Synthetic cable assembly supplier Applied Fiber, based in Florida, USA, says its new haul truck tieback cable is a purpose-built, high-strength, synthetic-fiber cable used to keep a haul truck body safely in raised position during maintenance. Because the product maximizes the performance benefits of lightweight synthetic fiber cable while addressing some of the drawbacks of traditional round slings, it offers users a lighter-weight option compared with OEM steel body-up cables, and a safer, alternative to aftermarket synthetic round slings, according to L&H Industrial, Casper, Wyoming, USA, which handles orders and customer service for the product.
Available in either 15- or 23-ton rated versions, the tiebacks are engineered with aircraft aluminum end fittings and steel hardware that provide rugged, convenient connection points at the truck body and axle box. The fittings and hardware are built to reduce the potential for improper installation or misuse, and they are compatible with and designed to meet the original equipment load specifications on Caterpillar, Komatsu, Liebherr and Hitachi haul trucks, according to the vendor.
Because an ongoing concern with cables of all types is determining whether a specific unit has been abused or over-used, the Applied Fiber tieback incorporates a number of inspection features to remedy these shortcomings, including overload indication and clear go/no-go cable inspection criteria. For example, overload indication is integrated into the shackle-free fork fitting; the user can easily inspect the cable for an overload condition by using a precise pin gauge to measure for fitting deformation from overload conditions.
The tieback features a tough, extruded bright yellow polyurethane exterior jacket and cut- and-heat resistant braided Aramid fiber. The cable’s jacketing material serves as a wear indicator and provides two-layer protection for the core’s strength member. The core is sealed for protection against contamination or abrasion. In addition, the product allows the user to check beneath the outer jacket and view the core fibers at the area of highest wear, near the end fittings. The cable has a two-piece clamp at each end that, when removed, allows for full inspection of the core fibers.
According to the vendor, maintenance personnel will appreciate the tieback’s design and construction that makes them lightweight, easy to install and eliminates any need for heavy shackles. They won’t absorb water—getting extremely heavy at the wash stations as round slings often do—and they won’t freeze.
Fighting Cable Fatigue with FBG
As The Netherlands-based synthetic cable supplier FibreMax points out, draglines and electric rope shovels are among the most valuable production assets in surface mining. These machines must operate in a 24/7 environment—preferably without the need for costly and unexpected downtime due to failure or unplanned maintenance on IBS (intermediate boom suspension) or main boom suspension cables. These cables are subjected to fatigue loading and corrosion—which affects their longevity—and they are generally replaced during regular shutdowns, regardless of any possible remaining service life. Because the cost of lowering the boom on a dragline, for example, to replace its suspension cables can easily be $100,000, operators have a high level of interest in cables that not only have a longer service (or fatigue) life, but also can be monitored for wear during operations.
To this purpose FibreMax has developed the iPendant, an intelligent cable monitoring system that can be supplied in main boom suspension cables or IBS cables. The iPendant is a lightweight Aramid-fiber suspension rope with a built-in optical fiber that allows operators or mining managers to monitor the condition of these cables in real time. Using proven Fiber Bragg technology (FBG) the iPendant will convert any deviation in elongation of the suspension ropes into data to analyze or identify opportunities to improve machine performance.
As explained by FibreMax, the FBG is an optical sensor residing within the core of a standard, single-mode optical fiber using spatially varying patterns of intense UV laser light. Any deviation—such as that caused by a variation in elongation, for example—in the wavelength of the light is detected by the sensor and interrogated by a transducer. The signal from the transducer can be translated into data to analyze or identify opportunities to improve machine performance. When analyzing the number of load cycles or the elongation over time of the pendant, it is possible to predict the exact service life or maintenance schedule required for the pendant cable. The integrated optic fiber allows operators or managers to monitor the condition of the lines in real time. With proper software it is even possible to monitor dipper loads.
The optical fiber is integrated into the iPendant, encased in a protective tube placed between the load-bearing fibers. The optical fiber is attached to both end terminations of the pendant, where IP65-rated connectors lead to the interrogation unit. The monitoring system can be used in stand-alone setups or can be integrated into shovel or dragline monitoring systems.
A typical reading from the optical fiber system shows the displacement of the fibers during and after a certain number of load cycles until the maximum advisable number of load cycles has been reached. At that point, fibers typically start chafing and eventually lose strength. Using data collected by iPendant, FibreMax will advise users of the proper time to change the pendant.
FBG sensors and transducers have significant advantages over conventional electrical sensor technologies, according to FibreMax:
- FBG sensors are passive and use no electronic components. As a result, they provide offer long-term survivability in extreme environments. They retain signal stability over time, with zero drift, and can be used for years without need for recalibration, which makes them highly suitable for remote monitoring.
- They are immune to interference from electrostatic, electromagnetic or radio frequency sources.
- FBG sensors do not exhibit signs of fatigue even after millions of load cycles. They will easily survive the service life of the pendant.
FibreMax said it can supply iPendant cables in lengths up to 140 m with tolerance of 1 mm, in any rated breakage strength desired. The synthetic cables weigh up to 90% less than equivalent steel wire rope and require no greasing, painting or other routine maintenance, according to the company.