1.1    Preface
　　The airtightness testing instrument is a testing instrument for checking the airtightness of various product parts and finished products. In order to allow you to use this equipment correctly and quickly, be sure to read this manual carefully before operating the equipment. This manual introduces the setting, maintenance, and operation methods and precautions of this instrument. Please read this carefully before use
　　Read this manual and keep it properly.
 

1.2    Safety Precautions
　　This manual describes how to use the leak detector safely and correctly, and explains the content to prevent harm to yourself or others. Be sure to operate the instrument according to the operating procedures described in this manual.
Precautions:
(1) Please ground the instrument when connecting to the power supply.
(2) Do not use power supply voltages outside the specified range, otherwise it may easily cause fire and electric shock accidents.
(3) When adjusting the inflation pressure of the instrument, do not exceed the upper limit of the instrument's indicated range to avoid damage to the instrument's core precision components.
(4) Do not disassemble the instrument without authorization, as this may easily cause electric shock and damage to the instrument.
(5) If you find any abnormal noise from the instrument, please cut off the power immediately.
(6) Do not use the instrument in humid, direct sunlight, high temperature, or extremely cold environments, as this may prevent the instrument from working properly.
(7) Do not install or remove piping while the gas source is connected, otherwise it may easily cause injury.
(8) Please operate according to the contents recorded in this operation manual, otherwise the instrument may be damaged.
 

1.4    Instrument application fields

Features:

　　(1) It adopts the direct pressure principle for detection, which is simple to operate and easy to learn and understand.

　　(2) Because air is used as the detection medium, there is no operating cost.
　　After pressurizing the standard product and the test product at the same time, close the pneumatic valves 1 and 2. If there is a leak in the test product, the pressure on the test product side will drop. The pressure difference between the test product and the standard product is obtained through a differential pressure sensor to determine whether the test product has a leak.
　　(1) The pressure of both the test product and the standard product will fluctuate due to temperature and deformation of the test product. The differential pressure type

The test method can offset the impact of this change;
　　(2) Because air is used as the detection medium, there is no operating cost.

　　The basic principle of flow testing is: to fill the test piece with gas at a specified pressure, maintain a certain pressure in the workpiece through a pressure reducing valve, and the instrument measures the current gas flow.
Features:
　　(1) The flow generated by the leak remains very stable over time.
　　(2) Because air is used as the detection medium, there is no operating cost.
6.3     Basic Knowledge of Leak Detection
　　Currently, there are two main detection methods for airtightness testing instruments: differential pressure and direct pressure. Since the detection of minute pressure is affected by various factors such as temperature and air pressure, the detection results of leakage will also be affected. Factors affecting leakage results: Leakage is calculated from the pressure drop and cavity volume of a closed cavity, and the magnitude of the pressure drop is closely related to the detection pressure and detection time. Any change in parameters will directly affect the detection results.
6.3.1   Detection Pressure
　　Whether the leakage of the workpiece is qualified should be judged under the detection pressure given by the corresponding standard. For leak holes of the same size, when the detection pressure changes, the pressure drop caused in the same time will change.
　　Similarly, for the workpiece under test with a slight leakage, the leakage amount will also be different under different detection pressures.
6.3.2   Detection Time
　　The detection process of the leak detector is divided into 4 stages: inflation, stabilization, detection, and deflation. Each stage requires time setting, and the gas needs to reach a stable state before the leakage can be detected. Ideally, the longer the detection time, the higher the accuracy of leakage detection, but in use, a reasonable time range needs to be determined according to the actual situation to ensure efficiency.
6.3.3   Detection Interval Time
　　According to the ideal gas equation:
　　PV = nRT
　　Where: P—pressure of the ideal gas; V—volume of the ideal gas; n—amount of gas substance; T—thermodynamic temperature of the ideal gas. It can be seen that the pressure of the gas is related to the volume and temperature. During the leak detector detection process, the gas is compressed in a closed cavity, which will cause the gas temperature to rise, and the temperature change has a greater impact on the detection of minute pressure, which will ultimately affect the detection result of the leakage. Therefore, when using the leak detector for the second detection, it is necessary to wait for the gas in the differential pressure sensor and the air circuit to return to the original temperature and deformation state. Since the gas temperature in the cavity is difficult to detect directly, the interval between the two detections can be increased to ensure that the gas returns to its original temperature.
6.4     Volume of the Cavity of the Workpiece Under Test
　　During the detection process, the gas leakage of the workpiece under test is determined by the pressure drop and cavity volume of its internal cavity.
　　Calculated:
　　ΔV =  P root VΔP
　　Where: ΔV—calculated value of volume change; V—sealing volume of the leak detector on the side of the object under test and the volume of the connecting air circuit; P0—atmospheric pressure; P—detection pressure; ΔP—measured value of the leak detector pressure drop. It can be seen that when the detection pressure and pressure drop are the same, the cavity volume of the workpiece under test is proportional to the leakage amount. Therefore, the accuracy of the cavity volume measurement will affect the magnitude of the leakage amount.
6.5     Parameter Capture Method
　　(1) Test pressure: Determine the test pressure according to the working conditions used by the workpiece.
　　(2) Inflation time: a. The inflation time should be greater than 2 seconds; b. The larger the product volume, the longer the inflation time; conversely, the shorter. c. The smaller (softer) the product rigidity, the longer the inflation time; conversely, the shorter. d. The greater the detection pressure, the longer the inflation time; conversely, the shorter. First set the inflation time in the parameters to a relatively long time, such as a few minutes. Then exit to the main interface, put the workpiece to be tested in the fixture, and then press the start button. At this time, observe the pressure curve on the instrument. When the pressure curve reaches a flat line, the inflation time value displayed by the instrument is set as the inflation time. (That is, the time required for the pressure curve to climb from 0 to the inflation pressure
Time)
　　(3) Balance time: The principle is equal to or approximately less than the inflation time.
　　(4) Detection time: a. The detection time should be at least greater than 3 seconds; b. The maximum leakage of qualified products should be less than the minimum leakage of unqualified products, less than 100pa. c. The larger the product volume, the longer the inflation time; conversely, the shorter. d. The greater the detection pressure, the longer the inflation time; conversely, the shorter. Capture method: Use the water immersion method to find 3 qualified products and 3 slightly leaking products. Put the 3 qualified products on the instrument for testing, and repeat the test five times for each product (the more the better) to record the maximum value of the leakage. Then put the 3 unqualified products on the instrument for testing, and repeat the test five times for each product (the more the better) to record the minimum value of the leakage. If the minimum value of the unqualified product minus the maximum value of the qualified product is less than 100pa, extend the detection time; otherwise, shorten the detection time.
　　(5) Exhaust time: The exhaust time is related to the volume of the workpiece test cavity. The larger the volume, the longer the exhaust time. The time required from the full gas state to the zero pressure state can be seen from the test curve as the exhaust time. (That is, the time required for the pressure curve to reach the zero pressure state from the test pressure state)
　　(6) Leakage: After setting the detection time, take the value with the smallest leakage amount among the values measured in the limit leakage workpiece and take an intermediate number between the largest reading value among all the test times of the OK workpiece as the set leakage amount. For example, the minimum leakage amount of the limit leakage workpiece is 200Pa, and the maximum leakage amount of the OK workpiece is
If the leakage is 100Pa, the leakage can be set to 150Pa.

8     Pressure Unit Conversion Table

10     Flow Rate Conversion Table