Weir Slurry North America, a pump manufacturer, converted to pulsed MIG for its welding requirements. The result for them was a rapid recovery of their machinery investment because of energy savings, increased productivity, and lower consumable costs.

Kevan Kokkonen, district manager, Miller Electric Mfg. Co.

Weir produces state-of-the-art, heavy duty slurry pumps for a range of abrasive and corrosive services, including mining, power generation, paper mills, and other industrial applications.

Welding applications at Weir involve the design and fabrication of pump accessory parts, including the bases upon which the pumps are mounted. These are machined from A36 mild steel and vary in thickness, from thin gauge to heavy plate, based on the customer's needs. The bases range in length from 3 - 10 ft. and in width from 24 in. - 8 ft.

What if you were told that buying new welding equipment could improve your shop's productivity and efficiency so much that your savings on energy, maintenance, and consumables would pay for the new equipment in about six months? Somebody did tell that to Weir Slurry North America, Madison, WI, and it actually happened.

Like others switching to energy-efficient inverters, Weir found that using them not only saved money in energy and consumables — helping them re-cover the cost of the equipment — but also increased productivity, cut maintenance costs, and improved weld quality for operators at all levels.

Weir Slurry North America
Weir Slurry North America is a division of The Weir Group PLC, a UK-listed engineering company. Weir produces state-of-the-art, heavy-duty slurry pumps for a range of abrasive and corrosive services, including mining, power generation, paper mills, and other industrial applications. The company manufactures pumps under the names of Warman, Galigher, ASH Pump, and Hazleton. Weir also manufactures other equipment such as cyclones and knife gate slurry valves.

Everyday welding applications at Weir involve the design and fabrication of pump accessory parts, including bases upon which the pumps are mounted. These are machined from A36 mild steel and vary in thickness, from thin gauge to heavy plate, based on the customer's needs. The bases range in length from 3 to 10 ft. and in width from 24 in. to 8 ft. All welds are horizontal — mostly T-joints — to increase weld strength, and must meet USB 1 code.

Weir has been a customer of AGA Gas in Madison for more than 15 years. During that time, AGA sales representatives have developed great relationships and a deep understanding for Weir's equipment needs.

And, in fact, it was AGA's representative that recommended the inverters that Weir decided on. "We came in with something that we thought they would benefit from," said Rick Block, AGA's local representative. "Weir took it upon themselves to work with them, and they've done a good job in educating and training with their employees to make their selection a success."

Inefficient Welders Cost More
"Working with both manufacturing and purchasing, we were looking for creative ideas to reduce costs," Block says. "We met our goal through reduced filler metal costs, increased productivity, reduced cleanup after welding, fewer reworked weldments, greater power source efficiency, and reduced MIG gun consumables. The operators took to the pulsed MIG process because of its favorable over-all welding characteristics."

What the folks at Weir decided to try were two new pulsed MIG welding systems featuring the XMT 304 multi-process power source from Miller Electric Mfg. Co., Appleton, WI. The units offer easy-to-use controls and built-in programs.

It's a Clean Machine
Historically, older machinery breaks down more often. This can be caused by many factors related to use, including worn out or broken parts, dirt or mishandling, or the machine simply being past its prime. It is quite common for breakdowns to occur due to dirt, dust, and other contaminants. These affect the machine's internal components by entering it and wearing down parts.

To combat this, the Miller units offer Wind Tunnel Technology, which shields the internal components from external contaminants, helping to reduce maintenance and increase productivity the units' productivity.

"I've seen older welders that we've taken apart and how dirty and grimy they get," says Al Larson, Weir's weld and fabrication team leader. "I can see where Wind Tunnel Technology will help us reduce maintenance and cleaning time on the machines. They pretty much keep themselves clean."

Energy Efficiency
Compared to more modern units, older welding equipment uses more energy because it converts incoming line power to welding output at only 60 to 70 percent efficiency. Inverterbased power sources convert power at an average of 85 percent efficiency, reducing utility bills.

