Quality Control Is the Way to Go

Particle size analyzer gives pavement aggregate production an easy passing grade.

The best pavement is produced when you start with the best raw material. It makes sense, doesn't it? A reliably conforming raw material that maintains a consistent size and texture promotes greater process efficiency, which results in a higher quality product. In the aggregate business, there is a trickle down effect. A quality aggregate enables contractors to build smooth, durable pavement. And since a large percentage of motorists quickly tire of maneuvering around pothole-crowded avenues, smooth, durable pavement is a highly desired outcome.

Across the board in manufacturing, the emphasis on quality is leading to innovative technology, streamlined processes and best practice methodologies that are revolutionizing how things get done from start to finish. Toward that end, the Gradex 3000 particle size analyzer is a fully automated machine that makes the journey to quality pavement a smoother ride for the aggregate production industry.

It significantly reduces the amount of time to conduct tests and with greater accuracy due to computer controlled measuring and reporting functions that remove technician errors. Faster, more precise, and at less cost — it's taking quality control in the aggregate industry to a whole new level.

For Dan Crago, environmental and quality control manager at Valley Asphalt Corp., Cincinnati, OH, purchasing a Gradex 3000 from Rotex, also located in Cincinnati, was a smart investment from both a financial and quality control point of view.

"Investing in this unit was at first a simple matter of economics for me," says Crago. "It allowed my testing lab to conduct quality control tests on aggregates in a fraction of the time it used to take with standard testing. It didn't take long for me to do the math and realize the value this offered our quality assurance program. And when I considered all the other benefits the unit offered, it was simply a no-brainer."

Quality control = mandate for precision

Often, a competitive marketplace drives the incentive for quality control. The better, faster and more efficiently you're able to produce a product, the higher the quality of product that you have to sell and the more product you have for customers to buy. But other rules and standards also apply. And generally, the government makes sure that everyone plays according to the same rules.

In the case of asphalt, the state government maintains a specification book detailing the size requirements for every aggregate produced in Ohio. At one time, the state department of transportation assumed a major role in testing aggregates to insure that producers met specifications. But this has slowly changed and now contractors are expected to perform most of their own testing. Therefore, those manufacturers that can test quickly and efficiently, and produce the most finished material at the highest level of consistency will have the greatest competitive advantage.

For companies like Valley Asphalt and its subsidiaries that produce aggregates for a regional territory that includes Southwest Ohio and extends into Kentucky and Indiana, quality control is a matter of constant vigilance.

"We produce aggregates at 16 different sites and each one is manufacturing as many as five different materials," says Crago. "Up to eight of those sites may require testing on any given day, which means our lab might test up to 40 different materials daily."

Companies like Valley Asphalt also deal in huge quantities. A single plant may produce an average of 400 to 500 tons of material an hour. Typically, the plants build stockpiles of material for customers, which may amount to 3,000 to 5,000 tons of material in one day. Therefore, ongoing testing — generally a minimum of two tests per week for each material — is an important part of quality assurance to insure that the material meets specification.

"We don't want to make 10,000 tons of material during the week and then discover it can't be used because it doesn't meet the state's required specification," says Crago. "That kind of waste would have a very negative economic impact on our company's bottom line. This unit has been an effective tool in making certain that doesn't happen."

Goodbye old, hello new

In spite of this new innovative technology, many aggregate companies today still use a manual testing process. This typically involves loading aggregate samples in a nest of six to eight screens, which can take 10 to 15 minutes to weigh out the material. Then, when the machine is done shaking, the screens must be taken apart, the aggregate individually weighed, and the data manually recorded. Not only is the entire process labor intensive, it presents a greater chance of human error when recording the data.

In contrast, the Gradex 3000 takes only two to three minutes per test to set up. It utilizes a stack of standard 12-inch round test sieves that can be easily changed to suit specific test requirements and provides the same rotary shaking/tapping motion as manual sieve shakers. It allows for individual or multiple samples to be loaded, and it automatically classifies and weighs each sieve fraction, calculates and stores weight values and reports the data to a PC or controller, which virtually eliminates human error when transmitting data.

"I can't imagine going back to the old way we used to test our material," says Crago. "I'm able to conduct more tests with fewer people and a greater level of accuracy. And when I factor in the number of tests we perform and the amount of time we save, this unit will pay for itself in less than a year."

Greater flexibility for many applications

Because sieve analysis takes place in many different environments, the Gradex 3000 has been designed to provide the greatest level of flexibility.

Windows-based software makes it user friendly and easy to operate by offering preset test configuration files for the operator to choose from when setting up for tests. Test results can be printed in standard and customized reports so that data can be presented in a variety of formats.

It's AutoFeed function allows you to load multiple samples and perform continuous testing. This may involve the same sample or six different ones that can be individually programmed. And once setup is done, the operator is free to perform other work, which allows multi-tasking and promotes a more efficient use of time.

Furthermore, the unit can be located where it delivers the greatest benefit. For example, because it is automated, it can be set up and used in the test lab or any other environment where a standard PC can be operated.

An on-board controller feature allows it to be used in environments where PC operation is not practical like plant floors, shipping docks or around hazardous materials. Results can even be transmitted to a remote PC through an RS-485 interface to insure that data is routed to wherever it needs to go. A final control system option includes a freestanding console that serves as an operator workstation and houses the PC keyboard, monitor and printer as well as its own cooling fans.

"The flexibility we've achieved with this unit has revolutionized our aggregate testing and made us much more efficient in how we work," says Crago. "Rather than us having to flow our work habits around a procedure, it allows us to fit the procedure around our workflow. Any aggregate producer interested in improving its testing speed, accuracy, and cost efficiency should seriously consider adding this unit to its quality control program."