On an average day, 450 log trucks rumble in and out of the woodyard at a paper mill in southeast United States. On a really good day, 600 trucks, each carrying 30 tons of pine or hardwood, queue up to be unloaded by one of two CAT® 990H wheel loaders or a 40-ton P&H portal crane.
The CAT wheel loaders were purchased in January 2010 to replace two log stackers. “The log stackers are good machines built well for unloading log trucks,” explains the mill’s woodyard superintendent. “It was more a reliability issue; they just would not hold up in our environment. The 990s were a Godsend. It was a nightmare when our old log stackers were our only machines.”
The woodyard superintendent is responsible for overseeing all activity in the yard from unloading log trucks to ensuring there are enough wood chips to keep the pulp mill well-fed 24/7. Basically, he’s got to keep the wood moving. “My biggest challenge now is making sure we have enough wood chips to feed the digesters of the pulp mill. We have to run very consistently, very reliably to keep the mill running,” he says.
Early in 2009 the biggest challenge was at the beginning of the process — getting log trucks unloaded quickly and consistently. “We would have problems with the log stackers. They would be down and trucks would back up for a half a mile out on the highway. We’d actually end up cutting trucks off for the day because we couldn’t get them unloaded because nothing was running,” he recalls.
Mill management decided to buy two new pieces of equipment. The main requirements for the new machines were: enough capacity to unload a log truck in one pass, stability to lift a full load off the ground without tipping and, of course, reliability. Bottom line, it was all about getting trucks unloaded and out of the woodyard in a timely manner.
Show and Tell
The team charged with determining what machine to buy included the mill manager, the procurement manager, the woodyard superintendent and a woodyard senior operator. They evaluated several makes and models of wheel loaders and log stackers. Besides the CAT 990, they also considered the smaller CAT 988 wheel loader. They still had a 1984 CAT 988B that had already gone through one rebuild and, at 100,000+ hours, now was used as back-up.
After doing their homework, they told their CAT dealer rep, Mike Farris with Thompson Machinery in Tupelo, Miss., that they wanted to go look. So Farris arranged for a one-day whirlwind tour on the company jet to several locations in Georgia and South Carolina to see both the 990 and 988 working in mills doing the same work they needed them to do — unloading 30-ton trucks and reclaiming wood off the ground.
The evaluation team concluded that the 988 could do the job unloading 60,000 lb. truckloads in one pass, but it would be working at close to its maximum tipping capacity of about 65,000 lbs. They were concerned that the machine wouldn’t survive its full life cycle working at the maximum every minute of every day. On the other hand, with a tipping capacity of about 90,000 lbs., the 990 could unload 60,000 lb. truckloads, with another 30,000 lbs. of available capacity to spare.
One mill they visited in South Carolina had two 990s. “The company shared its maintenance records that showed one of the wheel loaders had 30,000 hours and basically no down time other than a hose or two. That’s what the company was looking for — a machine they did not have to work on,” Farris says.
The senior operator was able to ride along with the 990 operator in the jump seat. “I could tell what the machine was capable of doing, just riding with him,” he says. “I didn’t actually unload a truck or handle any wood, but I did operate the machine just to get the feel of it and the functions.”
He asked himself if he would want to run the 990 on a daily basis. “Comparing it to all the machines I’ve experienced in my years at the mill, I thought this was going be a real nice machine — a lot easier to operate, a lot more comfortable,” he says. “The cab was roomy and all the controls were user friendly and handy.”
He especially liked the joystick operation compared to the steering wheel in the old 988 back in the woodyard. “The joystick just seems to give you more room in front. You don’t have that big steering wheel right there in front of you. And I feel like I have a little more control, too.”
According to Farris, by the end of the day, the mill team had pretty much made up their minds that the 990 was the machine size they were looking for.
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