What Is Welding Inspection And Why Is It Needed?
The principal objective of inspection or quality control is to ensure the high quality of products through the careful examination of the component parts at each stage of manufacture.
Systems of inspection or quality control vary from factory to factory and from industry to industry, depending on the type and scope of production, managerial structure and technical standards.
When properly organized, inspection should be able to cover each link of the production chain so as to prevent spoilage, to trace out its causes when it occurs, to suggest ways and means of eliminating it and to certify quality of the finished product.
Inspectors should therefore have a working knowledge of the relevant drawings, procedures and specifications. In a welding shop, proper organization of weld inspection is essential because it reduces rework costs and ensures high quality weldments.
Apart from the welded joints, the quality of the weldment depends on certain other factors:
a) Whether or not a given design is convenient for welding; the magnitude of residual strains and stresses ser up by welding heat; and the layout of welded joints from the viewpoint of load distribution;
b) The quality of parent metal, electrodes, welding wire, flux and shielding gases;
c) The quality of work preparation and fit-up
The quality of welded joints depends on the performance of welding equipment, on whether or not the proper welding procedure has been chosen; and on the skill of the operator.
The inspection (quality control) department must therefore see to it that;
a) the parent metal, electrodes, welding wire and flux comply with the appropriate specifications; in the absence of certificates covering these materials, they should be tested for quality by suitable procedures;
b) the joint is prepared and the work is fitted up properly; and more specifically, whether
(i) the components are formed and dimensioned within the tolerance limits in accordance with the blueprint specifications;
(ii) the parts to be welded are spaced properly at the joint
(iii) fit-up produces no initial stresses and
(iv) the fusion faces are free from dirt, rust, grease etc.;
c) the operator uses the correct welding procedure, including welding current, electrode size, welding sequence and number of layers, arc length, rate of arc advance, inter-run deslagging, chipping back when sealing run is applied etc.
Methods of Welding Inspection
Welds may be inspected and tested in a variety of ways, depending on the nature and type of a given welded structure, its application and the test equipment available. However, broadly they can be divided into two parts:
- Destructive Testing – Undertaken in either Workshops (Tensile, Bending, Impact, Hardness, Fatigue, Cracking) or Laboratories (Micorscopic, Macroscopic, Chemical, Corrosive)
- Non-Destructive Testing (NDT) – This in itself is a wide area of study. The methods include visual, radiographic )X-rays, Gamma-rays), ultrasonic, magnetic, electrical (Eddy current methods), liquid penetrant, acoustic emission, thermography, optical holography etc.
To read more about NDT and welding inspection techniques, here is a list of few useful pages
Firms undertaking NDT inspection in India:
Here we have tried to bring together a list of firms that provides NDT services inIndia.
Courses & Training on Welding Inspection
To learn more about courses, click here.
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