Helical pipe (commonly known as spiral pipe) is formed by processing steel coil through state of the art milling and welding equipment. The PSLNA facility utilizes advanced technology that produces spiral pipe in a high speed Two Step process.

   In the First Step, pipe forming takes place as the steel coil is straightened and then turned to form the desired OD through the formation mill. During this process the free edge of the de-coiled steel is prepared for welding prior to being formed into a spiral shape. The free edge forms a spiral joint where a continuous tack (root) weld is applied to complete the formation process. The pipe forming and tack welding is done with a welding speed of up to 33 feet per minute. 

   In the Second Step, the previously formed pipe requires additional welding along the spiral joint. The welding takes place at a Final Welding Machine (FWM) that utilizes digital welding technology and optical seam tracking. The FWM utilizes a Submerged Arc Welding (SAW) process that is applied along the spiral joint at the inside and outside diameter (ID and OD) of the pipe. The PSLNA facility utilizes 3 - FWM’s, each capable of welding at speeds of up to 8 feet per minute.

   The SAW process employed at the FWM’s utilizes digital welding technology. The digital welding is implemented through combined use of PLC and HMI systems. This integrated system was developed in collaboration with two leading German companies, PWS and iSAM.

  The welding heads remain in a static position requiring the pipe to be rotated and moved longitudinally. The crucial pipe movement is monitored by a laser sensor allowing the weld path to be tracked in-line with the weld heads. Additionally, the speed of the pipe movement, depositing of flux and weld electrode, monitoring of amperage, voltage, and weld profile, is adjusted constantly to meet pre-set targets. The readjustment, through digital controls, occurs in milliseconds.

   While several US manufacturers currently produce "Helical Seam" pipe, almost the entire existing capacity is dedicated to water pipeline end users. Most existing US Mills are capable of converting steel of up to 14.3-mm thickness (0.562 inch) while most high-pressure gas lines require higher wall thickness and the more exacting standards of the American Petroleum Institute (API).