Keeping pace with better ergonomics
Pentair integrates automated lifting in a rolling line without WIP
Every employee at Pentair operates under PIMS, or the Pentair Integrated Management System. PIMS encompasses everything from continuous improvement and hiring practices to safety and ergonomics. Concerning the last, the company instituted new material handling technology within a tightly run tank fabrication line in Delavan, Wis. The line has no WIP and, hence, little margin for error.
If he were alive today, Eli Goldratt probably would need only a glance at Pentair’s tank fabrication line, plate roll and seam welder and all, to see the beauty of it. Inside its Delavan, Wis., plant off I-43, midway between Beloit and Milwaukee, the line produces three assembled tanks every two minutes, a steady drumbeat set to the pace of the constraint process that produces a circumferential weld, attaching the tank head.
The cell uses ideas promoted by the theory of constraints (TOC), an improvement method Goldratt developed decades ago, built (at least in part) on the premise that any manufacturing system is only as productive as its slowest process. Although not the sole source of inspiration for the tank line, TOC certainly has inspired Pentair’s overall approach to improvement.
“We’re making pressure tanks. If you have a house out in the country and you have a well, there’s a pump that moves the water up above ground. Most systems have what’s called a pressure tank, which empty is around 40 PSI. When the tank fills with water, it compresses the air to up to 60 PSI. In your house, you turn the faucet on, and the tank pushes the water out. Eventually, when the tank pressure goes down enough, a pressure switch activates to turn on the pump. When you turn off the faucet, the tank again fills up to compress the air to 60 PSI, ready for the cycle to start again.”
So said Brian Broga, product manager at Pentair. Before moving to his current position, he was value stream manager of the tank line, but that’s not the only reason why he knows about the basics of pumps and well systems. Every employee at the plant takes a course called “Pumps 101.”
“All new hires, whether they are in finance, marketing, or operations, take a series of online e-learning modules to help them get up to speed,” said Mike Bothwell, senior marketing communications manager, whose team helps design and implement the online seminars.
The thinking goes that everyone, from the accounts payable clerk to customer service reps to product engineers, should know the basics about what the company sells. It’s what the customer cares about, and the customer, of course, makes any company’s existence possible.
The courses are an integral part of the Pentair Integrated Management System (PIMS), introduced to everyone the first day on the job, including all 500 workers at the Wisconsin plant, which is part of the Pentair Flow Technologies business unit. PIMS encompasses everything from hiring to continuous improvement to safety and ergonomics. The last has been given increased scrutiny in recent years, particularly when it comes to lifting. The company ultimately made investments in various areas of the plant. Workers in the finished-goods warehouse, for instance, now use a pick-and-place hoist to move boxes.
Efficiency and safety often go hand-in-hand. If a material handling job is easier on a worker’s back, the worker can probably move more in less time. But this wasn’t the case on the tank line. The line has no work-in-process, so work must move from one point to another at a pace no slower than the drumbeat defined by the constraint process.
Until recently workers manually moved three rolled shells off the plate roll every two minutes, with an average per-cylinder rate of 40 seconds. It usually wasn’t a problem; they could easily beat that 40-second time limit. But the repetitive motion was an ergonomics problem. Transferring three rolled shells every two minutes, even for short periods, isn’t easy on the back. Managers needed to integrate a material handling alternative, whatever the solution, in a tightly integrated production line that had been running like clockwork since the 1980s, so workers could both keep pace and keep safe.
A Large Product Family and No WIP
When implementing its version of lean several decades ago, Pentair didn’t just shun all inventory. It needed some finished-goods inventory, but it carefully sets the level to meet customer demand, determined by analyzing some forecast data but primarily historical sales data. It also keeps a set amount of raw stock, which can be turned into a variety of things of value.
But work-in-process can’t be sold, and midproduction it can be turned into only one product, or at most one model in a product family. So working under PIMS, managers ensure that they maintain as little WIP as possible, governed by the cycle time of the constraint process.
