Fire resistant (FR) hydraulic fluids are used where there is a risk of fire. Molten metals, open flames, electric arc, hot metal surfaces, and high operating temperatures are all potential fire hazards.Welding equipment, die casting and extrusion machines, foundry equipment, forging presses, furnace and glass forming machines, injection molding machines, steel and metal working industries, and mining machinery are some examples of where FR fluids are extensively used. The need for FR fluids was realized in the 1950s, when many fire accidents took place in mining and other industries due to the leakage of high-pressure mineral oil. It should be noted that hydraulic fluid-related fire accidents still take place. Twenty-five people died and 50 were injured in a fire in a food processing factory in the U.S. when a hose burst and pressurized oil sprayed onto a fryer in 1991 . To avert such accidents, FR fluids have been made more fire resistant. Also, worldwide concern for safety in the workplace is increasing. Consequently, hydraulically operated devices (instead of people) now perform operations near heat or fire sources, and use of fire resistant fluids is expanding. Tighter government regulations, better understanding of fire hazards and consequent development of test procedures have also made significant contributions toward the development of fire resistant hydraulic fluids. Details on the FR fluids commonly used in industries are covered in this chapter. Any fire resistant fluid must possess the following characteristics:
• The fluid must resist ignition.
• It should have the ability to snuff the flame and prevent it from spreading when the source of ignition is present.
• The fluid must be self-extinguishing when the source of flame is removed.
It is important to realize that FR fluids are neither flameproof nor fireproof; fire resistance means only that these fluids have a higher resistance to ignition than other fluids, and that even if ignited, the fluid has properties that will arrest the spread of flames. The prime reason for using a fire resistant fluid is to reduce the possibility a fire in the workplace. The fluid must also be nontoxic and meet the other technical requirements of a normal hydraulic fluid.