Across the web and pack
- Vertical, horizontal and format-specific seal locations
- Every lane on multi-lane machinery
- Left, centre and right positions where a wide web or jaw requires it
- Gusset, corner, zipper, notch and code interactions where present
Finished-pack quality guide
VFFS seal integrity testing guide
Build a test plan that separates visual seal condition, seal strength and package leak evidence, then links the selected methods to the real film, product, pack format and distribution risk.
Direct answer
Seal settings create the process; the integrity plan decides whether the finished pack is acceptable.
A practical VFFS seal-integrity plan combines defined visual and dimensional checks with an application-appropriate strength or leak method. The plan identifies seal locations, sample events, acceptance criteria, equipment, conditioning, failure modes and escalation. No single check proves every aspect of package performance, so the evidence must reflect the actual product, film, distribution route and quality risk.
Visual evidence
Inspect every relevant seal location
Record seal width and position, folds, wrinkles, contamination, channels, unsealed areas, burn-through, distortion, knife damage and interactions with gussets, zippers, notches or code areas. Visual inspection is fast and valuable, but its sensitivity depends on material transparency, contrast, lighting, training and the defect itself.
Strength evidence
Measure the seal specimen and failure mode
A controlled peel or tensile test can compare seal locations and process conditions. The record should identify specimen width, orientation, conditioning, test configuration, peak or average result as applicable and whether failure occurred in the seal, film, laminate or elsewhere. Strength does not automatically equal leak tightness.
Leak evidence
Select a method that suits the complete pack
Leak methods may use pressure, vacuum, dye, gas or another validated principle. Some locate leaks; others provide only pass/fail evidence. Some are destructive. Product, headspace, porosity, pack flexibility and required sensitivity determine whether a method can produce useful results for the actual VFFS pack.
Test hierarchy
Use different evidence for different quality questions
The site quality team should approve the applicable method, equipment, sampling and acceptance criteria.
| Quality question | Possible evidence | Important limitation |
|---|---|---|
| Is the seal continuous and presented correctly? | Visual and dimensional inspection by seal location. | Some channels, pinholes or weak bonds may not be visible. |
| How much force separates a defined seal specimen? | Controlled seal-strength or peel testing with failure-mode recording. | Tests a specimen, not necessarily the complete package or leak performance. |
| Does the complete package contain a detectable leak? | Application-appropriate pressure, vacuum, dye, gas or other validated method. | Sensitivity, fixture, package contents and destructive/non-destructive status vary by method. |
| Will the pack withstand expected handling? | Defined handling, compression, drop, vibration or distribution evidence where relevant. | Distribution performance is broader than seal settings and needs a realistic protocol. |
| Is the sealing process stable through production? | Trend samples across lanes, reel positions, starts, refills, speed changes, stops and restarts. | A single average can conceal a weak location or intermittent event. |
Established methods
Use standards as controlled methods, not generic pass marks
ASTM F88/F88M describes seal-strength measurement for flexible barrier materials. ASTM F1886/F1886M covers visual integrity inspection, while methods such as ASTM F2338 or ASTM F3039 address particular leak-detection approaches. Applicability, sensitivity, conditioning, equipment and acceptance criteria must be selected and validated for the actual packaging system; a standard number alone does not establish product suitability.
ASTM F88/F88M seal-strength method
ASTM F1886/F1886M visual integrity method
ASTM F2338 vacuum-decay method
Machine process
Link every failure back to product, film and machine condition
Record film structure and batch, sealant side, jaw identity, temperature indication, pressure or force setting, dwell or cycle condition, speed, cooling, product contamination, product temperature, lane and seal location. Preserve failed and accepted comparison packs. Change one controlled factor at a time where practical and repeat the agreed method before releasing the process.
Sampling plan
Cover the events that can change the seal
Across production
- Start-up and stable running
- Reel change, splice and registration recovery
- Product refill, speed change, planned stop and restart
- End of run, changeover and cleaning reassembly
Across materials
- Approved film structures and normal batch variation
- Representative product condition and credible contamination risk
- Normal ambient and product-temperature range
- Retained accepted and failed reference packs
Buyer questions
Questions about VFFS seal integrity testing
What is the difference between seal quality and seal integrity?
Seal quality describes visible and measurable characteristics such as width, alignment, appearance and peel behaviour. Seal integrity asks whether the complete pack maintains the required barrier and containment for its intended product and distribution route. A visually neat seal can still contain a channel or weak location, so the acceptance plan should combine suitable evidence.
Is visual inspection enough to release VFFS packs?
Visual inspection is an important first control but is not automatically sufficient. It can reveal wrinkles, contamination, incomplete seals, distortion and obvious channels, yet some leak paths or weak seals are not reliably visible. The quality plan should select additional strength or leak methods according to the pack, product, risk and required sensitivity.
What does a seal strength test show?
A controlled seal-strength test measures the force needed to separate a defined seal specimen and records how the specimen fails. It can compare process conditions and identify weak locations, but it does not by itself prove that the complete package is leak-free or suitable for every storage and distribution condition.
Which leak test should be used for a VFFS pack?
There is no universal VFFS leak test. Method choice depends on whether the pack is porous or nonporous, contains air, liquid or product, can be tested destructively, needs leak location or only pass/fail evidence, and what defect size matters. The method and acceptance criteria should be validated for the actual pack.
How many VFFS packs should be tested?
Sample quantity should follow the site quality plan, process risk, number of lanes or seal locations, production duration and the events that can change the process. Include start-up, stable running, reel joins, product refill, speed changes, stops, restarts and changeover. A small convenience sample from one stable period may miss systematic faults.
What should be recorded when a seal fails?
Preserve the failed and comparison packs, then record product and film batches, machine and recipe, lane, seal location, time, settings, operating event, defect appearance, test method, acceptance rule and disposition. Link corrective action to a controlled retest so the team can distinguish a temporary adjustment from a verified process recovery.
Seal-trial review