Circumferential weld seam

Stiffeners should never be located over circumferential weld seams. If properly spaced they may also double as insulation support rings. Vacuum stiffeners, if combined with other stiffening rings, such as cone reinforctunent rings or saddle stiffeners on horizontal vessels, must be designed for the combined condition, not each independently. If at all... 

After the circumferential weld seam was completed, the tie strap on the inside of the RPV was removed, the surface back-grooved to remove any potential slag inclusions, an MT inspection performed, and the weld was completed manually to fill in the back-groove on the inside surface of the RPV. A UT examination of the weld was performed, followed by PWHT, radiographic inspection and back-cladding. 

Stiffeners should never be located over circumferential weld seams. If properly spaced they may also double as... 

Figure 6.9 Irregular deposit and corrosion-product mounds containing concentrations of sulfate-reducing bacteria on the internal surface of a 316 stainless steel transfer line carrying a starch-clay mixture used to coat paper material. Attack only occurred along incompletely closed weld seams, with many perforations. Note the heat tint, partially obscured by the deposit mounds, along the circumferential weld.

Except for large L/R ratios or A > R/2, the governing stress is circumferential bending at the horn of the saddle. Weld seams should be avoided at the horn of the saddle. 

T vo basic methods of RPV fabrication have been used. The first method used rolled and welded plates to form separate shell courses. Thus, an RPV fabricated in this manner has both longitudinal (axial) and circumferential (girth) weld seams. In some of the older (pre-1972) PWR RPVs, these longitudinal seams are of particular concern for RPV integrity due to high levels of Cu in the welds. All BWR and most of the PWR RPVs used this rolled and welded plate construction. 

On a practical note, circumferential welds should always be replicated at the four quadrant positions as damage distribution can vary significantly due to the bending stresses often operating in pipework. Also, in view of the higher consequences of failure, 100% NDF coverage of seam welds is normally advised. 

DOTS or 8 AL. These are welded steel cylinders for acetylene service only and are made to the single authorized service pressure of 250 psig (1724 kPa). Such specification cylinders may have a longitudinal welded seam and circumferential seams. These cylinders must also contain a permanent monolithic porous inner filling material which absorbs a specified amount of a solvent, usually acetone, which absorbs the acetylene. 

In the multiwall technique (developed by the Struthers Wells Co.), single thick-walled layers are shrunk onto each other and this is followed by longitudinal seam welding. The sections produced in this way can be connected by circumferential welding or by welding the forged ends. 

Circumferential and longitudinal seam welds-allowable weld height and distortion tolerance. (Weld height is defined as the plus variation from the plane of the welded sheets of steel.)... 

Circumferential Seams To check this particular concern, take a 16" (406 mm) long straight edge, plumb it on the weld so that 8"... 

Longitudinal joints in sheet steel ductwork shall be lock-seamed, riveted, or welded. Circumferential joints shall be fastened and lapped in the direction of the airflow. At least every fourth joint shall be flanged or bolted. 

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. 

Example 8.2. A seamless cylindrical shell with an outside diameter of 30.0 in. is butt-welded to seamless ellipsoidal heads. The circumferential seams are not x-rayed. Find the required shell thickness if the allowable stress is 15,(XM) psi and the internal design pressure is 250 psi. Use Section Xni, Division 1 rules. 

An internal inspection of the vessel revealed that portions of the circumferential and longitudinal seam welds, in addition to the leaking nozzle weld, displayed intergranular corrosion. At the point of leakage, there was a small intergranular crack. 

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