When the need arose to replace bearings supporting a curved pulley on a ship load conveyor at an iron ore port in Australia, NSK designed a solution using spherical roller bearings that were not only made from its own weather-resistant HTF steel, but also featured a nitrile seal. The result was an extension of service life that led to significant savings in downtime costs.
Due to the operating environment, the mining and quarrying industry requires highly reliable equipment that can withstand harsh conditions. So, when the bearings on a curved pulley serving a marine cargo carrier had just six months of operational life remaining, the iron ore port turned to NSK's expertise to devise a better solution.
NSK's team of experts investigated the bearing failure and discovered that ingress of iron ore particles and water contamination in the lubricant of the defective bearing compromised the service life of the flexible pulley. Any conveyor component that has a reduced operational life will result in costs for maintenance hours and lost production.
To solve the problem, NSK engineering experts began designing a new solution based on the company's proven line of spherical roller bearings. First, NSK decided to produce the bearings with its unique durable HTF steel. Heavy Duty Steel is an effective countermeasure to wear commonly found in the outer ring race, where the fixed load zone material is subject to wear when subjected to ingress of fine particles.
NSK's long-life HTF series bearings utilize advanced material engineering and heat treatment technology, facilitating superior resistance to wear, seizing and elevated temperatures. The result is a significantly longer service life and reduced maintenance costs and unplanned downtime. In fact, HTF series bearings can offer up to 10 times longer service life under contaminated lubrication conditions, such as those experienced at iron ore port facilities.
Another important design feature of the NSK proposal was the alloy spring seals with removable nitrile gasket (HNBR), which compensate for seal wear to further extend its operational life. Lip contact maintains pressure even in the event of misalignment.
In addition to extending service life – NSK's sealed spherical roller bearings achieved 12 months of trouble-free operation – the removable seal provided the iron ore port facility with the ability to check internal radial clearances using feeler gauges during the assembly process .
In short, this notable design feature enables precise management of the correct clearance as part of bearing assembly procedures. The concept centers on a seal mounted on a ring/bracket that is fully detachable (via screws), providing sufficient access to the feeler gauges to perform gap measurements. Furthermore, this unique design offers full interchangeability with existing solutions.
At iron ore port facilities, reduced downtime from lost production was the main contributor to cost savings, totaling €77,376 per year.
