Checkweigher increases accuracy and productivity

Rinker Materials Corp. is one of the largest producers of bagged cement, ready-mix concrete and concrete block in the U.S. Its cement terminal in Port Everglades, FL, is a major packer and supplier of bagged cement and bulk products. Rinker wanted to increase cement production at their Port Everglades terminal by improving the efficiency of production and the weight consistency of their cement bags. They were looking to set up a system that would help their packaging process run smoother and produce bags that were even closer to their target-weight goals, while providing the safest environment possible for their employees. The requirements included an in-motion checkweigher, data collection software and a packer upgrade.

When asked what first inspired Rinker to look for a checkweigher for their terminal, Juan Alvarez, who was terminal manager at Rinker Materials at the time of this project, says, "We were looking to increase our production rate, and safety was another main reason. We were using manual labor to determine the weights of the bags. This required us to stop the process and have someone pull a bag and put it on a scale to check the weight. We were checking bag weights every thirty minutes, which was difficult for our workers and took away from production time."

Thompson Scale Co. (www.thompsonscale.com) , in conjunction with Choice Bagging Equipment (www.valvebagfiller.com) , had already developed and successfully installed electronic upgrades in Rinker's sister plant in Miami, as well as at several other companies in the same industry. This made Thompson Scale and Choice Bagging obvious vendors for this upgrade, says Alvarez.

The small amount of space available in the existing conveyor line made installation of a checkweigher a real challenge. Normally, heavy-duty checkweighers require about four feet of linear space to properly weigh a bag. Rinker only had three feet in which to install the unit. They also needed a product rejector powerful enough to remove off-spec bags from the production line, yet able to be located within the same space. The bag-flattening incline conveyor in place immediately following the checkweigher would also make it more difficult to obtain accurate bag weights. The immediate slope at the infeed of the incline causes the bags to create a downward force on the checkweigher as they go up the conveyor, potentially altering the readout. "We only had a small amount of space available between the turning conveyor and the bag-flattening conveyor. This made the addition of a checkweigher more difficult," says Alvarez.

To assist in targeting their optimum bag weights, Rinker knew they would need data collection to analyze weights and generate reports. These reports would be a valuable source of data, assisting management in making informed decisions. The challenge with this phase of the project was that the management office is located in a different building than the packing warehouse. To complicate matters, the road between the two buildings is a heavy traffic area for semi trucks. Any cables would have to be hung high overhead or dug into the ground, which would be expensive, says Alvarez.

The four-spout impeller packer used by Rinker has the spouts on close center-lines, which presented several engineering challenges. The loadcell flexure assemblies would have to fit into an extremely restricted access area. A fill spout and product cutoff assembly needed to be designed to place the fill spouts in exactly the same position as the old mechanical system, so that the existing automatic bag placers and takeaway conveyors could be used without modification. The product cutoff assembly would also have to be designed to eliminate product spillage, yet keep the fill nozzle and spout from plugging between fills.

To meet these requirements, Thompson Scale installed a Model 4693 heavy-duty checkweigher and StatPak-PC real-time data collection and reporting software from its wholly owned subsidiary, Telemetry Solutions Co. (www.statpak-pc.com) . Thompson Scale also upgraded Rinker's cement packaging machine. "We have another terminal in Miami that has a couple of these checkweighers installed, and we are very pleased with their performance," says Alvarez.

The 4693 checkweigher, with weight ranges from 1 to 500 lb and production rates in excess of 50 units/min, is specifically designed for the harsh, abusive, dirty environments commonly found in the cement, concrete, soil, bark and carbon-black products industries. Conveyor belts are laced and include a V-guide for positive tracking. The checkweigher uses a single S-Type loadcell in an extremely accurate flexure-scale base residing below the conveyor.

Thompson Scale met the lack-of-space challenge by designing a unique, compact checkweigher with a space-saver reject ram. The smaller-sized 4693 unit still provides the same accuracy, features and functionality of a full-sized unit, along with extremely fast weighment cycles to meet the application requirements. The innovative reject device is built onto a support that is isolated from the scale, yet places the reject pusher plate directly at the discharge end of the scale. The plate is suspended from an oversized, rodless cylinder capable of ejecting an off-spec bag and returning to the home position before the next bag enters the scale, even at high production rates.

Helping make this installation possible, a photoeye on the checkweigher quickly terminates the weight, which allows for more accurate weighing in such a tight space. This also assists the bag-reject system by obtaining the weights quicker than normally possible.

Another feature of Thompson Scale checkweighers are their easy-to-use controllers. "The checkweigher controller is very simple for our operators to use. There are even additional functions available that we could also use if needed," says Alvarez. These include options such as settable filters and bilingual menus, as well as the ability to store 75 different product types and to display errors for mechanical and system faults.

