Wouldn’t it be nice if a manufacturer offered a service program designed to supplement an asphalt producer’s routine maintenance plan — one that proactively uncovers the problem areas, which rob plants of production capacities and profit potential— a program that looks for ways to optimize plant efficiency and reduce operating costs and that provides a detailed report with a checklist of items inspected and component conditions?
How beneficial would it be for an operation to know that it is operating with the most up-to-date plant equipment and controls? Imagine the peace of mind that comes with an industry expert inspecting the plant and offering recommendations on what is needed to maximize plant uptime.
Terex Roadbuilding, Oklahoma City has put an end to this speculation with a first-of-its-kind Plant Audit program that targets optimizing plant efficiency and maximizing uptime. The manufacturers of Terex drum mix plants, formerly branded CMI and Cedarapids/Standard Havens, started this program in February 2005, and it is steadily gaining momentum with over 30 plant inspections completed to date.
These audits are beginning to show trends in common plant issues. “We typically find that producers are spending much more than they need to on fuel,” says Burl Wilkins, plant audit specialist for Terex Roadbuilding. “We’ve been able to save companies significant sums of money just by recommending adjustments to burners and improvements to airflow at the baghouse.”
No matter the age, size or type of asphalt plant, the new audit program will generate a report that details ways to improve plant performance and dependability. With more than 35 years in the asphalt industry, Wilkins has performed audit inspections on plants with only two seasons in the field and those with more than 25 years of asphalt production behind them. Small operators with only one or two plants along with national producers with hundreds of plants are taking advantage of the program.
Although developed by Terex Roadbuilding, the program is not limited to the Terex brand of asphalt plant. The audit technicians have ample field expertise to inspect the technologies from other plant manufacturers. They also run the full gamut of the various types of plants in the market, from counterflow and parallel flow drum mixers to batch plants.
These audits are especially beneficial for producers with mature plant technology that cannot keep up with today’s production demands or produce complex mix designs. For example, Wilkins cites an operation using an older parallel flow plant that wanted to increase the amount of RAP in its mix designs in order to save on rising liquid AC costs. “The company’s goal was to increase the amount of RAP to 25 to 30 percent,” he says.
However, this parallel flow plant with its wet-wash scrubber system could not handle the increase. At the 20-percent mark, the plant started producing blue smoke and fell out of environmental compliance. “The audit showed that it was going to cost more than it was worth to upgrade all the components to run high RAP content,” adds Wilkins.
This audit program has also helped producers to outfit their plants with the latest technologies and make upgrades to the drum mixers to meet anticipated production goals, while still maintaining environmental compliance. A number of audits have been completed in the southern states, as producers seek to ensure their plants are operating at peek efficiency to supply the increased asphalt demand from contractors repairing the damaged roads along the hurricane-ravaged Gulf Coast.
Conducting the audit
The onsite auditor is just the program’s visual helm of a full support staff that consists of engineers, parts specialists and company management. Together there is more than a century of asphalt production experience behind the Plant Audit program.
“It’s not the auditor’s job to know and do everything,” explains David Emerson, Terex Roadbuilding’s director of product management. “There’s a talented team here to support him.”
A full day process, the onsite audit begins before the start of the day’s production and ends after the last load of hot mix has been delivered. The systematic process includes hundreds of component inspections from the conveyors and idle bearings to the drum mixer and storage silo. “I like to start at the cold-feed bins and work my way through the plant,” says Wilkins.
At the bins, he checks for adequate storage capacity and inspects the liners, dividers, extensions, vibrators and air cannon. According to Wilkins, “One of the most common recommendations at the bins is for a liner replacement.”
From there, the inspection covers the belts, belt wipers, idlers, and drives and continues through the aggregate and RAP screening and weighing systems. Moving forward, the auditor comes to the heart of the plant and one of the most critical inspection points, the drum mixer.
External drum inspections include the tire mounts and drive trunnion, chains, sprockets, and assembly as well as the drum auger, shell thickness and slinger feeder. Additionally, the auditor inspects the inside of the drum to look for, among other items, flight problems and liner wear.
With today’s rising natural gas and fuel oil costs, the exhaust gas analysis performed by the auditor offers a huge benefit for the producer. With this exam, exhaust temperatures are compared to mix temperatures. “We want to see the exhaust at or below mix temperatures,” comments Emerson. If exhaust temperatures are higher, fuel is being wasted.
Adjustments can be made to the burner and flights to correct this problem, which saves producers money every day the plant is running. According to Wilkins, “We have saved producers 5 to 10 percent in fuel costs alone with this analysis. With today’s high prices, this is significant.”
Another hot spot for inefficiencies is the baghouse. Auditors thoroughly comb through the bags to check for plugging and remaining service life. They also inspect airflow pressure along with the shell thickness, screw auger and hanger bearing performance. Emerson states that airflow problems are related to poor baghouse performance and achieving the right airflow can improve combustion efficiency by as much as 25 percent. Switching exhaust fan motors on the baghouse remains the biggest energy savings potential the auditors have uncovered to date. Most plants will have one or two 200 horsepower, constant-speed motors running at full tilt to power the fans. The installation of energy efficient, variable speed motors that run only as fast as and when necessary have generated significant savings for producers. At today’s energy prices, most operations can recover the cost of variable speed motor installation within a single season.
The audit concludes with detailed inspections of the rest of the plant components, including the controls package. “Control software is continuously being updated to help increase plant operating efficiency,” says Ken Cosby, Terex Roadbuilding’s manager of computer controls. “This is one of the first items outdated on a plant.”
Upon returning to the factory, the auditor shares his findings with a team of specialists that includes plant engineers, technicians, parts personnel and managers. In roughly a two-week time frame, the team analyzes the findings to develop a series of recommendations, a parts needs list and upgrade cost estimates. “All recommendations are based on the premise optimizing of plant production and maximizing uptime,” says Emerson.
The final recommendations are compiled into a 16-page report that is personally delivered to the customer. “This is probably the most important step in the audit program,” comments Wilkins. “Delivering the report in person allows us to answer any questions the customer may have and explain how we came to our conclusions.”
To ensure that a producer is committed to improving plant efficiency, there is a minimal charge for the onsite inspection and final report. The report can be used to help generate or expand upon the customer’s daily, weekly, monthly and yearly inspection and maintenance programs. Once the report is delivered, the customer is not obligated to buy the plant parts from Terex Roadbuilding.
But for Wilkins, the new Plant Audit program is not about component or parts sales. “This program is a proactive drive to ensure the customer is aware of the latest technology on the market, so it can produce asphalt more efficiently.”
Information provided by Mark Spicer and Mike Rodriguez of Terex Roadbuilding.