mig controlwasteTOMindexlogo 



Narrow Gap Welding

Increasing welding productivity is important in today's competitive world.  In addition, the significant welder shortage makes automatic welding attractive. 

The desire to weld in joints with minimum gaps has existed since I entered the industry in the mid 1960's.  However it is even more important today to increase weld completion time and reduce the amount of welding consumables needed. 

My early career was in one of the most prestigious Research and Development Laboratories in the USA.  We had over 100 professionals in an era where TIG welding was gaining popularity and MIG welding was just being introduced.  Stick welding represented over 75% of the weld metal being deposited.  I initially worked in the Submerged Arc field optimizing processes and developing new ones like a 3 wire all AC power system that controlled arc deflection in a way that allowed welding speeds to be increased over 50% for the manufacture of gas and oil transmission pipe.  Speeds over 125 ipm were achieved in production where previously 60 to 75 ipm was considered the limit. These systems were used in four pipemills in the USA (those willing to invest in the material handling needed.)  It was also installed in pipemills in Japan, Italy, the UK, Middle East and Mexico.

My next project, adapt the 3 wire process for welding heavy sections in a relatively narrow gap.

The photo top of page, shows two of the few weld samples kept over the years because of their uniqueness.  The Submerged Arc weld cross section, upper photo right side, was made with a 3/4 inch root gap, very low angle sidewall  (<12 degrees) and utilized a two pass per layer split bead technique.  This was the typical joint used for making 12 inch thick reactor vessels for nuclear power plants.  This  joint and split bead technique were used by US manufacturers of main reactor vessels, namely, Combustion Engineering, B&W and CB&I.  They used AC-AC power connected employing a 90 degree phase shift called the Scott connection.  This provided a controlled arc deflection and assisted achieving consistent side wall edge wetting.  The use of all AC power avoided arc blow.

As we had done with the manufacture of gas and oil transmission pipe my associate and I developed a three electrode, all AC power system to increase welding speeds and metal deposition rate over the two wire (electrode) AC-AC systems these vessel manufacturers were using.  Note, during this time our company (now owned by ESAB) sold specially designed fused fluxes to both the line pipe and nuclear vessel industries and had essentially 100% of the flux and wire business.  We provided the welding technical support to both of these high technology industries.  The concept of using all AC power was developed over many years in the 'late '50s and early 60's and several technical papers were published on the subject in the AWS Welding Journal.  Refer to the this web page on the History of Submerged Arc welding and the references sited

Our three wire, all AC power system used the same power configuration we developed and that was being employed successfully by many pipemills in the US, Canada, Mexico, the UK, Japan and several other countries.  Weld metal deposition rate was up to 75 lbs/hr with total welding current exceeding 3000 amps.  The power was all AC with arc deflection controlled with the proper phasing of one arc to the other.  The photo upper right is a commercial installation of the three wire all AC power system in production. 

Some believe that a DC lead will provide significantly more penetration than AC power.  However in a deep groove arc blow can effect penetration and side wall fusion when DC is used limiting maximum current levels.  A penetration equation developed by Clarence Jackson after making hundreds of welds defined that weld penetration  was proportional to Amps4.  AC power does have less penetration than DCRP when making simple bead-on-plate deposits.  However using Jackson's equation we can show a 5% increase in AC current compensates for the decrease and provides an arc much less susceptibility to arc blow.  A report available for purchase on Multiwire Submerged Arc welding systems covers from 2 to 4 wire systems and includes this current and penetration analysis.


Sub Arc Narrow Gap Summary:

We worked with one of the major nuclear vessel producers in a field test of this all AC power, three electrode system.  Longitudinal test welds were successful.  What were the problems encountered?  Why was it not successful at the time for the key circumferential weld joints where the increased speed was most important?  A confidential report can be prepared to discuss the system, and these issues.  With today's technology these shortcomings can be overcome. 

Email for a quote.




A report was recently prepared for a client with these "relatively narrow gap procedures"  for welding 11 inch thick HY-80.  The resulting weld joint required 75% less welding materials than  conventional procedures with much less distortion.  This approach also produced crack free deposits without stress relive heat treatment.  A past experience welding 12 inch thick HY-100 was also used to provide these recommended procedures, welding flux/wire recommendations, expected weld properties and special welding nozzle design.



The weld section, left in the picture on the top of this page, is even more unique.  This cross section is from a MIG weld made in 2 inch thick plate with a 1/2 inch gap and  straight sidewalls.  These are some details: 

* The weld beads were placed one above the other. 

* Weld deposition rate was 25 lbs/hr! 

* How was that deposition rate achieved with solid wire? 

* How was uniform side wall wetting achieved? 

All those answers and more are available in a Confidential Report, available for a fee.

We put a similar weld sample from our archives on our web site several years ago.  It was a 2 inch Aluminum Electroslag weld cross section (photo right.) We provided a Confidential Report to a company and helped them develop the process into a viable manufacturing tool.  It was recently used very successfully for joining aluminum bussbars over 10 inches thick and over 3 feet high!  The welding time was less than 30 minutes!  Click for additional  details.

We are offering a similar proposal for Narrow Gap Welding.  The  proposal is useful for the Submerged Arc Three Wire all AC power or the very creative MIG Narrow Gap System which can have broad appeal.  The Report(s) consist of detailed information about the original development process efforts. 

With today's economics, as with Aluminum Electroslag, the right time may be now!

Interested in the Innovative Narrow Gap Welding Techniques Report(s) Email and we will provide more details and the cost.