Производство оборудования
для нефтегазовой отрасли
Производство оборудования
для нефтегазовой отрасли



Visual measurement control is one of the methods of non-destructive testing of an optical image. It is based on obtaining primary information about a controlled object by visual observation or with the help of optical instruments and measuring instruments. This is organoleptic control, i.e. perceived by the senses (organs of sight.)

Requirements for optical inspection methods

GOST 23479-79 "Nondestructive control. Methods of optical appearance "establishes the requirements for methods of monitoring optical species.
External examination (PIC) checks the quality of the preparation and assembly of blanks for welding, the quality of the welds during the welding process and the quality of the finished welded joints. As a rule, the external inspection controls all welded products, regardless of the use of other types of control. Visual control in many cases is quite informative and is the cheapest and operational method of control.
The visual control method allows detecting discontinuities, deviations of size and shape from given values of more than 0.1 mm when using instruments with magnification up to 10 х.

Visual inspection usually performed with the naked eye or using magnifying loupes up to 7 h. In doubtful cases and with technical diagnostics, the use of loops with magnification up to 20 h is allowed.

Before carrying out a visual inspection, the surface in the inspection zone should be free from rust, scale, dirt, paint, oil, metal splashes, and other contaminants that impede inspection.

For the Visual-Measuring Inspection of welds, the inspection zone is the weld and the adjacent base metal parts with a minimum width of 20 mm to each side of the weld from two surfaces, if both are available for inspection.
Visual inspection performed prior to other control methods. Defects detected by visual inspection must be repaired before testing by other methods.

Measurements are made using instruments and tools:

 measuring loupes;
 calipers;
 metal measuring lines;
 protractors;
 squares;
 probes;
 Templates, etc.

Visual inspection and measurements are made:

 at the stage of input control of the material to identify surface defects (cracks, delaminations, nicks, sunsets, shells, slag inclusions, etc.), as well as deviations of the geometrical dimensions of the blanks from the design ones;

 at the stage of preparation of parts for assembly and welding to confirm compliance with the established requirements of structural elements of cutting and clean edges and adjacent surfaces, the absence of angular and surface displacement, the size of the gaps, the number, location and quality of tacks;

 at the end of welding, or at its separate stages - to identify surface defects and discontinuities in a welded joint (cracks, cavities, pores, fistulas, undercuts, burn-throughs, swellings, coarse flaking and sticking between rollers, poor penetration, etc.); as well as deviations of the geometric dimensions of the weld from the requirements established by the standards.

 at the stage of technical diagnostics - to identify deviations in the size and shape of the structure from the design; operational defects of the base metal and the weld (fatigue cracks, corrosive ulcers, pittings, etc.)

Visually-Measuring Control is a simple method; however, it can serve as a highly effective means for the prevention and detection of defects. Only after visual inspection and correction of unacceptable defects are welded joints subjected to inspection by other physical methods (x-ray control, ultrasonic control, capillary control) to detect internal and surface defects.

Some manufacturers, in order to save or incompetence, ignore the visual measuring and other methods of non-destructive testing of products or remember it only at the last stage of assembly, or just before the object is handed over (and this leads to additional time loss and unforeseen expenses), when the control is technically impracticable. Such an attitude to quality control often leads to emergencies during operation and can even lead to technological disasters.

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