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Keywords
Noise, Hazards, Manufacturing industry, Stress, Mechanical engineering
Abstract
Reducing noise and vibration is an increasingly important objective for designers and users of a wide range of mechanical systems. Lubricants can contribute to reduction of overall noise and vibration generated by machines, both by reducing generation of acoustic energy in lubricated contacts and by modulating the transmission of vibration through the lubricant. This paper outlines various mechanisms by which the lubricant may affect the generation and transmission of acoustic vibration. Examples from the area of refrigeration compressor lubrication are presented, demonstrating that correct design and selection of lubricant can have a significant impact on noise and vibration.
1. Introduction
Modern industrial society frequently exposes people to high levels of noise, which are increasingly recognised to be hazardous. In the long term, high noise levels have physiological effects, which can lead to deafness or hearing impairment. In the shorter term noise can compromise workplace safety by impeding communication and can lead to illness through psychological stress.
Lubricated machinery is very often a significant source of noise. In the industrial workplace such sources include motors, compressors, gearboxes, hydraulic systems and metal-working operations. In the field of transport, internal combustion engines and transmissions in cars and trucks are obvious noise sources, but there are also other examples, such as compressors in refrigerated containers, and wheel-to-rail contacts in railway systems. In the home, domestic appliances such as washing-machines and refrigerators can contribute significantly to overall noise levels.
Reducing noise improves quality of life in both working and domestic environments. In the workplace, permissible noise levels are now typically controlled by legislation (Faulkner, 1976). In the home, low noise is an increasingly important performance requirement for all types of domestic appliance. Practical alternatives to mechanical modifications for control of noise and vibration are of commercial interest to machine manufacturers. It is therefore not surprising that lubricant optimisation as a means of controlling noise and vibration, in all types of machinery, is attracting increasing attention.
2. Noise generated in lubricated contacts
In many cases, the relative motion of components in a lubricated contact gives rise to noise and vibration. This section will outline some of these mechanisms and suggest how lubricant optimisation can contribute to reduction of...