1. The helium leak detection method of high purity bulk gas pipeline should adopt inward leak detection method, valve seat leak detection method and outward leak detection method.

2. the inward leak detection method (helium injection method) should be adopted in the high purity gas pipe inside the vacuum, helium injection method for leak detection.

3. The valve seat leak detection method should be filled with helium in the upstream of the valve and vacuumized in the downstream.

4. Outward leak detection method (suction gun method) should be used to fill helium or helium nitrogen mixture inside the high purity gas pipe, and check the possible leakage point externally with suction gun.

5. Helium leak detection instrument shall adopt mass spectrometer helium detector, whose detection accuracy shall not be less than 1

Helium Gas

6. the leakage rate of high purity gas helium leak detection should meet the following requirements:

6.1 The leakage rate measured by the inward leak detection method shall not be greater than 1*10-9mbar. l/s

6.2 The leakage rate determined by valve seat leak detection method shall not be greater than 1*10-6mbar. l/s

6.3 The leakage rate determined by the outgoing leak detection method shall not be greater than 1*10-6mbar. l/s

7. After the leakage points found by helium leak detection are repaired, the air tightness test shall be carried out again and qualified, and then helium leak detection shall be carried out according to the provisions.

8. All possible leakage points should be isolated with plastic bags.

9. After the system is tested, it should be filled with high-purity nitrogen or biogas and purged. 10. After the test, the test report shall be submitted.