If cycle times between the constraint and nonconstraint processes vary greatly, the company makes use of a WIP buffer. For instance, in one castings line, the constraint step involves a machining process that takes about 15 minutes, while the downstream assembly takes only about two minutes. In this case, the line needs several machining centers feeding castings to downstream assembly to keep pace. With no WIP buffers, if something were to happen to that constraint process—say it produces a bad part—it would cause workers downstream to be idle for at least 15 minutes. So the company maintains a WIP buffer to avoid those prolonged line stoppages should something unforeseen happen.
But the tank line is different, because its constraint process cycle time (and by definition all other processes) is so short, and so it has no real need for WIP. Should the plate roll, welding station, or any other operation produce a bad part, it does shut down the line—because, again, there’s no WIP—but the constraint process’s cycle time is only two minutes, so the work stoppage usually isn’t detrimental. Cross-trained workers can move where needed to get production back up and running.
Shutting down a line for two minutes costs less than maintaining a large WIP buffer, not just from a material standpoint, but also from a quality perspective. If a bad part should emerge from the plate roller, the downstream technician catches it immediately, and within minutes the problem can be corrected. In batch production, the error may not be caught until the entire batch moved to the next process. With a batch of 50, all of them would need to be scrapped and fabricated again, and this would certainly starve downstream processes for more than a few minutes.
This isn’t a job shop, although technicians do choose different CNC programs, depending on the product iteration, which can vary widely. Tank diameters are 12 to 24 in., and thicknesses are from 0.058 to 0.072 in. of cold-rolled steel. Widths also vary; 24-in.-diameter shells are 59.5 in. long and weigh 84 pounds, but not all shells are that heavy or long. Still, they don’t have elaborate setups to worry about. Everything in the line is designed around a defined product family.
Over the years the company has worked to reduce variability, including the possibility of unplanned line stoppages, via preventive maintenance of machines and quality certifications of material. The company purchases 11 different precut blank sizes, which are certified by the material supplier. From there the sheets feed into a four-roll plate roll, which has an upper support to ensure the thin-gauge shells maintain the specified diameter during rolling.
The plate roll is carefully sequenced to match the line’s drumbeat. Every two minutes, one large tank is rolled, followed by a setup in which two smaller tanks are rolled at once. After rolling, the parts are removed and sent downstream to a process that welds the longitudinal seam, a washing station, and a mechanized wire welding process (the constraint) that adds the circumferential weld, another washing pretreatment station, then finally to powder coating.
The entire line calls for careful synchronization, not only because it lacks WIP, but also because certain operations like welding have two stations side by side that process two parts at once. They then flow from two lanes to one, into the wash line, then spread to two lanes again before returning to one line for pretreatment and powder coating. It’s a single-piece-part-flow tango, and the material handling time between operations must follow in step.
Moving Shells in Step
When it came to offloading the shells from the plate rolls to the tack welding station, efficiency wasn’t an issue; for years operators had simply manually fed the blank into the plate roll, then lifted the shell from the plate roll to a station that tack welded the two ends of the longitudinal seam. But having operators muscling around blanks and rolled shells, all day every day, wasn’t ideal.
As Broga explained, “Our big challenge was that we would run as many as 600 of these during a shift, and a person had to lift them repeatedly. Some of them are small and don’t weigh very much, but when you get to the big ones, those 5 ft. wide and 84 lbs., it was quite a burden.”
Automating the loading called for a plate roll with automated loading, provided by IMCAR (sold in the U.S. through Carell Corp.), which not only eased worker ergonomics, but also kept technicians away from pinch points in the roller itself. Offloading, though, wasn’t as straightforward. The steel shells, which after rolling are pushed by an arm to an offload table, could have a diameter between 12 and 24 in. Vacuum lifting wasn’t a safe option, considering that at this point in production the shells are coated with oil. A magnetic lift could work (all material is cold-rolled steel), but conventional magnetics and cylindrical objects don’t always work well together (see Figures 1-3).
