The myriad number of machines used in producing pulp and paper that are considered as balance-of-plant or auxiliary machinery. Here you will see a number of machines that are not adequately monitored or not monitored at all but still have a sizable impact on maintenance costs, production downtime and quality. Where are these machines, and what kind of cost-effective monitoring solution would be needed to monitor them?
Paper use is more important than you think
The demand for paper products is actually increasing, not decreasing, and flexibility for production is increasing as well. Digital transformation is coming to the pulp & paper industry to improve processes, but at the same time the industry is becoming more competitive. From the production point of view, machine downtime, paper quality and maintenance costs have a huge impact on profitability. This is where machine condition monitoring comes in. The monitoring requirements for the machines, however, depend very much on the process, machines, operation and maintenance.
There are a lot of machines – Making paper is more complex than you think
In simple terms, wood fibers are converted into paper products. The real process, however, is actually more complicated than this, since it involves many individual mechanical and chemical processes and a large number of machines. Moreover, it is not just wood that is needed for making paper, wastepaper is also recycled and used in the paper-making process. And it is not just the machines used making pulp and paper, there are also many other machines used in a Pulp & Paper mill, such as for in the utilities for power production and steam and for wastewater treatment. All in all, with so many machines, maintenance plays a big role in the mill’s profitability. What are the processes in the Pulp & Paper mill, which machines are used in these processes, what can go wrong with the machines, and finally how can these faults be cost-effectively detected and diagnosed before a failure?
Maintenance challenges
There are many critical machines used in the typical Pulp & Paper mill, and there are many more auxiliary machines. The auxiliary machines not only support the critical machines, but also form part of independent processes. Many of these machines are older assets with a greater risk of maintenance issues popping up. The question comes up, how do plant managers take care of all these machines, and what role does condition monitoring play into it? In the Pulp & Paper industry, there is a wide range of strategies to deal with this.
From a maintenance point of view, many mills rely primarily on interval-based maintenance strategy, both calendar or counter based, for their balance-of-plant machinery with no condition monitoring system at all, or monitoring is limited to routine inspections for some machines. As production flexibility becomes an important business strategy for many mills, an increasing number of auxiliary machines are operating under variable loads, which makes it more difficult to plan when maintenance should be scheduled.
There are also maintenance challenges due to the environment. Caustic chemicals and high temperatures are used in some processes. There can also be paper dust and wood products, which are abrasive. The pulp slurry can also be contaminated with foreign objects such as rocks, clay, etc. This not only affects the rotating pulp treatment components, but also the bearings, gearbox and motor. Another key system is the air ventilation system. If those fans don’t work properly or become damaged, a corrosive atmosphere is developed mainly in the drying section that over the long term will damage the equipment. Moreover, the contaminated air poses a safety risk for workers, including low visibility and slippery surfaces.
Monitoring challenges
For those mills that are using a condition monitoring solution, many use hand-held vibration instruments for much of their balance-of-plant machinery. This strategy may be fine for non-variably loaded machines where the bearing failure mechanism is slow, linear and predictable, but it may be a problem for monitoring other types of potential failure modes. Fast developing faults such as lubrications problems, manufacturing faults in the equipment, bearing contamination due to worn seals, and even improper assembly or operation may not be detected by walk-arounds because these can occur between readings. Another disadvantage of using hand-held instruments is that there are more stringent safety regulations for operators going around in potentially dangerous areas of the mill. Last but not least, hand-held instruments are also mostly designed to deliver just data, without any actionable asset insights. This therefore requires skilled resources to interpret the data, which may be lacking at the mill.
An online monitoring system would solve many problems, but for a Pulp & Paper mill, it can’t be just any system. The auxiliary machines often operate in a noisy environment, which would require advanced monitoring techniques to extract vibration response only due to developing faults. Also, many of the machines are turning at a slow speed, which also require specialized monitoring techniques. For variable loads, the monitoring system must distinguish between the various operating classes and monitor each of these with individual alarm limits.
An online monitoring system with advanced monitoring capability would solve many of these problems, but this may not necessarily convince the plant manager to invest in the system. Firstly, they think an online monitoring system with advanced monitoring techniques is only for critical machines, not the smaller auxiliary machinery. Secondly, they may not have the experience, manpower or the diagnostic expertise to operate it. The trend for many Pulp & Paper mills is to reduce opex, not increase it by hiring diagnostics specialists. Lastly, interrupting production to install a system and the wiring is another issue, in addition to paying capex for the monitoring system itself and providing extra work for IT to take care of the monitoring servers.
For these reasons, many mills have not installed an on-line monitoring system for their auxiliaries. There is, however, a solution to solve these problems.
Monitoring solution
In principle, the online monitoring system for auxiliary machines has to be both cost-effective, accurate, easy to deploy and require no specialist knowledge from the user.
Many auxiliary machines can be monitored by an off-premise monitoring solution such as Brüel & Kjær Vibro’s BKV Beyond. Wireless accelerometer sensors are installed on the machines’ bearing housing and/or casing, and a gateway takes in the raw vibration data and sends it to the cloud for remote processing. This solution includes monitoring machine faults, performing diagnostics of detected faults and providing notification of maintenance action that has to be taken. For this type of monitoring application, no monitoring data acquisition and processing hardware has to be installed onsite nor monitoring and database servers connected to your network. It is all done remotely. The advanced monitoring techniques needed for accurate and early fault detection monitoring could be supported by AI algorithms and confirmed by remote diagnostic specialists at the Brüel & Kjær Vibro Monitoring and Diagnostic Service Centers as service providers.
For those applications where an off-premise solution cannot be used, the cost-effective VCM-3 field monitor also offers a monitoring solution with advanced condition monitoring capability for auxiliary machines. As with the off-premise solution, diagnostic services can be provided to support the user, if needed. If the Pulp & Paper mill has an enterprise-wide AVEVA™ PI system™ data historian, this would be better since no stand-alone database server will be needed onsite.
Conclusion
A large number of auxiliary machines typically found in a Pulp & Paper mill require a lot of attention because they can significantly impact maintenance resources. In practice, however, little attention is given to these assets in many Pulp & Paper mills. Fortunately, there are solutions, thanks to digital transformation that is currently shaping the industry.
BKV Beyond and the VCM-3 field monitor can provide the ideal solution for monitoring auxiliary machines. Little or no hardware has to be installed onsite, and diagnostic support can be provided as a remote service. For critical machines, the rack-based SETPOINT® solution is ideal since it can provide both protection, condition monitoring and performance monitoring. For a plant-wide monitoring solution, there can be a mix of all three systems.
Few dispute the fact that the pressure for greater business profitability, higher product quality, lower maintenance costs and more reliable production is increasing. However, the accuracy, reliability and cost-effectiveness of monitoring systems has also increased, so there is no longer any reason to neglect the Pulp & Paper balance-of-plant healthcare.