History of Fire Resistant Fluids
Fire resistant hydraulic fluids resist, or prevent, the propagation of fire either by means of their water content or by their chemical structure.

As the name implies, the original fluid in hydraulic applications was water, and it offered the highest degree of fire resistance possible. However, acceleration in the performance potential of fluid power systems dictated a need for much higher lubricating requirements that could only be satisfied by oil-based fluids.

Apart from isolated segments of basic research, little progress was made in developing suitable fire resistant fluids until the end of World War II. During the war, tragic incidents related to hydraulic fluid fires and major property losses at steel mills and foundries illustrated the urgent need for something to be done. Similar incidents in captive environments such as coal mines during the rapid postwar industrial expansion helped motivate a major joint research effort between government and industry. This work was directed at developing fluids that could replace oil-based hydraulic fluids at a reasonable cost and with no significant reduction in hydraulic system performance. Two basic approaches were undertaken. The first involved the introduction of water into the fluid, and the second a synthetic, non-aqueous product whose chemistry resisted burning or generated products of combustion that helped extinguish any flame.

There are two major groups of equipment - water and oil hydraulic equipment, each totally different in design and price. Water hydraulic equipment can operate with pure water as hydraulic medium, but to avoid corrosion of the system and bacterial growth in the water, specific additives are needed and are combined in the HFA concentrates. It is rare to use other fluids than HFA emulsions or solutions in water hydraulic equipment.

The more usual hydraulic equipment is originally designed for operation with mineral oil and with some modifications, these systems can be converted to operate with other types of fluid, with the exception of HFA emulsions or solutions.

Commercial products in both categories evolved during the '50s and '60s and are still in use today. In those days, Quaker Chemical marketed among others HFD-R (phosphate ester) fluids and was confronted with many disadvantages regarding the application of these fluids including:

• use of special seal material and hoses
• use of special paint
• toxicity
• high specific gravity
• hydrolysis
• heavy smoke formation
• high pour point
• low viscosity index
• high price

In the early 1970's, Quaker Chemical pioneered a new synthetic fluid, the 820 series of polyol esters, a highly successful concept because it eliminated most of the phosphate ester related problems. Twenty-five years later, we still lead the market with these products with their rare combination of excellent technical properties, fire resistance and biodegradability.