workshop: vacuum metrology for industrial environments 27 june 2013

Workshop:Vacuum Metrology for Industrial Environments

27 June 2013

QUALITATIVE AND QUANTITATIVE QUALITATIVE AND QUANTITATIVE METHODS FOR LEAK TESTINGMETHODS FOR LEAK TESTING

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LEAK TESTING: definition

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Leak Testing

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TIGHTNESS mbar·L/s

Water tight 10-2

Vapor Tightness 10-3

Oil and Gasoline Tightness 10-4

Bacteria Tightness 10-5

Virus Tightness 10-6

“Absoluta” Tightness (technique) 10-10

Pressure

Varation

Volume

TimeLeakrate

in mbar·L/s

1 mbar 1 L 1 s 1 = 100

1 mbar 0,1 L 10 s 0,01 = 10-2

0,01 mbar 0,1 L 100 s 0,00001 = 10-5

The unit of measurement of gaseous flow: mbar·L/s

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The Correct Approach

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Methods for Leak Detection

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Pressure Change Method

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Pressure Change Method

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Pressure Change Method

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Bubble test

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Bubble test

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Bubble Test Application(vacuum)

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Ultrasonic Detection

The directionality of ultrasound is a fundamental characteristic, while the intensity is an inverse function of

source-sensor distance.

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Ultrasonic Detection

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Ultrasonic Detection

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Tracer Gases

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These characteristics varies with dependence from molecular size and speed. They can be used with different gas or gas mixtures, since each of them

produces a different thermal conductivity respect to the air.

Tracer Gases:Thermal Conductivity

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Tracer Gases:Thermal Conductivity

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Tracer Gases:Thermal Conductivity

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Tracers Gases: Mass Spectrometry

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Tracers Gases: Quartz Capillary

In this leak detector, the detection system of the tracer gas (helium) is constituted by a membrane in quartz, permeable only for helium and not other

gases present in the atmosphere.

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Test Methods with Mass Spectrometry

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Test Methods with Mass Spectrometry

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Test Methods with Mass Spectrometry

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It is firstly possible distinguish two different types for the leak testing:

A) Leak Detection Methods (QUALITATIVE), generally controlled by Leak Detection Methods (QUALITATIVE), generally controlled by operator, with localization of leakoperator, with localization of leak:

• Method in Water with pressurized piece (visual inspection); • Method with Bubble (soap solution) with pressurized piece (visual

inspection); • Method with Ultraviolet Lamps with pressurized piece (visual

inspection); • Method with Hot Air (visual inspection at infrared);• Method with Dielectric Variation on plastic components (ionic

system at high voltage).

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B) Leak Detection Method (QUANTITATIVE) with indication of Good, Leak Detection Method (QUANTITATIVE) with indication of Good, Reject Piece and value of leakrateReject Piece and value of leakrate:

• Measurement with presurized gas (Helium);• Measurement the flow meter of the pressurized piece;• Measurement of the pressure differential between the pressurized

piece and the reference sample;• Measurement of the pressure decay of the pressurized piece;• Measurement “compliance” of pressure increase in vacuum bell.

The instrumentation of this type allows you to monitor in time any drifts of quality, if it is applied throughout the production.

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Metrological Laboratory

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Gas Injection System

Pumping System LT-SP-1

Leak in Calibration

Reference Capillary Leak

Reference Capillary Leak

Reference Capillary Leak

Reference Permeation

Leak

Pumping System LT-SP-2

Mass Spectrometer

Pressure GaugeLT-TP-1

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Scheme of calibration system

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The calibration requires a calibrated device:

REFERENCE LEAKREFERENCE LEAK

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JRP14i – Joint Research Project - Work Packages 2 – Optimization of the process of measurement and leak testing in an industrial environment.

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JRP14i – Joint Research Project - Work Packages 2 – Optimization of the process of measurement and leak testing in an industrial environment.

Manufacturing of Capillary Leak with Gas Refrigerants (respect to atmosphere).

Study of the behavior of the flow of Gas Refrigerants through capillary leaks.

Study and analysis of the main parameters of the leak detector for refrigerants.

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