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Bursting Strength Apparatus: Example SOP for Operation and Calibration

Last reviewed 29 Oct 2026 · 5 min read

Contents
  1. 1. Objective
  2. 2. Scope
  3. 3. Responsibility
  4. 4. Procedure
  5. 4.1 Before you start
  6. 4.2 Instrument controls (typical layout)
  7. 4.3 Testing a sample
  8. 5. Calibration
  9. 5.1 Calibration check with a certified reference
  10. 6. Records
  11. 7. Training and distribution
  12. 8. Annexure
  13. Related reading
  14. Frequently asked questions
  15. Abbreviations
  16. References

In short: A bursting strength tester measures the pressure at which a clamped sample of packaging material (paper, board, foil) ruptures. This example SOP shows how to operate the instrument, how to check it against a reference material, and what to record. Adapt it to your own instrument model and quality system.

1. Objective

This example SOP describes how to operate and calibrate a bursting strength apparatus used to test packaging materials in the Quality Control laboratory.

2. Scope

It applies to the pneumatically clamped, motor-driven bursting strength tester installed in the Quality Control laboratory. Controls, menus and key names differ between manufacturers, so follow the instrument manual for model-specific steps.

3. Responsibility

  • Analyst / section head: operates the instrument as per this SOP and completes the usage log and test records.
  • Head of Quality Control (or designee): ensures the SOP is implemented, calibration is done on time and out-of-tolerance results are investigated.
  • Quality Assurance: reviews the calibration records and approves any change to the procedure.

4. Procedure

4.1 Before you start

  1. Confirm the instrument is clean, the calibration status label is valid and the test method for the material is available.
  2. Open the compressed-air supply to the instrument (ball valve parallel to the line, as per the manual) and check the supply pressure is within the range given in the manual.
  3. Switch on the mains. The plunger should return to its start position if it is not already there.

4.2 Instrument controls (typical layout)

Many testers have function keys and an alphanumeric keypad. A typical layout is shown below; confirm against your manual.

KeyTypical use
Set ModeSelects the test mode (for example paper, board, foil, other) and its set points
Time/DateSets time and date
CalCalibration and editing of set-point limits (restricted to authorised persons)
Batch InfoEnters sample details such as supplier, sample code, analytical report number, batch number and analyst ID
Start / StopStarts the cycle / aborts it
PrintPrints the result of the last cycle
UnitDisplays the peak value in other pre-set units
Next / EnterMoves the cursor / saves the entered value

Select the test mode that matches the material before testing, and enter the sample details.

4.3 Testing a sample

  1. Enter the sample details as described above.
  2. Place the sample flat between the clamps, covering the diaphragm area, with no wrinkles.
  3. Press Start. The clamp closes pneumatically.
  4. The instrument then raises pressure on the sample at a controlled rate until it bursts.
  5. The plunger returns automatically and the peak burst value is held on the display.
  6. Record the value (or print it), and repeat for the number of specimens required by the material specification or test method.
  7. Fill the instrument usage log each time the instrument is used.

Bursting strength is commonly tested by standard methods such as ISO 2759 (board; ISO 2758 is the corresponding paper method), TAPPI T 403 (bursting strength of paper) and the Indian IS 1060 series (methods of sampling and test for paper and allied products). Use the method named in your approved packaging-material specification.

5. Calibration

Frequency (example in-house criterion): quarterly, and after repair or relocation.

US FDA 21 CFR 211.68(a) requires routine calibration, inspection or checking of equipment under a written program with written records, and 21 CFR 211.160(b)(4) requires calibration of instruments at suitable intervals under a written program with directions, schedules and accuracy and precision limits. Using reference materials traceable to a national standard is good practice.

5.1 Calibration check with a certified reference

  1. Place a reference material of known bursting strength (for example a certified aluminium foil, or the reference supplied with a traceable calibration kit) over the diaphragm.
  2. Determine the bursting strength at three places on the reference.
  3. Compare each result with the value on the reference certificate.

Acceptance (example in-house criterion): each result lies within the tolerance given on the reference certificate or in the instrument manual.

If a result is outside tolerance, label the instrument “Out of calibration – do not use”, inform QC and QA, and assess the impact on materials tested since the last good calibration.

6. Records

Keep the usage log, calibration data sheet (Annexure I) and test records. Retain GMP records for at least 1 year after the expiry date of the respective product batch (EU GMP Part I, Chapter 4, §4.11; 21 CFR 211.180(a)), or longer if local law or the marketing authorisation requires.

7. Training and distribution

  • Trainer: Head of Quality Control. Trainees: section heads, analysts and officers.
  • Controlled copies: Quality Assurance and Quality Control. The original copy is held by Quality Assurance.

8. Annexure

Annexure I: Calibration data sheet (instrument ID, date, reference material and certificate value, three readings, result, done by / checked by).

Frequently asked questions

What does a bursting strength tester measure? The pressure at which a clamped, diaphragm-supported sample ruptures, expressed in kPa or similar units.

Why calibrate with a reference material? It shows that the readings are accurate and traceable before they are used to accept or reject packaging material.

What if the instrument fails calibration? Stop use, tag it, raise a deviation and assess results generated since the last passing check.

Abbreviations

QC: Quality Control; QA: Quality Assurance; SOP: Standard Operating Procedure.

References

  • US FDA, 21 CFR 211.68 (automatic, mechanical and electronic equipment) and 21 CFR 211.160(b)(4) (calibration), eCFR, current.
  • US FDA, 21 CFR 211.180(a) (record retention); European Commission, EudraLex Volume 4, Part I, Chapter 4 (Documentation), §4.11.
  • Instrument manufacturer’s user manual (model-specific operation).
  • Test standards for bursting strength (ISO 2759; TAPPI T 403; IS 1060 series) as named in the material specification.

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