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Apr 4, 2018

Improve analyzer availability with the Outotec equipment health indicator

Efficient flotation process control is essential in order to achieve higher performance in terms of concentrate quality and recovery of valuable minerals. This is usually achieved using real-time measurements taken by an online analyzer. If the accuracy and availability of the analyzer are compromised, the flotation process will suffer, leading to a decrease in productivity and profitability. Monitoring analyzer health using an equipment health indicator allows its availability to be optimized, leading to improved performance downstream.
Equipment Health Indicator dashboards
Figure 1. Outotec Equipment Health Indicator dashboards on different devices.

Online elemental analyzers provide real-time measurement information from different locations in the flotation process. This information allows efficient process control and affects the economic performance of the whole plant. To enable optimal control and performance, it is essential that the online analyzer is available to measure critical process streams and provide accurate measurements that represent the true status of the flotation process. In other words, to achieve optimal flotation performance we must ensure that the analyzer is also performing optimally.

Making good maintenance even better

High-quality equipment alone cannot guarantee high availability, even with proper design and implementation. Minimizing unscheduled downtime – and being able to plan scheduled downtime optimally – can lead to a significant increase in productivity. With efficient maintenance in place, it is possible to directly affect the availability of equipment and in some cases production quality. For example, proper calibration of an on-stream analyzer will reduce fluctuations in controlling concentrate grade.

The traditional factors that define good maintenance include availability of spare parts, capability of service technicians, and fast response times. However, new digital technologies and Internet of Things connectivity provide the opportunity to improve service quality even further. Outotec has developed a visualization and notification app – the Outotec Equipment Health Indicator – that monitors the health of online analyzer equipment and assists users to improve the availability of the assays. The aim of the app is to make analyzer availability and performance transparent, offer the best possible support to maximize equipment utilization, and enable continuous improvement in equipment performance.

The challenges of calculating availability

The Outotec Equipment Health Indicator provides automatic reports on Key Performance Indicators (KPIs) covering various components of the online analyzer system, including the analyzer probe, multiplexer units, and individual sample lines. Using this information it is possible to focus maintenance actions on problematic areas and systematically improve the overall availability of the analyzer. During development, it became apparent that calculating analyzer availability – and the availability of critical components – was far from trivial.

Following Nakajima (1988), Utilization can be calculated using the following equation:

Utilization equation

Where Loading Time is planned production (or equipment usage) time:

Loading time equation

Authorized Downtime includes all planned downtime, for example scheduled maintenance shutdowns.

Availability can be calculated based on Nakajima’s (1988) original formula with Jooste’s (2004) addition of DeviationTimeM:

Availability equation

Unauthorized Downtime is the result of technical, operational, or quality deficiencies, such as equipment failure. DeviationTimeM is additional downtime caused by inefficiency during the maintenance operation. One example of this kind of inefficiency is lack of on-site spare parts causing additional downtime due to waiting for delivery of the parts.

When Utilization and Availability are automatically calculated, it is essential to separate Unauthorized Downtime from Authorized Downtime. The advanced self-diagnostics of a modern elemental analyzer enable failure detection in most main system components, meaning unauthorized downtime due to equipment failure can be automatically calculated in the majority of cases.

However, there may be times where the self-diagnostics system shows that the analyzer is fully operational, but it cannot carry out assay measurements because of operator overrides, such as switching the system to standby. In these cases, user input is required to categorize the reason for the downtime and enable calculation of utilization and availability. The reason for the downtime may be a scheduled maintenance shutdown (Authorized Downtime) or it may be the repair of a failed component not covered by the self-diagnostics system (Unauthorized Downtime). When the Outotec Equipment Health Indicator detects a situation where the type of downtime cannot be automatically concluded, it sends an enquiry to the user for clarification.

The benefits of equipment health and maintenance information

The information collected by the Outotec Equipment Health Indicator can be used for a wide range of purposes. Equipment manufacturers may use it for quality monitoring purposes, focusing R&D efforts on components that tend to fail or wear out frequently. Maintenance teams can use it to schedule maintenance shutdowns and ensure that they have the required spare parts in stock on site.

Availability and utilization provide historical information about the long-term development of equipment use and health. When combined with information on root causes that lead to reduced (or increased) availability, they serve as an effective tool for continuous improvement and better maintenance planning. However, they don’t provide information that would help to prevent unexpected equipment failures. With the Outotec Equipment Health Indicator, our aim was to develop indicators that can predict future equipment failure in order to minimize downtime with preventive maintenance actions.

Modern elemental analyzers include built-in features to collect information that can be used for preventive maintenance purposes. This information is highly technical and there are several interdependencies between sources, making it difficult for normal users to interpret. Our goal was to provide users and maintenance technicians with clear instructions about how to prevent unauthorized downtime and when to perform the necessary actions. For example, if the analyzer experiences multiple power cycles during a short period of time, the Outotec Equipment Health Indicator can warn that frequent power cycles increase the risk of x-ray tube failure and suggest using standby mode for short shutdown periods of less than two weeks.

Essential warnings ensure higher availability

One key part of optimizing maintenance and equipment availability is to ensure that only essential warnings are signalled. If the system is continuously giving false alarms there is a risk that maintenance personnel will very quickly stop taking these warnings seriously. Equally important is that correct alarms are relayed to the correct people. A warning about a malfunctioning cooling system, for example, should be relayed to the person responsible for maintaining analyzer electrics. A warning about sample transfer system performance, on the other hand, should be relayed to personnel responsible for resolving process piping blockages.

By ensuring warnings are relevant and timely, online analyzer availability can be optimized and critical process streams measured accurately, leading to efficient flotation control. The Outotec Equipment Health Indicator consistently monitors the health of the analyzer and alerts users and maintenance technicians to problems and potential issues, including timescales to help with maintenance planning. This supports a preventive maintenance approach, which in turn minimizes unauthorized downtime. The information collected also helps to build a picture of the root causes of downtime, enabling continuous development of maintenance practices, while identifying misuse of equipment and providing users with clear guidance.

The Availability dashboard in the Outotec Equipment Health Indicator
Figure 2. The Availability dashboard in the Outotec Equipment Health Indicator.

References

Nakajima, S., 1988. Introduction to TPM: Total Productive Maintenance, Productivity Press, Cambridge, MA.
Jooste, W., 2004. A Performance Management Model for Physical Asset Management, South African Journal of Industrial Engineering, January 2004 Vol 15 (2): pp 45 – 66.

 

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