Maintenance of Aggregate Crushers

08 September, 2017

First published in the September 2017 issue of Quarry Management as Failure is Not an Option

Failure to adequately maintain crushers can come at a high price, as Eric Jones, Weir Minerals’ global service director for the comminution aftermarket, explains

Crushers operate at high power, force and capacity in order to produce the required materials. This puts a great deal of strain on the crusher and its wear parts, which operators must be aware of when carrying out maintenance. Failure to do so may have a big impact, both in terms of financial cost and potential loss of production.

The maintenance plan

Performing regular maintenance on crushers is integral to the reliability, performance and output they achieve. Prevention is better than cure; by carrying out regular inspections operators will ensure that their crusher runs for a longer period of time with minimal unscheduled downtime.

The most important aspect is to have a maintenance plan in place and execute it. Following a maintenance plan and carrying out daily inspections can yield increased service life. The plan should adhere to the recommendations of the manufacturer.

Maintenance plans may differ slightly depending upon the machine, but most follow an initial 40h schedule post commissioning, followed by regular 250h inspection/maintenance intervals throughout the annual cycle. Within these intervals there are prescribed tasks that an operator will need to carry out, including:

Checking the air filter to ensure the crusher is vented properly and that unwanted contaminates are not entering the breather
Checking the strainer basket on a cone crusher and ensuring that there are no signs of excessive wear or damage to internal components
Greasing bearings if required to ensure proper lubrication and cooling of those bearings.

The consequences of inadequate maintenance inspections

If operators do not follow a maintenance plan and carry out daily inspections, it can have detrimental effects on the crusher.

Where there have been insufficient maintenance inspections, the most common problem that Weir Minerals witness is premature bearing failure. For example, the operator may fail to notice that a breather has been knocked off, which fills the oil chamber with dust or debris; or they may overlook a grease line that has ruptured, causing the bearing to no longer receive the required lubrication; or they may not check the oil levels, resulting in a bearing failure due to a lack of oil.

These are all common problems that can be avoided if a full maintenance plan is put in place and adhered to.

Extending the life of crusher wear parts

Whilst wear part replacement is a necessary feature of any crushing operation, there are steps operators can take to extend the service life of crusher wear parts.

For example, always ensure the wear parts are fastened into the machine properly. With jaw crushers, if the jaw dies are allowed to move during operation they can cause damage to the frame of the jaw crusher. Similarly, loose liners in cone crushers may damage the head or bowl.

It is also advisable that operators frequently look for holes, cracks or flat spots that could potentially damage the machine over the long term or be an indication of another issue.

Further to that, operators should track tonnages. As cone crusher liners wear, the operator threads the bowl inwards, bringing the bowl liner closer to the head, which reduces the feed opening. The reduced feed opening may decrease crusher throughput at a cost; once that cost is greater than the price of the liner change the operator should consider changing the liners. At a glance, the liners may still have what an operator would perceive as usable wear left, but at a loss of tonnage that does not benefit the plant.

Detection of wear-part damage

If an operator observes significant wear-part damage during regular inspections, the crusher manufacturer should be consulted to find out if immediate stoppage is warranted.

Determining whether to stop production to change a wear part entirely depends upon the severity of the damage. For example, a damaged rotor tip in a vertical-shaft impact (VSI) crusher may make it through the shift and not cause unwanted downtime. However, a broken jaw die with parent steel exposed may cause significant damage, and it is vital that the operator stops the jaw crusher and changes the die in order to protect the crusher frame.

Common mistakes

Failing to take care of damaged wear parts can increase wear on the entire machine, which can lead to expensive failures.

A common misconception is that operators think they should wear down jaw dies until they are completely flat or develop a hole or crack. By running these wear parts for a longer period of time, operators often think they are extending the wear life, but in reality they may be causing unnecessary stress to the jaw frame.

Another common mistake Weir Minerals have witnessed is that operators run cone crusher liners past their useful operational life. The resulting lost tonnages can cost the operator a great deal more money than the cost of a liner change.

Safety – the number one priority

Cone crushers have evolved from the earlier models introduced in the 1920s, with most manufacturers now designing cone crushers with advanced hydraulic systems to raise, lower and adjust the machines safely with minimal effort. To clear a cone crusher, users simply depress a button, click a mouse or toggle a switch. This removes the risk of people manually clearing a stalled cone crusher by hand or using straps, chains and rolling stock to adjust the crusher.

At Weir Minerals, safety is the number one priority and the company’s latest designs reflect this. For example, the Trio TP cone crusher range is designed with self-protecting features to help achieve high levels of mechanical reliability under severe operating conditions, whilst ensuring the safety of both the operator and the equipment.

In addition, Weir Minerals’ latest Trio CTHT-series jaw crusher includes a hydraulic toggle relief system. This innovative, built-in system protects the jaw crusher from overloads caused by uncrushable material. The hydraulic toggle is designed to be a reliable and safe relief system, without any unnecessary complexity for the operator.

Operators who do not properly maintain their crushers may experience poor performance and decreased service life of the machines. It is suggested that operators seek expertise to create and execute a maintenance plan to increase the service life of their crushers. At Weir Minerals, the company’s skilled service teams can provide professional on-site training for operators’ personnel to ensure smooth, safe and efficient plant operations and maintenance.