Welded pipe joints

Shielding and backing gas used for welding pipe joints shall be per ASME BPV Code Section II, Part C, specification SFA-5.32. 

Water-based fluids can be contaminated in various ways. In new systems, debris from welding, pipe joints, and other residues previously left over from the installers may be present. If not cleaned properly they can contaminate the water-based fluids. Fluxes used for soldering may contain chloride salts that are highly corrosive to metals including stainless steel. 

Describe how iridium-192 can be used to find leaks in welded pipe joints. 

A fuel leak from the fuel supply pipework is foreseeable. It may arise following assembly, either when new or following maintenance, since the fuel pipework is routinely dismantled for turbine maintenance at intervals of one to three years. Gas turbines should operate without excessive vibration, and vibration detectors are often, but not always, fitted to larger units to detect bearing failmre. Such vibration could also cause fuel pipe joint failure. Catastrophic, sudden guillotine, pipe failure is very improbable, but a fuel leak from a control valve, flexible pipe, or flanged, screwed or welded pipe joint is a hazard against which appropriate precautions should be taken. 

Plain-end pipe used for socket-weld joints (Fig. 10-126) is available in all sizes, but fittings and valves with socket-weld ends are limited to sizes 3 in and smaller, for which the extra cost of the socket is outweighed by much easier alignment and less skill needed in welding. The joint is not so resistant to bending stress as the butt-welded joint but is otherwise equal, except that for some fluids the crevice between the pipe and the socket may promote corrosion. ANSI B16.il—1973,... 

SE values shown in tliis table for welded pipe include the joint quality factor E, for the longitudinal weld as required by Fig. 10-164 and, when applicable, the structural-grade quality factor Es of 0.92. For some code computations, particularly with regard to expansion, dexibility, structural attachments, supports, and restraints, the longihidinal-joint quality factor E, need not be considered. To determine the allowable stress S for use in code computations not ntdizing the joint quality factor E, divide the value SF shown in tliis table by the longitudinal-joint quality factor E, tabulated in Fig. 10-164. 

The heart of any drill pipe string is the threaded rotary shoulder connection (Figure 4-133), known as the tool joint. Today, the only API standard tool Joint is the weld-on Joint shown at the bottom of Figure 4-133. 

Internal coatings are usually applied at the factory and no difficulty exists in field construction if flanges, screwed, or spigot and socket joints are used, nor is there any difficulty with welded pipes above, say, 750 mm diameter, where patching can be carried out on the joints from the inside. Repair of internal coating on smaller-bore welded pipes presents many problems, which have not yet been satisfactorily overcome for all conditions. 

Consumable inserts may be used, provided they are of the same nominal composition as the filler metal and will not cause detrimental alloying of the subsequent weld deposit. The welding procedure using consumable inserts shall be qualified as required by para. GR-3.2.4. The consumable insert shall be used for welding the root pass of butt welded pipe components requiring complete weld joint penetration (CWJP) utilizing the GTAW or PAW processes. 

C) is the sum of the allowances for corrosion and thread cutting and it is assumed that, for preparative columns, there is no corrosion and the connections are made to the pipe by flanges, as a consequence (C) is taken to be zero (S) is the allowable stress and for Stainless Steel. TP 316 is taken to be 18750 lbs/sq,in. over the temperature range of 0-)000C,(3) (E) is the longitudinal weld point factor and is taken for double welded butt joints as 0.85(3)... 

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