Various test methods and their selection

Select by test pressure

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		Advantages	Disadvantages
Pressurization method	Test by applying pressure. Target: Works whose internal pressure increases when in use, and works that have liquid inside.	Increasing the test pressure increases the detection capability. Leaks can be located by visually checking for air bubbles.	Susceptible to temperature changes, deformation, and other pressure changes.。
Vacuum method	Test by vacuum pumping. Target: Works used under vacuum, or works that change temperature or deform during testing.	Not easily affected by temperature change, deformation, or other pressure change factors.	Test pressure is limited compared to positive pressure. Also, the amount of leak is smaller for the same hole diameter. Affected by the vapor pressure of water and oil.

Select by work shape

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		Advantages	Disadvantages
Differential pressure method	Measure the inside of the works. Target: General works, Works with many openings.	Fixtures are cheaper than those for the external pressure method. Using cores to reduce the internal volume leads to higher sensitivity.	Susceptible to temperature deformation at higher test pressures.
Differential pressure method	Normal method. To improve detection accuracy and reduce test time, insert cores so that the work volume is as small as possible.
Pressure change chamber method	・Pressurize the inside of the work placed in a chamber and measure the pressure change in the gap between them. Target: Works with few openings and less uneven shape.	Short measurement time and high detection accuracy regardless of the test pressure. This is particularly advantageous when the test pressure is high.	Fixture costs are relatively high. It may be difficult to seal the openings and visual inspection may not be possible.
Pressure change chamber method	For works with a large internal volume or those that are easily sealed in a capsule, measuring the leaking side at atmospheric pressure reduces test time
Sealed chamber pressure change method	Large leaks are detected by converting the gap volume between the capsule and the work into a differential pressure. Target: Sealed products without air inlet holes, watches, electronic parts, etc.	Capable of detecting both large and small leaks, with no dead zone. Even small works can be tested.	Requires a capsule. Requires a certain amount of internal space volume in the works. The price of the tester will increase due to the need for a mechanism to detect large leaks.
Sealed chamber pressure change method	This method is used for sealed works. The outside of the work is pressurized or evacuated before measurement. A process for detecting large leak is provided, allowing detection of such large leak that makes the inside of the work reach the test pressure when pressurized.

Other applications of test method

Simultaneous testing of multiple works

Method: Tests multiple works simultaneously.
Target: Used for works with small internal volume or when there is sufficient margin for detection. Used when a longer Pressurization time is required (e.g., when there are deformation effects).
Advantage: Shorter test time per work.
Disdvantage: Cannot be used when accuracy is required or when the defect rate is high. Multiple test fixtures are required.

Simultaneous measurement of two chambers

Method: When a work has two chambers for separate measurement, use two testers to apply a different test pressures to each chamber and measure simultaneously.
Advantage: Test time is reduced.
Disadvantage: If leak occurs between the chambers A and B, the tester with high test pressure will judge the work as Fail, while the tester with low test pressure will judge the master as Fail, so caution is needed when processing the judgment signals.
Exhaust Interference Prevention: If one tester completes judgment and exhausts first, it may affect the measurement of the other tester. To cope with it, tester models that can be externally controlled to have simultaneous exhaust are also available.