Hydraulic systems contaminant levels

Hydraulic system contamination can arise from a number of sources, including accumulation of debris that results from the hose assembly process itself. A number of methods are available to manufacturers to allow them to quantify the level of contaminants in such systems and optimise their production processes. 

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. 

Accuracy and repeatability of temperature/time/velocity/pressure controls of injection unit, accuracy and repeatability of clamping force, flatness and parallelism of platens, even distribution of clamping on all tie rods, repeatability of controlling pressure and temperature of oil, oil temperature variation minimized, no oil contamination (by the time you see oil contamination damage to the hydraulic system could have already occurred), machine properly leveled. 

Oils used to lubricate machinery, motors, hydraulic systems and other mechanical devices can sometimes contaminate fuel systems. These oils often carry with them low levels of the metals which wear from the lubricated surfaces of the mechanical components. Some common wear metals and possible sources of origin are listed in TABLE 4-12. 

Hiac PC4000 portable liquid particle counter is a contamination measurement tool, designed to run on-line analyses of hydraulic systems and fluids. The fully self-contained counter operates in the light-blocking mode using a laser diode and reports contamination levels at 4, 6, 10, 14, 21,38 and 70 pm at a flow rate of 60 ml min. ... 

All hydraulic systems are contaminated, although the level of contaminant varies considerably depending on the environment and the use for which the system exists. 

In fact, in excess of 70% of hydraulic system failures are caused by contamination or poor fluid condition. Hence filters are essential in modem hydraulic systems, to provide a particular or specified level of contaminant removal. This can vary with the type of system, types of components involved, application and duty cycle. 

Filters fail because they either burst open or clog up. If a filter is left in a hydraulic system long enough, one or other of these two failnre mechanisms wiU occur. For the precise needs of hydraulic system design, a snitable scheme for representing contaminant levels is required. 

Selection and care of the hydraulic fluid for a machine will have an important effect on how it performs and on the life of the hydraulic components. During the design of equipment that requires fluid power, many factors are considered in selecting the type of system to be used-hydraulic, pneumatic, or a combination of the two. Some of the factors required are speed and accuracy of operation, surrounding atmospheric conditions, economic conditions, availability of replacement fluid, required pressure level, operating temperature range, contamination possibilities, cost of transmission lines, limitations of the equipment, lubricity, safety to the operators, and expected service life of the equipment. 

GeoSiphon has several potential limitations and will not be applicable at all sites. Groundwater at a site must demonstrate a difference in hydraulic head in order for the system to operate. In addition, fluctuations in the water table may inhibit the system s performance. The technology may not be applicable at sites with deep contamination and nonsurficial aquifers. When iron is used as the reactive media, performance may also be limited by factors such as pH and high nitrate levels in groundwater. 

Polychlorinated biphenyls (PCB), are a family of toxic, oily, non-flammable chemicals. They are man-made products and were first commercialised in 1929 (by Monsanto). They were mainly used in electrical equipment (e.g., transformers and capacitors), as heat transfer and hydraulic fluids, and as plasticisers from World War I until recently, mainly due to their exceptional thermal and chemical stabilities. Although their production in the USA was stopped in 1977 (they were banned worldwide), some production still continues, and it is believed that large quantities of PCB may still be present in some old transformer and capacitor systems. PCB are certainly still present in the USA in some electrical equipment and are frequently found at toxic waste sites and in contaminated sediments worldwide. The sealants based on polysulfhide polymers that were used in buildings some 20-40 years ago contained PCB, which has been shown still to exist at alarming levels in some houses in Sweden, [24]. 

A significant reason for the majority of oil and fuel system failurcs is the presence of high water levels as dissolved, dispersed, and free water, which degrades the fuels and oils. There are mainly four types of nonwoven filter media fiequently used for the removal of water contaminations contained in a wide range of fuel and oil products, such as aviation fuel, automotive diesel, and hydraulic oils. They include ceUulosic pulp filter, man-made fibre filter, glass fibre media, water adsorption (eg. 

Resuspension of bottom sediments into the water column of aquatic systems represents an important source of particles and particle-associated contaminants into the water column. Unlike deposition, the resuspension process is very sporadic and short-lived, but when it does occur, the flux is generally quite large. Sediment resuspension occurs when hydraulic shear stress at the sediment-water interface rises above a critical level, sufficient to dislodge particles. Shear stress (x, dyn/cm ) is calculated as a function of shear velocity ( , cm/s) and water density (p, g/cm ) ... 

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