Ultimately, the company used a custom magnetic lifting device from Industrial Magnetics. The V-shaped magnet that works with various cylinder diameters is connected to a “smart” Gorbel hoist system that knows where it is and sets upper and lower travel limits. Workers use the lift for 16-, 20-, and 24-in.-diameter shells, and for each the hoist knows how far to travel. If, say, it picks up a 16-in. shell, the hoist knows that it needs to drop several feet to the adjacent tack welding station.
Such automation was critical, because as soon as the roll stops, the clock starts ticking, and an operator has 40 seconds to move the shell to the next station and fixture it in place. Managers didn’t want operators having to think about how far the shell needed to descend to the tack welding fixture. They wanted to make moving the shell as natural and intuitive as the manual operation, without the pain of repeated lifting.
“This way, the people operating the lift don’t have to think about how far to ease a unit down to the tack weld station,” Broga said. “Picking up and dropping off, it’s very repeatable.”
As sources explained, Pentair is continuing with its improvement efforts in the tank production line. Up next: A move in which the seam-welded tank is moved to the vertical position for the circumferential weld—not the easiest feat for lifting devices, but the company continues to hunt for alternatives. True, workers have been moving those cylinders manually for decades, and the drumbeat of the line—three tanks every two minutes—has kept beating. Of course, that doesn’t mean their jobs can’t be made easier and, most important, safer.
During a morning conversation in June, Gloralee Dixon was about to head to a root cause countermeasure (RCCM) meeting in regards to health and safety. Until recently she was Pentair’s lean enterprise manager for North America, but has recently moved on to become environmental health and safety manager.
Whatever the topic, RCCM at Pentair takes a holistic approach. It doesn’t focus on just the machine or workers in question; it also looks at front-office operations—design, order entry, purchasing—as well as operations after manufacturing, including warehousing, distribution, and general fulfillment. No process is an island.
“It’s not just problem-solving,” Dixon said. “It’s problem-solving to the nth degree. You analyze the problem and break it down and set a target you need to achieve. You do the root cause analysis, ask why, and then you develop the countermeasures around that and how you are going to fix it going forward.”
In certain areas, including health and safety, results from RCCM events are cataloged onto a corporatewide Microsoft SharePoint® system to share the knowledge among Pentair’s 30,000 employees around the world. According to Dixon, the company has plans to implement such cataloging across all RCCM events in the near future.
Like everything else at Pentair, RCCM is part of the Pentair Integrated Management System, or PIMS, which lives with employees from their first day on the job. “It really governs everything we do,” said Brian Broga, product manager. “It’s our overall system for how we manage talent, how we do lean, how we work on projects in the front office, on the floor—it’s overarching.”
According to the company website, Pentair divides the system into three major elements: lean enterprise, talent management, and growth. Lean involves the tools that talent uses for the company to succeed and grow, both organically and through acquisitions.
“When we look to acquire a business, we are always looking at it from a PIMS level,” Dixon said, “to see what we can integrate immediately. Usually we can realize some gains right away by implementing lean tools into a business. From an internal growth standpoint, PIMS gives us flexibility. We can run multiple products on multiple lines. Our workforce is thoroughly cross-trained to work in different areas, and we’ve created standard work for all of our processes.”
In a sense, PIMS is a system in which tributaries of minutiae flow into a river of the broader goals of the business. A lifting device in the tank fabrication line may not show up on an investor’s radar when analyzing Pentair’s global success, but it’s still an important, albeit small, tributary that helps make the river’s flow a little stronger.
The FABRICATOR is North America's leading magazine for the metal forming and fabricating industry. The magazine delivers the news, technical articles, and case histories that enable fabricators to do their jobs more efficiently. The FABRICATOR has served the industry since 1971.