Most industries have suffered setbacks related to the global pandemic, and while the shipbuilding industry saw a nearly 8 percent drop from 2019 to 2020, the rebound has begun and the
industry is expected to hit nearly $162 billion by 2023. Getting there, however, will require a re-examination of the tools currently in use and a likely investment in more efficient means of working with the various thicknesses of steel used in shipyards throughout the world. One cutting technology that stands out is plasma, which has numerous advantages over other options like oxyfuel.
Plasma technology – and the advantages it affords users – are outlined in a new report titled “Improving safety, productivity and cost containment in the shipbuilding industry,” which involved 18 months of research and 15 in-depth interviews with shipyard employees and industry executives around the world. Authored by Russ Diefenbach and Andrew Mumford the director and program manager of insights, innovation and market intelligence at Hypertherm, the report gives an overview of value-stream manufacturing assessments.
Throughout their research, the two authors uncover a variety of issues, including three critical areas that shipbuilders should consider: safety, productivity and cost containment. They also address how utilizing plasma cutting technology can assist in navigating the “troublesome economic environment” that so many businesses are in.
Old habits die hard
In search of solutions to ongoing problems, some shipyards are quick to adopt new, proven processes. It’s not uncommon, however, for some to be reluctant to try new methods, favoring traditional cutting methods, such as oxyfuel, instead. While oxyfuel is a fairly reliable technology, it also comes with its share of drawbacks, including the use of hazardous and expensive gases. It’s also a time- and labor-intensive technology that can cause cut-quality and distortion issues.
“While change may come very gradually,” the report says, “shipbuilders are learning that it is possible to reduce injury rates, improve quality and shorten delivery lead times, even while lowering costs. The key lies in eliminating activities that do not add value – excessive material handling and redundant secondary operations, for example – and adopting newer technology and procedures better suited to the realities of 21st century fabrication.”
One reason that shipbuilders often stick with oxyfuel is because it cuts slowly, giving them more time to react if they begin to make an error. Another reason is that the oxyfuel torch is longer, so workers are further away from the source and sparks. There’s also the fact that fitters are generally allowed to select their own tools to complete jobs, leaving an operation without standardized processes and tool requirements.
“Cutting faster with plasma creates more visible fumes and not all environments are set up to capture and filter the fumes,” Mumford says of another reason some shipbuilders stay with oxyfuel instead of adopting plasma.
If there is one argument that consistently convinces shipbuilders to try plasma, however, it’s the elimination of asphyxiation and fire risks associated with oxyfuel cutting. Ships have many confined spaces that are difficult to work in and increase the risk of asphyxiation.
“That’s a primary motivator,” Mumford says. “Reducing safety risks is also a motivator for all personnel, including fabricators, unions, site leadership and safety managers. Oxyfuel cutting requires ‘fire watchers’ along the gas lines, [whose job is to] shut off the supply of gas in the event of a fire. This is a very inefficient use of labor in an industry that is struggling to attract skilled labor.”
Safety is often the No. 1 workplace concern for shipyard operators. When a shipyard’s leadership fails to focus on providing a clean and safe environment for workers, hiring skilled workers
becomes an uphill battle. And despite investments made in keeping everyone safe, there is always more than can be done.
Just think of the hazards that shipbuilding workers encounter. Topping the list is hand injuries – either by being crushed, cut or burned. Metal chips and flash arc from welding are also a potential hazard for the eyes. Injuries to the neck, back and shoulders are included and are often caused by ergonomic issues. Tripping hazards cause injuries related to falls, and falls can contribute to fatalities on the jobsite as do severe burns and explosions.
“Hoses and lines throughout ships and shipyards present a very large tripping hazard,” Mumford says. “Oxyfuel hoses are susceptible to cuts from sharp edges of the ship during fabrication. Access to areas of the ship under construction is also very difficult, and large portions of the access ports can be filled with lines/hoses/ducts.”
Diefenbach and Mumford say that cutting and welding safety issues are often due to the use of oxy-acetylene welding and oxyfuel torches used for cutting. These combustible gases – especially in confined spaces – pose a serious safety risk.
