Automation in crushing

The greatest advances in aggregate processing equipment in recent years have been in the automation arena. The past 10 years have seen tremendous progress in technology that allows for better equipment performance and more proactive maintenance. Automation has enabled plants to produce material with more consistency, better quality and greater productivity. Real time automated equipment monitoring also reduces downtime by tracking maintenance needs. In fact, there are automated systems that can even remotely and automatically make some repairs. In short, automation has made our lives and our jobs easier.

In the past, producers only added automation to their plants as part of a new equipment acquisition. Today, existing equipment can be retrofitted to provide anything from basic machine control to a high level of process control to maintenance and service control.

Most companies that are interested in automation want assistance to maintain the plant. At the most basic level, an automated plant will monitor operational hours to better track scheduled maintenance.

Depending on the automation package the producer selects, a cone crusher package, for example, will enable the system to monitor things like differential pressure, the amount of coolant and the filter condition in the coolant system and the temperature and flow differentials in the supply and return lines. By monitoring the level of lubricant in the system, the automation software can maintain required temperature parameters. Cone crusher automation can track total motor hours, hydraulic pumps, lube pumps, main drives and bearing temperatures for longer bearing life. If the cone crusher is a bushing-type model, the automation system can measure for bushing wear to prevent failure.

For crusher maintenance itself, there are automation packages for gyratory crushers that include such functions as automated greasing systems, which will grease the bushings as a system sub-control. Because a primary gyratory crusher can be located hundreds of metres or even kilometres from the rest of the plant, it can be configured to run independently or tied in to the rest of the plant, based on the producer?s needs.

For operational controls, automation can manage the feed to the processing equipment and protect crushers from overload situations. It will handle the latter by sounding an alarm, correcting the loading or shutting down the equipment. The automation system can track pressure for clamping and the tramp release system. Most systems will automatically adjust crusher settings for production needs or compensate for liner changes. If the automated sensors detect problems, they can be configured to shut the equipment down or eliminate the problem without shutting down the equipment by sensing variables and making adjustments.

With these capabilities, it might seem that an automation package renders human operators obsolete. Today?s automation packages cannot replace the operator but they are useful in pinpointing the causes of problems. Automation systems also provide safety benefits because remote sensing allows for measurement without contact. Even a basic automation package helps with troubleshooting because the data that is collected can (and should) be checked regularly for trending, which can be interpreted to pinpoint an issue, eg if the operator notes the system repressurises repeatedly, he or she should realise it is not working properly and schedule a shutdown for service.

Automated packages can also improve overall plant performance. By logging production, the system allows the plant operator to track productive and unproductive time, so that he or she can analyse the data and compare it to the material produced. Any data can be trended, interfacing off the process equipment to provide operators and supervisors with such information as maintenance needs, schedules and downtime hours. The operator can then adjust the plant for better performance. Historical data can be tracked remotely or on-board for higher level management of overall site performance. All of this helps when tracking the bottom line for the cost of operation.

In a nutshell, real time monitoring maximises productivity and reducesdowntime by identifying bottlenecks, tracking equipment performance, scheduling maintenance and troubleshooting problems. From a proactivestandpoint, an automated system helps schedule and plan preventativemaintenance. From a service standpoint, trending helps operators to troubleshoot and then plan a plant shutdown and order requisite parts.

Advances in technology have enabled automation manufacturers to visit a plant?s automation system remotely to maintain the software portion of the system. While it should not replace a plant visit, remote software maintenance allows the manufacturer to provide system surveys, software product updates and troubleshooting.

Like home computers, developments in information technology (IT) can create issues, rendering older software and hardware obsolete. As changes in software occur at a swift rate, it is important to keep PC and Windows-based controllers up to date with software ? and less frequently ? hardware updates.

It is important that software updates are followed to avoid risks of viruses and hackers. Security risks grow when the plant is connected to an intranet or the internet. For the latter, manufacturers recommend the implementation of a firewall. As a rule, Microsoft produces a new Windows operating system every four years. New functionalities and features mean software or hardware for the system should be updated before it becomes obsolete.

The advantage of remote service capabilitiesis that the customer avoids downtime and the cost of a field service call, while realising higher performance of the automation system. A DSL, fibre optic or cable internet connection is best for remote access to the automation system, although the remote nature of some aggregate operations does not always make it possible. In this case, a connectivity solution could be provided via radio link or satellite connection.

An automation system helps to maintain aggregate processing equipment. But in an arguably dirty environment, what is the best way to maintain the automation package itself? Who watches the watchdog?

Automation system maintenance begins at the ordering process. Producers should be familiar with the system?s location and operating climate. They should specify this to the automation manufacturer who can design the correct enclosure for programmable logic controllers (PLC) and terminals.

The UK?s National Electrical Manufacturers Association provides ratings for panel seals to indicate their resistance to wet or dusty conditions. The main or mobile command centre building can also be protected against the environment. Keep temperatures in mind ? for the high end and low end of tolerances. Additional environmental controls can be added to the system, such as heaters for winter and air conditioning for hot climates.

When specifying the order, producers should keep in mind where the human/machine interface will sit, eg in the central control room or in a remote area. The location could require a climate-controlled enclosure. While a PLC might seem cost-effective, keep future needs in mind with the automation order, eg a touch screen monitor is easier to swap than a manual panel that needs diagnostics and greater work at replacement.

At the planning stage, good communication with the system developer will make the installation more smooth for everyone; bothparties know not only what is on-site and the facility?s climate, but also what?s beingintegrated with the automation. Communicationwill ensure return on investment, ultimately protecting equipment assets down the line.

Good housekeeping should start with the installation. For smoother installation, and easier inspections over time, the contractor should clearly label the cables. This might mean more time for installation, but it will pay off in the long run if a need arises for troubleshooting.

Today?s sensors are very rugged. Different sensors are made for different environments; so as long as the manufacturer knows the environmental parameters, the sensors should endure the daily abuse dealt out in given settings. But no matter how rugged a sensor is, misuse or abuse will cause failure. Something as simple as a hose rubbing a sensor limit switch will ruin the sensor. During installation, sensors should be placed in an area that will minimise their contact with the environment. Understandably, there are some limits to where sensors can be placed but an enclosure is the best scenario.

Daily. As part of a pre-start routine, verify that the system is reading and providing information and verify that there are no issues between the sensor and the HMI system, ie the computer. Basically any parameter that might cause the machine to shut down should be checked daily within the system, such as lubricant pressure.

Weekly. Monitor trending, eg if a bearing temperature rises, it could signal impending failure. Schedule the maintenance before it causes unplanned downtime. Check for dust build-up, corrosion and other environmental effects on sensors, controls and equipment units.

Monthly. If control enclosures are exposed to climate extremes, do a thorough monthly visual inspection. Keep general housekeeping in mind. Protect all cables not only from dusty environments, but other equipment, eg dripping oil on cable labels will make them unreadable.

Annually. Like every application, every installation is different. From the material size to be processed to the environmental and climate conditions, these parameters combine to create different conditions for the automation system that runs the processing equipment. Most manufacturers recommend an annual preventative maintenance visit for automation systems. During a maintenance visit, the specialist will test system functionality, revise configurations, adjust and calibrate the system, update the software and provide additional training for daily system users.

Garrett Forkner and Andy Rieland represent FLSmidth Pekin, in Wales, UK.
This article first appeared in the October 2010 issue of Quarry Management (UK) and is reprinted with kind permission.

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