The term fire-resistant often is mistakenly understood to be the same as fireproof. These terms are not necessarily the same. Almost all fire-resistant hydraulic fluids will burn under certain conditions. Water-based HFB and HFC fluids will ignite if a certain amount of water evaporates. Most HFD (synthetic) fluids will burn, but they self-extinguish when a flame is removed and do not propagate the fire. Only HFA water-based fluids can really be considered fire-proof.
Fluids can be tested to determine their fire resistance. The most common tests are those used by FM Global (formerly known as Factory Mutual Research Corp.), the testing and approval arm of a major industrial insurance underwriter. For many years, FM Global has maintained a list of less hazardous hydraulic fluids based on tests that simulate a high-pressure leak with an ignition source present.
FM Global published a standard based on tests of a fluid’s inherent capacity to ignite and propagate a flame. Beyond a simple approval designation, the FM Global standard calculates a value called the spray flammability parameter (SFP), with lower SFP values indicating better inherent fire resistance.
Fire-resistant fluids are grouped into three categories based on their calculated SFPs. Details of the new standard are available from FM Global. For more information on this topic, visit www.fmglobal.com (enter hydraulic fluids into the search window).
Beyond FM Global, many other organizations and companies have developed fire-resistance tests, usually to simulate a certain type of real-world accident. The U.S. Mining Safety and Health Administration has its own approval standard for FRHFs in underground mines. A person choosing a fire-resistant fluid should look for certification and details of the fire-resistance tests before selecting a particular product.