Worked Example: Process Validation (IQ, OQ, PQ) From Decision to Revalidation
By Ishan Maharaj, Founder and Principal Consultant. Last reviewed 26 October 2026.
Short answer: validate a process when its output cannot be fully verified by later inspection or test. Installation qualification (IQ) shows the equipment is installed to specification, operational qualification (OQ) shows the process works across its limits, and performance qualification (PQ) shows it works consistently under normal production. This example follows one sterile pouch heat-seal process through all three, then through a revalidation decision after maintenance.
Definitions used. The GHTF process validation guidance (GHTF/SG3/N99-10:2004) describes IQ as objective evidence that equipment installation matches the approved specification, OQ as objective evidence that control limits and action levels produce product meeting all predetermined requirements, and PQ as objective evidence that the process, under anticipated conditions, consistently produces product that meets all predetermined requirements. It says that if a process output is not verifiable, the decision should be to validate the process.
The situation
Northbay Wound Products (fictional), 40 people, seals foam wound dressings into sterile barrier pouches on a heat-seal machine and is certified to ISO 13485:2016. Clause 7.5.6 requires validation of processes whose output cannot be verified by subsequent monitoring or measurement. The company is qualifying a new sealer for pouch line 2.
1. Validation determination (VDF-2026-011)
| Process | Heat sealing of the sterile barrier pouch (Example). |
|---|---|
| Can the output be fully verified? | No. Seal strength is tested by destructive peel testing on samples, and a seal that passes visual inspection can still be weak. Verification of every pouch is not possible. |
| Decision | Validate. Recorded with the rationale and approved by QA on 6 April. |
| Critical parameters | Seal bar temperature, dwell time, seal pressure. Identified from the process FMEA (seal failure rated highest severity). |
2. Validation plan and acceptance criteria (VP-2026-011)
| Acceptance criteria (Example) | Seal width 6 mm or more along the full seal. Peel strength at or above the minimum set in the product specification. No channels or open seals on visual inspection. |
|---|---|
| Study design | IQ checklist; OQ of 8 runs at the corners of the proposed window; PQ of 3 consecutive production runs at nominal settings. |
| Sample size rationale | 59 samples per PQ run for peel testing, zero failures allowed. With zero failures in 59 samples, the result supports at least 95% reliability at 95% confidence. |
| Revalidation triggers | Replacement of the heater, controller or sensors; change of pouch material or supplier; relocation; trend signals in monitoring. |
3. Installation qualification (IQ-2026-011)
| Check (Example) | Requirement | Result |
|---|---|---|
| Model and serial number | Match purchase order and manufacturer specification | Pass |
| Utilities | Compressed air and power within supplier specification | Pass |
| Temperature sensor and pressure gauge | Calibrated, certificate in date, IDs recorded in the equipment register | Pass after deviation DEV-1 |
| Controller software version | Recorded and locked to the version tested | Pass |
| Maintenance plan | In place and linked to the asset register | Pass |
Deviation DEV-1: the thermocouple calibration certificate was missing at the first check. It was received the same day, reviewed, and the deviation was closed before OQ began.
4. Operational qualification (OQ-2026-011)
Eight runs test every combination of the low and high ends of the proposed window. The GHTF guidance says OQ should challenge the parameters under worst-case conditions, which is why the corners are tested.
| Run (Example) | Temperature | Dwell | Pressure | Minimum seal width | Peel test |
|---|---|---|---|---|---|
| 1 | Low | Low | Low | 6.4 mm | Pass |
| 2 | High | Low | Low | 6.5 mm | Pass |
| 3 | Low | High | Low | 6.4 mm | Pass |
| 4 | High | High | Low | 6.6 mm | Pass |
| 5 | Low | Low | High | 6.3 mm | Pass |
| 6 | High | Low | High | 6.5 mm | Pass |
| 7 | Low | High | High | 6.4 mm | Pass |
| 8 | High | High | High | 6.7 mm | Pass |
Conclusion (Example): all eight runs met the criteria, so the proposed window (temperature 175 to 190 °C, dwell 1.2 to 1.8 s, pressure 3.5 to 4.5 bar) is accepted for PQ. Nominal settings for PQ: 182 °C, 1.5 s, 4.0 bar.
5. Performance qualification (PQ-2026-011)
| Run (Example) | Lot | Peel test samples | Failures | Visual inspection |
|---|---|---|---|---|
| PQ-1 | 26-201 | 59 | 0 | 100% pass |
| PQ-2 | 26-202 | 59 | 0 | 100% pass |
| PQ-3 | 26-203 | 59 | 0 | 100% pass |
Conclusion (Example): three consecutive runs under normal production conditions, by different operators and on different shifts, met every criterion. Process capability on seal width: Ppk 1.52 against the target of 1.33 or higher.
6. Validation summary report (VSR-2026-011)
| Outcome | Validated. Approved by QA, production and engineering on 28 May. |
|---|---|
| Validated window | 175 to 190 °C, 1.2 to 1.8 s, 3.5 to 4.5 bar (Example). |
| Ongoing monitoring | Seal temperature, dwell and pressure logged for every lot; first-off seal width and peel check at start of each shift; trend reviewed monthly. |
| Records filed | Determination, plan, IQ, OQ and PQ protocols and reports, deviation record, raw data, calibration certificates, summary report. |
7. Revalidation assessment after maintenance (RV-2026-004)
| Trigger | Heater controller replaced during maintenance (Example). |
|---|---|
| Assessment | A change to a controlling component can alter the validated state. The GHTF guidance says changes should be evaluated for their effect and the extent of revalidation needed, and that revalidation can be narrower than the original study. |
| Decision | Repeat the IQ checks for the new controller, run OQ runs 1 and 8 (the extremes), and run one PQ lot. Production restarts only after the parameter check against the validation report and passing results. |
| Result | All results within criteria. Revalidation record closed by QA. Asset register updated. |
What this shows
- The decision to validate is recorded with a reason, not assumed.
- Acceptance criteria and sample sizes are fixed before the studies run.
- OQ challenges the edges of the window, and PQ shows consistency at normal settings.
- Monitoring and revalidation triggers keep the validated state from drifting. The worked CAPA example shows what happens when a controller is replaced without that link.
The templates behind it
The determination form, validation master plan, IQ, OQ and PQ protocols and reports, summary report, deviation and revalidation forms and the sample size workbook are in the Process Validation IQ/OQ/PQ Pack, which also includes its own complete heat-seal validation example. All of them are in the ISO 13485 Complete QMS Kit.
Sources: GHTF/SG3/N99-10:2004, Quality Management Systems: Process Validation Guidance, sections 2, 3.1, 5.3 to 5.5, 6.2 and 6.4. The 59-sample figure follows from the binomial calculation 0.95^59 = 0.049.