Hydraulic fluids contamination control

Hydraulic fluid contamination may be described as any foreign material or substance whose presence in the fluid is capable of adversely affecting system performance or reliability. It may assume many different forms, including liquids, gases, and solid matter of various composition, sizes, and shapes. Solid matter is the type most often found in hydraulic systems and is generally referred to as particulate contamination. Contamination is always present to some degree, even in new, unused fluid, but must be kept below a level that will adversely affect system operation. Hydraulic contamination control consists of requirements, techniques, and practices necessary to minimize and control fluid contamination. 

After the type of system has been selected, many of these same factors must be considered in selecting the fluid for the system. This chapter is devoted to hydraulic fluids. Included in it are sections on the properties and characteristics desired of hydraulic fluids types of hydraulic fluids hazards and safety precautions for working with, handling, and disposing of hydraulic liquids types and control of contamination and sampling. 

Maintaining hydraulic fluid within allowable contamination limits for both water and particulate matter is cmcial to the care and protection of hydraulic equipment. Filters will provide adequate control of the particular contamination problem during all normal hydraulic system operations if the filtration system is installed properly and filter maintenance is performed properly. Filter maintenance includes changing elements at proper intervals. 

Eleftherakis, J., A Proven Approach to Hydraulic and Lubrication System Contamination Control , Lubr. Fluid Power J. 2, 13-20, Aug 2001. 

Extraction wells are usually necessary to maintain hydraulic control of the plume and to ensure that the plume does not migrate into clean areas or accelerate migration toward sensitive receptors. Placement of extraction wells is especially important with systems that use nutrient injection wells or infiltration galleries. These sources of fluids can alter natural groundwater flow patterns, which may cause contaminant migration in an unintended direction or rate. If the natural groundwater system has a sufficient concentration of electron acceptors and nutrients, to achieve remediation at an acceptable rate, it may not be necessary to add any additional materials. 

Permeability and hydraulic conductivity are the controlling factors in the effectiveness of in situ treatment technologies. The ability of soil flushing fluids to contact and remove contaminants can be reduced by low soil permeability. Low permeability can lessen the volatilization of VOCs in soil vapor extraction or limit the effectiveness of in situ vitrification by slowing vapor releases. 

This ability of surfactants to solubilize NAPL components and coalesce into thermodynamically stable microemulsions is of critical importance in their selection for use in NAPL remediation. This is because microemulsions are highly fluid and can easily flow through permeable media and transport contaminants with them under the very low hydraulic gradients typical of shallow, unconfined aquifers. By contrast, macroemulsions, which are physical mixtures or dispersions of one liquid phase interspersed in another liquid phase are unstable, often very viscous, and do not flow easily or in a way that is predictable or easy to control, and thus are highly undesirable. 

---