Assessment of Bearing Grease Anti-Corrosion Performance Using EMCOR Washout Test Rig Rahul Meshram, A H Zaidi, Kailash Yadav, Ajay Kumar Harinarain, Dr Naveen Pokhriyal, Dr S K Mazumdar and Dr E Sayanna Indian Oil Corporation Ltd, R&D Centre, Sector 13, Faridabad (Haryana), India.
1.0 Abstract: Greases are designed to protect bearings from corrosion during operation. Bearing greases are supposed to withstand conditions of cooling water spray and washout. The SKF EMCOR test is an age-old, standard test method used for the evaluation of dynamic anti-rust performance in bearings. However, this evaluates the corrosion performance of greases with bearings remaining dipped in stagnant water. This may not be a true representation of the severe conditions in plants where the cooling water constantly flows through the bearing housing and may lead to the grease being washed out and not being available for corrosion prevention. To account for this aspect, the modified EMCOR test rig with a water washout attachment was used to evaluate greases simulating conditions in the laboratory closer to those present in a steel plant environment. The antirust performance of several greases was evaluated in the EMCOR test rig with and without water washout. A correlation was attempted based on these studies, and a better understanding of the factors affecting grease corrosion performance was developed during these studies. 2.0 INTRODUCTION: Greases offer significant benefits over oils in bearing lubrication. They provide inherent sealing properties
thus keeping contaminations away from the surfaces to be lubricated. They also act to resist the washing effect of water in bearings and machine components. Grease can be used in open bearing components and even in vertical orientations by virtue of its retentive properties. In bearings, the reservoir of grease (either moved to the side or kept on the side) takes care of replenishment when the thin film existing earlier degrades or dries due to oxidation, thus protecting components at all times. It is estimated that greases lubricate over 90% of all bearings (source?), thus it is the preferred choice for lubrication of bearings. Bearing lubrication presents several challenges to the grease formulators. They have to do a balancing act of working with minimal quantity lubrication coupled with long bearing life (the same as that of the bearing itself). Additionally, they have the above challenges of working to keep the contaminants out and being able to work with ingress of water. The performance demands on the grease include working at higher speeds, loads, and temperatures and for extended relubrication intervals. This imposes severe demands on the grease used in such bearings. In this context, it becomes a complex task to predict the lubricating life or the relubrication interval to prevent lubrication or bearing failure with
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