Biodegradable Hydraulic Fluids Prove Beneficial

Tony Noblit, Houghton International
Tags: bio-based lubricants, food grade lubricants

In 2000, Houghton International formulated a fire-resistant vegetable oil hydraulic fluid – Cosmolubric B-230. This technology made it affordable for manufacturers to switch to a biodegradable, oil-based, fire-resistant fluid without compromising performance.

After putting Cosmolubric B-230 to the ultimate test – continuous, daily use in heavy-duty applications – customers are pleased with its performance. Following are the experiences of Cleveland-based AK-ISG Steel and Dallas-based Chaparral Steel.

AK-ISG Steel: Safety is a Top Concern

Cleveland-based AK-ISG Steel is capable of producing 450 tons of flat-rolled electrogalvanized steel per year. The mill uses three hydraulic systems in its production process. Two of the three hydraulic systems use water-dilutable hydraulic fluid, but its 1,000-gallon Nireco Edge mask hydraulic system requires a straight mineral oil.

The pumps and pistons on this system need to be continually lubricated, and water-based fluids are incapable of doing the job. After a devastating fire in 2001 (caused by a spark that ignited hydraulic fluid), AK-ISG decided to evaluate its products, determined to find a fluid that met its performance requirements and was fire-resistant.

AK-ISG took no chance of another fire erupting. After consulting with its fluid supplier of 15 years, Houghton International, AK-ISG decided to switch to the Cosmolubric B-230.

Cosmolubric B-230 is a blend of natural esters rather than a synthetic oil. Because it is made from a canola oil base along with a unique blend of additives, Cosmolubric B-230 is fire-resistant. Management was convinced of the product’s effectiveness after seeing an operator spray B-230 directly into a flame – with no flare-up.

While the product costs more than conventional hydraulic oil, it provides excellent lubricity and equal pump life. Most importantly for AK-ISG, B-230 yields the same performance characteristics as the previous fluid, making it an easy swap. “Although it is not an extreme temperature application, the Nireco system is touchy,” said Chris Pace, engineer for Hydraulic Systems at AK-ISG. “Changes in viscosity can change the performance of the valves, so we wanted to use a similar product.”

Because the hydraulic fluid is extremely stable, operators at AK-ISG have not had to change out the system since the fluid was introduced in 2001. The mill uses approximately 1,000 gallons per year, which it keeps in a tote to top-off the system as needed.

“We’re pleased with Cosmolubric. It hasn’t oxidized and our acid numbers, which we monitor constantly, are fine. I haven’t found a product that does what it does. Houghton samples our fluids monthly. Because we have 40 cylinders, mineral oil gets mixed with the fluid. Houghton conducts flash point tests periodically to make sure that the fluid maintains a high flash point. They do whatever is necessary to keep us operating efficiently.”

Chaparral Steel: Canola Tackles Oxidation

As the nation’s 10th largest steel mill, Chaparral Steel is a technologically advanced facility that recycles steel into bar and structural products. Chaparral’s products include specialty bar grades for use in the construction, automotive, railroad, defense, mobile home and energy industries.

Chaparral’s melt shop uses four different hydraulic systems to move red-hot steel out of the furnace and onto the cooling bed, then into the rolling mill for processing. Each system has a 600-gallon fluid tank that is topped-off on an as-needed basis.

Because Chapparal hydraulic systems operate under high pressures, between 1,800 and 2,000 psi, acid started to accumulate.

“These systems run hot, so condensation seeps in,” said Bob Davis, manager of crane and hydraulic steel production at Chaparral Steel. “In the past, we’ve had problems with the condensation turning the fluid to acid. We tried different hydraulic fluids, and they always had problems.”

Performance improved when Houghton recommended Cosmolubric B-230 as a cost-effective, stable, biodegradable oil-based hydraulic fluid to combat acid problems while maintaining its fire-resistance properties. After switching to the fluid in 2001, Chaparral performed ongoing testing and analysis. Houghton sampled the fluid on a quarterly basis as well, testing for acid and other physical characteristics. The fluid has never oxidized, and the acid numbers have remained low.

“Cosmolubric B-230 has been in the system now for four years, and we haven’t had any acid issues. It costs less than other synthetic fluids, and performs as well or better than the fluid originally recommended by the manufacturer for use with the system. I like the product, and recommend it to our other mills,” Davis said.

The Quest for the Perfect Hydraulic Fluid

The pressure is on. Today’s products and materials need to be biodegradable and environmentally friendly, pushing manufacturers to find alternatives to traditional products. This pressure includes hydraulic fluids – hauling gallons of mineral oil-based fluids because hazardous waste is no longer acceptable or cost-efficient.

Until recently, manufacturers haven’t had much choice. Synthetic alternatives to mineral oil, such as polyglycols and polyol esters, have been priced out of reach for most manufacturers. Those with high-pressure and other extreme applications requiring a fire-resistant hydraulic fluid have had to “bite the bullet” - paying up to six times more for synthetic hydraulic oils than they used to pay for petroleum-based products.

To answer this need, Houghton began to formulate an effective hydraulic fluid based on vegetable oil. Because vegetable oil is a naturally occurring ester, it is biodegradable. It also exhibits good lubricity, on par with synthetic polyol ester fluids. In addition, vegetable oil is a relatively inexpensive base stock. So what’s the problem?

These vegetable oils have traditionally exhibited low oxidative stability – a critical shortcoming which prevented their widespread use. However, Houghton continued its research and testing, working with additive packages and using selected base stocks, and at last created the fire-resistant fluid.

Cosmolubric B-230 is canola oil-based, and uses additive technology to successfully perform like polyol esters. It contains viscosity index modifiers, rust and oxidation inhibitors, extreme pressure (EP) additives, copper passivators and defoamers. These additives have improved the oxidation stability of vegetable oils so that they can equal the desired characteristics of synthetic polyol esters.

In benchmark tests comparing Cosmolubric B-230 to premium synthetic polyol ester fluids, Cosmolubric was found to provide overall comparable performance in lubrication, pump life and oxidative stability (Table 1).

Canola Oil
Synthetic polyol
Mineral polyol
Clear amber
Clear amber
Clear amber
ISO viscosity grade
Viscosity at 210°F
75 SUS
68 SUS
53 SUS
Viscosity at 100°F
335 SUS
305 SUS
330 SUS
Viscosity index
90 to 100
Acid number
Flash point, °F
Fire point, °F
Pour point, °F
Specific gravity
Table 1. Cost Comparison of Hydraulic Fluid Base Stocks

Houghton released Cosmolubric B-230 in 2001. The fluid is Factory Mutual approved as a “less hazardous fluid.” It also passed the ASTM D665A corrosion test. Among its physical properties are viscosity index of 214, ASTM flash point of 495°F (257°C), and ASTM fire point of 610°F (321°C) – all of these properties are par with the leading synthetic polyol esters. But the good news is that Cosmolubric B-230 costs less, making it a practical replacement for synthetic polyol esters, especially in applications where fire resistance is a paramount concern (Table 2).

Hydraulic oil type
Cost per unit
Mineral oil
Invert emulsion
Water glycol
Canola oil
Synthetic polyol ester
Phosphate ester
Table 2. Cost Comparison of Hydraulic Fluids Base Stocks