Municipal wastewater treatment facilities can significantly reduce the weight and volume of sludge using the J-Press® overhead filter press from USFilter Dewatering Systems, Holland, Mich. Producing higher cake (dryer) solids makes more efficient use of landfill space and reduces transportation costs.
USFilter recently applied the same criteria — compact, portable, efficient — when it selected new systems for TIG and flux cored welding from Miller Electric. Most importantly, portable and reliable Miller machines help USFilter meet its objective of shipping presses with extremely short lead times.
|The Dynasty 300 DX make precision pulsed TIG welds on stainless steel process piping used in a filter press.
USFilter, a Vivendi Environment company, is the world's largest manufacturer of filter presses for slurry dewatering and sludge handling systems. Its J-Press overhead and sidebar filter presses set the industry standard for performance and reliability. A J-Press consists of a heavy steel frame engineered to support a pack of 470 to 2,000mm square filter plates. The filter plates are recessed on both sides, creating chambers between them. The plate pack is clamped by a hydraulic cylinder.
A cycle begins when the sludge, slurry or process liquid is pumped through into the chambers. A cloth lining traps solids, while liquids escape through piped channels. The process continues until a solid “cake” forms in the chambers. The J-Press then opens, the plates separate and the cake is discharged.
“Because we specialize in piping systems and pump skids, we do a lot of inter-company work for the other USFilter locations,” says Jim Skinner, the Holland facility's manager of fabrication and machining. “As a result, we weld a tremendous amount of stainless steel piping, from .0625 in. wall, 1-in. diameter to schedule 40, 10-in. diameter pipe.”
The company also welds thick carbon steel. To clamp a hundred or more filter plates together with more than 800 tons of clamping force, a press frame uses 1- to 5-in.-thick A36 steel plate and heavy angle and beams. Room-sized settling tanks use thousands of square feet of 1/4-in. steel plate. This material requires a high amperage, high duty cycle flux cored welding system.
A combination of precision and power are needed to weld the stainless steel piping and thick steel plates on a J-Press overhead filter press.
Like many manufacturers, USFilter had a fleet of aging welding equipment. It needed four new TIG welding systems and wanted to begin replacing its 16 flux cored welding systems, most of which were more than 15 years old. When selecting new equipment, this savvy manufacturer heavily weighted efficiency in its criteria.
“We strive to improve efficiency. Any time we can cut long-term costs and save money, it is definitely a plus,” says Skinner. “We may spend a small premium up front, but it makes sense when looking down the road.”
“USFilter could have taken the traditional route and purchased Miller's Syncrowave® 250 DX. It's the industry's best-selling TIG machine, so no one would have challenged the decision,” says Vern Kragt of Lake Welding Supply, Muskegon, Mich., USFilter's distributor representative for 17 years. “However, Miller's Dynasty 300 DX, a 300-amp AC/DC TIG inverter, made better sense.”
Kragt explains that conventional TIG machines operate only on single-phase power. To weld at 250 amps (230 V primary) requires 96 amps of primary power for machines without power factor correction. Because of the significant load placed on the primary power line, some companies cannot add more TIG machines without spending tens of thousands of dollars to modify incoming service.
Inverters solve this problem because they can operate on three-phase input power. An inverter using three-phase power and welding at 250 amps requires 26.3 amps of primary current. If 460 V primary current is available, welding at 250 amps requires only 17 amps of primary current.
“Retiring just one old TIG unit could enable a company to add four new Dynasty inverters while reducing the load on incoming service,” states Kragt. “Anyone building or renovating a facility needs to be aware that if they use inverters, they can wire it for three-phase primary service. This will lower utility bills dramatically. Using inverters may also entitle you to rebates from the local utility.”
106 lb. of Portability
Boom-mounted, dual wire feeders provide the operator with comfort, flexibility and an expanded work area.
|Boom-mounted, dual wire feeders provide the operator with comfort, flexibility and an expanded work area.
While electrical efficiency is important, labor always accounts for the bulk of a welding project's cost, typically 75 to 80 percent. For example, cutting and fabricating the metal for a filter press typically takes 200 hours. Once they near completion, heavy presses, large pump skids and other process piping fabrications can only be moved by overhead crane. Thus, when last-minute engineering changes require altering pipe configurations, it may take a long time to bring piping to the welding machine.
In the past, moving a TIG machine to the work site took more effort. Traditional TIG machines weigh 400 to 500 lb. Given USFilter's emphasis on short lead times, it wanted the new TIG equipment to be more portable.
“The Dynasty's portability is fantastic,” says Welding Operator Juan Castorena. “We can move our own machines anywhere. This comes in really handy for making on-site modifications, whether in our shop or at a customer location.”
Kragt notes that the Dynasty's 106-lb. weight includes the optional 115 V auxiliary power. “Workstations don't need to have single-phase power, as operators can use the two 115 V outlets on the back of the Dynasty,” he says. “Juan's set-up is typical of a TIG operator. He uses one outlet to run a grinding wheel for tungsten sharpening and the other for his radio.”
“It's the best machine I've ever run for TIG welding,” says USFilter Operator Larry Brinks. “I've used two other brands of TIG machines, and there's no comparing them to the Dynasty. I like it for welding on stainless because I can set my pulsing variables without a lot of monkeying around. When I'm rotating a pipe, I vary the pulses per second to match the speed. This way, I get the same amount of penetration all the way around.” USFilters' Juan Castorena adds that, “The way everything works on the control panel is logical and easy to understand. It's certainly easier to set pulsing variables compared to other full-featured machines.”
Flux Cored Bonus: Power Efficiency
When USFilter needed new power sources for flux cored welding, it didn't want to sacrifice the reliability its old Miller Deltaweld machines offered. John Christensen, lead man in the weld shop, says, “Our Deltaweld 450 and 650 units deliver excellent reliability. I've been here 17 years, and we're just starting to replace the older units.”
Reliability is important because, “We have a lot of quick deliveries — three to four weeks on a smaller press and eight to 10 on a larger unit. We build hundreds of presses a year, and we need to manage work flow for that to be successful,” says Skinner. “Fortunately, we've only had to take one welding machine out of the shop for service in 15 years.”
Starting in September 2000, USFilter began a program to steadily replace its older machines with new Deltaweld 652 units and Miller's heavy-duty, dual- wire feeders with digital display. To improve comfort for the operators using the water-cooled guns, the feeder is boom mounted.
Operator Dave Bossardet reports that, “The system is really easy to use. The boom-mounted feeder and the Deltaweld's gun trigger hold definitely improve comfort. Otherwise, making a 3-ft.-long weld and trying to maintain a steady wire stick-out of 3/8 to 5/8 in. is just astronomically hard.”
While reliability and operator comfort are USFilter's top two criteria, Lake Welding Supply's Kragt says that, “Upgrading to the Deltaweld 652 will lower USFilter's utility by approximately $400 per year, per machine. Over the course of their life, the new Deltawelds will easily pay for themselves through energy savings alone.”
Kragt concludes that, “Many manufacturers and fabricators put off upgrading their equipment until a crisis occurs. It makes no sense to risk missing a deadline because of machine failure. Hopefully, the proven payback, efficiency and operator satisfaction offered by power sources like the Deltaweld and Dynasty will prompt people to upgrade before it's too late.”