Primary safety
October 13, 2008 By: Jim Schreiner Pit & QuarryTo quote a wise crusher operator, “Crushing is not just about tons per hour; it’s about safe tons per hour.” But consider that a safe workplace is not achieved via mere lip service and signage, but rather from the right mindset -- from owners, managers and workers -- and from the manufacturers of each piece of processing equipment.
The crushing arena is a hazardous environment. Large material and debris can jam inside the crusher, damaging components and causing costly downtime. Importantly, manually digging out the crusher before repairs or restarts puts workers in dangerous positions. The Mine Safety and Health Administration (MSHA) has reported numerous injuries and fatalities incurred when climbing in or under the jaw to manually clear, repair or adjust the typical older-style jaw crusher.
As such, a welcome market entry is that of modern crusher design, derived from a major impetus to put safety first while also meeting demand for far greater productivity and ease of maintenance. A recent example is the newly designed Telsmith 3258 jaw crusher, a model engineered with innovative hydraulic systems that handle all of the “heavy work,” maximizing uptime and eliminating the need for maintenance personnel to climb into or under the jaw.
The hydraulic chamber clearing system on the Model 3258 jaw automatically opens the crusher to a safe position, allowing materials to pass. Its hydraulic relief protects parts and components against overload damage, and its hydraulic adjustment reduces maintenance time and maintains safe, consistent crusher output without the need for manual intervention. A closer look at these hydraulic systems illustrates how each affects safe operation and increased productivity.
Hydraulic chamber clearing
Whether a crusher is jammed by large material or uncrushable debris, or stalled by a power failure, the chamber must be cleared before restarting. Manual clearing is a lengthy and risky task, especially since material can be wedged inside the crusher with tremendous pressure, and dislodging poses much danger to workers placed in harm’s way inside the crusher.
Unlike that of the older-style jaw, the Model 3258 jaw clears itself automatically with hydraulics that open the crusher to a safe position and allow materials to pass. If a feeder or deflector plate is installed under the crusher, uncrushables will transfer smoothly onto the conveyor without slicing the belt.
Hydraulic relief and adjustment
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.
An Ohio-based crushing operation said that hydraulic relief is “a huge advantage” for it. The operator explained that like typical older-style crushers, its previous jaw made use of a “shear toggle that acted somewhat like a fuse.” In other words, the toggle was designed as a weak link that would bend or break away when pressure became too great and prevent further damage. However, once the toggle was sheared or broken, the maintenance crew would spend up to four hours to remove and replace it, and that assumes the part is available. With toggle shear occurring more than five times per year, high maintenance costs adversely affected profitability. So, hydraulic relief was a big part of the operation’s decision to invest in a new Telsmith crusher.
Telsmith engineers have designed the Model 3258 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 needed at any time. This is a key development as many accidents and injuries have occurred during shim adjustment, a process that has no less than 15 steps as described in the primary crusher shim adjustment training program offered by MSHA.
Safe toggle removal
The hydraulics in modern jaw designs are integral to fast, safe toggle maintenance, say Telsmith engineers. As shown in the accompanying illustration, the process is initiated by hydraulic adjustment cylinders that push the pitman forward where it is locked into position with lockout pins that insert from the side. Then hydraulic tension cylinders, mounted on the side of the toggle, pull the toggle beam back, allowing it to be safely lowered away. Toggle lifting eyes assist in safe, speedy toggle removal.
Note that older jaw designs would often require that the pitman be held forward with chains and a winching device that is not always easy to secure. Also, a worker would be required to climb under the jaw to remove the tension assembly before the toggle could be lowered -- a risky task that puts the worker directly under the loose toggle.
Modern jaw designs eliminate the need for workers to go under the jaw until after the loose toggle is safely lowered.
A safety-focused culture
Safety is a culture and should be championed by every worker in the operation. At the same time, management should respond immediately to each worker’s safety concerns and successes, rather than monitoring only overall team efforts and targets. And, manufacturers should engineer greater safety as well as productivity into their units while accompanying their equipment with strong operational and safety training programs.
It has never been more important to consider the potential hazards of conventional, older-style crushers versus modern jaw crusher design. And even during today’s challenging economic climate, safety should never be minimized due to a need to achieve lower prices or costs. Modern crusher design is a major development in safe material processing -- one that allows operations to maximize productivity while putting safety first.
Telsmith Inc., www.telsmith.com
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