Beyond the Booth: A Practical Guide to Field Thermal Spraying

Thermal spraying in the field (outside the comfort of the job shop) is bread-and-butter work for many in our industry, including the coating of bridges and pipelines; the interiors of power plant boilers and hydroelectric waterways; and thousands of square feet of pipelines, refinery structures, and offshore rigs. For others ­— particularly those of us accustomed to spray booths and robots, jigs and fixtures, metallurgical lab coupons, and coordinate measure machine (CMM) inspections — the idea of doing what we do in a remote location is both intimidating and exhilarating. As part of ITSA’s mission to grow and develop the thermal spray industry by sharing knowledge among its users, applicators, and vendors, this article intends to make the prospect of field work a little less scary and a little more accessible.

From the Industry’s Roots to Today’s Reality

Field-applied coatings have been an important part of our industry since its inception. Before spray booths and dust collectors were commonplace, Metco salesmen were out in machine shops, paper mills, and utility plants promoting the use of thermal spray technology to repair pump shafts and bearing fits, engine blocks and lathe beds. Any place metal had been lost due to wear or damage, thermal spraying was offered as a way to restore surfaces to good-as-new or better. The U.S. military embraced the technology and developed procedures and specifications to apply coatings for all kinds of repairs and enhancements, and wire spray guns and combustion powder setups found their way into shipyards, automobile repair shops, and millwright toolboxes all over the world.

The proliferation of spraying led hand in hand to the parallel proliferation of bad spraying, work done poorly without proper care and attention. As a result, many in our industry suffered under the reputation that thermal spray coatings would fail or “fall off.” We entered a long period of rebuilding characterized by the development of newer, more robust spraying technologies, and tighter and better process controls and quality management practices, leading, eventually, to where many of us are today, with neat rows of spray cells and dust collectors, metallurgical labs, and clean rooms comfortably contained within our own buildings.

But it never changed the fact that our process is so very well suited to fixing things in the field, quickly and effectively, if done carefully and with good planning. Field work is a competency like any other, and field work performed well can do a great deal to get mission-critical machinery back online quickly and safely, provided the work is well organized, the limitations of working in the field are well understood, and both the customer and contractor reach an agreement about what constitutes a successful repair. This last element is especially important, and we will discuss it in detail later.

Managing Risks Outside the Shop

First, why risk it? Thermal spray repairs in the field serve a unique purpose in modern manufacturing. After a machine failure, usually of a rotating element, the owner of the equipment faces steep losses in downtime and repair. If the machine’s function is critical to a community, such as a power plant or water treatment facility, or if the value of lost productivity is significant, such as in a paper mill, automotive line, or food processing plant, every minute lost is a significant and expensive burden on the operator. If the equipment is too large to make spares reasonably available, conventional repairs might require disassembly, shipping, inspection, overhaul, return shipment, and reassembly. Each phase adds time and expense. Imagine if the repair isn’t right the first time, and the job must be reworked. Each of those costs is doubled. If the repair could be done onsite, much of the delay and cost would be removed: less disassembly, less inconvenience, lower risk of shipping delays and issues, and the problems that do arise could be corrected right away.

In the examples given earlier, power generation, water treatment, heavy or complex manufacturing, oil drilling and refining, the cost of downtime is significant, and the advantages of being able to restore operations quickly become apparent.

Entering this line of work has its challenges. Teams deployed to work in the field should have deep experience both in applying coatings and in understanding how they will perform. They must often work completely autonomously; if issues arise on the job, they must be able to manage them independently. These issues can be equipment related, such as a non-functioning powder feeder or a misbehaving blaster. They can be operational, such as inadequate compressed air supply or incorrect facility voltage. They can be engineering-oriented, such as inadequate access to the working area or an unreasonable expectation for dimensional tolerance or surface finish. Or, they can be political, such as battling with customer representatives about building access or job acceptance criteria. As with all things in manufacturing, good and talented people are at the core of any successful job.

Many of these risks can be relieved with thorough job planning. Broadly, job planning for a field project involves a set of categories: job scope, requirements, subcontracting, permitting, transportation, and completion. Comprehensive groundwork for these domains can alleviate (if not eliminate) the kinds of pitfalls described in the previous paragraph.

Setting the Foundation for Execution

Job scope is often the simplest part of the plan. It means identifying and agreeing with the customer on the materials to be used, which process(es) will be employed, any masking requirements, and the desired target dimensions, including surface finish. This bare-bones information is an essential part of any thermal spray estimate, but for field work, coming to an early agreement on these items will determine much of how the rest of the project planning and execution will go.

