Engine-Driven Welding Generators Matched with Inverters Save Contractor $7,000 per Service Truck

Engine-Driven Welding Generators Matched with Inverters Save Contractor $7,000 per Service Truck

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K.S. Mechanical combines Miller Electric Mfg. Co.'s PipePro™ 304 with XMT® 304 inverters and Spectrum™ 2050 plasma cutters to build aggregate processing plant.

Executive Summary:

  • Engine drive with strong, simultaneous welding and generator power creates two-arc system.
  • $7,000 saved per truck by adding inverter instead of a second engine drive.
  • Generator power allows second operator to run 300-amp welder or 55-amp plasma cutter.
  • 12 kW generator sufficient to start/run 1- to 5-HP motors, eliminating need for standalone generator.

Contractor Relies On Miller Products For Large Sand and Gravel Project

An Ice Age ago, just east of Los Angeles, mountain streams flushed massive amounts of rock and sand down the San Gabriel Mountains. The rushing water slowed as it reached the foothills, depositing its rich load of sediment near what is now historic Route 66 in Irwindale. Today, Vulcan Materials Company's Reliance Rock plant sits on this ancient alluvial fan. Millions of tons of "24-inch minus rock" are in reserve, but the rock has no value until it is removed and processed. As a preferred vendor for Vulcan, Ken Stiles is one of the men who will make that happen.

President and co-owner of K.S. Mechanical, based in Romoland, Calif., Stiles has more than 25 years of experience in the sand and gravel business. He started driving a tractor on the family farm while in grade school. Since then he's worked on the back end of a shovel, operated and serviced the equipment and started his own contracting business.

A New Plant

The work at Vulcan exemplifies the range of services that K.S. Mechanical provides. Stiles, Mark Reimers, the job superintendent, and 12 other K.S. Mechanical associates are in the process of erecting conveyors, crushers, screens, washing equipment, piping and clarifying tanks. This equipment will separate rock, gravel and sand into specific sizes and ready it for use in the concrete and asphalt industries. The job started on March 18, 2002, and was scheduled for completion last October. However, because K.S. Mechanical is one of a limited number of contractors that meet Mine Safety Health Administration (MSHA) standards, the job continued into 2003.

Mark Reimers (left), job superintendent, and Ken Stiles (right), president of K.S. Mechanical, check out a screen tower.

"Because of our MSHA approval, we also end up working on a lot of strange add-on projects, such as bathroom work or stud-welding bed liners inside a massive Komatsu haul truck," says Stiles. "Most of our projects take three to four weeks using one to three welding machines. The work here at the Vulcan Reliance is exceptional."

The Vulcan project is so large because the company's current processing plant sits directly on the richest reserves. By building a new plant in the already-excavated, half-mile square pit and then removing its old plant, Vulcan will gain access to material that will last for decades.

Equipment List

To build the new plant, K.S. Mechanical's skilled crew "will use all types of equipment: cranes, man baskets, telescoping reach lifts and, of course, welding machines," says Stiles. As a base for its large service trucks, which carry welding and other equipment, K.S. Mechanical uses 32,500-lb.class trucks from International Truck & Engine. These oversized trucks (compared to what most contractors use) stand up to the rough work that has sent lighter-duty trucks into early retirement. They also lock completely to protect the truck's contents.

"We've equipped four service trucks with two of everything: two people, two grinders, tPlasma Cutterswo torches and two welding machines. It's basically a doubled-up truck so we can get more accomplished," says Stiles.

While the truck may be doubled up, each truck carries only one engine-driven welding generator: the PipePro™ 304 from Miller Electric Mfg. Co. This engine drive has a 5- to 400-amp welding output and 12,000 watts of continuous generator power. Even when welding at 150 amps - more than enough to run the 1/8-in. diameter E7018 Stick electrodes K.S. Mechanical operators use - the PipePro still has 9,500 watts of generator power to spare.

K.S. Mechanical uses that extra generator power to run Miller's XMT® 304 or a Spectrum plasma cutter (both lightweight, inverter-based machines), a grinder and the most important item of all: Mark Reimers' microwave oven during the lunch break.

For applications that require generator power while welding, the PipePro is Millers premier machine. This lets K.S. Mechanical equip its trucks (left) with two men and one engine drive each.

"Our trucks are capable of hauling two welding generators, but who in their right mind would want to service and maintain two engines instead of one?" says Reimers. "If I can have one engine drive and power two welding arcs with it, it doesn't take a rocket scientist to figure out that our maintenance costs are cut in half. It's a smart business decision."

Diesel engine drives in the PipePro's class have a list price of more than $10,000. By adding an inverter, which sells for about $3,000, instead of a second diesel engine drive, K.S. Mechanical saves more than $7,000 per truck. It also gains numerous advantages not possible with other welding machines.

"Every operator, bar none, loves the XMT inverter's arc characteristics," Stiles says. "Furthermore, it's easy to set up, dependable and light (76 lb.). We can take the inverter and bring it 5 or 10 stories high in a rock plant and plug into the plant's electrical power, then the next day we could be running it off the engine drive. The versatility of an inverter is just astronomical."

