Automation Systems can be complex, with many solutions available to keep them running reliably.
Talk about reliability in manufacturing and the word that probably springs to mind is “motor.” Certainly, motors and other rotating equipment must be kept moving. No work is done unless a motor turns. Not surprisingly, suppliers have invested in technology to improve the reliability of these workhorses of manufacturing. Other parts of the automation system have gone under the reliability microscope, as well. As automation becomes more software intensive, it is imperative that engineers pay attention to reducing computer down-time. From sensors to software, engineers have used their ingenuity and technology to create a dependable automation system.
How about avoiding emergency shutdowns and saving your company $300,000? One paper plant invested in technology that monitors rotating equipment. The result was avoiding an emergency shut down, saving $180,000 in lost production and replacement parts, and another $120,000 on “machine clothing (Fourdranier Wire—a belt of woven wire used on the wet end of a Fourdrinier Machine, which is used to form a web of paper.).”
Typing and copy paper is made on very large and complicated machine trains comprised of dryers, siphons, motors, ventilation systems and a wide range of rolls, drives and webs. These machines produce paper at 3,200 feet per minute, and operate in a hot, wet, dirty and dusty environment. They require downtime every six weeks for adjustment, cleaning and replacement of worn parts and critical components.
Capacity on these machines means a loss of $15,000 an hour if an unexpected machine fault requires a shutdown. “An emergency unscheduled outage to change one of these rolls will cost us at least 12 hours,” says the plant’s fine paper machines Vibration Analyst. “That’s just the downtime, not counting a messed-up journal, bringing repair people in, and ordering emergency replacement parts.”
Constantly checking
Tending the machines is a constant job. Vibration monitoring with the CSI 2130 Machinery Health Analyzer and analysis with the AMS Suite Machinery Health Manager from Emerson Process Management, an Austin, Texas, technology supplier, for each of the fine paper machines at this plant is scheduled monthly, but sometimes even that is not enough. So the company added a CSI 4500 Machinery Health Monitor for continuous monitoring.
As the Emerson team was testing network connections for the installation prior to commissioning on the machine, an inner race bearing fault was detected on the breast roll in the Fourdrinier section of the machine. The expert vibration analyst verified the fault with the CSI 2130 portable analyzer. “The pattern showed up plain as day.” The roll wasn’t due to be checked again until after the scheduled outage. This would have triggered an unscheduled shutdown. Instead, repairs were made during the planned outage and no production time was lost.
The Emerson system saved the company $180,000 in production and $120,000 in machine clothing replacement before it was even commissioned. This plant now has 46 CSI 4500 Machinery Monitors keeping track of about 600 sensors on hundreds of rolls turning from 160 revolutions per minute (rpm) up to 2000 rpm on each fine paper machine. The monitors continue to prove their value.
Adding sophisticated sensors and the analysis tools to gather and interpret the data is seen as a growing competitive advantage—and not just in process automation such as the paper plant just discussed. “In this more competitive environment, even automotive companies are starting to look at reliability, predictive maintenance and condition monitoring as a competitive advantage,” notes Preston Johnson, segment manager for the sound and vibration team at National Instruments Corp. (NI), the Austin, Texas, supplier of data acquisition and automation technology.
Johnson relates a story about an NI systems integrator in Michigan who repairs robots for automotive customers. It built a database of information collected from customers to help them reduce repair time. The integrator worked with NI to put sensors on robots in order to enhance the data acquisition by monitoring repair points. Many of the robots and conveyors needed parts monitored in hard-to-reach places, making remote data acquisition more beneficial than depending upon manual inspection.
Best sensors
Steve Garbrecht, director of product marketing at Wonderware, an Invensys-owned software supplier located in Lake Forest, Calif., maintains that the best sensors in a plant are not connected to any control or database. “You might have 20 to 40 people in a plant on a human-machine interface (HMI) terminal sharing information with each other and the system,” he says, “but there may be another 600 people who don’t use computers as part of their jobs. They are walking around the plant all day seeing things that should be investigated, but with no way to connect back into the system to send alerts to maintenance to check things out.”
