Maintaining a Strong Performance in the Mill
by Torbjörn Idhammar
High investment costs mean that it is the interests of paper makers to look after their equipment. After all, prevention is better than cure.
In today’s highly competitive market, mills cannot afford to be let down by their machines, so maintenance procedures are a crucial element in any company’s performance strategy. In a bid to improve reliability and performance, mills can chose one of two ways to carry out their maintenance tasks, both of which lead to higher production throughput and lower costs.
Using the first approach, mills can invest in maintenance prevention. Under this system, it is essential that companies specify and buy the right equipment. Added to that, attention needs to be paid to basic operations such as lubrication, alignment, balancing, proper storage of components, filtration and detailed cleaning. Where possible, mills should also look into using a Fixed Time Maintenance (FTM) program. And, last but not least, it is crucial that mills follow proper operating practices.
The second way in which mills can improve their maintenance performance is to carry out the remaining maintenance work in an efficient manner. This can only be achieved with adequate planning and scheduling, which involves leaving enough time between identifying and carrying out the work. Prioritizing requests and condition monitoring must be standard practices at mills that go for this approach.
Clearly, there is nothing new or revolutionary about these two methods, but in most organizations the improvement potential of these processes is huge. Mills often overlook the opportunities on offer, but improvements can easily be achieved if companies go back to implementing the very basics of maintenance. Few investments in maintenance improvements pay off faster than the implementation of new or revised cost-effective preventive maintenance procedures.
The IDCON maintenance consultancy recently worked with two pulp and paper mills to carry out basic preventive maintenance inspections. Experience showed that the secret to getting the most out of a company’s money lies in improving the very basics of operating and maintenance procedures. Following the work at the two mills, cost savings at both plants totaled more than $1 million in little more than six months and 12 months, respectively.
It may come as a surprise that vibration analysis (VA) accounted for just 7% of all problems identified, but this particular mill had been running an excellent VA program for close to 10 years. Even so, the VA program had failed to identify problems such as worn out V-belts, sheaves, sprockets, chains, coupling elements, coolers close to failing and internal hydraulic leaks.
It is also revealing to see what a difference can be made if high intensity light is used for inspections. Before this method was used, employees used only regular flashlights. When they started using lamps with one million candlepower light intensity, a new world opened up and problems that could not be seen with a normal flashlight were identified. Meanwhile, many of the problems detected with the infrared (IR) thermometers used related to mis-aligned couplings. Most of these couplings would later have been detected with VA, but the IR method is faster and simpler and it also generated a heightened interest among operators to carry out inspections.
In both mills, the results highlighted the importance of training operators and tradesmen to carry out inspections. Most tradesmen are good at repair work as the majority of training programs are focused on fixing components. By contrast, very little training focuses on how to carry out basic inspections. For example, without training, the inspection of a cooler would simply involve checking for leaks and whether the cooled media is at the right temperature. After receiving training though, operators would note the position of the bypass valve or water inlet valve. If a water inlet valve is almost fully open in the month of May, it is easy to understand what will happen in June, July or perhaps November if the mill is in Australia.
The key to a successful preventive maintenance system comes down to paying attention to detail. The people involved in maintenance prevention and condition monitoring must be trained to become detectives of possible failures, not just observers that casually pass by the equipment. For example, one person may note that an electrical motor is hot and then report the problem to an electrician so that he/she can check out the problem. In contrast, a detective would scan the motor and note the location of the hotspots. A detective always continues to ask why a problem is occurring.
If we take one typical example (Figure 3), the detective in this case may wonder why the shaft side of the motor is hotter than the middle of the motor. From the data, it is clear that the motor needs to be cleaned, but it is still unusual that the shaft side is hotter than the middle of the motor. After cleaning the motor and checking its load, it became obvious that the front bearing was the heat source. The outstanding question was why.
The detective has two main hypothesizes for the cause of the failure - lubrication or misalignment. Taking the temperature of the coupling and the shaft side pump bearing clarifies that misalignment was the actual cause of the failure. After further inspection, it was noted that the foundation was poor and the base had corroded. In other words, the foundation was at the root of the misalignment problem and this made it impossible to realign the motor to specification.
The corrective work in this case was extensive because there were a variety of failures associated with the problem that were not detected in time. The mill in question had just started its preventive maintenance process and it became obvious that there were many faulty bases and foundations onsite. A preventive maintenance process helped this mill to focus on the very basics that made its operations run.
On the record
At both of the mills that IDCON worked with, all inspections were documented in an inspection system and those carried out by operators or tradesmen were given the highest priority. A key to success is that inspection results are acted upon so that a problem only needs to be reported once. In addition to savings in increased reliability as well as lower maintenance and operating costs, it is also very common to see a reduction in the total hours and material spent on preventive maintenance. If carried out correctly, the vast majority of inspections can be made while the equipment is in operation.
Another cost saving opportunity that mills can take advantage of is to have all its preventive maintenance activities documented in the same system. This makes it possible to see all the activities per equipment piece in one document, eliminating unnecessary duplications of preventive maintenance work.
As paper companies increasingly look at ways to cut costs and run more efficient operations, it is worth bearing in mind that forewarned is forearmed. Or to put it more plainly, it is 5-20 times more expensive to react to a problem then to prevent it.