LimsPulse
Tap density tester · Calibration procedure

Drop height and tap rate

Checks that the cylinder falls the specified distance and at the specified number of taps per minute, and that the tap counter is correct.

Illustration of Tap density tester
PURPOSE

Why this is checked

Tapped density depends on how hard and how often the powder is tapped. If the drop height or tap rate drifts, tapped volume, Carr's index and Hausner ratio all change.

Frequency

Typically every 6 months or annually, and after repair, as defined in your calibration SOP.

Learn how the Tap density tester works
YOU WILL NEED

Standards & tools

  • Calibrated dial gauge, height gauge or set of slip gauges
  • Calibrated stopwatch
BEFORE YOU START

Prerequisites

  • Tester clean and on a level, stable bench
  • Empty cylinder holder fitted (or cylinder of standard mass, as per SOP)
PROCEDURE

Step by step

  1. 1Drop height: turn the cam by hand to the highest point of the holder and measure the lift above its resting position with the dial gauge.
  2. 2Repeat at several cam positions or several cycles and record the maximum lift.
  3. 3Tap rate: set the counter to a known number of taps (or run for exactly 60 s) and time it with the stopwatch.
  4. 4Calculate taps per minute.
  5. 5Counter: run a set count (e.g. 500 taps) and confirm the displayed count against a manual or timed count.
RECORD

Example observation table

CheckNominalObserved% error
Drop height (method I)14 mm14.3 mm+2.1
Tap rate300 taps/min298 taps/min−0.7
Tap counter500 taps500 taps0.0
CALCULATION

How to calculate the result

% error = (Observed − Nominal) ÷ Nominal × 100
  1. Tap rate: 298 taps counted in 60 s; nominal 300 taps/min
  2. % error = (298 − 300) ÷ 300 × 100 = −0.67%
  3. Drop height: (14.3 − 14) ÷ 14 × 100 = +2.1% (14.3 mm lies inside 14 ± 2 mm)
ACCEPTANCE CRITERIA

Pass if

  • Drop height within the pharmacopoeial tolerance for the method used: typically 14 ± 2 mm (USP <616> method 1) or 3 ± 0.2 mm (method 2). See the current chapter.
  • Tap rate close to the nominal rate for the method (typically about 300 taps/min for method 1, 250 ± 15 taps/min for method 2), within the tolerance in your SOP.
  • Counter shows the exact number of taps set.
IF IT FAILS

What to do

  • Label the tester 'Out of calibration'.
  • Check the cam, anvil and holder for wear and the drive belt for slip; repair and recalibrate.
  • Assess density results reported since the last passing calibration.
In LimsPulse · Calibration Management

LimsPulse schedules this calibration, records the result against limits, and blocks the instrument everywhere if it fails or goes overdue.

See how