In order to connect these resources in a plant, Wonderware recently acquired SAT Corp., manufacturers of the Intellitrack product line. These are handheld computers that connect wirelessly into the Wonderware HMI system. “Intellitrack brings these additional people into the process,” says Garbrecht. “They capture information from stranded assets (those that don’t have instrumentation or connections) whose failure could bring down an entire line. Maybe they see a pump leaking. They can enter the observation directly into the system so that someone is notified immediately to check it out.”
Making cement is a dirty, expensive manufacturing process. Bob Wright oversees the electrical operation of Ash Grove Cement’s century-old facility in Chanute, Kan., one of the leading cement manufacturer’s nine plants. Combined, the plants have an annual production capacity of nearly 9 million tons of cement. Like other companies in the cement industry, Ash Grove faces heightened competition, ever-fluctuating demand and intense pressure to efficiently increase productivity.
To maximize production, the Chanute plant manufactures cement all day, every day. Nearly 1,000 motors generate a combined 45,000 horsepower, driving the production of five tons of cement per minute. “The success or failure of our plant depends on our motors,” Wright says. “We need reliable equipment and ongoing maintenance to protect our motors, control production and operate efficiently.”
To resolve problems with an unreliable, antiquated motor-control system, Ash Grove invested in an unusual, yet effective, solution—installing a technologically advanced, low-voltage variable frequency AC drive to its existing 2,300-horsepower, medium voltage AC motors. Ash Grove not only updated its drive technology, it modernized its approach to maintaining capital investments. The result so far is an initial savings of $250,000 and 90 percent uptime. “Not too long ago, manufacturers had a ‘run-it-until-it-breaks’ mentality. But now, we have the tools to protect capital investments like our motors,” Wright says.
To produce the clinker used in the cement making process, Ash Grove uses limestone mined from on-site quarries, mixes it with other ingredients and heats the material up to 2,000 degrees Fahrenheit in a 150-foot-long rotating kiln. Still piping hot, the clinker, which ranges from marble-sized to three inches in diameter, goes through a cooling process before a mill filled with steel balls grinds it into powdery cement.
Spotting trouble
Workers at Ash Grove had trouble when it came time to service these three ball mills each month. For technicians to enter the mill for servicing, they used an antiquated 60-horsepower generator motor to rotate the mill inch-by-inch until it reached an exact position.
The process of manually positioning equipment, called “spotting,” became difficult because technicians had no effective way to accurately apply torque to the medium voltage motor directly from the power system—the technique used to slowly rotate the mill. “Along with the problems we had moving the bulky mill to a precise position, the cogging, or abrupt starting and stopping of the motor, can cause mechanical and electrical damage to equipment,” Wright says.
The issue interfered with the company’s goal of minimizing downtime while maximizing production. “Each hour we shut down operations to perform routine maintenance or resolve a fault translates to 300 tons of cement that could have been produced,” Wright explains.
Fed up with the frequency and expense of the problem, Wright shared his frustrations with his sales contact at Rockwell Automation Inc., Ash Grove’s automation supplier for the rest of the facility. “Traditionally, this situation called for a new spotting controller and gear motor or a medium voltage drive,” Wright says. “But Rockwell Automation engineers designed an AC drive solution that outperforms the other solutions at a fraction of the cost.”
Ash Grove replaced the generators that powered the mill spotting with preconfigured, 480-volt, 450 horsepower, AC variable frequency drives from Milwaukee-based Rockwell Automation. The Allen-Bradley AC drives power three existing 4,000-volt, 2,300-horsepower AC motors exclusively during the spotting process to efficiently rotate the ball mill and bring it to a controlled start and stop.
“With over 30 years of experience in the cement industry, I consider myself a DC devotee,” says Wright. “I never believed AC technology could produce 100 percent torque at zero speed until Rockwell Automation developed an AC motor control solution for a high-torque application.
“Rockwell Automation engineers helped us commission the drive and get everything up and running within an hour of their arrival,” Wright recalled. “This seamless, quick transition helped reduce the time between integration and actual machine operation.”
