, 11 Commerce Boulevard, Middleboro, MA 02346. Tel. 508 946 6200. Website: www.brookfieldengineering.com. 30 March 2016 Tablets & Capsules Figure 2 Tracking changes in powder properties b. Bulk density graph showing pass/fail limit a. Flow function graph showing pass/fail limit Very cohesive Cohesive Easy flowing Free flowing Data set #1 Data set #2 Data set #3 Major principal consolidating stress (kPa) Major principal consolidating stress (kPa) Test sample failure 0 1 2 3 4 5 6 7 8 9 10 11 12 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 1000 950 900 850 800 750 700 650 600 550 Test sample pass Control sample Test sample Control sample Control sample/fail line Failure at final bulk density value Control pass/fail point Unconfined failure strength (kPa) Bulk density (kg/m 3 )