Learn how to calibrate the Friability Test Apparatus used to test the friability of tablets and its formula for calculation. Step-by-step calibration procedure, limits, frequency, and GMP documentation requirements explained.

The Friability Test Apparatus is a critical quality control instrument used in pharmaceutical manufacturing to evaluate the mechanical strength of tablets. It determines the ability of tablets to resist abrasion and shock during handling, packaging, and transportation.

Proper calibration of the friability tester ensures reliable results, regulatory compliance, and consistent product quality. This article explains how to calibrate the Friability Test Apparatus used to test the friability of tablets and its formula for calculation, along with standard operating steps and acceptance criteria.

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Objective

To describe the standard procedure to calibrate the Friability Test Apparatus used to test the friability of tablets and verify that the instrument operates within specified limits.

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Scope

This procedure applies to the calibration and routine verification of the Friability Test Apparatus used in pharmaceutical quality control laboratories.

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Principle of Friability Testing

Friability testing measures the percentage weight loss of tablets after subjecting them to mechanical stress in a rotating drum. The test simulates real-life handling conditions to determine whether tablets maintain their physical integrity.

A properly calibrated instrument ensures:

• Accurate rotation speed
• Correct revolution count
• Reliable time measurement
• Consistent test conditions
• Compliance with pharmacopeial standards

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Equipment Required

• Friability Test Apparatus
• Weighing Balance (calibrated)
• Stopwatch (if required)
• Standard Tablets or Test Samples
• Calibration Logbook

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Step-by-Step Procedure to Operate and Calibrate the Friability Test Apparatus

1. Instrument Initialization

1. Switch ON the power supply.
2. The drum will automatically initialize to the loading position.
3. The display will show “Start.”

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2. Sample Preparation

After weighing the initial sample weight (A):

• For tablets ≤ 650 mg:
  Take a sample of whole tablets corresponding to 6.5 g
• For tablets > 650 mg:
  Take a sample of 10 whole tablets

Gently place the tablets into the drum through the side slit.

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3. Selecting the Operating Mode

4. Select the desired mode:

• TIME MODE
• REVOLUTION COUNT MODE

Press the TIME/COUNT key to choose the mode.

5. The MODE indicator LED will show the selected mode.
6. The display will show previous time or count values.

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4. Setting Test Parameters

7. Enter the required value:

• 25 rpm
• 4 minutes
• Or as specified in the individual product monograph

8. Press the ENTER key to register the value.

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5. Running the Test

9. Press the RUN/HALT key to start the test.
10. The drum will begin rotating.
11. The display will show elapsed time or revolution count.

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6. Completion of the Test

12. When the test finishes:

• The drum rotates in reverse direction
• Tablets are discharged into the tray
• The drum oscillates gently to ensure complete discharge
• The display shows “END”
• An audible beep indicates test completion

13. The drum returns to the loading position and displays “Start.”

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7. Handling Interruptions

If parameter changes are required during testing:

• Press RUN/HALT to pause
• The LED will blink, indicating HALT state
• If a value below the elapsed time/count is entered, the display shows:

“Err”

Press RUN/HALT again to resume the test.

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Calculation of Friability of Tablets

To determine tablet friability, calculate the percentage weight loss after the test.

$\text{Friability (\%)} = \frac{A – B}{A} \times 100$Friability (%)=AA−B​×100

Where:

• A = Initial weight of tablets before testing
• B = Final weight of tablets after testing

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Acceptance Criteria

Typically:

Friability Limit:
Not more than 1.0% weight loss

Unless otherwise specified in:

• Product specification
• Pharmacopoeial monograph
• Regulatory requirement

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Calibration of Friability Test Apparatus

Calibration verifies that the instrument produces accurate rotation counts and timing.

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Calibration Frequency

Calibration should be performed:

• Monthly
• After major maintenance
• After relocation
• After repair
• As per GMP requirements

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Calibration Parameters and Acceptance Limits

Sr. No.	Parameter	Standard Value	Observed Value	Acceptance Limits	Remarks
1	Count	50 revolutions / 2 minutes	2 minutes	49 – 51	Pass/Fail
2	Count	100 revolutions / 4 minutes	4 minutes	98 – 102	Pass/Fail
3	Count	150 revolutions / 6 minutes	6 minutes	147 – 153	Pass/Fail

Documentation Requirements

After calibration:

• Record results in the calibration logbook
• Document observed values
• Verify acceptance limits
• Sign and date the record
• Affix the calibration label

Proper documentation ensures:

• GMP compliance
• Audit readiness
• Traceability
• Data integrity

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Common Sources of Friability Test Errors

• Incorrect sample weight
• Improper drum loading
• Wrong time or revolution settings
• Uncalibrated balance
• Mechanical wear of the drum
• Incorrect rpm setting

Routine calibration helps prevent these errors.

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Regulatory References

• USP (United States Pharmacopeia)
• IP (Indian Pharmacopoeia)
• BP (British Pharmacopoeia)
• WHO GMP Guidelines
• Pharmaceutical Quality System (ICH Q10)

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Conclusion

Properly performing and documenting calibration is essential to ensure the Friability Test Apparatus used to test the friability of tablets provides accurate and reproducible results. Following a standardized calibration procedure, verifying rotation counts, and applying the correct formula for calculation ensures compliance with GMP and pharmacopoeial standards while maintaining product quality and patient safety.

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10 Frequently Asked Questions (FAQs)

1. What is a Friability Test Apparatus used for?
It is used to evaluate the mechanical strength of tablets by measuring percentage weight loss after rotation.

2. What is the standard rpm for friability testing?
Typically 25 rpm, unless otherwise specified in the product monograph.

3. What is the acceptable friability limit for tablets?
Generally not more than 1.0% weight loss.

4. How often should the Friability Test Apparatus be calibrated?
Usually monthly and after major maintenance.

5. What is the formula for calculating friability of tablets?
Friability (%) = (Initial Weight – Final Weight) ÷ Initial Weight × 100.

6. How many tablets are used in the friability test?

• Tablets ≤ 650 mg: Sample equal to 6.5 g
• Tablets > 650 mg: 10 tablets

7. Why is calibration of the Friability Test Apparatus important?
It ensures accurate rotation speed, timing, and reliable test results.

8. What happens if friability exceeds limits?
The batch may fail quality specifications and require investigation.

9. What parameters are checked during calibration?

• Revolution count
• Time
• Rotation accuracy

10. What records are required after calibration?

• Calibration log entry
• Observed values
• Acceptance verification
• Calibration label