Hydrogen generating
H2Gen Innovations Inc., in Alexandria, Va., designs and manufactures small-scale, on-site hydrogen generation modules [HGM] that produce pure hydrogen from natural gas and water. The process that occurs inside one of these miniature chemical plants, known as steam methane reforming, is nothing new. It’s the size and automation of H2Gen’s machines that make them revolutionary. The company’s executive team is convinced the HGM, with its groundbreaking footprint and Siemens control system, will crack the age-old chicken-and-egg dilemma that has dogged the automotive fuel cell market for years.
Developers are reluctant to spend big money producing fuel cells until a reliable and economical hydrogen distribution solution is found. And investors are leery to bet on infrastructure until consumers are kicking the tires on hydrogen cars.
“Our hydrogen generators can be installed virtually anywhere, since they’re fed by the natural gas pipelines and water mains that are flowing below every boulevard in America,” explains Barney Rush, H2Gen’s chief executive officer, who is focused on serving markets that can benefit today from the company’s hydrogen generators and recycling machines. “We’ve got more than 15 of our hydrogen generators in the field supporting a variety of current customer needs, and new orders are on the rise.”
Kelly Leitch, director of field operations, says, “We used full design-for-manufacture-and-assembly for all the equipment. A 3D model was developed in the computer-aided-design application, with care to assure that everything was placed for building and for servicing. With the full 3D model, we also could design for the shipment container. We might go through 30 revisions before the first pipe is cut. It’s the same with the software. We develop the programmable logic controller (PLC) program in Siemens Step 7, targeting the S7-300 PLCs in parallel with the machine design. We can simulate machine operation, taking in either data from the real sensor or with manually entered values to test the system before the prototype is even built.”
Using Siemens HMI and Web-enabled monitoring, H2Gen engineers can see the same screen as the remote operators. “I was just at the airport in Houston talking with a customer,” relates Leitch, “and I was able to go into the system and see the screen he was looking at to help solve the problem.”
Reliable design
With machines located at customer sites where there may not even be a controls engineer, this care in the design of the machine and control system pays off in reliable operation. The push-button start style, ease-of-use and dependability of H2Gen’s devices are a hit with specialty steel makers, gas separators, food processors and other manufacturers that rely on hydrogen in production. Many companies have seen just how fragile, unpredictable and expensive trucked-in hydrogen supplies can be in the wake of big storms and volatile demand.
While the bulk of current demand for H2Gen’s hydrogen generators comes from manufacturers who’ve lost confidence in traditional hydrogen suppliers, leading automotive and energy companies are eyeing H2Gen solutions with growing interest.
“Our remote capability has really generated customer confidence in our solutions,” says Leitch. “Traditional chemical plants require three or four operators sitting in front of screens monitoring and running the operation around the clock. Siemens Step 7 software is robust enough to run the process automatically and alert us ahead of any potential issues.”
Many control and information systems run on a Windows operating system from Microsoft Corp., Redmond, Wash. Both the operating system and the application programs undergo periodic upgrades. Throwing complexity into the mix, the interrelationship of the operating system to the various applications running on top can be thrown out of kilter by seemingly innocuous changes in one or the other.
Shawn Gold, global program manager for open systems services at Honeywell Process Solutions, in Vancouver, British Columbia, Canada, oversees the company’s managed services program. There are several circumstances in which users face potential system degradation or even lock-up. “Operating system patches and keeping up with the latest anti-virus software are an added load for our customers, who often don’t have time to investigate all the changes. We constantly investigate the impact that anti-virus changes have on operating systems and on the entire system. We can also help the customer maintain up-to-date software.”
Then there is the potential problem of the computer system losing performance or stability due to the organic growth of the control system. “All control systems grow, for example, by adding additional input/output channels,” says Gold. “You need to watch the system to see if the growth has hit the tipping point that will degrade the performance of the system. We have programs to continuously monitor and manage these problems. We can check and download and install updates automatically. We can detect performance degradation well before it has an impact on the system. With an offline test bed, we can check out the impact of software changes before the customer has to deal with them.”
From sensors to software, potential reliability problems are everywhere. With monitoring and ingenuity, engineers are keeping their equipment running longer and in the manner for which it was designed
