Common Defects of Butt Welded Pipe Fittings

Butt welded pipe fittings are made by welding steel plates together after mould pressing. These fittings mainly include butt weld elbows, butt weld tees, butt weld reducers, etc. The fittings are low in price, thin in thickness and simple in the manufacturing process so that they can be produced by general pipe fittings manufacturers. And the butt welded fittings can be made with a large calibre. Demerits are also obvious. Because of the simple welding technology and molding process, the fittings is easy to have blowholes, weak welds, cracks, etc. The article will describe what is the common defects of welded pipe fittings and how to avoid them.

Butt welded pipe fittings are easy to produce blowholes, cracks, untight welds, etc. Blowholes which is originally the burning gas exist between weld gaps, and they are all inside, so it is difficult to see them. Only through inspection can they be found. The way to avoid the blowholes is to use fuels with less impurities and to clean the surface of welded steel plates to remove oil, gas and moisture.

The causes of cracks are that there is a low-melting-point iron sulfide in the segregation band and hydrogen exists in steel. The way to avoid cracks is to clean the weld surface and clean and dry the flux.

Untight welds refer to that there may be a gap between two steel plates of welded pipe fittings, which has a great effect on the fittings. The most direct detection method is to see if there is any water leakage through pressure test. The measure to prevent the untight welds is to adopt a good mould for mould pressing, make specifications and shapes meet the standard, and polish the weld to make it flat and smooth without rust.