🔧 Helium Leak Test
Detection and location of leaks in components and installations using helium leak detector (mass spectrometer). Most sensitive available leak testing method.
Overview
Helium leak testing (HLT) is the most sensitive leak detection method, achieving sensitivity on the order of 10⁻¹² mbar·L/s. Standard PN-EN 1779 defines criteria for selecting leak testing method and technique depending on required sensitivity, object size and test conditions. Helium is an ideal tracer gas — it is light, chemically inert, non-toxic, non-flammable, and its content in the atmosphere is only ~5 ppm, ensuring low background level.
The method is widely used in the automotive industry (air conditioning systems, radiators, fuel injectors, fuel tanks), aerospace (cabin sealing, pressure vessels), vacuum (chambers, scientific apparatus), refrigeration and medical (implants, sterile packaging). Standard PN-EN 1779 classifies leak testing methods from A (highest sensitivity — vacuum helium) to I (lowest — bubble method).
Helium techniques are divided into: integral vacuum method (tested object in vacuum chamber, helium inside), local vacuum method (suction probe on surface), pressure method with sniffing probe (helium inside, sniffer probe outside) and accumulation method (helium collection in closed volume). Each technique has different sensitivity and application.
Helium leak detectors are based on magnetic mass spectrometer tuned to mass 4 (⁴He). Main manufacturers are Pfeiffer Vacuum (ASM series), Agilent (HLD series) and Leybold. Device cost is 100 000–200 000 PLN.
Method principle
Helium detector contains magnetic mass spectrometer selectively tuned to atomic mass 4 (⁴He). In vacuum method: tested object is filled with helium, placed in vacuum chamber connected to detector — helium penetrating through leak is detected by spectrometer. In sniffing method: object filled with helium under pressure is scanned with sniffing probe — helium escaping through leak is sucked into detector. Vacuum method sensitivity reaches 10⁻¹² mbar·L/s, sniffing — 10⁻⁹ mbar·L/s.
Applications
- Leak testing of automotive air conditioning systems (R134a, R1234yf)
- Quality control of fuel injectors and fuel pumps (automotive)
- Leak testing of vacuum chambers and particle accelerators
- Electronic enclosure sealing (IP67/IP68)
- Leak testing of refrigeration and cryogenic installations
- Sterile packaging control in pharmaceutical and medical industries
- Testing of pressure vessels and pipelines
Key parameters
| Parameter | Value |
|---|---|
| Minimum detectable leak (vacuum) | 1 × 10⁻¹² mbar·L/s |
| Minimum detectable leak (sniffing) | 1 × 10⁻⁹ mbar·L/s |
| Tracer gas | Helium (⁴He), atomic mass 4 |
| Helium concentration in atmosphere | ~5 ppm (low background) |
| Test pressure | 0.1–30 bar (depending on application) |
| Detector response time | < 1 s (typically) |
Standard
- Standard number
- PN-EN 1779:2004
- Title (PL)
- Badania nieniszczące — Badania szczelności — Kryteria wyboru metody i techniki
- Title (EN)
- Non-destructive testing — Leak testing — Criteria for method and technique selection
Step-by-step procedure
1. Object preparation
Clean tested element from contaminants (grease, dust). Close all technological openings. Check connections.
2. Detector calibration
Connect reference calibrator (standard leak). Check detector reading — deviation max ±20% of certified value.
3. Technique selection
Select technique for requirements: integral vacuum (highest sensitivity), sniffing (localization), pressure (large objects).
4. Filling with helium
Fill object with helium (or He/N₂ mixture) to test pressure. For vacuum method — place object in chamber and pump down.
5. Background stabilization
Wait for detector background signal stabilization. For vacuum method — stabilize chamber vacuum < 10⁻² mbar.
6. Integral measurement
Monitor detector signal. Signal increase above background indicates leak. Record leak value in mbar·L/s.
7. Location (optional)
For sniffing method: scan object surface filled with helium with sniffing probe. Signal increase indicates leak location.
8. Calibration verification
After measurements, check calibration again with reference calibrator. Drift > 20% disqualifies series.
9. Result assessment
Compare measured leak with acceptance criterion. Object tight/leaking. For location — mark leak site.
10. Documentation
Prepare test report: object identification, technique, test pressure, result, criterion, environmental conditions.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Helium leak detector | Pfeiffer ASM 340, Pfeiffer ASM 310, Agilent HLD PD03, Leybold Phoenix L300i | 100 000–200 000 PLN |
| Test vacuum chamber | Steel chamber with connections, dedicated to tested element geometry | 10 000–100 000 PLN (depending on size) |
| Auxiliary vacuum pump | Turbomolecular pump + backing pump (dry screw) | 20 000–50 000 PLN |
| Sniffing probe (sniffer) | Pfeiffer PS 400, Agilent sniffer probe | 3 000–8 000 PLN |
| Leak calibrator (standard leak) | Pfeiffer TL7, Agilent standard leak 10⁻⁸ mbar·L/s | 5 000–15 000 PLN |
| Helium cylinder (5.0) | Helium purity 99.999%, cylinder 50 L / 200 bar, Air Liquide / Linde | 800–1 500 PLN / cylinder |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Helium gas (purity 5.0) | 7440-59-7 | Purity ≥ 99.999%, as tracer gas for filling tested objects |
| Helium/nitrogen mixture (10% He) | — | Cheaper alternative to pure helium — used in large installations |
| Reference calibrator | — | Calibrated helium leak with certificate (e.g. 10⁻⁸ mbar·L/s ± 15%) |
Health and safety (OHS)
- Helium — asphyxiant gas at high concentrations (displaces oxygen), room ventilation
- Vacuum chambers — implosion risk, do not open under vacuum without procedure
- Test pressure — observe maximum working pressure of object
- Gas cylinders — secure against tipping, store vertically
- Helium is non-flammable and non-toxic, but in closed rooms can displace oxygen