Tap Density Tester
Taps a graduated cylinder of powder a set number of times from a fixed height so the bed packs down. The starting and final volumes give bulk density, tapped density, Carr's index and Hausner ratio.
- Pharmaceutical
- Nutraceutical
- Chemicals
- Food & beverage
- Powder metallurgy
What is Tap density tester?
A tap density tester lifts a graduated cylinder containing a weighed powder and lets it drop a fixed distance, over and over, at a set rate. Each tap shakes the particles into a tighter packing until the volume stops changing.
The volume before tapping gives bulk (poured) density; the volume after tapping gives tapped density. Comparing the two shows how compressible the powder is, which is a quick indication of how well it will flow.
In QC it is used for APIs, excipients, blends and granules. Density data help set die fill, capsule fill weight and blend container size, and are often part of excipient and API specifications.
Used for
- Bulk and tapped density of APIs and excipients
- Carr's index and Hausner ratio as flow indicators
- Granule and blend characterisation during development
- Choosing capsule size and die fill depth
- Comparing batches or suppliers
How it works
- 01
Sieve and weigh
The powder is passed through a sieve to break up lumps and an accurately weighed amount is taken.
- 02
Fill
The powder is poured gently into a dry graduated cylinder without compacting it.
- 03
Read V0
The unsettled (bulk) volume is read to the nearest graduation.
- 04
Tap
The tester drops the cylinder a fixed height a set number of times.
- 05
Read Vf
Volumes are read after set tap counts until the change is within the limit; the final reading is the tapped volume.
- 06
Calculate
Bulk density, tapped density, Carr's index and Hausner ratio are calculated.
Advantages
- Simple, cheap and quick
- Pharmacopoeial method with standard cylinder and drop height
- Counter gives exact numbers of taps
- Many testers hold two cylinders for duplicate runs
Limitations
- Reading the powder level by eye is subjective, especially for uneven surfaces
- Results depend on how the cylinder is filled
- Only an indirect measure of flow
- Cohesive powders may not settle evenly
1 calibration procedure
Methods that use Tap density tester
Keep every Tap density tester in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.