Wireless Integration Ensures Wastewater Plant Reaches Its Upgrade Goals

Upgrading the control system for a municipal wastewater system was going to be costly and time consuming until facilities engineers reviewed available wireless technologies. The Persigo Waste Water Treatment Plant serves the City of Grand Junction, Colo., and the surrounding communities. The facility, which cost about $28 million, was put into service on Jan. 16, 1984.

 After two decades of operation, the existing control infrastructure was in need of replacement and upgrade. Although, it originally had been designed to use the most reliable communications signaling technology available at the time, buried multi-conductor copper cables, age and constant use had heavily degraded the performance. As a result, maintaining the system became expensive.

Ed Tankersley, Lead Plant Mechanic, summed up the situation at the time: “Our wires underground were failing; therefore we were trying to get our plant-wide SCADA system running so everything in the plant would come back via wireless Ethernet. However, we had a relatively primitive communications system.”
Additionally, Tankersley realized, the entire system could be made more reliable, easier to maintain and more energy efficient if the controls for the dozens of pumps, blowers, valves and sensors were upgraded to take advantage of the latest Totally Integrated Automation (TIA) technology from Siemens Industry, Inc. The system Persigo now employs has two types of wireless data communications and a full complement of TIA-based controllers, HMIs and SCADA software.

To plan the system upgrade, Tankersley contacted Cody Lange at automation-technology distributor Crum Electric for help. “Ed’s vision was that he and his staff in the plant would have all the knowledge needed to not only integrate the system, but also to carry out maintenance into the future,” Lange recalls. “He wanted to have the knowledge to repair and improve the plant internally without having to call in external people or [reach out to third parties for] support.”

“My part,” Lange continues, “was primarily to help with the architecture and [provide information about] different types of I/O and processors available in the TIA portfolio. I also provided technical support as far as programming and Ed worked with Siemens’s Technical Support Hotline.”

The system Tankersley designed with Lange’s assistance relies on wireless networking throughout. For communication within the Persigo facility itself, where communications links span distances of a few hundred yards at most, they opted for a Siemens Scalance W Wireless Ethernet network. To communicate with control systems at the lift pumps miles away, they chose FHSS radio technology from wireless system developer FreeWave.

They simplified and upgraded the control architecture by adopting Siemens Totally Integrated Automation (TIA) technology. TIA is a networked control system philosophy that stresses harmonization and integration of all control-system components to reduce installation costs, with integrated diagnostics to make the installed system as easy to maintain as possible. The TIA system maximizes re-use of software components, and provides hardware components designed to work together seamlessly.

For example, Siemens S7-200 PLCs are used for small local-control systems, such as lift pumps, while Siemens S7-300 PLCs control larger, more complex equipment in the main facility. Siemens Simocode intelligent motor overloads were used on critical motor loads such as the three 300HP blowers, and Siemens WinCC SCADA (Supervisory Control and Data Acquisition) visualization software was used for plant monitoring and operation. WinCC also acts as an OPC server to Canary Labs Trend Link, logging any process variable every quarter second.  This enabled Tankersley to use Siemens Simatic Manager software to program the entire plant.

Huge Service Area
Robust long-range control communications are crucial in wastewater treatment facilities because these facilities generally serve a large geographic area, and their processing facilities tend to be spread out as well. Persigo’s service area currently contains 488.8 miles of sanitary sewer lines, and this increases each year with the continued growth in the Grand Junction area. In addition, three Sanitation Districts send sewage to Persigo WWTP for treatment, including: Central Grand Valley Sanitation District (78.6 miles), Orchard Mesa Sanitation District (34.3 miles ), and Fruitvale Sanitation District (29.9 miles).
As one would expect, the wastewater flow channels to the plant resemble tributaries draining a river-system watershed. The communications-network physical topology mimics the wastewater collection system’s topology. The network is a modified star configuration (in information network parlance). Of particular interest is control communications for the network’s lift stations.

Gravity drives wastewater flow through most of Persigo’s collection system, but some parts of the system require additional pressure boosts to pass obstacles, such as hills and valleys. Hence the need for lift stations, which are automated pumps providing the additional boost on an as-needed basis.
At each lift station Persigo is using a Siemens S7-200 PLC with a Freewave FGR2 RS 485 radio for communications. Some of the closer lift stations not only provide their own data back to the plant, but also repeat data from lift stations further away.

“Our farthest jump is 20 plus miles,” Tankersley says. “The radios’ maximum range depends on how much you want to spend on antennas and, of course, line of sight. They are only one watt, but I imagine you could get 30 miles in this terrain if you selected more powerful antennas.”

