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Machines get health checks online

Condition monitoring is a proven valuable tool for optimising maintenance strategies. Ian Liebler, Rockwell Automation integrated conditioning monitoring solutions architect, explains how integrated condition monitoring can provide even greater production and maintenance efficiencies through streamlining real-time information flow.

To ensure the ongoing efficiency and operation of plant, machines must be maintained and serviced. Yet while too little maintenance will result in breakdowns; too much will cause needless machine downtime and reduced productivity. The optimum maintenance schedule lies somewhere between, demanding methods of predicting when servicing might be required, so that maintenance can be carried-out more strategically.

Regular monitoring of machine health—or condition monitoring—has proven a valuable tool for providing operational continuity, regulatory compliance, safety and reliability of plant operations. Fundamentally involving the collection of key machine data, condition monitoring techniques can be used to identify changes in machine operations and instigate strategic condition-based maintenance (CbM) as required.

Traditional ICM compared with Online ICM. ‘Online’ ICM removes the need for separate data collection.

Conventional condition monitoring is intermittent, often using handheld devices, and is by nature isolated from other plant control-systems—including machinery protection systems. However, the emergence of integrated control technologies is promoting a shift towards ‘integrated condition monitoring’ (ICM), where control, protection and condition monitoring are merged into a single integrated architecture.

ICM aims to leverage existing infrastructure to incorporate CbM strategies and improve the flow, accessibility, and ‘actionability’ of information. Ideally, ICM will provide full connectivity between the condition monitoring system and the plant enterprise—including computerised maintenance and monitoring systems (CMMS)—plus supports multiple types of data and data-collection strategies. However, the level of integration will ultimately depend on the infrastructure present.

In many plants, maintenance personnel collect and analyse condition monitoring data; concurrently, control data is collected for operational requirements. The two distinct and separate types of monitoring are then integrated into the same system.

‘Online’ integrated intelligence
It is possible to take the integration one step further. ‘Online’ ICM removes the need for separate data collection. Here, all field sensors—maintenance and operations—feed signals to the controller to allow it to perform auto-diagnostics. Current information can be accessed in real-time, and viewed on any SCADA or HMI. Real-time data can alternatively be routed to personnel as required, or passed back to a database or software interface for functions such as maintenance scheduling, data analysis or historian trending.

Monitoring of discrete narrow-band frequencies allows a real-time view of the health of various components of a machine.

The ability of online ICM systems to handle machine vibration data is fundamental. Vibration magnitude at key narrow-band frequencies can be used to diagnose issues such as imbalance, misalignment, blade pass and blade pass harmonics. The vibration frequency associated with each potential issue can be monitored; if measured above the designated threshold—indicative of a specific fault—a real-time message specifying the fault can be sent to the machine operator, to facilitate corrective action.

ICM systems can also leverage the intrinsic intelligence of the controller. The controller can be programmed to provide not only real-time operator alerts, but also protection or remedial control action.

For excessive vibration on a conveyor, for example, the controller could be programmed to reduce belt speed, thus minimising vibrations while allowing the unloading of material already on the conveyor. Similarly, vibration alerts from a bearing shaft caused by excessive friction can be used to task an auto-lube function through the controller. Control actions that minimise or rectify machine faults are especially valuable where—due to process or safety considerations—machines cannot simply be shut-down.

The provision of real-time data will provide a more accurate picture of the health of key machines—those that are critical to production or safety, difficult or expensive to repair, have a history of inherent faults, or are prone to catastrophic failure. This will enable targeted maintenance-activities to be provided only when required. Furthermore, ICM functionality can provide increased levels of protection and control to machines and processes, elongating the working-life and ensuring maximum productivity for minimised downtime.