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Web Exclusive: Baking in the desert
June 1, 2009Super-high temperatures at a desert operation force processing equipment to show its mettle.
Edited by Darren Constantino
For the most part, being an asphalt and concrete recycler in the Phoenix area is as good as it gets. Warm temperatures, low humidity and an economy that seems impervious to downturn are all elements for success. When those temperatures exceed 110° for extended periods of time, however, key processing equipment such as crushers and screens can be stopped cold. For Mark’s Valley Grading & Excavating, a combination of wise equipment purchases and a comprehensive maintenance effort has helped make certain that doesn’t happen. The success of those efforts was proven last summer when the firm operated without downtime during a 48-day span of 110+° days.
Established about 22 years ago, Mark’s Valley provides a broad range of services in and around the Phoenix area. According to site foreman Steve Rhodes, the company’s name belies its capabilities.
“We do grading and excavation, but we also do a good deal of residential and commercial demolition, removal of pads from housing and large buildings, and more. That type of work obviously produces a sizable volume of recovered concrete and asphalt, which prompted our owner, Mark Haight, to establish a site at which we could stockpile and process material from our own projects.”
That was about three years ago, but Rhodes said the effort has been so successful today it is a full-fledged material-recovery facility called Contractor’s Landfill where material is taken in from area contractors and made into usable product.
But it’s a dry heat
Under most circumstances, the recycling site operated by Mark’s Valley is similar to those found elsewhere. The firm takes in concrete debris and asphalt from throughout the area, does a bit of pre-processing when necessary, and feeds it to a Construction Equipment Corp. (CEC) impact crusher/screen plant to create product.
“The overwhelming majority of what we make is base material for use in road work, general construction, pad work and so on,” Rhodes said. “The CEC [plant] is set up with 1.25-in. screens for creating the base material. Then all the fines — we generally use dirt — are added to meet the desired Maricopa Association of Governments specifications. The processing itself is fairly typical of what you might find anywhere else in the country. What sets us apart are the operating conditions, and that’s where the reliability of the equipment comes in.”
Rhodes cites a period last summer in which temperatures got as high as 122° during the day and on many occasions barely dropped below 100° at night. Severe even by Phoenix standards, the conditions lasted for more than a month and a half.
“It was an unbelievable stretch,” he said. “It’s hard to believe equipment can even run in that kind of heat, let alone do something as tough as crushing and screening rock, but our system never let us down. The units are equipped with high-volume radiators, which kept things under control, but we still had to constantly check the onboard indicators to monitor water, oil and hydraulic fluid temps.
Rhodes said, “In a situation like that, the biggest thing we can do to beat the heat is get as much processing done in the early morning hours as we can. So it’s not unusual for us to start getting things going at 4:00 a.m. and have almost a full day’s processing in by the time most people are breaking for lunch.”
Inside the iron
The primary system in place at Contractor’s Landfill features a CEC model 133 x152 impact crusher feeding a 6 x 16 Screen-It dual-deck screen plant, also from CEC.
“On average, we regularly crush 300 tons of concrete an hour through the plant,” Rhodes said. Rates for ground, screened asphalt, because it is a softer material, will be a bit higher, pushing the 350-400 tph range. So with average conditions, we can easily do 2,000-2,500 tons of material a day.”
In addition to the main crushing/screening spread, Mark’s Valley has a CEC Track Screen-It plant with twin 5 x 12 screens through which the company makes several products; everything ranging from track out rock, to 3-6-in. rip rap, to topsoil blends. Mark’s Valley also recently added another crusher to process river rock prior to sending it to the impact crusher to make their base material.
“The crushers and screens are our bread-and-butter equipment,” Rhodes said. “Other than the support vehicles such as loaders and trucks, the only other specialized equipment we have is a pair of excavators with concrete pulverizer attachments on them that we use to crush large concrete debris and free up any rebar. Ultimately, it’s all about getting it small and sized right.”
Holding down costs
In severe conditions like those experienced last summer, efforts made in the design of the crushing and screening equipment to minimize maintenance-related downtime really pay off. According to Howard Glemming, CEC’s area sales representative, those efforts can start with something as basic as designing the crusher’s blow bars for easy top-load replacement.
“While we maintain a nice inventory of replacement parts, CEC has also worked hard to standardize replacement parts for the customer’s convenience,” he said. “Hoses and connectors, for example, can be purchased at any major auto parts supplier in town. So now, if a hose breaks, the customer can simply call the store, tell them the length of the hose and the size of fitting, and be back up in no time.
“Also, the manufacturer has done an excellent job of reducing screen-cloth costs, again through the design of the Screen-It unit itself. The angle of the screen deck is relatively steep, reducing the likelihood that material will bounce high off the deck surface and cause excessive wear. These, and other features have kept costs – and production interruptions – down,” Glemming said.
Today, Mark’s Valley works throughout a 75-mile radius and employs more than 120 people company-wide. The Contractor’s Landfill site has become an important supplier of base material to area contractors.
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