Semi–Automatic Systems

When automatic welding is not advisable due to different reasons, the most prospective welding technology employed at the present time in the construction of cross country pipelines is one which combines manual stick welding (either basic or cellulose) for the root pass with semi–automatic welding of fill and cap passes using flux–cored wire such as Innershield.

The equipment needed for this technology comprises:

• a universal welding power supply with CC (for stick electrode welding)
  and CV (for wire welding) volt ampere characteristics,
• a wire feeder with welding torch and adapter.

The advantage of self–shielded flux–cored wire (FCAW–SS) Innershield lies in its high deposition rate and the fact that it requires no gas.

Over the last few years a new technology of semiautomatic welding has emerged in which the root pass
is welded by wire using the STT process, and the fill and cap passes are welded using Innershield wire.

There are numerous advantages to using this method: guaranteed penetration, the lowest hydrogen content
in the weld metal, a magnificent back bead, high production characteristics, lack of smoke and spatter, less skill required of the welder. These advantages clearly outweigh the small inconvenience of needing to use gas
for the root pass.

Success has been achieved in using semiautomatic welding for the entire girth weld with STT
from the root pass to the cap pass, all on a pipe with wall thickness up to 10 mm. technology,

When wall thickness exceeds 12.7 mm, a combination of technologies is recommended, in which the root is welded with STT, while the fill and cap passes are welded with Outershield wire in a gas environment. The use of Outershield flux–cored wire, with its high arc deposition rates, increases welding productivity even more without any additional overheads.

A set of equipment for semi–automatic welding with STT includes:

• STT welding power supply;
• wire feeder with welding torch and adapter.

A set of equipment for welding the fill and cap passes
(in situations where they are not welded with STT) includes:

• welding power supply (CV);
• wire feeder with welding torch and adapter.