NSK has improved the competitiveness of an OEM manufacturer of concrete head vibrators, by providing a bearing substitution and lubrication programme that is delivering operating cost savings of €306 pa on each vibrator, plus improving operating life and reducing maintenance requirements, mainly for replacement bearings.
NSK became involved with the project following the design and development of a new type of electric poker for concrete head vibrators. The OEM manufacturer had specified a deep groove ball bearing as an integral part of the new design. The major new operating target placed upon the bearing, a unit specified with C3 clearance and a steel riveted cage, was that it should last over 1000 hours; however, most bearing types that were tested had failed to reach even 100 hours.
NSK was consulted by the customer and asked to analyse the problems with the existing bearing specification, and to provide possible solutions that would meet the exacting specification for the new poker design. Concrete poker vibrators are used to dispel bubbles in wet concrete that can form as it is poured from the mixer truck, and air voids that become trapped in deep channels and columns.
When the wet concrete is poured into wall forms or foundations, air voids can occur deep within the mixture. After the concrete dries, large air voids can ruin the aesthetic look of exposed surfaces and also reduce the item’s structural integrity. The heavy end of a poker vibrator used to solve the problem is dropped deep into the wet concrete attached to a thick cable which terminates at a power source creating a high frequency vibrator unit, which puts huge stress on the rotating bearings in the system.
After an in-depth analysis, NSK first recommended replacing the oil used in the application – which didn’t have the required viscosity – for another, specific NSK oil. Secondly, NSK also suggested the type of bearing used in the design should be retained, but that it should be supplied with a larger radial internal Clearance (C4) to allow greater lubrication and allow for increased vibration damping within the bearing unit itself.
These modifications were made to a series of four bearings, which were then subjected to extensive testing. The tests validated entirely NSK’s recommendations, as all four bearings exceeded the previously unattainable 1000 operating hours and are now being specified for production.
The changes required to achieve this Olympian level of performance were small, but their value can be judged from the fact that they have helped the vibrator manufacturer introduce the new poker design, achieving target operational life and enhanced competitiveness, by saving €306 on each electric poker produced.