Uniform Size

The material the Reliance Rock plant works with is called "24-inch minus rock." This means the largest rock has a diameter no greater than 24 in. and the smallest material is sand. After a giant dragline sled scrapes the side of the pit (see photo) to loosen material, a front-end loader dumps material into a jaw crusher. The crushed rock is screened and large rock goes into a second crusher; sand goes past the second crusher into a surge pile along with the crushed rock.

From the surge pile, material goes to screen tower 1, which segregates the large rock from the smaller rock and sand and then sends the larger rock to the tertiary crushers. Smaller rock and sand will go to tower 4. The tertiary crushers crush the rock and send it to screen tower 2 and, if it meets the criteria for the respective sizes, it gets sent onto screen tower 3; otherwise, it is crushed again. Together, the screen towers produce sand and rock of uniform size.

"We don't do the concrete slab and electrical work, but other than that, K.S. Mechanical will erect, refine and perfect all four towers," says Stiles. Most of the tower's steel is W10 I-beams and angles (10-in. wide, weighing 45 lb. per foot), 1/4-in. thick steel, diamond plate for the decks, thousands of grated steps and miles of 2-in. diameter steel tubing for the handrails.

"Most of our welding comes on the hand rails and deck plates," Stiles says. "For the deck plate, we'll weld continuously for 6 in. at the end, and for the middle we'll weld 2-on-6 or 4-on-12 (e.g., weld 4 of every 12 inches of plate). Given that we get a breeze almost consistently in the afternoon that would blow away the shielding gas, MIG welding just hasn't panned out. Unless customers specify a particular flux cored wire, we stick with a E7018 electrode for outdoor welding."

Generator Power

In addition to uniform rock size, the concrete industry needs its sand and gravel washed. With both land and water at a premium in the L.A. area, tapping a mountain stream and sending dirty water to a large holding pond is not practical.

Instead, K.S. Mechanical will erect a clarifying unit and fresh water tank from Phoenix Process Equipment. The clarifying tank has an outside diameter of 59 ft. and holds 330,000 gallons of used wash water. To reclaim this water, huge rakes (paddle-like structures) turn at 1 rpm in a clockwise direction. Like a giant centrifuge, this concentrates mud in the bottom of the tank where it can be conveniently pumped out. At the top of the tank, clean water washes over serrated edges and moves into the holding tank for reuse.

Using a Miller XMT 304 powered by the PipePro welding generator, a K.S. Mechanical operator Stick welds on one of four screen towers that produce sand and rock of uniform size for the concrete and asphalt industries.

Even though the rakes are bolted to the center pivot, these 3/4-in. thick steel plates must be multi-pass welded to ensure the rake doesn't come loose.

"A loose rake in a tank full of mud is the worst possible thing that can happen," says Stiles, speaking from experience. "You have to drain the tank, climb in and dig it out by hand. It's shoveling a muddy mess."

When building the clarifying unit, K.S. Mechanical needs to turn the rake to ease assembly, align the rakes and to test it. A 5-HP motor turns the rake, while a 1-HP motor raises and lowers it.

However, during construction, "This whole area of the pit is electrically dead. There is no power down here other than what we generate," Stiles says. "As opposed to bringing in a regular generator, which would add to our costs, we powered both motors with the PipePro's generator power."

"The generator power of the PipePro keeps working for us," says Stiles. "Since come-alongs are too slow and too short-stroked to effectively move beams and chute liners, we have a 220-volt winch on the truck, powered by the engine drive, that lets us move them 100 ft. at a time. We also use generator power to run capstans and belt-spoolers (a giant reel to spool the long conveyor belts when they are removed). It seems like everytime we turn around we find another use for generator power. If it's electrical, we'll run it off the PipePro."

A Good Partner

Compared to other contractors in the business, K.S. Mechanical has an advantage beyond individuals who know the sand and gravel business inside and out: namely, Ken Robinson, sales manager at Airgas' Corona, Calif., store (Airgas is a welding supply distributor).

"Ken is very knowledgeable and has worked in the field," says Stiles. "Consequently, he knew what I was looking for. I was contemplating another couple of Miller's Big 50 Diesel™ engine drives, and then Ken calls me up out of the clear blue and tells me that the PipePro is what I needed for the best welding and simultaneous generator power."

Pound-for-pound, the PipePro and its conventional technology cousin, the Trailblazer® Pro 350 D, provide more generator and welding power than any other diesel engine drives available.

Although the PipePro is the world's most advanced welding machine, Stiles did not hesitate to make the purchase.

"I have no regrets about going with new technology because I trust that Airgas and Miller will take care of me," Stiles says. "In fact, warranty issues are the big reason I switched to Miller. With my old machines, I couldn't get parts quickly, couldn't get them fixed correctly and the manufacturer never responded to my letters. Since they didn't call me or talk to me, I solved the problem - I started buying Miller's."

For more information about the PipePro 304, Miller XMT 304 and Spectrum 2050 plasma cutter, visit MillerWelds.com or call 1-800-4-A-MILLER.

Updated: May 12, 2020
Published: April 1, 2007