Fundamentals of Leak Detection

Do you know how many ways to test leaks? JIS-Z2331 defines 8 major methods.

(1) Spray Method

・To detect helium coming inside the test object by spraying helium with a spray gun after evacuating the inside of the test object.

・Suitable for finding a small leak point, applying to finding a relatively small leak. If quantification of the total leakage of the test object is required, a hood method is more suitable.

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(2) Vacuum Hood Method

・To detect helium coming inside the test object after evacuating the inside of the test object, hooding the outside of the test object and filling helium gas in the hood.

・Possible to quantify the total leakage of the test object that can be evacuated, but impossible to find a leak point. If finding a leak point is required, the spray method is suitable.

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(3) Sniffer Method

・To detect helium coming outside through a leak point by sniffing with a sniffer probe that is connected to LD, after pressurizing of the test object.

・Effective method to find a leak point in such following conditions.


 ・In case of doing the test at a higher pressure than atmospheric pressure.
 ・In case is impossible to hood the test object because of its complicated shape.
 ・In case of finding a leak point after detection of the big leak by pressure accumulation method.

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(4) Pressure Accumulation Method

・To capture and detect helium coming outside through a leak point by sniffing with a sniffer probe that is connected to LD, after pressurizing the test object with helium gas and covering the test object with a hood.

・Owing to accumulating leaked helium gas for a certain time and increasing the helium concentration, more detectable for small leak than sniffer method. Furthermore suitable for high accuracy leak tests at a higher pressure than atmospheric pressure.

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(5) Suction Cup Method

・To evacuate the test object partially.

・Applicable to big-size vacuum containers or other pressure containers that cannot be evacuated or pressurized by the whole body because of a manufacturing process or condition of products.

・Example of application
 ・To check the manufacturing process of big-size vacuum containers.
 ・To find the regional leak.

testmethod5.jpg

(6) Bell Jar Method

・To detect leaks after pressurizing (atmospheric pressure or more) the inside of the test object with helium gas, putting the test object into the test chamber and evacuating it.

・Owing to as high detection sensitivity as vacuum method, applied in the case that higher detection sensitivity is required, compared to sniffer method or pressure accumulation method (which are pressure methods). But impossible to find a leak point, another method is required to find a leak point.

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(7) Bombing Method

・After putting test objects in a bombing tank, pressurizing them with helium gas and keeping for a certain time, to pick them up, put them in a test chamber and evacuate them. If there is some leak with test objects when pressurizing with helium gas, some helium gas goes into the test objects, they come to inside the chamber. To detect it.

・Applied as a method to judge sealing or airtightness of closed container whose inside is vacuum or filled with air or certain gas (package IC, quartz oscillator, etc).

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(8) Arbitrary Pressure Method (*)

・Application developed by ULVAC for low-pressure resistance products, proven in various fields. Possible to do high accuracy and high-speed test.

Consists of a pumping system similar to that used at sniffer method with an auxiliary pump. Test at a higher pressure than LD connecting pressure is available. The test pressure is arbitrarily adjustable.


〇Application for closed objects: Drug package, medical use package, etc.

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Application for splay method: Low-pressure resistance containers, etc.

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(*) Arbitrary Pressure Method (Coined word by ULVAC)

Which Way Is For You?

Leak test method.png

(※)Arbitrary Pressure Method(Coined word by ULVAC):ULVAC applications for the Work that is sensitive to pressure differences.

HOW TO

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