Hydraulic fluid, sometimes referred to as hydraulic oil, is a large and loosely defined class of materials with a variety of uses as a medium by which energy is transferred. They are typically a mixture composed of a base fluid with various additives creating a proprietary product with specific chemical characteristics designed for a specific use. The most common uses are within hydraulic machinery as a means of transferring pressure.
History of Hydraulic Fluid
Dating as far back as Ancient Egypt, water was utilized as the original hydraulic fluid. As its uses expanded and technology advanced, more options for hydraulic fluids have emerged. Beginning in the 1920s, petroleum derivatives became the preferred base due to their desirable chemical properties. Moving forward to today, hundreds of millions of gallons of hydraulic fluids are sold each year in the united states alone. They can be found in industrial machinery, vehicles, aircraft, drilling equipment, and other powered equipment. A multitude of different hydraulic fluid base liquids are used today, but the most common are mineral oils, organophosphate esters, and polyalphaolefins.
The most desirable chemical properties of all hydraulic fluids are low compressibility, low volatility, low flashpoint, and low corrosiveness to allow for use in machinery under high pressure. More specific chemical properties such as flammability, temperature stability, and conductivity can be chosen if it is beneficial for a specific use.
Effects of Hydraulic Fluid Releases
Releases are typically sudden, easily observable, and quickly identified. Although they typically break down in air or soil, hydraulic fluids are likely to adhere to soil particles. The exact chemical properties and potential health effects of hydraulic fluids will vary widely based on their composition. Some may cause nervous system issues, some may be carcinogenic, and some may be completely harmless to flora and fauna. Due to the lack of a specific chemical of concern, the regulations specifically regarding hydraulic fluids are sparse. Although the disposal of hydraulic fluids is regulated under the Resource Conservation and Recovery Act (RCRA), no remedial standards have been established. In most cases, determination of remedial completion will be based on comparisons with background levels.
Sources of Hydraulic Fluid Releases
Due to the variety of use cases, hydraulic fluids can enter the environment through a variety of pathways. Failures in equipment are the most common, often resulting in hydraulic fluid releasees at active construction sites. Backhoes, manlifts, drilling equipment and other hydraulic machinery have been known to fail during operations. These types of equipment are frequently used in many remediation strategies, which presents a risk for comingling in areas of historical impacts. Hydraulic fluids are sometimes stored in above or below ground storage tanks prior to use. If containment systems fail, larger quantities of hydraulic fluid can be released. This type of release can require significantly more cost and effort to successfully remediate. Another common source of hydraulic fluid contamination is cars and trucks. Virtually all vehicles on the road today utilize hydraulic break and steering systems. During an accident, hydraulic fluids can be released along with other fuels, oils, and cargo. Mineral oil or polyalphaolefin based hydraulic fluids may overlap in constituents with other petroleum-related releases. In all cases, determining the composition of the hydraulic fluid in question becomes key for selecting analytical methods and remedial goals.