Forest industry operations rise or fall on system reliability and energy efficiency. Traditionally, geared drive motors have been the workhorse of pulp and paper mills, and thousands are still in place globally. In many ways these are simple designs, however they come with complexities and limitations due to a number of moving parts. Maintenance requirements are typically high to ensure reliability and availability, but over 20-30 years deterioration is inevitable.
A gearless direct drive motor system, such as those available from ABB, bring benefits and savings to the user, particularly when it becomes a ‘connected drive’ through digital solutions. These direct drive systems are based on a permanent magnet motor and connect directly to the production equipment without a gearbox. ABB has developed and delivered this technology to more than 60 pulp and paper mills around the world and several advantages have been identified from seeing direct drive systems in action. These are energy efficiency, precise torque control, reliability, safety and security, lower engineering costs and reduced maintenance.
Nuts and bolts
Removing the gearbox from the equipment set-up and replacing its functions with a modern, fit-for-purpose alternative coupled directly to the paper machine has proven to be practical and efficient. A gearbox suffers from energy losses during mechanical movements, which means higher energy consumption. When the drive is directly attached to the production machine using the permanent magnet technology, energy consumption is reduced.
The main advantage of this direct drive access is that it is gearless. When there are no gears, the motor speeds are lower. This way, a much longer service life can also be expected from the bearings. In ABB motors these last up to 200,000 hours or approximately 23 years in operation. The system is reliable right from the start and remains this way throughout its lifecycle, reducing electricity consumption and reaching high horsepower at low voltage.
Due to the permanent magnet motor, stator current is not needed for rotor magnetization, which further increases energy efficiency. This system has energy savings of around five percent compared to conventional induction motors. This is significant when the lifecycle of 20-30 years is also considered.
The permanent magnet technology combined with ABB's patented direct torque adjustment (DTC) mean it is possible to achieve high torque at low speeds. The specific energy efficiency achieved and the wide range of torques separate ABB's direct-use solution from those of other manufacturers. ABB's solution includes motors with over 50,000 Nm of torque.
AC-powered permanent magnet motors have proven high performance over a wide speed range of approximately 200-600 rpm. Reliability is simply increased by the fact that they have fewer moving parts. Moreover, ABB's patented DTC solutions do not require any pulse sensors for precise speed control, which improves reliability.
Data drives higher performance
Paper mills have the potential to gain a deeper understanding of drives system performance when digital monitoring services are applied to collect and analyze data. Paper Machine Drives Performance is an ABB Ability™ service that captures and continuously updates performance indices to provide maintenance and production teams with up-to-date drive performance status, advanced warnings on potential failures and predictive root cause insights.
Runnability and quality improve with better coordinated drive control performance while availability increases through predictive monitoring. Providing a digital twin of the system, it can assess the number of deviations or errors impacting performance and can be used to define limits to form predictive alerts. With better root cause analysis mill operators can focus their attention where it is most critical, resulting in improved runnability and high drive reliability.
A clear vision of the future
ABB launched direct drives more than 20 years ago, with energy efficiency essential. Today, direct access technology still provides an excellent opportunity for forest industry operators to improve productivity and achieve significant energy savings.
Digitalization of the system uses advanced analytics and ABB’s proprietary data analytics tools. These are available via an operator-friendly interface and dashboards, and customers can receive industry-proven expert support and advice from ABB.
Overall, safety, security and maintenance risks can all be lowered through the use of direct drives and associated digital solutions. With fewer components configurations are straightforward and installations easier, with the floor area of the factory also more efficiently used. There are also fewer consumable parts which also reduces requirements for spare parts stocks. As mechanical gears and pulse sensors are not required, this reduces the amount of equipment and space needed. Subsequently, this means lower installation and commissioning times.
ABB's direct drives design focuses on energy efficiency and an economical set-up, which creates value for customers. The system fulfils all necessary functions while minimizing energy losses and enabling cost-effectiveness throughout the system's lifecycle.