NB/T 20003.8-2021Non-destructive testing for mechanical components in nuclear island of nuclear power plants - Part 8: Leak testing (English PDF)

3.1 standard leak

calibrated leak with known leakage rate to dry air (dew point temperature below -25°C) under specified conditions (inlet pressure: 100kPa ± 5kPa; outlet pressure: less than 1kPa; temperature: 23°C±7°C)

3.2 calibrated leak

leak providing a known mass flow rate for a specified gas under specified conditions

3.3 background signal

indication of stable or fluctuant output signal produced by the leak detector due to the presence of residual tracer gas or other factor that may cause response of the testing element, when no tracer gas is applied

3.4 Bourdon tube type pressure gauge

high-precision differential pressure gauge with the function of zero compensation

4.1 Qualification of testing personnel

The requirements specified in 5.1 of NB/T 20003.1-2021 shall apply.

4.2 Testing documents

The testing procedures, testing process cards or other testing documents shall meet the requirements of NB/T 20003.1-2021. The leak testing shall be implemented according to effective testing procedures.

The testing procedures shall cover at least the following contents:

- - scope of application: type, size, testing range and material of the workpiece under test;

- - quoted laws, regulations, codes, standards, design documents, etc.;

- - qualification of testing personnel;

- - information of the testing piece, such as name, shape, size, testing area and volume;

- - testing equipment and devices, such as leak detector, pump, pressure gauge, vacuum gauge, standard leak, calibrated leak and tracer gas;

- - testing requirements, such as testing time, surface preparation requirements and testing methods used;

- - testing process and testing technique;

- - evaluation, recording and acceptance standard of testing results;

- - content and format of testing report.

The supplementary requirements of different leak testing methods to testing procedures shall meet the relevant requirements specified in A.1, B.1, C.1, D.1, E.1 and F.1.

4.3 Procedure demonstration

4.3.1 Scope of application

The testing procedure demonstration shall be performed under the following conditions:

- - the workpiece is subjected to the leak testing for the first time;

- - the testing conditions and/or technical requirements (specified value or numerical range of essential variables in the annex) change;

- - specified in relevant product design documents or purchase specifications.

4.3.2 Implementation of procedure demonstration

Under the testing conditions specified in the procedure, the testing personnel shall conduct leak testing on the demonstration specimen containing calibrated leak according to the requirements of the procedure. If the leakage of calibrated leak is detected, the procedure shall be considered as valid.

The above procedure shall be recorded and documented.

4.4 Testing scope and proportion