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Hydraulic Oil Filter Applications of Walking Beam Furnaces


Hydraulic Oil Filter Applications of Walking Beam Furnaces

Hydraulic oil filters are used in the hydraulic systems of walking beam furnaces to remove large particles and contaminants that cause (1) hydraulic failures in components such as, piston rods, seals, valves, and pumps, and (2) system operational problems such as, power reductions and slow response that can result from heavily contaminated hydraulic fluid. They also can provide protection against contaminants in new hydraulic fluid since most pumps draw fluid from the bottom of an oil drum where most contaminants settle. Other advantages of hydraulic filters are that they can reduce waste oil disposal volume as well as reduce lubrication and hydraulic oil purchases.  In general, there are two types of oil filters used for the hydraulic systems of walking beam furnaces: inline filters and tank filters. Inline filters can be standard inline filters or the spin-on type. Tank filters can be spin-on filters located at the top of the tank, or tank immersed filters. These filters are typically designed for high pressures, fast cycle times and a long service life.

The Causes of Hydraulic Oil Contamination

While hydraulic oil filters are required to eliminate contamination, particulate and debris from hydraulic drive systems, the source and causes of this contamination is varied. In general, there are five sources of hydraulic oil contamination in walking beam furnaces:

¨        Particulate Matter

¨        Moisture

¨        Acidic Conditions

¨        Oxidation

¨        Changes in Viscosity

Particulate matter occurs from impurities in new oil that is introduced into the hydraulic system. Particulate matter can also find system entry through storage tank breather caps from air pollutants and moisture. Seals, piston rods and other moving parts can introduce contaminants into hydraulic fluid. Moisture in a hydraulic system usually signifies a problem with the cooling system (heat exchanger) resulting in condensation, or some other type of component failure. Acidic conditions in a hydraulic system are usually caused by chemical processes within the hydraulic oil as a result of moisture and particulate matter. Oxidation occurs when the oil interacts with oxygen in overheated conditions. While filters cannot correct for overheated conditions, they can remove particulate matter needed to drive the oxidation reaction. Changes in viscosity occur when oil degrades and is generally caused by moisture and oxidation reactions.

Considerations for Oil Filter Selection

There are a number of factors to consider when replacing or specifying a hydraulic oil filter. The filter’s flow capacity is of primary importance. A filter should never be installed if its maximum flow specification is below the hydraulic system’s rating. All filters have a maximum pressure rating. In high-pressure systems used in walking beam furnaces, the selected filter should be able to withstand maximum hydraulic pressure including pressure spikes. The filter should be rated for the maximum temperature of the fluid and ambient temperature. The minimum particle size rating of the filter (in microns) rates the smallest particulate matter that can be removed from the system, which is, in essence, the filter’s level of filtration. The efficiency rating should be considered when selecting a filter. The type of filter cartridges should be considered. Cartridges are made of different materials that are not always compatible with all hydraulic fluids. Refer to the filter manufacturer’s specifications to determine the compatibility of the filter to the specific hydraulic system application. The type of container or housing should also be considered for mechanical installation and environmental considerations.