Welding operations

Residual. Stress-relief-anneal components and assemblies following cold working or welding operations. Note, however, that annealing has no effect on applied stresses. 

Critical factors. In general, porosity is caused by the entrapment of gas during the welding process or during solidification of the weld metal. Surface contamination may provide a gas source during the welding operation. 

Stainless steel is susceptible to sensitization when it is heated to the range of 900 to 1550°F (480 to 850°C). Since any welding operation involving stainless steel will produce such temperatures in the metals being joined, it would appear that all welded stainless steel would sensitize. However, sensitization is a function of both time and temperature, occurring most rapidly at temperatures near 1250°F (675°C). Metals that cool rapidly through this temperature range will not sensitize. Consequently, thin metal sections, which cool rapidly, are less susceptible to sensitization than thick sections. 

To allow for welding time, a buffer of a certain sheet length, in the form of entry accumulator, is maintained, generally in a vertical formation, to save space. This feeds the line ahead until the welding operation is completed and the second route is installed to feed the process. 

Fig. 15-10 Stray current interference of ships at the supply quay from welding operations with a central welding transformer.

Does the SAHP designate an individual responsible for authorizing eutting and welding operations in areas not speeifieally designed for sueh proeesses [OSHA Referenee. 252(aX2Xxiii)(B)]... 

Resistance and arc welding operations, and plasma and laser cutting produce fumes by expulsion or evaporation of the base material, coating, and electrode wear. Larger particles deposit on the surrounding surfaces, while smaller particles move upward with convective flows. Specific contaminants associated with different welding and cutting operations are listed in AWS. ... 

Thermal Hazards. These hazards include liot surfaces, fire produced by reacting substances, and flame contacts from heat-producing equipment, welding operations, and so on. 

Fires of tliis origin are most coimnonly caused by sparks and hot metal from cutting and welding operations, by defective gauges, or deteriorated gas lines on welding equipment. 

Bimetallic corrosion of nickel-iron alloys may be of significance in welding operations. Ni-45 Fe alloys are used as filler materials in the welding of cast irons but the favourable area relationship of weld metal to base plate... 

Fusion welding operations are rather more difficult with brasses than with other copper alloys (because of evolution of zinc fume from brasses). 

As with most other metal and alloys systems, nickel and certain of its alloys may suffer intergranular corrosion in some circumstances. In practice, intergranular corrosion of nickel alloys is usually confined to the vicinity of welds as a result of the effects produced by the welding operation on the structure of the material in those regions. Alloys that are subjected to other similarly unfavourable thermal treatments may also become susceptible. The compositions of most commercial nickel alloys that are marketed today are. 

Brown has pointed out that Du Pont use evaluation tests for (a-) as-received unstabilised alloys containing more than 0-03% C to check the effectiveness of the final heat treatment and (b) stabilised or special low-carbon grades after a sensitising treatment (1 h at 677°C) to determine whether susceptibility might develop during a subsequent welding operation. 

Residual stress generally from the effects of metal rolling, bending, or welding operations... 

Stainless steel coil and sheet stock is unloaded and stored outdoors under protective cover. As it is needed, the coil stock is moved indoors by a forklift to one of six automatic tube mills where the sides of unrolled metal strips are curled up to form a continuous, cylindrical pipe. The seam of the resulting pipe is fused in an electric in-line welding operation. An abrasive saw is used to cut the continuously formed pipe to specified lengths sections of poorly welded pipe are cut away. 

A welding operation was to occur on the roof of a storage vessel. The tank contained a flammable, volatile liquid. The roof was equipped with a vent pipe with a flame arrestor. 

The foreman recognized a possible hazard from flammable vapor escaping from the vent pipe and igniting on the sparks from the welding operation. He connected a hose to the vent at the top of the tank and ran the hose down to the ground. Because the flammable vapors were water soluble, he stuck the end of the hose in a drum full of water. During a subsequent operation that involved emptying the tank, an accident occurred. Can you explain what happened and how ... 

It responds to electric arcs from welding operations. It can be affected by deposits of grease and oil on the lens. This reduces it s ability to "see" a fire. Lightning with long duration strikes can cause false alarm problems. Some vapors typically those with unsaturated bonds may cause signal attenuation. Smoke will cause a reduction in signal level seen during a fire. It may produce a false alarm response when subject to other forms of radiation such as from NDT operations. 

The use of two separate electrical or mechanical zones of detectors, both of which must be actuated before the confirmation of a fire or gas detection. For example, the detectors in one zone could all be placed on the north side of a protected area, and positioned to view the protected area looking south, while the detectors in the second zone would be located on the south side and positioned to view the northern area. Requiring both zones to be actuated reduces the probability of a false alarm activated by a false alarm source such as welding operations, from either the north or the south outside the protected area. However this method is not effective if the zone facing away from the source, sees the radiation. Another method of cross zoning is to have one set of detectors cover the area to be protected and another set located to face away from the protected area to intercept external sources of nuisance UV. If welding or lighting should occur outside the protected area, activation of the alarm for the protected area would be inhibited by second... 

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