An Introduction ToHelium Leak Detection

Technology

An Introduction ToHelium Leak Detection

Technology

Darrell R. Morrow, PhD

Leak Detection Associates, Inc.Blackwood, New Jersey

Why Helium? Low Background (5-20 PPM)Low Background (5-20 PPM) InertInert SafeSafe LightLight Low CostLow Cost

?

He N

O

FNe

Cl

Ar

Kr

Xe

H

Why A Helium Leak Detector?

SIMS 180TD+

High SensitivityHigh Sensitivity Wide RangeWide Range ReliableReliable QuantitativeQuantitative Dynamic TestingDynamic Testing NIST TraceableNIST Traceable

Analyzer Cell180o Deflection

+200VVAR.

FILAMENT

GROUND

TRIODE PLATEHEAVY IONS

HELIUM IONS

LIGHT IONS

REPELLER

HIGHPOWERSUPPLY

LOGAMPS

- +TARGET

RESISTANCE

HIGHVACUUMGAUGE

GROUND

MAGNETMAGNET

Helium Test Methods “Hard” Vacuum

Helium Pre-Filled Samples

SIMS180TD+

1E-2 mbar

Helium Leak Methods Sniffing Test

HeHe100%

HeSIMS 180TD+

ALCATEL

Helium Leak Testing: Vacuum ModeHelium Leak Testing: Vacuum Mode

The “hard” vacuum test procedure measures the package’s cumulative leak rate arising from all sources within the sample.

This method enables the barrier performance of seals to be quantified.

Helium Leak Testing: Sniffer ModeHelium Leak Testing: Sniffer Mode Individual packages containing helium can be

checked for leaks using a pencil-sized vacuum collector (sniffer) attached to a helium leak detector.

The rate of gas sampling (flow rate) is set at 1cc/second; enabling a (ambient pressure) leak rate to be measured in ppm, or in cc/second.

The sniffer mode test procedure is “site-specific” in that the probe collects helium escaping within ~ 1/8” of the leak site.

Virtual Leaks and Outgassing

Virtual leaks are small trapped volumes of gas at atmospheric pressure within the vacuum envelope which communicates with the vacuum

system by means of minute crevices, cracks, grooves, etc.

Outgassing is the desorption of atmospheric gases and contamination from the surface area within the vacuum system.

Fine Leak Rate RealityTheoretical hole diameter calculation in molecular flow regime

D = M L 1 6Q 0 .33

2 RT P1-P2

CONDITIONS 1E-6 atm cc/sec. He leak rate 0.6 cm. wall thickness 20 C ambient temperature Inboard He spray test

D = 4 (.6)(1)(6E-6) 0.33

2 (8.32E7)(293)

Size (microns) .0001 .001 .01 .1 1 10 100 1,000 10,000

PollenMicrobes

LintTobacco smoke

Household dustIndustrial dust

Acid fumesGas molecules

Finger printsAlcohol residue

D = .0009 cm. = 0.9 microns

1 meter=

1,000,000 microns

Pharmaceutical/Device Package Test Methods

Leak Test Methods Principles The most common concept behind the

« rapid »  detection of leaks in various packaging forms is the monitoring of changes in specific physical parameters such as fluid (gas/vapor/liquid) transport from one side of a « sealed » package to the other, such as bubble formation or pressure changes.

Pharmaceutical/Device Package Test Methods

Existing Test Methods Bubble Generation Test - Vacuum

(ASTM D 3078-94) Bubble Generation Test - Internal

Pressurization (ASTM F 515-95) Pressure Decay Test Dye Penetration Test Tracer Gas Leak Detection Test/s -

Helium, Oxygen, Argon, CO2