External Welders

CRC–Evans has developed a wide range of external welding machines, referred to as "bugs", for performing root, hot, fill,
and cap passes.

Today our customers can choose according to particular application demands among the complete line of external welding machines: P200, P300, P600, M220, or M300.



dual–torch welding (P600 bugs)


The bugs travel on a flexible, heat–treated steel pipe band 0.092" thick and 4.882" wide attached to the pipe for that purpose.

The band can be obtained as encircling pipe bands, internal pipe bands,
or in straight sections for use on flat or curved plate.

The band is mounted 4"–6.25" (dependent of bug model) from the land of the weld joint with the knurled edge of the band facing away from the weld joint. For high speed alignment and spacing of the Pipe Band on the Pipe, an Alignment Band
is available.

Bugs are available in right- and left-hand models to permit simultaneous welding by two units on a single pipe band. Each bug makes half a weld pass (180o); one clockwise, the other counter-clockwise.

Bugs for performing fill and cap passes start simultaneously but from different positions. Start positions are triggered for each pass in order to avoid overlapping of start and end points at twelve and six position, respectively.


two P600 bugs
welding simultaneously 


Each external welding bug consists of:

  • Carriage Assembly;
  • Control Box;
  • Power Supply Junction Box;
  • Welding Carriage (welding machine).

Three hardened–steel, idler rollers and knurled drive wheel are located on the underside jf the Carriage Assembly to provide the correct positioning and travel drive capability of the bug on the pipe band. Both the movable idler roller and the knurled drive wheel have eccentric adjustment so that they can be clamped in place on
a pre–positioned pipe band.


fill and cap passes
using external welding bug  М220