Background
A medical device contract manufacturer producing single-use catheters and pre-filled drug delivery systems needed to replace a water bubble test process with an automated dry-air leak test validated to ISO 11608 requirements. The water test was slow (15 minutes per batch), operator-dependent, and left residual moisture on components. The new process needed to support 100% inline testing at production speed and generate per-unit test records for regulatory submission.
Test Requirements
| Component | Test method | Test pressure | Leak limit |
|---|---|---|---|
| Soft-wall catheter (PVC, 4 Fr) | Differential pressure | 30 kPa | ≤ 0.02 kPa differential drop over 15 s |
| Drug vial rubber stopper seal | Differential pressure | 20 kPa | ≤ 0.01 kPa differential drop over 10 s |
| IV tubing set (infusion line) | Mass flow | 100 kPa | Flow: 0.8 – 1.2 L/min (upper and lower limit) |
Solution
Two instruments were deployed in parallel inline stations:
LD Series (differential pressure) for catheter and drug vial testing. The LD's bridge-compensation architecture fills both the test part and a reference cavity simultaneously. Any differential pressure indicates leakage in the test part — temperature drift and supply pressure variation affect both sides equally and cancel out. This is critical in the climate-controlled but not perfectly stable factory environment, where direct pressure methods produced unacceptable noise at low test pressures.
LF Series (LF-1005, 0–5 L/min range) for IV tubing flow characterization. Rather than testing for the absence of a leak, the LF verifies that the tubing flows within the specified resistance window — detecting both over-flowing (seal failure) and under-flowing (restricted or kinked path) simultaneously.
Custom silicone-plug fixtures for catheter ends and a soft-nest vial holder were designed to avoid deforming the test components. Standard leak holes at 0.01 kPa, 0.02 kPa, and 0.05 kPa equivalent were supplied for process validation documentation.
Results After Deployment
- Water test eliminated — zero residual moisture on components post-test
- Cycle time: catheter 28 s, vial 18 s, IV tubing 12 s (vs. 15 min batch water test)
- 100% per-unit coverage with serial number and batch traceability
- False reject rate: 0.05% (down from 3.2% with water bubble method)
- ISO 11608 process validation documentation supported by standard leak calibration records
Instruments Used
- LD Series Differential Pressure Tester — 0.01 kPa resolution, bridge compensation, low-pressure (10–50 kPa) specialist
- LF Series Mass Flow Tester (LF-1005) — 0–5 L/min range, dual OK/NG flow window
- Silicone-plug catheter end fixtures and soft-nest vial holders
- Standard leak holes at 0.01, 0.02, and 0.05 kPa for process validation
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