Once the scope is well defined and the customer and supplier are in agreement, the project requirements can be established: What is the ideal timeline required for the repair? Are there any applicable standards or specifications? What utilities and resources will the work require? Where will the work be done, and how much space is available for ancillary equipment and storage? What infrastructure is available for support (forklifts, cranes, scaffolding, shelter, exhaust, break room, restrooms etc.)? How accessible is the work zone (hours, escort requirements, availability of loading doors)? Much of this is cooperative in nature. Some things are fixed requirements of the work to be done and the equipment needed; others are finite resources of the customer’s facility. Planning ensures that both parties have what they need to get the job done effectively and with minimal risk.

Coordinating Execution in the Field

Subcontracting is often necessary for field work if parts of the repair fall outside the core competencies of the customer or the spray contractor. For example, millwrights may be needed to disassemble and clean the work zone. Pre-machining and finish machining may be required. The work may necessitate the application of paints and sealers, and third-party inspection may be a contract requirement. Of course, it is preferable for the customer to arrange and negotiate as much of this as possible. They are more likely to have these kinds of resources already on hand or know what is available in their area. Still, some sites prefer a turnkey repair, where the spraying contractor is expected to handle all coordination.

State and local regulations may require special permitting for thermal spraying onsite. Environmentally sensitive areas may have air-quality limits or water-usage restrictions. Most large facilities have safety-training requirements for contractors working in their buildings. Issues such as fire watch, parking and loading-zone restrictions, and the use of cranes and forklifts by noncompany employees all come to bear. It is essential to know which of these requirements may apply in order to avoid an unplanned shutdown of the job when a local inspector or irritated safety officer happens to stop by to observe.

All field jobs require “shipping” of equipment and personnel from the home office to the job site. For mission-critical jobs, it is highly likely that the customer’s planned outage window is tight and fixed, so contingency plans to ensure the field team and its tools arrive on time will be essential. In many cases, it is advisable to have both a primary and fallback plan for delivery so that an unexpected delay does not derail the project completely.

As mentioned earlier, agreement between the customer and the contractor on what constitutes job completion is fundamental to the job plan before any physical work is done. Continuity between the quote request, quotation, and job router is important, but it is equally important that the customer and spray contractor agree about how job success will be measured and by whom. Coatings applied in the field will often need to be less precise than coatings applied in a shop, where high-accuracy machine tools can be used to prepare and finish the work. Very often, the goal in a field-applied coating is functional rather than visual appearance. The customer and contractor must agree on dimensions and tolerances. Whenever possible, verbiage should be included to ensure that the contractor’s calibrated and traceable gauges are used for inspection rather than the customer’s, which may be of unknown status or reliability. If job acceptance cannot be agreed upon, there is a high risk of excessive unplanned rework costs, delays, and resentment from both the customer, who wanted the job completed quickly, and the field team, which just wants to wrap up and go home.

Often, in a field job, there will be customer personnel onsite who may have opinions on how the job should be done or how it should look when finished, but if those personnel are not part of the contract acceptance process, their opinion fundamentally means little. Ultimately, the objective is to ensure that the contract requirements are met and that the stakeholders agree on the method used to determine this. For this reason, it can be useful to control who has access to the work zone. Plant personnel are often curious about our work because it is unusual and visually surprising. Extra people can be stressful for the coating team, especially if things are not going according to plan. Having at least one senior team member onsite who is experienced and comfortable advocating on behalf of the team is incredibly helpful when disputes with the customer arise.

Finally, project timeline milestones can be immensely valuable for ensuring that everyone connected to the project is aware of the progress. Establishing a plan for team and equipment departure from the shop, arrival onsite, unloading and staging, setup, blasting, spraying, cleanup, packing, departure, and return will keep everyone coordinated if issues arise and will give both the home office and the customer assurance that work is progressing as planned or not. There is tremendous value in keeping everyone in the loop and a great deal to lose if stakeholders are left in the dark. Likewise, once a repair is complete and the team has departed, staying in touch with the customer in the weeks and months that follow will ensure that the repair is performing as needed and solidify confidence that the spray shop stands behind its work.

Conclusion

Performing thermal spray work in remote locations presents many challenges, but it remains both an integral part of our industry’s technical capability and an essential tool for getting mission-critical equipment back online quickly. Planning, redundancy, and skill are essential components for reliably delivering high-quality service in the field. Like any other capability, however, these essentials can be developed and strengthened. Hopefully, some of the common pitfalls outlined in this article can help remove the hesitation and fear that can come with taking thermal spray out of the shop and putting it on the road. Safe travels!

DANIEL C. HAYDEN (daniel.hayden@haydencorp.com) is president of Hayden Corp., West Springfield, Mass., chair of the AWS C2 Committee on Thermal Spray, and technical editor of SPRAYTIME.