Despite the severity of the conditions and applications they encounter, concrete crusher and mobile shear attachments are capable of providing hundreds of hours of useful operation — provided they are properly used and maintained.
“Proper operating techniques must be closely adhered to, as outlined in the manufacturer’s operating guide, to eliminate costly mistakes that will damage the attachment or supporting carrier,” says Kevin Loomis, business line manager for Construction Tools, Atlas Copco.
This requires an understanding of proper attachment operation. “Improper application of the attachment and incorrect choice of material will cause damage to wear items, like cutting surfaces, teeth and other components,” says Greg Smith, marketing communications manager, Allied Construction Products. “It also decreases the carrier life and causes damage to carrier components.”
Operating Practices to Avoid
There are a number of common misapplications that can result in premature wear and tear on crusher or shear components.
“With both rotating shears and concrete processors, a very common operator mistake is to use the rotator as a prying or twisting tool,” says Clay Sederberg, engineering manager, Stanley LaBounty. “The rotator is designed for positioning, saving time tracking the excavator and also performing difficult vertical processing.”
“The rotation group in a shear is designed to position it for the cut, not to aid in cutting by twisting or prying,” agrees Tim Alseth, technical services manager, Genesis Attachments. “Twisting and pulling is really hard on the rotation group.”
The rotation function of the attachment is designed to withstand the breakout forces (stick and bucket cylinder manipulation) of the excavator, but not the drawbar pull (tractive) effort, Sederberg explains. “Using the excavator tractive force is a common misuse in demolition applications, where the attachment clamps down on a structure and then back tracks with the force of the excavator,” he points out.
This can cause stress and potential damage to both attachment and carrier components. “When you’re pulling and twisting, or grabbing heavy objects on one end vs. grabbing in the middle, it will back drive the motor shaft through the gearbox, which has a tendency to break things,” says Alseth. “Motor housings and gearbox covers, etc., will typically fail from doing things like that.”
Another practice to avoid is rubbing a mobile shear attachment on the ground during cutting operations. This can accelerate wear on the chin plate and the front of the upper jaws. “[The dirt] acts like sandpaper. With the amount of weight that you’re putting behind it with the excavator, it just erodes the front of the attachment away,” says Alseth. It can also result in dirt ingress between the blades, accelerating wear of these components.
Alseth further advises against reaching into and attempting to cut through a material pile rather than cutting individual pieces. “That drags material into the lower jaw between the guide blades before the upper comes in, and it jams the shear,” he states.
Attempting to break rather than cut material is another common misapplication of shears, particularly when trying to process material that is harder than the blades, such as hardened steel. “This has a tendency to chunk the blades away and cause premature wear,” says Alseth. “Also, the decompression spikes damage hydraulic system components both on the shear and the excavator.”
“The excavator builds pressure which is abruptly released as the material breaks, causing a pressure ‘shock’ to the entire hydraulic system (causing O-rings to fail and premature wear on all seals) on both the shear and the excavator,” Sederberg elaborates. “Continued shock loading can cause structural issues such as cracking in the jaws of the attachment.”