Guaranteed tube life extension by restoring worn tubes and overlaying with ERNiCrMo-3

Boiler tubes can become weakened by fireside erosion and corrosion.  This results in costly repairs and downtime.  To solve this problem, GP Industrial Contractors Inc. applies a weld overlay.  This restores full strength to worn tubes.  With proper selection of alloyed filler materials this process provides improved resistance to erosion and corrosion, without adversely affecting the boiler's heat transfer characteristics.

Through our partner company, DIVERSE FIELD SERVICES, a division of Gulf Copper & Manufacturing, GP Industrial Contractors successfully provides a cost-effective alternative to traditional tube repair and replacement methods.  The result is reduced costs and increased tube life.  Traditional repair methods consisting of "pad welding" or  "tube replacement" prove to be short lived and costly when compared to boiler tube overlays, which repair and combat future tube wastage.

Boiler Tube Life Extension

Electric power and waste-to-energy facilities are now focusing on the life extension of power generating components.  Many older generating stations are now operating well beyond their designed life.  This can be credited to the proper planning and implementation of plant improvement and renewal programs now in place throughout the industry.

One area of particular concern is boiler tube failures, which typically cause emergency shutdowns, extended outages, and lost generating time.  Boiler tube failures are usually caused by installation errors or minimum wall conditions due to erosion/corrosion.  Failures due to water side degradation can usually be corrected through water chemistry.  However, fireside degradation is more common and troublesome.  Until recent years the solution to fireside attack has been tube replacements, pad welding, and thermal spraying.

Disadvantages of Tube Replacements

Replacing boiler tubes with identical tubes is expensive, and if a large area is involved, and extended outage will be required.  Even after installing new tubes, the service life may not be acceptable if no additional improvements are made in the operating conditions.  Replacement with upgraded tubes significantly increases the cost of such a replacement, but will yield increased tube life.

Disadvantages of Thermal Spiral Methods

Thermal spray process variations have achieved mixed results.  Some utilities using thermal spray processes report that erosion/corrosion has been reduced while others maintain that the coating spalled off during boiler operation.  Regardless of the short-term results, most coatings must be reapplied on a regular basis.  Thermal spray processes, like paint, only result in a mechanical bond.  These methods have been associated with spalling and greatly magnified repair problems.  Thermal spray processes do not enhance tube strength, and cannot correct a minimumwall condition.  In addition, deposit thickness limitations in conjunction with thermal spray processes preclude their use under severe wear conditions.

Advantages of Welded Methods

Unlike thermal spraying, welding achieves complete fusion.  Welding protects the fireside surface, while adding strength to the pressure boundary.  Welding achieves complete fusion by metallurgically bonding to the tube surface.  Another advantage of a boiler tube weld overlay, is the option of selecting a weld metal which possesses the mechanical and metallurgical properties to withstand the specific environment encountered in a particular boiler.  Single layer weld deposit thickness ranges from 0.060" to 0.100".  All positions, tube diameters, and configurations can be welded, with or without membranes.  Weld overlay costs are typically between thermal spray costs and tube replacement costs, but more importantly, overlays can significantly increase boiler tube life.

Cracking and Other Concerns

In the early years of tube overlays 309 and 430 stainless steels were used.  Problems with these and a few other alloys justifiably caused great concern for plant maintenance/management personnel.  During this period there was extensive experimentation with filler materials for protecting boiler tubes.  Results from these studies now provide the industry with crucial performance and cost data.  With thousands of properly overlaid boiler tubes in extended service, the industry has extensive empirical evidence of the effectiveness and safety of this repair approach.  Even diehard opponents are now becoming convinced that a corrosion resistant weld overlay is the best value over the long run.

Shop of Field

Tubes can be overlaid in place onsite, or pre-overlaid as individual tubes or as panel assemblies.
GP Industrial Contractors Inc. utilizes a CNC welding system for shop overlaid panels and pre-overlaid tubes.

Overlay Costs

There are a handful of other companies that also perform weld overlays.  Their "all-inclusive" prices usually range from $200 - $500 per square foot.  Our typical price per square foot is around $160 or less.  Why are our prices generally lower than our completion?  The reasons are simple.  First, we are a non-union company, though we often work in a union environment.  In fact, many of us were union boilermakers.  We understand the pros and cons.  Second, we are a diversified company with broad capabilities and expertise.  We've been around for nearly 50 years.  Third, our welders are based in the most affordable part of the country.  Last and most importantly, the work hard.  No magic, no hype, simply a common sense, const-effective way to get your boiler tubes overlaid.

Summary

We work with utilities and waste-to-energy facilities in addressing the issues of fireside erosion/corrosion.  By using state-of-the-art Gas Metal Arc Welding (GMAW) equipment, boiler tube overlays and weld buildups can be applied to large areas, with execellent results.

Our welding program is maintained in accordance with ASME Section IX, AWS, API, and ABS, in addition to posessing the "S", "U", "PP", and "R" stamps.  We are nearing ISO 9002 Certification.  Key employees have been involved with boiler tube overlays since 1984.

As stated, a large number of overlaid boiler waterwalls are currently in service on power and refust boilers with outstanding results.  Before making an expenditure for thermal spray or tube replacement methods, compare our weld overlay price with your other options.  When planning your next boiler outage, consider GP Industrial Contractors Inc. and the benefits of our high quality, competitively priced boiler tube overlays.