The four principal positions of pipe welding are classified according to the position of the pipe, not of the weld: 1G - pipe in the horizontal position that is rolled; 2G - pipe in the fixed vertical position; 5G - pipe in the fixed horizontal position; and 6G - pipe in a fixed 45-degree position. In addition to these four positions are special case positions or welds: R - pipe in a restricted position; F - a fillet weld; and G - a groove weld.
Gas tungsten arc welding, also popularly referred to as TIG, is slow and hot. Gas metal arc welding, also known as MIG, is faster than GTAW, but also requires a significant skill level. Shielded metal arc welding, commonly named "stick," can be expensive and time consuming due to frequent starts and stops. Flux core arc welding is similar to GMAW (or MIG) welding, using much of the same equipment and techniques but using a different type of electrode, which makes this type of welding wind-resistant and useful in the outdoors.
Of course, the situation of the pipe is going to play a key part in how the weld is planned and approached. Any combination of the above positions and welding methods can occur either in a confined space or outdoors. Confined space pipe welds will require extra care in terms of ensuring proper protection again gases. Confined space pipe welds may also require special positions of the welder, torch and equipment, all of which must be arranged with certain safety precautions in mind. Outdoors welding requires the technician to pay attention to safety precautions, but also to weather conditions, particularly rain and wind.