Logan Aluminum, Inc., located in Russellville, Kentucky, is a world class manufacturer of Aluminum sheet products. Since 1983, they have been involved in the fabrication of rigid container sheet, building products, automotive sheet, distributor sheet, and food can stock markets. Logan Aluminum is a premier manufacturing facility with modern, high-speed equipment and technology available in the operational areas of ingot casting, hot rolling, cold rolling and finishing. Logan Aluminum is an industry leader in terms of safety performance, product quality, customer service and cost performance, and receives broad-based recognition for its progressive management concepts. Logan Aluminum is proud to be a part of the Commonwealth of Kentucky and the community of Logan County.
New Equipment – New Monitoring Requirements
A new tab stock line was installed in the fall of 2007 (see Figure 2). The Level Clean Line is designed to a safety level that reaches Category 3, which is European Standard EN954-1. Many US companies have adopted this standard in order to meet safety requirements. The line is completely surrounded by fencing (see Figure 3) which meets ANSI standards for height, opening size, and distance from hazards. There are a total of seventeen gate entrances around the line that are safety interlocked using Fortress Interlocks. Each interlock requires that the operator press a button which acts as a request to enter. Once pressed, the safety PLC will put everything into a safe state and then release the solenoid on the interlock allowing the gate to open. Each gate is equipped with at least two safety keys which the person entering the gated area is required to take with them. By having the key on their person, it keeps the machine in a safe state, prevents the line from running, and prevents personnel from being locked inside the area.
The Challenge
The safety system posed a challenge due to the difficulty of gathering real-time critical information. Critical machine components, such as the unwind mandrels, rewind mandrels, and pass-line rolls, could not be accessed in order to gather vibration data in support of the Finishing Department. They were at risk of not being monitored, which left the line open to failure without prior warning.
The Planning
Due to the criticality of obtaining good information in order to have effective maintenance planning and long-term reliability, an initiative was presented to members of the management team, which included permanently mounting sensors inside the safe areas and utilizing junction boxes to access the vibration data. The Finishing PdM department was given the green light to develop a solution and provide a cost to implement this solution.
The Solution
There were many options available for the components necessary for the installation. The ideal installation would be three axis accelerometer on each bearing. However, that was not economically feasible, so critical areas were identified, and the selected pieces of equipment to monitor were high rpm rolls, gearboxes and motors. Since the main requirement was to access the vibration measurement points without having to enter the safe area, permanently mounted sensors were determined to be the best option.
Placing sensors permanently on the measurement points allowed for consistent measurement data with the ideal mounting method (direct mount to the bearing housings), which allowed the full utilization of the frequency response of the sensors. Mounting the junction boxes in a convenient location allowed direct access to multiple measurement points without having to move to each sensor location, allowing for more efficient data collection (see Figure 4).
The wet section pumps and motors were the only pieces of equipment that didn’t have the safety cages installed around them. For those measurement points, a portable measurement mounting system was used, which consisted of a triaxial sensor and a magnet.
Hardware Selection
Sensors – Most of the vibration measurements taken were targeting many types of faults, from chipped gear teeth to all bearing faults and motor failures. Top exit, multipurpose accelerometers (see Figure 5) were selected for this application due to the general frequency range of the sensors (.5 – 15,000 Hz), enabling data collection that would encompass the required frequency ranges, and also provide a low-cost solution.
Cabling & Connectors – Although there were no environmental chemical concerns, a red Teflon jacketed cable with permanent polycarbonate connectors using stainless steel locking rings, ensured proper connectivity from the cable to the sensor.
Junction Box – A vibration switch box was selected for the termination of the sensors and for access to the vibration data at a centralized location. The switch box (see Figure 6) assured further efficiencies because the measurement points were accessible through the turn of a switch.
Upon receipt of the costs, the decision to proceed with the purchase and installation of the remote system was granted. CTC was selected as the supplier for the accelerometers, cables, and boxes.
Installation
There were a few installation challenges that were required to be evaluated. Placement of the accelerometers required careful site planning to determine the best installation location of the sensors (see Figure 8). They had to be mounted in the load zone, while avoiding areas where they would be used as a foot peg (see Figures 9 and 10). Special consideration was also required when running the cables – they needed to be placed where they would not be a tripping hazard. The junction boxes were mounted on the back side of the line, out of high traffic areas. The installation of the project took 160 hours to do 215 points. The project came in under budget because no contractors were needed, which was critical, as the only time the points were accessible was on outage days or coming in on days the line wasn’t running.
Data Collection
Logan Aluminum has two manufacturers of data collectors that can be used - Azima/DLI, and CSI. The boxes were set up to be able to use either of these data collectors. The most popular data collector in the Finishing Department is the Azima/DLI. This data collector can take a triaxial reading by attaching a custom cable connector plug equipped with six BNC connectors, allowing multiple data collection for three simultaneous readings.
Other Technologies
Ultrasonic analysis and oil sampling are two other predictive technologies that are employed in combination with vibration analysis for condition monitoring. With the use of these three technologies, breakdowns are at a minimum.
Since Installation
Prior to installation, the complete line was prone to failures because there were no vibration sensors mounted on the equipment to monitor the condition of the machine. Since these permanently mounted sensors have been installed, the monitored points increased to over 200 measurement points. Several vibration related issues have already been identified, avoiding machine failure and down time. Based on these successes, more permanently mounted sensors will be added to the other lines to continue to increase the efficiencies, solve the issue of being blocked out due to safety, and continue to avoid costly unplanned downtime.
Conclusion
The enclosed safety system does exactly what it was designed for, which is to keep employees away from moving equipment. The challenge that the safety system presents is that it doesn’t allow you to feel, hear, or in some cases, even see the equipment. The costs of the remote vibration monitoring equipment are generally justified in cost avoidance of damaged or down equipment and the safety avoidance of injuries, minor or severe, for all those involved.
Tim Hunt works at Logan Aluminum and has been in the maintenance field for 18 years. He holds a Fluor Daniel millwright certification, as well as being a Level 1 Certified Vibration Analyst from Technical Associates and a Level 1 Certified Ultrasonic Analyst from UE. He has an associate’s degree from Mid-Continent University.
Tom LaRocque is an engineer at Connection Technology Center, Inc. (CTC), and has been involved with the vibration industry for over 11 years. He is a Certified Vibration Analyst: Category III from the Vibration Institute, and has a Bachelor of Science in Engineering from Clarkson University. Tom can be contacted by phone at 585-924-5900 Ext. 817 or by e-mail at tlarocque@ctconline.com
