FILL
Connect the part with the appropriate fitting or fixture and apply negative pressure.
Leak Test Method
Vacuum Decay Leak Testing
A vacuum decay leak test evacuates a sealed part, isolates the vacuum source, and measures pressure movement over time to make a pass/fail decision.
Vacuum decay is a non-destructive test for parts, packaging and industrial components. The part connects to the tester through a fitting or fixture, and the system applies negative pressure before measurement begins.
Once the selected negative pressure is reached, the sequence moves through settle and test stages. The pressure sensor watches for a rise toward atmospheric pressure, indicating that air is entering the test volume.
It replaces a traditional dunk test with a programmed sequence and a clear result. Common applications include medical catheters, fuel injectors, implantable devices, electronic enclosures, sensors, packaging, radios, cell phones and smartwatches.
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How is Leak Rate Calculated →What is a vacuum decay leak test?
A vacuum decay test checks whether a sealed part can hold negative pressure. After the part is connected, the tester evacuates it to the selected vacuum level and closes the valves. If outside air enters through a leak, the pressure moves toward atmosphere during the test interval.
It follows the same production discipline as pressure decay, but applies vacuum instead of positive pressure. That makes it useful when the part, its package or the intended application calls for negative pressure.
The tester returns a pass or fail against the programmed specification. It does not identify a leak’s physical location; use sniffing testing when location is required.
How a vacuum decay test runs
SETTLE
After the fill timer ends, allow the part to accommodate stretching or flexing before measurement.
TEST
Measure any increase in vacuum pressure during the programmed test interval.
VENT
Vent the remaining negative pressure in the system to atmosphere.
A part that remains within its pre-set vacuum-decay specification passes; a part that falls below its lower limit fails.
When vacuum decay is the right method — and when it is not
Vacuum decay is a fit when
- ✓A sealed part, package or industrial component
- ✓A non-destructive production test
- ✓Applications including implantable devices, electronic enclosures, sensors and packaging
- ✓A test sequence based on negative pressure
Choose another method when
- →A need to locate the physical leak site — Use sniffing leak testing.
- →A part requiring positive-pressure decay — Use pressure decay leak testing.
- →A flow-through part or a need to check blockage — Use mass flow or occlusion testing.
Sensitivity, cycle time and part volume
Zaxis vacuum decay testing produces results with resolution up to the fifth decimal place, or 0.00001 PSI. That resolution supports fast, repeatable test cycles.
Fill, settle, test and vent are programmed stages. The settle stage gives a part that stretches or flexes under vacuum time to stabilize before measurement begins.
The fitting or fixture connects the test volume to the part. A stable connection and a consistent programmed sequence support repeatable pass/fail decisions on the production line.
After the vacuum source is isolated, the tester measures pressure change over the selected interval. A part within the programmed limit passes; one that exceeds it is rejected without being damaged or opened.
Which Zaxis testers run vacuum decay
Every Zaxis air leak tester runs vacuum decay alongside pressure decay. They differ in channel count, interface and enclosure, so the choice comes down to where the tester has to live and how many parts it has to handle.
Z8Up to four test ports, an 8-inch touchscreen, and vacuum capability for automated production lines.
Z5A compact multi-channel tester with vacuum decay capability and a 6.5-inch-wide cabinet.
Z1A 2.6-inch-wide machine-integrated tester for pressure/vacuum decay applications.Applications for vacuum decay testing
Medical catheters and implantable devices
Vacuum decay is used to confirm that sealed medical components do not leak before they reach end users.
Packaging
Sealed packages can be tested with a non-destructive vacuum sequence.
Electronic enclosures and sensors
Enclosures, sensors, radios, cell phones and smartwatches are applications for vacuum decay testing.
Fuel injectors and industrial components
Industrial components can be connected through a fitting or fixture for a repeatable vacuum test.
Vacuum decay vs other leak test methods
| Method | Non-destructive | Needs an access port | Locates the leak | Typical use |
|---|---|---|---|---|
| Pressure decay | ✓ | ✓ | × | Sealed parts with a port |
| Vacuum decay | ✓ | ✓ | × | Parts and packaging |
| Mass flow | ✓ | ✓ | × | Flow-rate limits |
| Occlusion | ✓ | ✓ | × | Blocked passages |
| Burst | × | ✓ | × | Failure pressure |
| Pressure cracking | ✓ | ✓ | × | Valve opening pressure |
| Chamber | ✓ | × | × | Sealed parts, no port |
| Sniffing | ✓ | ✓ | ✓ | Finding the leak site |
| Hard vacuum | ✓ | ✓ | × | Hermetic, safety-critical parts |
| Accumulation | ✓ | ✓ | × | Large parts, total leak rate |
| Bombing | ✓ | × | × | Sealed parts, no fill port |
| Differential pressure | ✓ | ✓ | × | Large volumes, low leak rates |
| Trace gas | ✓ | ✓ | ✓ | Very small leaks, quantified |
Vacuum decay leak test FAQ
What is a vacuum decay leak test?
It applies negative pressure to a sealed part, isolates the vacuum source and measures pressure movement over a test interval.
Is vacuum decay testing destructive?
No. It is a non-destructive method for parts, packages and industrial components.
How does vacuum decay detect a leak?
Air entering the evacuated test volume causes pressure to rise toward atmosphere during the test.
What happens during the settle stage?
Settle time allows part stretching or flexing to stabilize before the vacuum decay measurement begins.
What resolution can Zaxis vacuum decay testing produce?
Zaxis vacuum decay testing produces results with resolution up to the fifth decimal place, or 0.00001 PSI.
What products can use vacuum decay?
Applications include implantable devices, electronic enclosures, sensors, packaging, radios, cell phones and smartwatches.
Can vacuum decay locate a leak?
No. It provides a pass/fail decision; use sniffing testing when the leak location is needed.
Related leak test methods
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For sealed pharmaceutical and medical packages, see Pharmaceutical & Medical Packaging Leak Testing for chamber, vacuum-decay and validation context.
For package-method scope context, see the ASTM F2338 explainer.
