What sort of rock breaker system should quarries invest in? And how can they ensure it will not impede production?
The first priority is to ensure the breaker is large enough to break the material quickly. The rock should break in three to five seconds. The occasional oversize should not take more than 10 to 15 seconds. A breaker that is too small will reduce production rates and put extra wear and tear on the breaker system, increasing maintenance requirements and production costs.
The next priority is to identify potential problem areas before selecting the location of the stationary rock breaker system, eg:
- Where does bridging or blockages occur?
- Is there compacted material in the rock box?
- Is there a requirement to rake material into the crusher or assist in the general feed of material?
- Is there a need to reposition material over a grizzly?
- Is there material build-up at dump areas?
- Will the boom interfere with haulage vehicles?
- Will the boom interfere with access to other pieces of equipment?
You may also need to size the length of boom (reach) to accommodate these problem areas. This may require coverage of the entire rock box/feeder and crusher.
Anticipated duty cycle
Some stationary rock breaker manufacturers have different classes of booms within a certain range of reach – light, medium and heavy. The selection of breaker should reflect your site requirements: light duty; soft to medium rock hardness, intermittent breaking with little or no raking; medium duty; medium rock hardness, intermittent to moderate breaking with some in-line raking; heavy-duty; medium to hard rock, moderate to continuous breaking with in-line and side raking. It all depends on the application.
Selecting too light a boom will cause increased maintenance and reduce the overall life of the stationary rock breaker system, increasing production costs.
Boom position is one of the most important factors for effective operation and reduced maintenance. Stationary rock breaker systems have a greater force when working in line with the material flow, as opposed to working perpendicular to material flow. If excessive raking of material is required, one would achieve higher production rates and reduced maintenance by mounting the boom in line with the feeder/crusher.
Mounting the boom perpendicular to the crusher can provide improved reach over the rock box, feeder and crusher with a shorter boom. Perpendicular mounting of the boom also typically allows for improved access to crushing equipment.
Whether the boom is in line or perpendicular to the crusher, the boom working area must be well within its optimum range of motion. This allows the boom to work with its hydraulic cylinders near mid-stroke, allowing for hydraulic cushioning of the hydraulic cylinders and for proper operation of hydraulic relief valves, which are used to limit undue stresses on the boom.
It is best to consult your supplier prior to installation to confirm the most suitable position for your application.
Crusher vibration
Crushers produce a lot of vibration. To isolate the vibration from the crusher to the stationary rock breaker system and hydraulic power unit, an operator can provide a separate tower for the rock breaker.
Installing a “breaker tool rest” will reduce the effects of crusher vibration on the boom structural joints when the boom is not in use, as it takes the overhung load off the boom. Hydraulic power units and motor starter panels should also be positioned in areas of low vibration with ease of access.
Lubrication of the boom and breaker’s moving parts is the most important maintenance requirement for maximum availability. Centralised or automatic greasing systems should be employed for the boom and breaker. Experience has proven that parallel type lubrication systems work better than series progressive type grease distribution systems in dusty and heavily contaminated applications such as quarry breaking. Regardless of the lubrication systems manufacturer, the series progressive type has much greater tendency to fail when compared with parallel systems.
John Wittenberg is a product development manager for Breaker Technology.