Advanced Technology

“One of the primary reasons they wanted to use wireless was because this is a very old plant,” Lange recalls, “and it is uneconomical to run copper wire out to all the locations. So wireless was really the preferred solution because it saved time, money, and effort, and eliminated the need to trench and get into the vaults.”
In addition, it is generally not good practice to run control and communications wiring in the same vaults as the 13,200VAC power cables. The communications signals can be disrupted by the electromagnetic fields produced by the power cables.

Tankersley says he considered a number of alternatives before deciding on this system: “At the very, very expensive end, you could run fiber, which is not practical. You could also run via satellite, which is another wireless technology, but requires monthly fees. Years ago we had a phone line to each station, but the monthly fees were killing us. You could also run cell phones at each station, but again you have a monthly fee.”

In the end, he chose to use Siemens’ Scalance Ethernet infrastructure, which is a combination of managed and unmanaged switches, and wireless and hard-wired switching. The system also includes multiple Siemens HMI panels and a WinCC Flexible runtime on a PC in the main operations building. This connects to the system’s data logging functions, and everything networks to an alarm dialing system.
One of Tankersley’s goals was to set the system up so that operators could access any process from any HMI panel in the entire plant or from the PC operator’s station in the main building. If, for example, an operator is in the digester building, he or she can look at the headworks, or the aeration basin, or vice-versa.
This is a huge advantage, particularly in the headworks building where all the sewage comes into the plant. “That’s not a place you want to spend a lot of time,” Tankersley says. To be able to look at the operations in that building from another location that is a little more pleasant was a key deciding factor. To not have to walk several hundred yards when diagnosing a plant issue, or to avoid going into an unpleasant environment to access data and control those stations, is more than convenient. It makes maintaining the plant much more efficient.

System Within a System
“Lift stations include a pump and a redundant pump,” Persigo’s Tankersley points out. Sometimes there’s a dry well for the pumps and a wet well next to it. Other times pumps are surface mounted, and then they have to vacuum pump the sewage into the pump to prime it. The bigger ones do have backup generators. Our biggest station has two 60 horsepower (HP) pumps, and the smallest stations have 2 HP pumps.”
Pump stations are automated by small, low I/O count control systems that run autonomously. Each pump station has a 24-V-powered S7-200 Siemens PLC as the controller. Each pump station also has a Freewave 900 MHz frequency-hopping spread-spectrum radio to communicate back to the main facility either directly or through repeaters (additional FHSS radios) via the Modbus communication protocol to a Siemens S7-200 at the main plant site.

The S7-200 is a data concentrator that brings everything into a second PC running Siemens’ Simatic NET OPC server. The OPC client is Win911, which is a commercial auto-dialer software that calls a phone list and relays messages to plant operators and maintenance staff for help based on alarm conditions.
Under normal circumstances each lift station runs autonomously, but they all report departures from normal operation, such as high wet-well level or power failures, back to the main facility. For example, some of the stations have backup generators. If the power fails, the generator starts up automatically. When the backup generator successfully starts, the power fail condition clears, but the original power-failure problem may still need attention. If nobody fixes it and resets the generator within a given time, the controller will call with a generator running alarm.

“At the main plant site, we are running S7-300 PLCs, which are much more powerful than the S7-200s in the lift stations,” Tankersley says. Additional equipment used in the main facility includes 8” HMI color touch panels, and 19” touch panel HMIs. All remote PLCs automating processes scattered throughout the plant have Siemens Scalance 788-1 PRO radios communicating with the main operations console via wireless Ethernet (WiFi) in the operations building.
There are two PCs in the operations building. One runs Win911 and the other is the WinCC Flexible HMI to supervise all plant processes. That second PC also data logs all plant processes, archiving the data. Because the system is stand alone, all PLCs, HMIs and PCs are synchronized to the exact time through a GPS time server.

Altogether, the system upgrade and wireless network have been successful. The new communications are much more reliable, while the new automation equipment proved simpler to install and easier to maintain than the old equipment. The staff at Persigo can now respond much more quickly to alarms at any of their locations, local or remote, and with more diagnostic information. This cuts down on their travel time for troubleshooting with most initial diagnosis able to be done remotely, eliminating wasted efforts for nuisance alarms. The new Siemens TIA based system provides an architecture that is compatible for easy future expansion, protecting the investment by Persigo and ensuring future sustainability.

