Once the installation of pipelines moved offshore in the 1960s, there was a drive to increase production rates due to the high cost of lay-barges and weather window limitations. Initially this demand turned to the use of semi-automatic gas metal arc welding (GMAW), but the high incidence of lack-of-fusion defects forced equipment developers to try to mechanise the process. While many tried, it was not until 1969 that CRC-Evans developed and utilised the first commercially viable mechanised pipeline welding system.
The CRC mechanised system utilised a narrow gap bevel to reduce the weld volume. The root pass was deposited from inside the pipe using a multi-head combination internal welder/clamp, while the hot pass, fill pass, and cap pass were deposited externally using an orbital carriage or bug mounted on a guide band.
