Worldwide, hydraulic equipment is a big consumer of lubricants, he points out. The global lube market overall in 2008 totaled about 40 million metric tons, according to Kline & Co. data, with slightly over half of that being automotive lubricants, said Hof, who is European technical service manager, lubricant oil additives, at the chemical company. Process oils accounted for another 12 percent of the total, and the next-largest product type was hydraulic fluids, with 11 percent of global demand. That makes them the largest category of formulated industrial product, ahead of general industrial oils such as turbine and compressor oils (9 percent), industrial engine oils (8 percent), metalworking fluids (6 percent) or lubricating greases (3 percent).

To make all these lubricants, the worlds lube manufacturers needed approximately 3.9 million tons of additives in 2008, or not quite 10 percent of the finished lubricants volume, he told the recent ACI European Base Oils & Lubricants Summit in London. But additives are not dosed at consistent rates across all products. Automotive lubes, for example, swallowed a disproportionate 66 percent of the additive demand, Hof said, again citing data from Kline, while metalworking fluids took another 17 percent. Only 3 percent of the worlds lube additives ended up in hydraulic fluids, because they are used at very low treat rates, often a mere 0.5 to 1.5 percent of the fluids volume.

And that, Hof said, means that while global hydraulic fluid demand in 2008 was 4.4 million tons of formulated oil, its additives uptake was around 100,000 to 120,000 tons. However, if you look at the lube additives market in terms of value instead, he insisted, youll see why hydraulic fluid is such an exciting area for additive producers. He pegged the global market value of hydraulic fluid additives at $230.4 million in 2008 – triple the value of additives used in industrial gear oils, and more than 10 times that for turbine oil additives. Whats more, this is an area where demand is expected to rise. This is a mature market in North America and Europe, he went on, but yes, its growing in Asia Pacific.

Upping the Stakes

The hydraulics market is characterized by a large and diverse number of players and stakeholders, including equipment manufacturers and end users who are putting greater demands on fluid performance. One can see a trend for changing hardware over the years, roughly equal to that seen in the automotive segment, Hof related. Hydraulic pumps are getting smaller and the equipment is being downsized, yet it must still be able to handle higher flow rates, pressures and temperatures. Everything is being miniaturized – and that includes the volume of oil being minimized.

With the oil sumps being smaller, theres less oil to handle the temperature than in the previous generation of equipment, he continued. So oil today sees more stress and pressure, more shear, and higher temperatures as it circulates in the system.

The market today seeks longer oil life, better equipment protection, higher purity, compatibility with a range of base oil types, and filterability. These needs have led OEMs to write their own specifications, Hof said, where generic industry standards once were acceptable as a baseline.

For example, some of the best-known lubricant industry standards are Germanys DIN 51 524 Part 1-3 standard for hydraulic fluids; the ISO 11580 fluid classification for biolubes; and ASTM D6158. On top of these, pump manufacturer Denison added its HF0, HF1 and HF2 specifications, which require rigorous in-house tests for water tolerance and other properties, and Bosch Rexroth wrote its own RE 220, 221 and 223 standards. Similarly, Eaton demanded fluids be approved to its I-286-5 or M-2950-5 specification.

Some national associations also have piled on, adding definitions and tests to address toxicity, biodegradability and other concerns, Hof told the ACI gathering on Sept. 23. The DIN standard for example outlines chemical properties and specifies some bench tests. But it only is valid for mineral oil based products – biobased fluids are not covered. So the national association standards fill a need. As examples, he cited Germanys VDMA 24568 and the Swedish Standard 15-54-34, which both include tests for biodegradability.

Tests and Hurdles

More and more, he stressed, industry standards only set the baseline for performance, while the OEM specs add more tests and emphasize their relevance to field performance. OEMs also are probing how hydraulic oil affects their equipment, and the chemicals used to address performance levels. They want to understand whats going into their equipment, so were seeing more interest in further testing and data, and it looks like more and more testing might be required.

End users are also asking for data, and even for certified test results, rather than simply accepting product claims from the fluid suppliers. In these cases, Hof hinted that equipment warranty issues may be coming into play.

Because of such demands, oil marketers will begin facing requalification hurdles for their hydraulic fluids, in order to sustain their product approvals. The buyers are not just accepting data from previous tests, but sometimes requiring them to rerun the test programs.

All these changes, Hof said, should be prompting fluid suppliers to ponder, How do I position my products, or decide whats needed? And how do I differentiate myself in the market?

First, he urged, look at the turf where the product competes. Is it a basic fighting grade, with just enough oomph to meet the industry specification? Is it a mid-tier product that can offer some additional attributes or perform to an OEM spec? Or is it a premium-tier product that delivers extra benefits to the user?

As you move up the tiers, you move into a more differentiated area, Hof said. So what can you do to upgrade? Base stock is an obvious answer, but additives can help blenders to offer greater oxidative stability for longer life, or sludge control and filterability for cleaner operation. Hydrolytic stability should be taken into account also, where needed.

Built-in Performance

While many European blenders use a mix of API Group I and Group II in their hydraulic fluids, Hof said, marketers in North America tend to use more Group II base oil in their higher-tier products due to its relatively easy availability. Group I base oils dominated the hydraulic fluid market in the past, and still do to some extent, but Group II and Group III are emerging as contenders, and synthetic base stocks are also more and more widely used. The future may even see some adoption of gas-to-liquids or other Fischer-Tropsch fluids.

Most blenders are aware that when they change base oils, they will change the properties of the resulting fluid. Moving from Group I to Groups II and III could require using more antiwear additives because of a loss in lubricity, for example, but that cost might be offset by less need for antioxidants. The key is to be sure the additive technology is fit for purpose in the targeted performance area, Hof emphasized, and that end users can see the value.

For example, longer fluid life can be a differentiating claim because many operators ask for results of the turbine oil stability test (TOST, or ASTM D943) as a way to evaluate oil life. The DIN standards baseline for TOST life is just 1,000 hours of operating life – but hydraulic fluid TOST performance can be boosted much further through both additives and base fluids.

In Europe, a number of fluid sellers now offer products that claim TOST to be between 5,000 and 10,000 hours, while one American company is claiming 18,000 hours on the TOST life, Hof observed.

Another differentiating approach can be to claim your fluid is ashless, versus having a standard zinc-based antiwear additive, he went on. A zinc-based additive in API Group I mineral oil would be considered a commodity-grade product, and most oil marketers wont spend much time and money on this. But if you can develop a product that is ashless, you can move up to the mid and premium tiers. We see most of the investment going here.

Another way to upgrade hydraulic fluids, said Hof, is by working to reduce energy consumption for the hydraulic equipment operator. The leading advocate of this approach, as reported in LubesnGreases, is Evonik RohMax, focusing on viscosity modifiers as a way to improve energy efficiency. Test data are available from other sources making similar claims, Hof observed, but there is no standardized test yet for hydraulic equipment energy efficiency, making objective evaluation difficult.

Efficiency is a combination of volumetric and mechanical factors, and using low-viscosity oils with high V.I. should help lower energy consumption, Hof said. Evoniks approach so far is a theoretical one and based on valid assumptions.

This would be attractive to end users, especially if they actually see an improvement. Even though its based so far on theoretical calculations, energy-efficient hydraulic fluids have gained ground, and are gaining in market acceptance. Im not sure yet it can be a differentiator by itself, Hof mused, but perhaps it will be possible to combine longer TOST life with energy efficiency in the same fluid. I do suspect that energy efficiency in hydraulics will gain more and more importance.