Packaging Company Saves Big on Vacuum System CostsCharles Landry, Maintenance Manager, Trinity Packaging Corp.
Trinity Packaging Corp., a privately held family business, is seeing excellent returns on a new system developed with products from AutomationDirect. Energy audits estimate an over 25% reduction in annual operating costs for bag-making machines after adding motor drives and a new monitoring system.
Founded in 1917 as a paper bag converter, Trinity Packaging installed its first plastics extruder in 1979. Since then it has expanded its focus to include the flexible films market, enabling the company to offer a wider variety of products. The company has three plant locations in the U.S. that manufacture plastic products for a broad base of American customers in a wide range of industries.
At a plant in Pueblo, CO, Trinity converts blown film into retail plastic bags. The converting facility has a variety of specialized equipment to create bags with complex features, such as multicolored printing or air-tight closures. The company started this project with the goal of improving the efficiency of their wicket-style bag-making machines.
Improving Efficiency in Bag-Making Machines
The five wicket-style bag-making machines use aluminum arms with vacuum holes in them to grab the bag after it has been cut. The vacuum holes then stack the bag on a conveyor. The Roots blowers used to develop the required vacuum pressure are multi-stage blowers with several fans stacked together.
Trinity's goal was to cut costs and increase efficiency by improving the vacuum system. Initially, each bagging machine required two centrifugal blowers, each using a 10 hp motor running at full rated speed, in order to create the required vacuum.
The reason for this was that the pumps sucked in much of the petroleum waste released into the air as a result of the bag-cutting and sealing process. As more residue built up on the blowers, the vacuum suction would weaken, making the blowers very inefficient. Since employees couldn't accurately monitor the machines to assess the amount of residue buildup, two blowers were kept running all the time to make sure there would be sufficient vacuum.
Moreover, they couldn't risk shutting down the blowers even when the machines weren't running because the amount of residue buildup would often cause the pumps to lock up and trip the control system at startup. Adding to the inefficiency, the motors always ran at full speed even when the process didn't need that level of vacuum. (Shown above right: These pumps create the required vacuum pressure for wicket-style bag-making machines.)
Improving Maintenance and Total Cost of Ownership
In an effort to improve efficiency in overall operations, the company conducted a pilot project on one of the machines. The first step was to install AutomationDirect ProSense? vacuum pressure transmitters at the pumps' inlet.
The ProSense vacuum pressure transmitter was selected because it's specifically designed to monitor relative system pressure for hydraulics and pneumatics applications. Easy to install, this compact pressure transmitter provided reliable pressure indication from its ceramic sensing element. In total, five transmitters were installed that measure the actual vacuum pressure at the pump and send an analog signal to the input card in the machine's AutomationDirect DirectLOGIC DL06 PLC.
Alarms are programmed to send a notification if the pressure rises too high, indicating that the filters need to be changed. If the pressure goes too low, another alarm is triggered telling that the pump has lost its belts. One ProSense temperature transmitter monitors the drive enclosure to turn the cooling fans off and on. ?
Potential Problem Discovered on First Day
The day Trinity switched to the new system, there appeared to be a problem with the controls because one line was showing very high pressure. A look at the machine revealed that one of the vacuum hoses had come off and sucked several bags in - a problem that would have gone undetected by the previous system.
Moreover, improved monitoring helped in creating a precise cleaning schedule based on data collected by the transmitters. This enabled the company to use the second blower as a backup blower, instead of having it run all the time. As a result, overall equipment and maintenance costs were significantly reduced.
Installing Drives Provides Big Savings
Next, one of the blowers was paired with a Durapulse variable frequency drive from AutomationDirect, and the results monitored for approximately six months.
As mentioned earlier, each blower is connected to multiple vacuum arms, which are periodically removed for cleaning. After being cleaned, the blowers run more efficiently, so less power is needed from the motors. However, without a drive, there wasn't any way to reduce the blower motor speed.
