Joints butt-welded

Imperfectionf When required examination is Girth and miter-joint butt welds Longitudinal butt welds 1 Fillet, socket, seal, and reinforcement attachment welds Welded branch connections and fabricated laps... 

Most of the adhesively bonded pipe joints used in engineering, such as adhesively bonded socket joints, butt-weld and strap joints and heat activated coupling joints etc., can be basically regarded as two pieces of composite pipes joined by a connection coupler via the bonding adhesive, as shown in Figure 5. In order to reduce the stress concentration influence on the joint system, the smart beam-like joint concept was extended to develop a novel adhesively bonded smart composite pipe joint system by integrating the smart piezoelectric... 

Valve bodies are also standardized to mate with common piping connections flanged, butt-weld end, socket-weld end, and screwed end. Dimensional information for some of these joints and class pressure-temperature ratings are included in Sec. 10, Process Plant Piping. Control valves have their own standardized face-to-face dimensions that are governed by ISA Standards S75.03, 04, 12, 14, 15, 16, 20, and 22. Butterfly valves are also governed by API 609 and Manufacturers Standardization Society (MSS) SP-67 and 68. 

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,... 

V-clamp joints (Fig. 10-140) are attached to the pipe by butt-weld or expanded joints. Theoretically, there is only one relative position of the parts in which the conical surfaces of the clamp are completely in contac t with the conical surfaces of the stub ends. In actual practice, there is considerable flexing of the stub ends and the clamp also complete contact is not required. This permits use of elastomeric gaskets... 

Butt-welded joint, reducer, or weld-neck flange Double-welded slip-on flange Fillet welded joint or pocket-weld flange... 

Subsection B This subsection contains rules pertaining to the methods of fabrication of pressure vessels. Part UW is applicable to welded vessels. Service restric tions are defined. Lethal service is for lethal substances, which are defined as poisonous gases or liquids of such a nature that a very small amount of the gas or the vapor of the liquid mixed or unmixed with air is dangerous to life when inhaled. It is stated that it is the user s responsibility to advise the designer or manufacturer if the service is lethal. All vessels in lethal service shall have all butt-welded joints fully radiographed, and when practical, joints shall be butt-welded. All vessels fabricated of carbon or low-aUoy steel shall be postweld-heat-treated. 

Butt weld with one plate offset—for circumferential joints only, see UW-13(c) and Fig, UW-13-l(k)... 

Joints and fastenings should be arranged to give clean uninterrupted lines. Welds are generally preferable to bolted joints, and butt welds to lap welds. If lap joints have to be used, then appropriate welding or filling may be necessary to avoid the entrapment of moisture and dirt (Fig. 9.15). 

It is obvious that these physical defects are dangerous in their own right but it is also possible for them to lead to subsequent corrosion problems, e.g. pitting corrosion at superficial non-metallic inclusions and crevice corrosion at pores or cracks. Other weld irregularities which may give rise to crevices include the joint angle, the presence of backing strips and spatter (Fig. 9.29). Butt welds are to be preferred since these produce a crevice-free profile and, furthermore, allow ready removal of corrosive fluxes. 

The design of pipework has to be such as to allow access to welds and bends for weld and surface preparation. It is preferable to use seamless tubing conforming to BS 806 1986. Where this is impractical, tubing in accordance with BS 1387 1985 is acceptable provided that the butt-welded joint seam does not restrict the bore by more than 0-25 mm. 

Figure 13.39. Weld profiles (b to e) butt welds (a) Lap joint (b) Single V (c) Backing strip (d) Single U ...

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. 

Fig. GR-3.4.3(b) Geometry of Weld Joint Detail Square Butt Weld...

This specification does not include requirements for 100% radiographic inspection. If this higher joint factor is to be used, the material shall be purchased to the special requirements of Table IP-10.5 for longitudinal butt welds with 100% radiography in accordance with Table IP-2.2.9. 

Welded Joints The most widely used joint in piping systems is the butt-weld joint (Fig. 10-128). In all ductile pipe metals which... 

Cement-lined pipe in sizes smaller than 1 Vk in is not generally recommended. Cement-lined carbon steel pipe can be supplied with butt-weld or flanged ends. Butt-welded construction involves the use of special joint grouts at the weld joint and controlled welding procedures. See Table 10-40. 

Only welded and seamless construction should be adopted. Butt welds in both butt joints and T joints should be made with more than one run of electrode or blowpipe. The weld should be ground smooth and flush. Welding should be done from the side to be rubber lined wherever possible, as shown in fig 6.4 A. Where... 

A spherical carbon-steel storage tank has an inside diameter of 30 ft. All joints are butt-welded with backing strip. If the tank is to be used at a working pressure of 30 psig and a temperature of 80°F, estimate the necessary wall thickness. No corrosion allowance is necessary. 

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