GB/T 41856.1-2022Non-destructive testing - Industrial endoscopy visual testing - Part 1: General requirements (English PDF)

1 Scope

Part 1 of China's national standard for industrial endoscopic visual testing, giving the general requirements. Visual inspection is the oldest non-destructive method and the only one that identifies a defect directly rather than inferring it from a signal, and the endoscope extends it into places a person cannot see: inside an engine without removing the head, along a heat exchanger tube, into a turbine's gas path, through a weld's bore. The requirements have to address what determines whether the inspection means anything - the resolution and the illumination at the working distance, the field of view and the distortion, the ability to measure a defect rather than merely see it, and the qualification of the person interpreting the image. That last is why this is a formal method rather than looking: an endoscopic image is distorted, oddly lit and hard to scale, and two inspectors can reach opposite conclusions from the same view.

This document specifies the method principle, environmental requirements, personnel requirements, testing system, testing, result evaluation, and testing report of industrial endoscopy (hereinafter referred to as endoscopy) visual testing. This document is applicable to the testing and evaluation of the inner surface state and internal structure of metal or non-metal parts and assembly components of industrial products.

2 Normative references

The contents of the following documents, through normative references in this text, constitute indispensable provisions of this document. Among them, for dated references, only the edition corresponding to that date applies to this document. For undated references, the latest edition (including all amendments) applies to this document.

GB/T 9445 Non-destructive testing - Qualification and certification of NDT personnel

GB/T 20737 Non-destructive testing - General terms and definitions

GB/T 41856.2 Non-destructive testing - Industrial endoscopy visual testing - Part 2: Atlas

3 Terms and definitions

The terms and definitions defined in GB/T 20737 apply to this document.

4 Method principle

Without damaging the tested part or the operation of in-service equipment, for the parts or inner surface conditions that are difficult to be observed by direct visual testing, endoscopy visual testing uses an endoscopy testing system to test and evaluate them by means of optical images or photoelectric conversion video images. By changing different endoscopy probes (also known as scope bodies); changing the viewing direction or improving the field of view; and applying optical or photoelectric principles, FIND defects clearly, intuitively and effectively. Compare the measured image with the typical atlas; analyze and evaluate the real situation of the tested area or structure.

5 Environmental requirements

5.1 The ambient temperature and humidity of the testing site shall meet the requirements of the testing system.

5.2 There shall be no electromagnetic interference affecting the testing around the testing site.

5.3 The endoscopy testing system should have its own grounding protection power supply or be grounded independently. It shall be equipped with a voltage stabilizing device, to ensure that there is no static electricity accumulation during the working process. The grounding resistance should not be greater than 4 Omega.

5.4 When testing, it is advisable to avoid strong light or direct sunlight; choose a soft and quiet environment.

6 Personnel requirements

The personnel, who carry out the testing, shall be subject to qualification and certification according to GB/T 9445 or the system recognized by the parties to the contract; it shall obtain relevant qualification certificates for visual testing. Or the employer shall provide job training and operation authorization for them.

9 Result evaluation

9.1 Identification of defect type Compare the image determined according to GB/T 41856.2 with the testing image, to identify the type of defect.

9.2 Defect measurement According to the testing requirements, select the measurement mode and reference geometric measurement datum. When measuring, the image should use a larger magnification. Repeat the measurement on the same measurement object; take the average value as the measured value. See Appendix B for endoscopy measurement methods.

9.3 Result evaluation According to the acceptance requirements, evaluate the type of defect and measurement data; give the conclusion of acceptance, repair or rejection.

10 Testing report

After endoscopy visual testing, the testing results and related testing parameters shall be recorded in detail. The testing report shall be filled out. Details regarding format and content should be specified in the application-specific documentation OR agreed between the contracting parties. The testing report shall at least include the following:

a) Entrusting organization and delivery-for-testing date;

b) Information of the tested part, such as name, material designation, and quantity;

c) Reference to this document or acceptance requirements;

d) Specification/model, measurement mode, and relevant basis of the testing instrument;

e) Testing area;

f) Testing conclusions (records are given in words or schematic diagrams; photos are provided if necessary);

g) Signatures of testers, report writers and reviewers AND their dates;

h) Testing report number and date.

Appendix B

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Note 3. 10. **Verification (USD

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