Persigo Waste Water Treatment Plant at a Glance
The treatment process at the Persigo Waste Water Treatment Plant includes four steps:
1. Preliminary Treatment
2. Primary Clarifiers and Activated Sludge
3. Final Effluent
4. Sludge Processing
Design capacity for the plant is 12.5 million gallons per day of wastewater generated at homes, schools, churches, and industries, anyplace that is tied into the sewer system. The wastewater travels to the treatment facility through 462 miles of pipelines. Average flow is 8.0 million gallons/day (30,283 m³/day). It takes about 14 hours for the water to go through the entire plant. In the main facility, there are five sewage lift pumps of 100 horsepower with a capacity of 6,950 gallons/min (10 million gallons/day) each.

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Solar Panel Assembly Made Easy

Precision manufacturing is key to producing weather-resistant solar panels. Integrated motion and control systems from Siemens provide the needed accuracy and performance.

A market growing at 45 percent per year looks like a good bet to get into. According to Mike Taylor, director of research and education, Solar Electric Power Association, the solar photovoltaic for electric generation market has been on that slope for the past three years. No wonder automation companies are developing solutions for the solar panel market.

Taylor says that Europe has been the photovoltaic leader, but that the U.S. market is rapidly developing. Putting to rest the myth that solar implementations require never-ending sun, the current market leader is Germany—not exactly a sunny country. Spain follows, with the United States third in market size.
“In the United States, we just broke the 300 megawatt (MW) barrier in photovoltaic electric generation in 2008. By comparison, in 2007 the total was 160 MW and in 2006 it was not quite 100 MW,” says Taylor. “With the entry of utilities and big box commercial stores into the (solar energy use) market, it’s just going to keep growing.”

Siemens has been involved in the solar industry for many years and has honed its automation offering to fit the needs of solar panel manufacturers. Apparently simple from the outside, these panels are multiple layers of materials that must be precisely sized, cut, stacked and sealed. If dirt, dust or contaminants land on any of these layers before the unit is laminated, it more than likely will affect the performance of the solar panel. The assembly process must assure the final product is impervious to weather and other outdoor environmental hazards.

Complex manufacturing
The manufacturing process includes accurately measuring, cutting, transporting, positioning and stacking insulation, protective film and other layers of proprietary films onto expensive and fragile sheets of photovoltaic silicone without contaminating any of the layers. If the silicone layer is dropped, bumped or hit with too much force, the sheets can crack or break into shards. The films come from rolls and are cut to length and registered to position onto the substrate. The end result is a hermetically sealed panel that converts solar energy into electricity for residential or commercial use.
A company located near Chicago specializes in building machinery to manufacture these panels. A Siemens 317T programmable logic controller

“This was a new project for this customer,” says Ken Brey, technical director for DMC Inc., an automation engineering and software services company located in Chicago. “This customer requested Siemens equipment to match the rest of their automation equipment. They know that Siemens equipment would not only give them continuity in the hardware and software, but would also give them the high level of performance and operation they expected. They also know from experience that Siemens service is much easier to get globally than other brands.”

(PLC) controls the process. This PLC employs CPU 317T-2 DP technology which adds powerful motion control functions to the existing range of standard central processing units (CPUs). These motion control functions are integrated in the CPU firmware and are supported by a co-processor for high-speed closed-loop control. This ensures that the performance of the CPU 317 for normal control tasks is maintained and that the motion control functions can be computed at a higher clock rate.

Like making a sandwich


As Brey explains it, the process of making these panels is similar to making a sandwich. Instead of bread, glass panels make up the first layer. Instead of meat or cheese, EVA and insulation material make up the second layer. The solar panels get placed into the sandwich and are put into a laminator to seal everything together.

“Our customer’s machines cut and place the middle layers onto a vacuum conveyor. The machine positions the panel under the leading edge of the EVA and feeds the panel and the EVA together to build our “sandwich.” The laminating process is done with another company’s equipment,” states Brey. “The end customer was building an entire factory from scratch with equipment from different vendors.  Standardizing on Siemens was the quickest and easiest way for the equipment to communicate as well as ensuring the job met the customer’s high expectations,” according to Brey.

