JS Pipe fittings

Q
Advantages and Disadvantages of Socket Weld fittings
A
Advantages and Disadvantages of Socket Weld fittings
ADVANTAGES
1. The pipe need not be beveled for weld preparation.

2. Temporary tack welding is no needed for alignment, because in principle the fitting ensures proper alignment.

3. The weld metal can not penetrate into the bore of the pipe.

4. They can be used in place of threaded fittings, so the risk of leakage is much smaller.

5. Radiography is not practical on the fillet weld; therefore correct fitting and welding is crucial. The fillet weld may be inspected by surface examination, magnetic particle (MP), or liquid penetrant (PT) examination methods.

6. Construction costs are lower than with butt-welded joints due to the lack of exacting fit-up requirements and elimination of special machining for butt weld end preparation.

DISADVANTAGES
1. The welder should ensure for a expansion gap of 1/16 inch (1.6 mm) between de pipe and the shoulder of the socket.
ASME B31.1 para. 127.3 Preparation for Welding (E) Socket Weld Assembly says:
In assembly of the joint before welding, the pipe or tube shall be inserted into the socket to the maximum depth and then withdrawn approximately 1/16" (1.6 mm) away from contact between the end of the pipe and the shoulder of the socket.

2. The expansion gap and internal crevices left in socket welded systems promotes corrosion and make them less suitable for corrosive or radioactive applications where solids buildup at the joints may cause operating or maintenance problems. Generally require butt welds in all pipe sizes with complete weld penetration to the inside of the piping.

3. Socket welding are unacceptable for UltraHigh Hydrostatic Pressure (UHP) in Food Industry application since they do not permit full penetration and leave overlaps and crevices that are very difficult to clean, creating virtual leaks.
The purpose for the bottoming clearance in a Socket Weld is usually to reduce the residual stress at the root of the weld that could occur during solidification of the weld metal, and to allow for differential expansion of the mating elements.

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