Introduction:
Here we will discuss about the qualification tests for welders, economic choice of tools, the environmental contingencies of open air welding and quality control. There are innumerable factors which can be considered in regard to site welding so no single operational policy can be established to cover all site conditions. Therefore some of the factors affecting site welding in general will be discussed.
Site welding vs Shop welding
One of the major decisions in pressure equipment construction work like vessels, exchangers, piping, etc concern the division of work between sub-contracts to permanent fabricating shops and the site forces. Generally, where the freedom of choice exists, the decision would favor the permanent fabricating shops rather than the site, but this is not always the case. Exceptions are large projects of such duration as to justify field shops, with facilities which may surpass those of competitive manufacturers, and which may be limited to welding operations or may include forming, bending, heat treatment, inspection, etc. In the absence of such field facilities, site assembly is limited to constructions whose dimensions exceed shipping clearances or acceptable shipping costs, and to let items which are switched to field fabrication as a result of vendor or mill delays, changes, additions, etc. Often such site welding will reach an impressive percentage of the overall project. From the unit cost stand point, shop fabrication is usually lower, although the difference is minimized and not infrequently reversed where the site has a favorable work load and attendant higher utilization of manpower or manufacturer handling cost are excessive owing to dimensions or weight or where delivery requirements involve appreciable shop overtime or bonus payment or where careful timing of delivery is necessary owing to space limitation and freight demurrage. As regards the relative quality of works performed, the site fabrication may surpass that of competitive manufacturers, because, the major factor is acceptance of the need for more adequate supervision and inspection to compensate for the disadvantages of less favorable conditions, in addition there is the greater availability at the site of the customer's inspection staff and engineers who have a direct concern as to adequacy of the work, whereas the manufacturer's shops are less conveniently located and his organization is much less directly concerned.
Welding operator force
Lack of successive project continuity and attendant economies militate against a permanent welding operator force that can be moved from job site to job site. The assembling of an adequate number of welders of the various degrees of required skill at a given location can be frequently be a major problem. The most that can be done progressively to improve the general level of skill and versatility is to maintain a nucleus of specialist for operations demanding maximum skill, who also act as instructors to the numerous project-hired operators, most of whom are new with the company and often unacquainted with the type of work involved. The remaining training burden must be carried by the supervisors, foremen and engineers. Standard qualification test for welding operators may be inadequate as a measure of ability to perform production work at a specific level of quality. For improved assessment after the qualification test, the operators are employed on non-critical work, such as temporary structures, supports, etc. which enables the welding supervisors and inspectors to evaluate individual skills and establish various degrees of proficiency so that tasks may be assigned in accordance with ability. Radio-graphic examination of qualification test plates would be helpful. However a test plate represents the best quality of which an individual operator is capable, rather than the average which he will attain in production. If at the job site, sufficient number of skilled workers are not available, two alternatives are available- to train welders at the site or to recruit skilled workers where available and transport them to the site. The first alternative, at many places, has been especially successful, particularly because of the usual willingness and enthusiasm displayed by unskilled or native labour when learning a trade. It is only natural that the importation of skilled labour is constructed as a reflection on their latent capabilities. A factor that usually militates against the importing of skilled labour is the psychological environmental effect. Men have been selected for foreign work on the basis of skill and productivity in their local environments and frequently at the destination become dissatisfied so that their skill and productivity deteriorated. This is particularly applicable to welding as contrasted to other crafts, probable owing to the less continuous and strenuous effort involved, and the consequent opportunity for the mind to wander. Therefore in selecting welders for overseas work, one would be well-advised to base selection on emotional stability more than on skill and productivity.
Site Welding - Part 2
Site Welding - Part 2