“Rope sheaves in the pulp and paper industry are notorious for frequently causing maintenance problems at paper mills, leading to unscheduled shutdowns that negatively affect production levels and drive up costs,” notes Frans Odendaal, SKF Product Manager – Power Transmission. He explains that if the sheaves are not running properly, the rope can slip, resulting in rope wear and paper tail tears.
He adds that worn ropes can break while lubricant leakage can lead to paper damage. “Furthermore, accessing hazardous locations to re-lubricate rope sheave bearings puts maintenance personnel at unnecessary risk.” Pointing to a less common but very important problem, Frans cautions about the dangers of sheaves falling off their shafts causing serious injury to personnel and damaging product, felts and rolls.
However, mills often accept these conditions as normal and have resorted to applying preventive maintenance to minimise the potential problems caused by malfunctioning rope sheaves due to bearing failures. Frans notes that inadequate lubrication and corrosion damage are two main causes of bearing failures. “Despite periodically removing and replacing the sheaves with new or refurbished units, or even dismounting the failed bearings and mounting new ones, rope sheave failures continue to occur, especially during machine start-up, when the units’ performance is critical.”
But mills no longer have to contend with the high costs of rope sheave maintenance. The fitment of SKF rope sheaves will increase uptime and dramatically reduce maintenance costs. The rope sheaves have been specially designed and engineered to reduce rope wear as well as the possibility of paper breaks. Mills are able to schedule planned stops for less urgent and routine maintenance.
The rope sheaves are based on SKF’s tried-and-tested wheel hub units which perform well even under extremely stringent conditions. Rope sheaves are fitted with two deep-groove ball bearings which are ideal for accommodating low loads and moderate speeds. Both the unit as well as the bearings are sealed for life, ensuring long maintenance-free periods.
Not only is the need for grease nipples and lubrication ducts which can potentially leak and contaminate the product eliminated, but personnel are no longer required to enter difficult-to-access potentially hazardous areas to re-lubricate the bearings. The zinc-coated, corrosion resistant SKF sheave rope units are also supplied with a special grease.
Furthermore, a patented security device locks the unit firmly in place, preventing the unit from falling off the shaft, even in the unlikely event of bearing failure, subsequently creating a much safer working environment for paper mill personnel.
Samantha Joubert, Marketing Manager, SKF
Tel: (011) 821-3602