“Fuel gases are a source of combustion and have caused fires and explosions at many shipyards,” the report says. “There is also a risk of asphyxiation in confined spaces, necessitating constant air monitoring. Exposure to fumes can have long-term effects on employee health, and governments are beginning to strictly regulate fumes related to cutting and welding operations.”
Beyond the risks associated with the combustion of gases, Diefenbach and Mumford’s report addresses enhanced safety protocols, such as skeleton removal where they recommend cutting the skeleton into smaller pieces, which makes the material easier and safer to handle. Rather than using oxyfuel cutting technology, which uses hazardous gas cylinders that are difficult and dangerous to handle, plasma technology eliminates those concerns. Furthermore, using an extended-length plasma torch offers a more natural and favorable ergonomic position where the workers don’t have to bend over, kneel or stand on the table.
The report also addresses bevel cutting safety issues, comparing oxyfuel to plasma. When mechanized CNC tables are used as the first machine in cutting parts and then followed by bevel cutting for weld preparation, oxyfuel cuts are usually required for grinding and cleanup. When using plasma, grinding isn’t as extensively used, which means less time and less vibration- and noise-related injuries.
“Grinding drives ergonomic risks,” Mumford adds, “as well as debris into the eyes.” The sparks it creates can also introduce a potential source for fires.
Shipbuilders often work with heavy plates – a large cargo ship can have a deadweight of up to 220,000 tons. The heavy plates involved require heavy-duty material handling equipment during fabrication, such as lifting eyes/lugs or stud weldments, which are used to stabilize subassemblies while they’re being welded. It’s a heavy lift.
As the heavy lifting continues into the finishing stages, the choice between oxyfuel and plasma is made even easier. When using oxyfuel or carbon arc gouging for cutting off the attachments, workers must grind the cut to get a flush finish. Again, because of plasma’s clean cut quality, the amount of grinding on the temporary attachments is minimized. On top of that, cutting these attachments with plasma is 50 percent faster than it is with other cutting technologies.
Furthermore, Diefenbach and Mumford say when workers cut 12-mm mild steel with plasma, they see productivity increases of up to 70 percent or greater over what’s achievable with oxyfuel. And, there are no gas hoses to monitor for gas leaks, which means there doesn’t have to be an employee dedicated to such a task, which can also lead to cost savings.
Finally, plasma is so easy to use that an operator can become certified on this technology in four hours, which is a drastic improvement over oxyfuel, which requires up to 40 hours of training.
The cost of quality
Competition is fierce, even in the shipbuilding industry. Excellence exists internationally, and knowing that, quality isn’t just a differentiator, it’s a requirement.
As far as quality is concerned, a common problem found in just about every shipyard is plate buckling and distortion. It requires time and money to correct or rework distorted plates, which disrupts workflow, costs money and at the same time introduces safety concerns.
Diefenbach and Mumford say that even after rework, it is sometimes necessary to use extreme force and exertion to bring the workpiece back into acceptable tolerances and fit. In their research, they have found that 80 percent of distortion is caused by excess heat generated by welding. About 20 percent of the distortion is caused by oxyfuel cutting.
The cause of typical distortion is often based in single-pass, deep penetration welds and other long welds on components like panel stiffeners. Long and slow cuts with oxyfuel are another culprit as is welding and cutting thin-gauge plates. Welding plates of unequal thicknesses can result in distortion, and submerged arc panel line welds and multi-pass long weld beads can also result in quality issues.
When using plasma, there is no need for purging or preheating, so the risk of heat-induced distortion is reduced. Plasma creates a smaller heat-affected zone, which allows for closer cutting without the risk of damaging the base metal.
Overall, the shipbuilding industry is not only in need of new technology adoption, but in the recruitment of a new generation of workers. By adhering to – and then exceeding – safety and quality issues, profitability is sure to follow. But it’s the adoption of new technologies that will truly be required for the sustainability of the future workforce.