Butt joints, double-welded

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

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-l00°C,(3) (E) is the longitudinal weld point factor and is taken for double welded butt joints as 0.85(3)... 

Allowable tensile stresses are one-fourth the ultimate tensile strength of the material of construction. Values at different temperatures are given in Table 18.4 for some steels of which shells and heads are made. Welded joint efficiencies vary from 100% for double-welded butt joints that are fully radiographed to 60% for... 

For double-welded butt joints Carbon steel -20 to 650 13,700... 

The ASME BPV Code Sec. VIII D.l Part UW describes the requirements for pressure vessels fabricated by welding. Limiting plate thicknesses are specified for each type of weld with the exception of double-welded butt joints. Requirements for radiographic examination of welds are also specified. Section UW-13 of the code specifies the types of welds that can be used to attach heads and tube sheets to shells. Section UW-16 gives rules for attachment of nozzles to vessels. 

Class I carrying lethal/toxic substances— full radiography is mandatory. Generally, double welded butt joints are used. Structural steels such as/N226/2062 are not allowed. Only IS 2002 GrA (boiler quality steel) is allowed for construction. 

For double-welded butl-jtrinl. eon.Htruclion, the above definition of p may be substituted into Eq. 3.16. When one U.SCS an allowable design stress of 21,000 psi for SA-7 plate and a joint efficiency of 0.85 for doubied-welded butt-joint construction, the following substitution results ... 

Example 8.1. A pressure vessel with an inside diameter of 50.0 in. is subjec-ted to an internal pressure of 100 psi. Using an allowable stress of 17,500 psi, find the required Sickness according to Section Vm, Division 1. Assume that all circumferential and longitudinal seams are double-welded butt joints and are spot radiographed. 

Figure 13.34. Weld profiles (b to e) Butt welds, (a) Lap joint, (b) Single V. (c) Backing strip, (d) Single U. (e) Double U. ...

Material thicker than 3 mm will benefit in joint strength if multiple weld runs are made on each side, ie 6 mm—3 runs, on each side 12 mm—6 runs on each side. The same applies to double V butts, although to obtain optimum strength from single V butts three weld runs should be made on 3 mm thick material and five on 10 mm thick. In all cases the prepared welding groove angle should be about 70 with a root gap of about 0.6 mm. Fig. 3 illustrates the various weld types and runs. 

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