It was once common to wait for equipment to fail before it was repaired. Indeed, maintenance was viewed as an expensive necessity, requiring skilled labour and machine downtime. Then came preventative and predictive maintenance programmes, spawning a new generation of diagnostic tools and software, designed to allow plant engineers to plan plant shutdown and repair.
The condition monitoring technology used for detecting problems has grown in recent years, with a range of diagnostic tools and software for monitoring machine performance on-site and remotely. Most importantly, these innovative devices have enabled engineers to manage efficiently the frequency and type of maintenance required to achieve optimum performance across quarries.
These latest instruments offer high levels of accuracy from compact, handheld units that can be used in wireless networks for remote interrogation and control, providing data that can be used for short term maintenance planning and long term plant cost control. The latest accelerometers used for vibration monitoring take advantage of piezoelectric technology, providing a robust, reliable way of measuring high and low frequencies, with low hysteresis characteristics and excellent levels of accuracy over a wide temperature range. To protect these devices against the ingress of moisture, dust, oils and other contaminants, they can also be packaged in compact stainless steel housings.
ACCELEROMETERS
Accelerometers are mounted in key locations on the equipment to be monitored, with output data read periodically using sophisticated handheld data collection devices for immediate analysis or being routed via switch boxes to centralised, higher level systems for continuous monitoring.
Handheld devices simplify machine maintenance and feature easy to use ergonomic designs, such as SKF?s Machine Condition Advisor (MCA). This unit measures velocity vibration signals from machinery and automatically compares them to pre-programmed ISO guidelines, while applying the SKF Enveloped Acceleration technique to compare readings with established bearing vibration guidelines. If the measurements exceed these guidelines, the unit?s display shows an alert to indicate bearing damage. The MCA also has a temperature sensor to check bearing temperatures for abnormal heat loads that indicate lubrication problems.
Similarly, the latest field mounted, wireless condition monitoring measuring devices, such as SKF?s Multilog WMx, have been developed to form a key component in advanced condition monitoring systems. They collect acceleration, velocity, displacement, temperature and bearing condition data that is automatically uploaded for fast, simple data analysis in a condition monitoring software suite. Moreover, they monitor hazardous, remote or inaccessible areas as they do not rely on wires or cables.
There are also software tools for improving data collection and analysis, which can be run on handheld and centralised computer systems, eg the SKF @ptitude platform allows detailed information on the condition of the equipment to be quickly viewed, analysed and communicated throughout an operation. Users also have access to online information to compare recorded data, resulting in improved efficiency levels as labour intensive data analysis is replaced by an automated process that identifies the machine?s probable faults and prescribes action.
ASSET EFFICIENCY OPTIMISATION
While these developments in condition monitoring technology present opportunities for cutting the cost and time of maintenance tasks, predictive maintenance is largely a reactive process that adds little to a company?s bottom line. What is needed is a holistic approach that optimises the efficiency of plant and equipment by proactively managing both system reliability and risk assessment across an entire organisation.
This strategy is known as asset efficiency optimisation (AEO), a tool to improve plant productivity and thus profitability. AEO creates a dynamic programme that combines traditional techniques with procedures that identify the root causes of machine and process problems, and empowers front line operators to own their machinery, identifying and conveying information to a plant wide team to maximise uptime.
A successful AEO programme consists of four key elements: maintenance strategy, work identification, work control and work execution.
The first process, maintenance strategy, is when a business sets its goals and objectives, assesses plant criticality and risk, and decides its priorities. This is essential to create a suitable maintenance plan, and sets in place a recognised company asset management strategy, which can be easily communicated throughout the organisation.
This information can be used in the work identification stage, where critical plant data is gathered and analysed, allowing for informed decisions and the undertaking of corrective maintenance operations. An Industrial Decision Support System (iDSS) can assist senior maintenance engineers by making condition based maintenance recommendations and specific expert knowledge on asset maintenance available online. Work requests can then be submitted to a Computerised Maintenance Management System (CMMS), to be combined with other corrective maintenance activities.
The work control stage relies on the outcomes of stages one and two, allowing maintenance activities to be planned in detail and scheduled, with tasks prioritised, eg timescales, man hours, data feedback and competence requirements. Effective planning, with good spares management, well defined job plans and trained staff, allows resources to be utilised in the most productive way.
With these three stages completed, the, work execution stage can be implemented, with detailed plans put into action and maintenance work done. Feedback should be collected via post-maintenance testing for continuous improvement and maximum return on investment to be achieved.
A holistic approach to quarry maintenance and asset optimisation can improve plant and equipment efficiency and establish effective lines of communication throughout the business. Overall, it is a sustainable approach with a positive long term effect on company performance and profitability.
Phil Burge is the communications manager for SKF (UK) Ltd. This article first appeared in the May 2010 issue of Quarry Management (UK) and is reprinted with kind permission.