Another problem with older welders is erratic output, which can cause problems such as poor weld quality and excessive spatter. One of the biggest downfalls Weir found with its older welding equipment was spatter, which required significant clean-up time and quite often left too much re-work, thereby hurting productivity. The incorporation of new welding equipment successfully addressed this problem.

"Some of the guys were literally spending hours just trying to clean up the spatter," Larson says. "We tried different types of spatter spray and it was still difficult to get our operators set up for less clean-up. We ran a test between the new units and the previous ones we were using. We timed it from start to finish, including cleanup, and the new equipment performed 22 percent faster with 40 percent less clean-up time, and an overall decrease in production time from start to finish of 30 percent."

Inverters Pay for Themselves
In many cases, companies can re-cover the cost of new welding machines in a relatively short time, generally within one to two years.

"When we purchase new machinery we have to do a cost justification," Larson says. "And one of the justifications for buying the XMT 304 was that it would pay for itself within six months." Although the savings come mainly from the productivity increases and power source efficiency of the new equipment, Weir also found that using the newer equipment was saving on consumables, including contact tips, nozzles, and diffusers.

"Before, we were changing nozzles once or twice a week due to the spatter," Larson says. "One of the new machines has been running for more than two months and we still haven't changed the nozzle. It's a little worn, but you can't see it in the weld bead. The guys are still getting plenty of gas from it. It's fair to say we've reduced our costs in consumables by nearly 50 percent all around."

Why Pulsed MIG Welding?
Prior to using the pulsed MIG features of the new equipment, Weir's nine welding operators were predominantly working with spray transfer. Pulsed MIG, also called pulsed spray transfer, improves the spray transfer process by pulsing small droplets of filler metal across the arc at a controlled time in the welding cycle. The pulsing occurs because the power source switches welding output rapidly between a high peak current to a low background current. The peak current pinches off spray-transfer droplets and propels them toward the work piece for good fusion. Because there is no metal transfer during the background current, the weld puddle has an opportunity to freeze, as opposed to spray transfer where molten drops are continuously transferred.

Pulsed MIG was a better choice for Weir because it maintained high metal deposition rates and good fusion while increasing welding speeds. In addition, pulsed MIG's lower required heat input helped weld a wider variety of metal thicknesses with a single wire diameter, helped with out-of-position welding, and created a higher quality, more attractive weld.

The XMT 304
Weir became interested in testing the XMT 304's pulsed MIG capabilities at a product showcase held by AGA Gas, Inc.

"Rick suggested we bring some of our guys out to test this new XMT 304," Larson says. "The guys liked it, so we got Rick to bring one in for a demo test and then we purchased two new units."

The XMT 304 CC/CV model delivers a smooth and stable arc in all welding modes within its 5 to 400 A welding range (300 A at 60 percent duty cycle). It can perform Stick, TIG, pulsed TIG, MIG, pulsed MIG, and air carbon arc cutting and gouging. Its digital volt and ammeters insure operators are welding at desired parameters. The unit weighs 76 lb., is por-table and, coupled with running gear, makes for good equipment for welding anywhere in Weir's shop.

"The newer equipment is userfriendly," Larson says. "We have a couple less experienced operators, and putting them on these machines allowed us to bring them along faster."

The efficiencies Weir realized with these units have earned Weir the attention of a sister company in Sydney, Australia, after a worldwide convention of Weir's slurry pump operations managers was held in Madison.

"We had all of our worldwide mineral counterparts here for a plant tour, and the one from Australia re-ally liked the welders," said Larson. "I've already forwarded him a copy of our cost justification."

WHY PULSED MIG? Pulsed MIG, also called pulsed spray transfer, improves the spray transfer process by pulsing small droplets of filler metal across the arc at a controlled time in the welding cycle. The pulsing occurs because the power source switches welding output rapidly between a high peak current to a low background current. The peak current pinches off spray-transfer droplets and propels them toward the work piece for good fusion. Because there is no metal transfer during the background current, the weld puddle has an opportunity to freeze, as opposed to spray transfer where molten drops are continuously transferred.

For additional information contact Miller Electric Mfg. Co., Appleton, WI. Ph. (920) 734-9821; Fax ((920) 735-4013; or visit www.millerwelds.com