T-32 turbine oil is used in modern steam turbines that are typically used for the generation of electricity. To maintain the perfoamance characteristics and extend the service life of oil, it must be filtered regularly so that it remains as free as possible from contaminants. Below, we look at the various filter media for turbine oil filters including those used to filter T-32 oil.
First we will look at some of the more general requirements for oil filters. After analysis of using filters for purification of oil products, the following conditions are a must:
- High specific throughput and minimum flow resistance;
- Guaranteed fineness and degree of filtration remain constant throughout operation cycles;
- Maximum service life retaining all performance qualities;
- Sufficient rigidity, especially for reversal and vibration loads;
- Mechanical durability must not be decreased by cooling or heating;
- The filtered oil must not be destructive to the filter and the filter should have no negative influence on the oil;
- The media must not acquire an electric charge while filtering turbine oil;
- The cost of the media should be reasonable and it should be made of readily available materialsl;
- and If at all possible, the filters should have the capacity for regeneration, i.e. for restoration of performance after a service cycle. If the filter is disposable, it should be designed with disposal in mind.
These are the general requirements for oil filters, but other specific conditions, due to the nature of the filtered product, use of the filter, filter element design may also be important.
In practice, turbine oil can be filtered using various materials with a wide range of filtration parameters and properties. They vary in chemical composition and are made in many different ways. Until recently, filter materials were classified by functional principle into surface and depth filters. The main difference was that the thickness of surface filters was only several times that of the size of the contaminants. The thickness of depth filters are several times more than the size of the filtered contaminants. It was considered that filters made of surface filter media retained particles on the surface while the depth filters trapped them in the pores of the filter medium. This classification was quite vague since most materials used to make turbine oil filters now cannot be unambiguously classified as either depth or surface media.
In terms of physical properties, filters can be compressible, uncompressible, flexible or stiff. The most important property of filtering medium is compressibility.
Flexibility or stiffness shows not only the filter’s physical properties, but also the principle of its operation.
The filtering ability of media depends a lot on the properties of the filter’s porous barrier. If filter pores are used as a reference for classification, some of the parameters for such classification are pore size, structure of the material, and the pore structure. In terms of size, there are macropores (larger than 0.2 micron), mesopores (0.2-0.03 micron) and micropores (less than 0.03 micron).
From the practical viewpoint, the most interesting classification of porous material is based on the geometry of the material. The structure of all filter media used for industrial oil can be either fibrous or globular.
Organic and non-organic fibers of natural and artificial origin are widely used for the production of filter media. Some of the natural fibers are flax, silk, wool, cotton, wood, and felt. Some of the artificial fibers include rayon, acetate fiber, and casein. These are similar to natural fibers. There are also fibers with properties which do not exist in natural form such as capron, lavsan, and polyethylene.
Other materials used for production of filter media include carious granulated organic and non-organic origin (quartz, diatomite, chromite, glass, steel, nickel, copper-titanium, chrome, bronze, monel).