Welded-Joint Design

Process vessels are built up from preformed parts cylinders, heads, and fittings, joined by fusion welding. Riveted construction was used extensively in the past (prior to the 1940s) but is now rarely seen. 

Cylindrical sections are usually made up from plate sections rolled to the required curvature. The sections (strakes) are made as large as is practicable to reduce the number of welds required. The longitudinal welded seams are offset to avoid a conjunction of welds at the comers of the plates. 

The design of a welded joint should satisfy the following basic requirements  

Give good penetration of the weld metal from both sides of the joint, if practicable. 

Incorporate sufficient flexibility to avoid cracking due to differential thermal expansion. 

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J. G. Hicks, Welded Joint Design, Granada Publishing, 1982. 

Unfired steam boilers with design pressures exceeding 345 kPa (50 Ibf/in ) have restrictive rules on welded-joint design, and all butt joints require full radiography. 

Pressure vessels subject to direct firing have special requirements relative to welded-joint design and postweld heat treatment. 

This subsection includes rules governing welded-joint designs and the degree of radiography, with efficiencies for welded joints specified as functions of the quality of joint. These efficiencies are used in the formulas in Subsec. A for determining vessel thicknesses. 

Fig. 13.15 Typical friction stir weld joint designs...

An ultrasonic welding joint design where the welding action is parallel to each part surface. 

Preliminary drawings should show shell thickness, tie rods, reinforcements at nozzles, corrosion allowance, details of welded joints, design and test pressure, radiography/electrode specifications... 

PFR steam generator (two types SG tube-to-tube plate weld joint designs have been studied for PFR SG traditional, e.g.,for fossil boiler a and a new b (was used in PFR SG). 

Titanium alloys may be subject to localized attack in tight crevices exposed to hot (>70 °C, or 160 °F) chloride, bromide, iodide, fiuoride, or sulfate-containing solutions. Crevices can stem finm adhering process stream deposits or scales, metal-to-metal joints (for example, poor weld joint design or tube-to-tube sheet joints), and gasket-to-metal fiange and other seal joints. 

Hicks, John, Welded Joint Design, 3rd edition. Industrial Press, Inc., New York, NY, 1999. Bednar, Pressure Deisgn Handbook, 2nd Edition. Van Nostrand Reinhold Company, NY, NY, 1986. 

Hicks, John, Weld Joint Design, 3rd edition. Industrial Press, Inc., New York, 1999. 

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