An important part of Rinker's production process is the real-time data-collection and reporting software system that they wanted installed. With its concise design and powerful reporting tools, Telemetry Solutions' StatPak-PC system allows users to easily view production data on a PC, so they can quickly and easily adjust production to optimal levels and analyze production flow over a period of time. "We installed the system to double-check the paperwork that the bagging employees submit by comparing it to the production rates we show in the system to monitor performance in the terminal," says Alvarez.

The software proved to be easy to install, configure and use. A wireless modem was set up to transmit data to the PCs in separate management offices without incurring the additional expenses of running cable. This worked very well, even with the heavy truck and plant radios used throughout the day, says Alvarez. Data was flawlessly received without running any wires.

StatPak-PC monitors 100 percent of production in order to track production rates. "We bag throughout the week, and we monitor production rates at the close out of each day by running a report from StatPak-PC," Alvarez adds. Everyone from line operators to experienced production supervisors and corporate management has access to the information they need to help them make more informed decisions that have an effect on the profitability of the company.

Thompson Scale upgrades filling machinery from counterweights and manual controls to a system with automatic controls and a loadcell for more efficient use of older technology. The company worked with Choice Bagging Equipment, which was involved with the design of a number of mechanical parts, mechanical fabrication, installation and startup of the filler upgrade. Thompson Scale provided the controls and technology to complete the upgrade process.

"The machines were getting old and required a lot of maintenance. We used mechanical scale beams that were only accurate up to plus or minus one pound," says Alvarez. "We wanted to get the accuracy to plus or minus half a pound. The other goal was to increase the overall speed. The terminal in Miami upgraded their packing equipment first, which worked well. The equipment is almost maintenance-free. That made our decision very easy. The installation went smoothly, and there weren't any major issues. Three different companies worked together to upgrade our equipment, and everything worked out great." The system that Thompson Scale designed for Rinker is extremely easy to maintain, with few wear parts and quick changeover of replacement parts.

Rinker has experienced many benefits since installing the 4693 heavy-duty checkweigher in their cement-production system. "The main improvement is our increased bag-per-manhour rate, which has gone up over the last couple of months. Now, we can constantly monitor weights without having to stop the operation," Alvarez says. "The other important aspect is safety. The risk of injury is less. Our employees enjoy the improved safety and have more comfortable working conditions by not having to handle the bags to weigh them. Also, if we have any reject bags, the checkweigher rejecter pushes them off the conveyor without someone having to handle the bag. We have really noticed the increase in our cement-production rate."

StatPak-PC allowed Rinker to quickly and easily adjust their production lines to even better levels. Since installing the reporting software, they have noticed the benefits through more efficient production. "We track and monitor production through the data we get from the StatPak-PC system," says Alvarez. "We also track inventory better through the computer and analyze data, such as number of bags per minute, total weight and any variance. The reports we generate are really helping us in monitoring the terminal. The software helps us maintain a constant quality and weight on the bags. This accuracy also makes the appearance of the bags on the pallets look even better."

When StatPak-PC software is used, the results are an increase in efficiency and quality. This optimized production leads to decreased expenditures and substantial cost savings over time. Says Alvarez, "We like the StatPak-PC reports that can be run. We get a lot of valuable information that used to be created manually."

When asked about the improvements seen due to the packer upgrade, Alvarez says, "The number-one thing is a significant increase in production. Before, our filling time was twelve to fifteen seconds per bag. We operate at eight or nine seconds now. Another bonus is that only one person has to run the bagging equipment since it's automated. Now, the system can be run with one operator, who can see the automatic bag placer at the same time as the controller and can easily check the weights of each bag. This has saved us a lot of manhours. Along with that is improved safety, because our employees do not even have to be near the conveyor belts anymore.

"In addition, the operation is running smoother now with almost no maintenance required. The calibration is simpler, too. Before, we would have to have an outside contractor come in to do the calibration for us. It's easy enough for us to do it ourselves now. The changeover is also greatly improved, and the equipment is more reliable now."

Another improvement made to the packer was in product spillage at the fill spouts. The original filler design allowed product to spill freely from behind each spout, even when the spout was filling a bag. The upgrade eliminated almost 90 percent of this spillage, reducing dust in the area and greatly reducing reclaim. "We did a quick study that showed an increase in production, while there was a sharp decrease in labor and maintenance. It's significant enough that we should see a return on investment within a relatively short time," says Alvarez.

The consistent drive to make continuous improvements such as these is one of the reasons Rinker Materials remains a leading manufacturer and distributor of high-quality cement. Thompson Scale, along with its subsidiary, Telemetry Solutions, met the challenges that Rinker faced with adding new equipment to their packaging line by using innovations and new product designs. To sum up the installation and Thompson Scale's products, Alvarez says, "It was a very good experience. I will definitely recommend Thompson Scale."