How hydraulics can elevate crushing safety

Little has changed in basic crusher design over the years, other than improvements in speed and chamber design.

Rebuilding and keeping the same crusher in operation year after year has long been the approach of aggregate producers. More recent developments, however, brought about the advent of new hydraulic systems in modern crusher designs – innovations stimulated by the need for greater productivity, as well as a safer working environment.

The hydraulic systems in modern crushers are engineered to deliver greater plant uptime and eliminate the safety risks associated with manual intervention. The crushing arena, after all, is a hazardous environment. Large material and debris can jam inside, damage components and cause costly downtime. Also, manually digging out a crusher before repairs or restarts puts workers in extremely dangerous positions.

The Mine Safety & Health Administration (MSHA) has reported on a number of injuries and fatalities that occurred when someone climbed in or under a jaw to manually clear it, repair it or adjust the typical older-style crusher.

Consider that fatalities and injuries can occur even when the machine is locked out and tagged out. Examples from over the years include an injury that was sustained while a foreman attempted to dislodge a piece of steel caught in the primary jaw crusher. Another accident happened when a maintenance worker was removing the toggle plate seat from the pitman on a jaw crusher. The worker stood on a temporary platform when the bolts holding the toggle seat were removed, causing the pitman to move and strike him.

Fortunately, the hydraulic systems on modern crusher designs eliminate the need for workers to put themselves in or under the crusher. An overview of hydraulic system technology points to three key elements:

• A hydraulic chamber-clearing system that automatically opens the crusher to a safe position, allowing materials to pass

• A hydraulic overload relief that protects parts and components against overload damage

• A hydraulic adjustment that eliminates the maintenance downtime associated with manual crusher adjustments and maintains safe, consistent crusher output without the need for worker intervention

Hydraulic chamber clearing

Whether a crusher is jammed by large material, tramp iron or uncrushable debris – or is stalled by a power failure – the chamber must be cleared before restarting.

Manual clearing is a lengthy and risky task, especially because material can be wedged inside the crusher with tremendous pressure. Dislodging poses danger to workers placed in harm’s way inside the crusher.

Unlike that of the older-style jaw, the modern jaw will clear itself automatically with hydraulics that open the crusher to a safe position, allowing materials to pass without the need for manual intervention. If a feeder or deflector plate is installed under the crusher, uncrushable material will transfer smoothly onto the conveyor without slicing the belt.

Hydraulic relief

To prevent crusher damage, downtime and difficult maintenance procedures, the hydraulic overload relief system opens the crusher when internal forces become too high, protecting the unit against costly component failure. After relief, the system automatically returns the crusher to the previous setting for continued crushing.

Hydraulic adjustment

The modern crusher is engineered with oversized hydraulic cylinders and a traveling toggle beam to achieve reliable overload protection and simple crusher adjustment. All closed-side setting adjustments are made with push-button controls, with no shims being at any time.

This is a key development, as many safety incidents occurred during shim adjustment – a process that has no less than 15 steps as described in the primary crusher shim adjustment training program MSHA offers.