Automatic Welding of 42-in. Drive Pipe Proves Successful Offshore
Authors: Meeks W.R. , Mahmoud S.E. , Newman H.E. 
Published: October 2008

An automatic flux-cored arc welding (FCAW) system was field tested on an offshore well in Turkey to confirm the system's reliability and productivity to weld 42", 1–1/2" wall thickness, drive pipe. One manual, shielded metal arc welding (SMAW), weld was made to provide a basis for an economic evaluation. FCAW proved to be reliable and a viable alternative to manual welding and mechanical connectors. The system's productivity, measured in weld metal deposited per hour, exceeded laboratory and shop results. The purpose of this paper is to make operators aware of the capability of an automatic welding system specifically designed for welding large diameter, thick-walled pipe and how established deposition rates can be used to determine weld-out times on upcoming welding operations.

Introduction

Operators are commonly faced with determining the most economical means of joining drive pipe or offshore piles. Automatic welding systems offer certain technica1 and economica1 advantages over the manual and semiautomatic welding systems presently used. The most significant feature of automatic welding is the high deposition rates which result in less weld-out time. This, in turn, improves driving efficiency and reduces time dependent costs and the chance of down time due to periods of bad weather.

In 1983 Exxon Production Research Company conducted a study to evaluate automatic welding of offshore pilings. The study included a literature search for candidate welding systems and found that the FCAW system was the most likely to succeed. Laboratory and mock field trials using this system were conducted to simulate welding of pile sections with typical field fit-ups. The physical and metallurgical properties of the welds were measured and found satisfactory. The experiments resulted in developing and qualifying a welding procedure for welding piling add-ons. While mock field trials successfully evaluated the capability of FCAW to make welds on pipes and the metallurgy of the welds, a field trial was necessary to evaluate the equipment's reliability and confirm its productivity.

In 1985, an opportunity to field test the automatic welding system on 42", 1–1/2" wall thickness, drive pipe arose on a jackup location in Turkey. Due to a short lead time, mechanical connectors could not be obtained for the job, so welding the add-ons was the only alternative. Therefore, an economic study was made to evaluate the manual welding system against the automatic welding system. The automatic welding system was favored based upon potential cost savings. The automatic welding system was tested in the field and proved economical over both mechanical connectors and manual welding.

This paper describes the capability of an automatic welding system for welding drive pipe and demonstrates how an operator can determine weld-out times given joint geometry and using deposition rates established in the field. Considerable savings may be realized after carefully evaluating various welding processes and mechanical connectors for joining drive pipes and other offshore applications.