A typical motion control application like this assembly process needs to control 2 to 8 axes. The Siemens 317T PLC can control up to 16 axes. In addition to accurate single axis positioning, the technology CPU is particularly suited for complex, synchronized motion sequences, such as coupling with a virtual or real master, geared synchronous motion, electronic cam discs and print mark correction. Print mark registration is particularly important in the solar panel lamination process so film is properly aligned onto the photovoltaic cells. Using Siemens STEP 7 software, only one program is needed for PLC and motion control, making configuration and programming significantly easier and faster.
The processor in the solar panel assembly machine has motion control functions integrated into the CPU that guide four servo axes to position the film. It allows the process to run at high speeds without a separate motion controller. Accurate registration of the film is achieved using the built-in geared synchronous motion and measuring probe functions of the 317T PLC. Siemens solution provider, DMC, Inc., installed the control system at the manufacturer’s facility near Chicago and the machine now resides in the photovoltaic panel plant in Europe.

SEPA’s Taylor has calculated from public announcements of utilities that 2,500 MW of electric generation from photovoltaic panels is projected for manufacture in the next five years. With utilities and large commercial enterprises such as Wal-Mart looking at adding solar generating equipment, the demand for these Siemens controlled assembly machines should be sky high.

For more information on Siemens Solar Industry Solutions, please click here.

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Robotizing, Unified Control and Clouds Ahead for Robots

Image via Wikipedia

Industrial robots and growth seem made for each other. 

But the growth will be narrowly focused, predicts Erik Nieves. “Robotizing” what’s already automated is one way, says the technology director for supplier Motoman Robotics (www.motoman.com), Waukegan, Ill., a division of Yaskawa America Inc. While that provides flexibility, “effectively, you’re just making an improvement, though probably not in reliability. You’re leveraging the flexibility that robotics affords,” he observes. Whatever changes, though, robotizing of already automated functions “is not going to be the ‘sea change’ in our industry.”

Another trend he sees, unified control, could be part of such change. In this control infrastructure, especially in emerging markets that haven’t existed long enough to assume separate controls is correct, “you make a decision about who’s responsible for everything,” Nieves explains. “Can I program not just the robot with the robot controller but all the peripherals?” If so, there won’t be a programmable logic controller (PLC) involved, he continues. This control unification for robots hasn’t yet hit the factory floor, he says, but it’s coming.

What Nieves considers the real “sea change” is dual-armed robots. These perform tasks with the dexterity previously possible only with humans, he comments. The big leap was not from a single-arm to a dual-arm robot, though, he asserts. “That was natural. The leap was from six to seven axes. Once you have a seven-axis arm and you have all this dexterity, then it is very organic to apply two seven-axis arms to a common torso.” And that, Nieves states, was how the dual-arm robot was born.

The seven-axis arm allows movement without affecting position and orientation, he adds. And such dual-arm robots provide gains in productivity. But these robots, which are in their infancy, will never be dominant, Nieves predicts. “You will always have tasks that six-axis robots are suitable for, such as tried-and-true applications such as spot welding.”

Besides more mechanical functionality, robotics’ growth also focuses more on interconnectivity and traceability, suggests Rush LaSelle, global sales and marketing director for vendor Adept Technology Inc. (www.adept.com), Pleasanton, Calif. One pathway is through information-technology clouds. This technology implies that the computing resources exist somewhere else, “out there,” and, as necessary, that users will connect. “The benefit of processing and its interrelationship with the cloud is in its relative infancy throughout manufacturing and, certainly, within the context of robotics.” But, says LaSelle, “ ‘cloud’ or resource sharing has been used in the automation industry for as long as there have been networks.”

Cloud coverage

Another real-world cloud example he provides is inventory control, in which robots palletize and handle products in warehouses and distribution centers. “Inventory information is largely managed in the cloud and the addition of intelligent robotic automation acts as a vehicle to reconcile what’s ‘expected’ in the digital world—that is, what is captured in databases throughout planning and finance—and what actually ‘exists’ in the physical world—that is, pallets of products in warehouse racks,” LaSelle explains.

Besides clouds, end-users will benefit from being freed of having to program robots. “Our team is evaluating technologies and developing methodologies so that users will be able to teach, not program, robots,” LaSelle states. Options he mentions include gesture-based teaching and other human-machine interfaces beyond the traditional interface on a teach pendant, programmable logic controller or personal computer.

Sensory inputs comprise another growth area of value-add focus. “Portion control and product grading for the handling of primary foods, especially those in the protein category (e.g. meat, fish and poultry), are active areas of development,” LaSelle notes. What could the net benefit be? Robots will not only locate, pick and place products into packaging, he says, but will determine size of the products. That’s so the robot can place the correct weight of products into a package and conduct real-time quality control.

C. Kenna Amos is an Automation World Contributing Editor.

Motoman Robotics
www.motoman.com

Adept Technology Inc.
www.adept.com

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