NB/T 47013.7-2012Nondestructive testing of pressure equipments - Part 7: Visual examination (English PDF)

4.1 General

The general requirements for visual examination shall not only comply with JB/T 4730.1, but also meet the requirements of Sections 4.2~4.4.

4.2 Examination personnel

The non-corrected or corrected near vision and far vision of visual examination personnel shall not be less than 5.0 (accurate to 1.0) and the examination method shall meet the requirements of GB 11533. The examination personnel shall have vision examination every 12 months, in order to guarantee normal or correct near-distance visual capacity.

If the examination has special requirement of color recognition, then color recognition examination should be supplemented for the examination personnel upon agreement by the contracting parties.

4.3 Procedure specification

4.3.1 Procedure specification of visual examination shall be formulated in accordance with the requirements in JB/T 4730.1, and shall include but not limited to.

a) Application scope;

b) Normative regulations and standards;

c) Examination personnel qualification;

d) Testing apparatus;

e) Inspection methods;

f) Examined piece, position, accessibility and geometrical shape;

g) Examination scope;

h) Examined surface structure;

i) Lighting requirements of the examined surface;

j) Examination time;

Visual examination technique includes direct visual examination, remote visual examination and translucent visual examination. Generally, visual examination is primarily used for inspecting the surface of materials, parts, components, equipment and welded joints, as well as the alignment, deformation or leakage of fitting surface. Besides, visual examination can be adopted to reflect the undersurface state of the composite material (translucent laminate board).

5.2 Direct visual examination

5.2.1 For direct visual examination, the distance and angle between the eyes and the examined piece surface shall be optimal. The distance from the eyes to the examined piece surface shall be less than or equal to 600 mm, and the included angle between the eyes and the examined piece surface shall not be less than 30°.

5.2.2 For direct visual examination, reflector can be used to improve the inspecting angle and low power magnifier specified in GB/T 20968 can be used to recognize subtle defects.

5.2.3 The area of direct visual examination shall be provided with adequate lighting condition with at least 500 lx lighting intensity and at least 1000 lx for those areas requiring careful inspection or further inspection and examination due to abnormal conditions.

5.2.4 For the best examination effect, the lighting condition shall meet the following requirements.

a) The angle between the lighting ray direction and the inspection point shall be optimized;

b) Surface glare shall be avoided;

c) The color temperature of light source shall be optimized;

d) The lighting level matching surface reflection shall be used.

5.3 Remote visual examination

5.3.1 The remote visual examination may be adopted in the examination position and area where it is difficult or impossible to carry out direct visual examination.

5.3.2 Lighting source, reflector, telescope, endoscope, optical fiber, camera, video system, automatic system, robot and other applicable visual aids can be used for remote visual examination.