Oil be back - why getting lubrication right is a slippery subject

Using the right lubricants can make the difference between smooth operation and premature failure, and can even improve energy efficiency. E&T casts oil on troubled machinery.

On the factory floor, one of the big success stories of the past few years has also been one of the least obvious - better lubrication practices. Fuelled by the likes of 5S techniques for well-organised workplaces and 'visual factory' devices that provide early warning of low levels of lubricant, a huge change has taken place in shopfloor lubrication management.

Improved industrial relations have played a part, of course. In the bad old days of British manufacturing, factory floor operators operated machines, while fitters maintained and repaired them. Asking operators to check oil levels - never mind top up any found to be low - involved crossing demarcation lines that separated pay levels, organisational reporting lines, and trade unions.

Those days are gone. But if the gearboxes, pumps and machine tools that populate factory floors are being topped up as never before, there is still - sadly - no guarantee that they are actually being replenished with the intended oil.

"One of the biggest problems we find is that the wrong oil has been used," says Tom Kent, an applications engineer with Littlehampton, Sussex-based condition monitoring and lubrication analysts Kittiwake Developments.

Damage from oil with the wrong viscosity

Whether topped up from the wrong barrel, or - worse - filled entirely with the incorrect lubricant, such as hydraulic oil in place of regular gearbox oil, the use of the wrong oil can and does have a significant effect on equipment performance and effective life, he explains.

"With a viscosity that's too thin, exceptional wear can occur, while with a viscosity that's too thick, you're not getting enough oil into the right places," he points out. "Plus, of course, the wrong oil will usually mean the wrong additives, introducing another variable."

It's easy to blame sloppy maintenance practices. But in reality problems can begin much earlier. Manufacturers, it seems, tend to fall into two categories.

First, there are those who slavishly follow original equipment suppliers' lubricant recommendations in terms of oil manufacturer and grade, and consequently wind up stocking a large range of often identical oils. Second, there are those who attempt to impose some order on the ensuing chaos, standardising on specifications, and eliminating unnecessary duplication.

Both approaches have their dangers. Clearly, and especially so with oil selection delegated to factory-floor operatives at point of use, having more barrels to choose from multiplies the risk of the wrong choice being made. Rationalise the stocks, though, and inappropriate decisions may be made about which oils should no longer be purchased.

And there's another danger, too: choices about oils being made on grounds of price, rather than fitness-for-purpose.

"While the typical spend on high-performance oils is relatively small, the potential impact on cost through increased wear, scrap and energy use is much higher," says John Hopkinson, marketing manager for industrial lubricants and services at Swindon-based oil giant Castrol. "But, as a general rule, we do see customers willing to pay a higher price when they see the benefits."

That, though, requires a certain breadth of perspective that may not always be present. While Hopkinson is happy to cite examples such as Ford, where careful cost-benefit analyses make the economics of high-performance oils crystal clear, lower down the corporate pecking order different imperatives may apply.

"It's surprisingly common to find buyers just going out and getting the best price they can," says Richard Jones, head of supply chain at specialist consulting firm Newton Industrial Consultants. "They're looking at price, rather than what's 'best value' for the business - and a cheaper oil reflects favourably on the purchasing department, while improved gearbox longevity doesn't."

Yet help is at hand. Millers Oils of Brighouse, west Yorkshire, is one of a number of firms that aim to cut through the confusion and provide advice both on rationalisation and the most efficient use of oils in the workplace maintenance environment.

The ideal lubricant

"In a perfect world, with a machine running at a steady speed, under a steady load, and at a steady temperature, it's possible to calculate the ideal lubricant," explains Martyn Mann, technical director at Millers. "But once you start changing the variables, life gets complicated - especially if you're running close to a machine's maximum design parameters. Oil is seen as something of a black art, and it's quite common for us to be asked to advise."

Where the problem is a proliferation of oils, Millers can help cut the range down by identifying equivalent specifications - and, if needs be, supplying its own-brand alternative, thereby cutting costs as well as the number of oils stocked.

And, being independent, companies such as Millers can choose the best base oil, Mann explains: the oil majors, generally speaking, are constrained to use base oils from their own upstream operations. Even supposedly similarly-specified oils from the oil majors can vary in performance, he notes: for irrespective of proprietary additives, base oils themselves have different properties.

But rationalisation can also bring other benefits. The savings generated, for example, might permit a manufacturer to 'trade up', by going for a superior grade, with improved anti-wear characteristics. Another option is a multi-grade oil, which spans several viscosities in a single oil, and proves useful in circumstances when a machine's operational envelope has changed, or is variable.

With more expensive oils, manufacturers might wish to re-think their oil replacement policies, adds John Chappell, maintenance services director at Stockport-based maintenance consultancy AV Technology. Condition monitoring, he points out, offers both insight into machine wear as well as oil quality.

"Good contamination controls and filtration strategies extend the life of the oil, as well as prolong the life of the machine in question," he says. "With synthetic oils, you can throw out the oil when it becomes degraded, and not just because it has reached a given service interval."

Energy-efficient oils

A new generation of energy-efficient oils looks set to compound the confusion, calling for even more careful cost-benefit analyses. The pitch is simple: as crude oil prices soared towards a peak of $147 a barrel in the summer of 2008, manufacturers around the world experienced sharply higher energy bills.

"We've seen a lot of interest in energy-efficient oil - although it's still unclear if it's a passing phase, fuelled by last year's spike in the price of crude, or something of a longer-term development," says Castrol's Hopkinson.

But Shell has made up its mind, launching the latest of a series of energy-efficient oils earlier this year. Shell Tellus EE is Shell's first hydraulic fluid that has been designed specifically to help improve the energy efficiency of the machinery in which it is used, and has been shown to help companies reduce the energy consumption of their hydraulic machinery by up to 8 per cent.

The oil works by reducing friction loss in hydraulic pipework - which is typically some 45 per cent of the total loss, explains Ahmet Guven, global product application specialist at Shell Lubricants. "Friction loss is directly correlated with viscosity," he explains. "As the pressure in hydraulic systems increases, the volume of the oil decreases - but Tellus EE decreases in volume less than mineral oils, and remains relatively thinner at increased pressures. The higher the pressure, the more energy-efficient the oil is."

But will the savings be enough to compensate for the higher price? Castrol's Hopkinson, for one, worries about translating gains in the laboratory into shopfloor reality. "Energy efficient lubricants seem like a good idea, but the problem is making it scalable enough to have sufficient impact," he notes. "We've run comparisons of energy-efficient oils, and the savings are genuine, but not always meaningful. A 5 per cent saving or so over a handful of pumps isn't a huge deal."

That said, he notes, the trend in equipment design is towards machinery with smaller oil sumps, placing a higher reliance on high quality - and energy-efficient - oils. But replacing the oil in existing equipment, particularly if it's more than a few years oil, may contribute only marginal savings.

In lubrication, it seems, the trick lies in figuring out where savings really arise - a trick that's still at times more art than science.

Recent articles

Info Message

Our sites use cookies to support some functionality, and to collect anonymous user data.

Learn more about IET cookies and how to control them

Close