Machinery Lubrication

Machinery Lubrication May June 2015

Machinery Lubrication magazine published by Noria Corporation

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20 | May- June 2015 | IN THE TRENCHES WE S CA SH | NORI A CORPOR AT ION ynthetic" is an all-encom- passing term used to describe manmade base fl uids utilized in the formulation of lubricants. Synthetics can have sharply different performance attributes and can at times be mutually incompatible. The differences between these base fl uids must be understood in order to accommodate the needs of the machine application as well as the proper- ties of the lubricant. What Makes a Synthetic? Synthetic lubricants do not originate from crude oil like conventional mineral oil. Instead, synthetic lubricants are formu- lated from derivates of natural gas and other base materials. For instance, polyal- phaolefi ns (PAOs), which are among the most common synthetic base oils, are formulated from ethylene and decene (largely derived from natural gas). Through the process of polymerization, these mole- cules are built from the ground up and offer a number of benefi ts. Unlike mineral oils, in which a single batch of oil may contain millions of different molecular structures, the molecular sizes and shapes within a single synthetic oil are much more consis- tent. This leads to more consistent fl uid properties and predictable life cycles. Synthetic Benefits Perhaps the most common advantage associated with synthetic fl uids is that they last longer in service. This is due in large part to the consistency of their molecules and the lack of aromatic structures. These molecules are much more robust and better able to handle the rigors of opera- tion without oxidizing or thermally degrading rapidly. Another benefi t is the increased viscosity index. Viscosity index is the relationship between a change in viscosity and a change in temperature. The higher the viscosity index, the smaller the relative change in viscosity with temperature. This allows for a single fl uid to maintain its viscosity at all in-service temperatures without having to change viscosity grades between seasons. Synthetics also have improved low-tem- perature performance characterized by a low pour point. Fire resistance is a common requirement for most turbine hydraulic systems. The majority of these systems use a synthetic fl uid to achieve this fi re resistance. One of the properties that helps with a fl uid's fi re resistance is its fl ash point, which is the temperature at which a fl ame propagates across the surface of the oil. Synthetics generally have higher fl ash points than their mineral oil equivalents. Synthetic lubricants not only have high-performance basestock but usually also benefi t from premium additive systems. In fact, many of the benefi ts that are commonly attributed to synthetic lubricants actually come from the addi- tives with which they are formulated. Synthetic Drawbacks The biggest drawback to using synthetic base oils is the additional cost associated with them. They may be anywhere from three to 15 times more expensive than mineral oil. If you are considering making a switch from mineral to synthetic oils, you must be sure that the benefi ts to be real- ized will make up for the additional front-end cost. There are several ways in which this cost can be recouped, such as extending oil change intervals, employing product consolidation or decreasing machine failures. Another risk with synthetic fl uids is the compatibility issues that come with using these lubricants. Some synthetics have been known to cause seals to swell and reduce lubricant fl ow, while others can dissolve seal materials, allowing leaks and possibly severely damaging the machine. Not only do some synthetics have compatibility issues with seals, but most have compatibility issues with other fl uids. Polyalkylene glycol (PAG) base oils are UNDERSTANDING the Differences Between SYNTHETICS S " 55 P E R C E N T of lubrication professionals use both synthetic and mineral-based lubri- cants at their plant, according to a recent survey at Machinery-

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