With the addition of a drive, the motor speed can now be adjusted according to the amount of vacuum required, which increases energy efficiency significantly. When everything is clean the motor only needs to run at half speed. Based on readings from the vacuum transmitter, the drive increases the motor speed automatically as the arms get dirtier, to maintain the required vacuum pressure.
The result from the initial undertaking was so impressive that the company decided to expand the pilot to all their wicket-style bag-making machines. (Shown right: New blower motor drives dramatically reduce energy costs by allowing motors to run at less than full speed, depending on machine requirements.)
Adding Advanced HMI
Better pressure and vacuum monitoring along with the variable speed motor drives supplied useful data, so an AutomationDirect C-more? HMI touchscreen panel was added to the control system to display and help interpret this data. An Ethernet card in the DL06 PLC communicates the data to the C-more touchscreen HMI. This enables monitoring of the data either on the panel or remotely, which also helps employees respond quickly to any possible issues.
Drives communicate directly with the HMI using the Modbus protocol. This was the first time the company had used Modbus, so a bit of help from the AutomationDirect support team was needed. One of the reasons Trinity chose AutomationDirect was the economical price of its products, but learning that a great price can be coupled with superior technical support was a pleasant surprise. The AutomationDirect support team was very responsive and helped get the system up and running quickly.
Using the Modbus protocol meant that a lot of wiring and associated costs could be eliminated because there was no need to buy many analog sensors to send current, rpm, and other readings to the C-more HMI - the information is simply transmitted in digital form from each drive to the HMI.
HMI screen shown above displays information from a variable speed drive and associated valving, allowing more precise monitoring and control of machine operation.
Valuable Information at Their Fingertips
Programming the C-more HMI using the Windows-based graphical editor was very easy. For example, ?simply entering setpoints for low and high pressure enabled creation of alarm parameters. When an alarm is triggered, it automatically appears on the screen, and an email is sent.
The company also monitors the amount of hours each pump is running; an alarm indicates when to change the oil to increase both operating efficiency and the lifespan of the machine. If any drive fault, belt failure, or pressure fault occurs, the PLC opens the backup gate and turns the backup pump on. The system then emails the event tag from the HMI. The best part is that this happens instantly and automatically, allowing production to continue as if the event never occurred.
When ?the project started, images and specifications were saved of every AutomationDirect component used in the system from AutomationDirect's website. This information was converted to bitmaps and imported into the C-more HMI. This has been a great tool, because now if information is needed on any part, it can be pulled up immediately on the plant floor from the HMI touchscreen.
Dramatic Savings
The new automation system has greatly reduced energy use and cut the number of blowers needed for regular operations in half. This has significantly decreased overall operating costs on these machines. As energy prices continue to rise, Trinity has been able to offset those increases with energy saved by running the blowers only as needed to maintain sufficient vacuum pressure.
The old system needed two 10 hp motors running at full rated speed for the two centrifugal blowers to successfully operate each machine. By removing the need for a second full-time blower on each machine, approximately one week of maintenance has been eliminated for each pump on the five machines in operation. The load on the remaining motor has also been reduced because the drive can adjust motor speed to deliver only the amount of vacuum that is needed to hold the bags in place.
As a result, a dramatic drop in energy usage was seen after installing the automation system. An outside firm was recently hired to perform an energy audit and calculate the overall expected savings. Using a total annual operating cost of $49,000 per year for the wicket bag-making machines as a basis, the audit showed an expected $13,000 a year savings in operating costs.
Trinity Packaging has been so pleased with the success of the improved vacuum system for their wicket-style bag-making machines that they are now developing a project to use the newest AutomationDirect programmable automation controllers to upgrade older equipment in other parts of the plant.
Overall, the following benefits were credited to the new system:
Over 25% decrease in energy and operations costs Motors can now operate at reduced speed Advanced monitoring and control eliminates the need for second blower Easy HMI programming and alarming Modbus protocol reduces wiring and labor costs.
