In another eco-friendly effort, Lockheed Martin is using Schneider Electric’s Telemecanique 5-hp to 250-hp VFDs tied to Rockwell’s Allen-Bradley CompactLogix PLCs to run two 600-hp, 300-psi biomass-fueled steam boilers in its helicopter and flight control plant in Oswego, N.Y. The boilers will burn waste wood and supplement the plant’s oil and gas boilers, which supply the plant’s HVAC and controlled-environment facilities, including temperature and humidity controls, liquid nitrogen pressure in its test chambers and several product inspection sites.
“A lumber mill down the street processes 200 tons of logs per day, and since 48% of each log is still scrapped, we’ll get about 95 tons per day of chips and sawdust,” says Michael Magill, Lockheed’s site energy program manager. “Because waste wood is one-half to one-third the cost of oil or gas, we’ll be able to cut that portion of our energy bill in half and save $125,000 to $150,000 per month.”
Rick Kirkpatrick, Baldor Electric’s variable-speed drives product manager, adds, “VFDs have always been able to take on varied roles, but recently they’ve become dependable and reliable enough—and energy costs have gone up enough—for them to be used in even more process applications, and because VFDs allow you to vary the speed of an AC motor using PLCs, many added benefits have emerged as motors have become efficient. For example, in pumps or fans bearing quadratic or centrifugal loads, using a VFD means you don’t need to deliver full power to the motor to save a lot in energy costs. Now, as the motor slows, we even have automatic energy optimization routines in the drives, and these can automatically adjust power and voltage to reach an optimal point.”
Mark Kenyon, marketing manager for ABB’s low-voltage AC drives, adds that coordinating multi-drives fed from a DC source can help save power because using 100-hp motoring and 100-hp braking won’t use up power losses in the form of heat, as happened in the past. Instead, multi-drives allow feed power back into their application and so recover 95% of the power cut into transmission.
“We’ve been using inverse-gate, bipolar transistors for very fast, 16,000-Hz on/offs, and I think we’re now up to about 30-hp drives on a DIN rail,” says Kenyon. “HMI and SCADA software and other interfaces to drives have taken the user experience from using screw-drives to change switches to programming drives like a cell phone or iPod. Network capabilities have gone from discrete inputs and pulling six power leads and 12 controls leads at $150 each to two-wire fieldbuses, and now to Ethernet and to wireless in the future. Finally, PLC functions in eight I/O blocks have been added to many drives, so users can just program a drive instead of a PLC.”
Drives, Motor Controls Aid Process, Eco-Friendly Apps
Users are implementing smart drives and motor controls in a wide variety of process-related and environmentally friendly applications. Here are some of the most interesting:
- To maintain steady pressure and flow in backwash funnels in the dionization/regeneration section of its Tulsa, Okla.-based water bottling facility, Culligan uses PID functions in Baldor Electric’s H2 inverter drive. So when water demand slackens, the drive goes into sleep mode, and when pressure drops below a setpoint, the drive wakes and tells the motor and pump to re-pressurize the pipe. This occurs in a seamless transition, so operators can fill one to 32 of Culligan’s 8-oz to 5-gal containers more quickly and consistently. “Before this new setup, we had to walk 300 feet back and forth to start and stop our motor, and the pressure in the pipe was only a good guess,” says Chip Pierce, Culligan’s operations VP.
- Calgary, Alberta-based Q’Max Solutions’ patented mud-stripping water-recycling process removes solids from drilling water in oil and gas wells. The water lubricates the drill bit’s cutting action and cleans the well bore, and is then pumped back to the surface with up to 25% solids that must be removed before the water is used again. Q’Max’s clarification tanks and pump systems reduce wastewater by 50%, and then use Baldor’s H2 drives to monitor return flow to the well. The drives also adjust pump speed to maintain proper flow rate, which can change dramatically depending on the rock type being drilled through. “If we didn’t have these drives, operators would be opening and closing valves all day long as the flow rates change, and the pumps could run dry or lag behind and overflow the tanks,” says Lorne Onstad, Q’Max’s general manager.
- To help load and position 2,000-ton barges, Wintech in Shreveport, La., employs Baldor’s 18H vector drives to run dual winches in its barge-moving systems at Liter’s Quarry Terminal in Louisville, Ky., and at Mulzer Stone in Tell City, Ind. The drives provide smooth acceleration/deceleration, infinitely variable line speed and controlled back tension on the trailing winch. Jim Leslie, Wintech’s president, proposed replacing the mover’s former hydraulic system with vector drives, and Dallas-based system integrator M-Tech helped design the solution. The vector drives eliminated the need for tug boats and needed only one of two former operators to control the pulling winch and the tensioning winch.
- Lewis Corp. of Pocatello, Idaho, and Bollinger Enterprises, North Warren, Pa., recently developed their 42-ton Bollinger Briquette Press, which converts coal dust into industrial briquettes, while also reducing pollution from mining and power applications. The press mixes the dust with a binding agent and then compresses it in large drums powered by Baldor’s 5011 Frame 300-hp, eight-pole motors. The resulting briquettes can be sold to mining companies or electrical utilities for fuel.
Slightly Slower = Big Energy Savings
Centrifugal loads, such as those on pumps and fans, offer the greatest potential for energy savings when operating at less than 100% of required flow or pressure conditions, says Dale Basso, of Baldor-Dodge-Reliance in Greenville, S.C., in his presentation “Energy Team Meeting: Energy Savings with AC Motors.”
For example, a 100-hp induction motor running at 100% speed and 100% load will cost $27,139 per year to run, according to the following formula: (100 hp) x (1/95% eff.) x (.746 kw/hp) x (.08 $/kWh) x (12 h/day) x (360 day/year) = $27,139.
However, the same 100-hp induction motor running at 60% speed and 22% hp will cost $5,970 per year to run, according to the same parameters: (100 hp) x (0.22) x (1/95% eff.) x (.746 kw/hp) x (.08 $/kWh) x (12 h/day) x (360 day/year) = $5,970.
Consequently, the resulting savings of $21,169 per year occur because affinity laws for motors reduce the horsepower required to run a motor by the cube of its speed. In this case, 0.60 x 0.60 x 0.60 = 0.216.