Wear particles standards

The RFS technique is used as a comparative method due to the unavailability of oil standards with known gravimetric concentration of particles for each element measured by the spectrometer. In practice, a used oil sample is first analyzed using the standard RDE technique, which provides an analysis of dissolved and small wear particles. A second analysis of the same sample using the RFS technique detects large particles. The two analyses provide an indication of the wear particle size distribution in the sample. A sudden presence of large wear particles will not be seen by conventional analysis alone. Their presence, however, will be readily evident throu the RFS analysis. 

Rotrode Filter Spectroscopy (RFS) is a recently improved technique that has been shown in actual freld applications to provide important additional information about large wear particles, information that may be missed with conventional techniques. It is applied with existing instruments to provide two analyses on the same used oil sample. The first, using the standard RDE atomic emission technique, detects and quantifies dissolved and small wear metals and contaminants. The second analysis, by RFS, qualifies and serai-quantifies larger particles. This paper has shown how the early version of the RFS system has been improved and updated to provide better sensitivity, repeatability, faster sample throughput, and improved particle capture capability. 

Mabrey J.D., A. Afsar-Keshmiri, G.A. Engh, et al. 2002. Standardized analysis of UHMWPE wear particles from failed total joint arthroplasties. J Biomed Mater Res 63 475M83. 

The solid wear particles from ZDDP films produced in lubricated contacts contain phosphorus, sulfur and zinc from the ZDDP molecule and oxygen mainly from the surrounding air environment. They also have a low iron content. Ex situ examination by XAS, EELS and CEMS of these particles (configuration shown in Fig. 5a) has been carried out to provide local analysis of the iron atoms, since their localized environment in the surface film is of great interest it is related directly to the wear of the steel surface and can also play a key role in the adhesion mechanisms of the film. In order to investigate this aspect, a study was made by XAS (EXAFS plus XANES) of a collection of wear debris from two lubricated tests, with and without ZDDP in the lubricant base, respectively. The processed EXAFS data presented in Fig. 8 show the RDFs of iron atoms (noncorrected phase shifts) in four samples data from the standards, pure crystalline iron and iron oxide have been included for comparison. From this EXAFS study, some important results can be deduced [4] ... 

It has been recognized that a standardized method of particle retrieval from the tissues and simulator lubricants, followed by debris characterization and quantification, is required for a uniform approach to debris response investigations. However, there are a number of different standards available from the British Standards Instimtion (BSI), International Organization for Standardization (ISO), and the American Society for Testing and Materials (ASTM), which currently offer conflicting advice for isolation of wear particles from periprosthetic tissues and simulator lubricant samples. 

The British standard (BS ISO 17853 2003 Wear of implant materials—Polymer and metal wear particles— Isolation, characterization and quantification) [53], and... 

Brown C, Williams S, Tipper JL, Fisher J, Ingham E. Characterisation of wear particles produced by metal on metal and ceramic on metal hip prostheses under standard and microseparation simulation. J Mater Sci Mater Med 2007 May 18(5) 819-27. 

Wear of implant materials, polymer and metal wear particles. Isolation, characterisation and quantification. ISO Standard 17853 2003. 

Barium metal and most barium compounds are highly poisonous. A notable exception is barium sulfate which is nontoxic because of its extreme iasolubihty ia water. Barium ion acts as a muscle stimulant and can cause death through ventricular fibrillation of the heart. Therefore, care must be taken to avoid contact with open areas of the skin. Workers must wear respirators (of type approved for toxic airborne particles), goggles, gloves, and protective clothing at all times. The toxic barium aluminate residue obtained from barium production is detoxified by reaction with a solution of ferrous sulfate and converted iato nontoxic barium sulfate. According to OSHA standards, the TWA value for Ba and Ba compounds ia air is 0.5 mg/m. ... 

Current designs for venturi scrubbers generally use the vertical downflow of gas through the venturi contactor and incorporate three features (I) a wet-approach or flooded-waU entry sec tion, to avoid dust buildup at a wet-dry pmction (2) an adjustable throat for the venturi (or orifice), to provide for adjustment of the pressure drop and (3) a flooded elbow located below the venturi and ahead of the entrainment separator, to reduce wear by abrasive particles. The venturi throat is sometimes fitted with a refractoiy fining to resist abrasion by dust particles. The entrainment separator is commonly, but not invariably, of the cyclone type. An example of the standard form of venturi scrubber is shown in Fig. 17-48. The wet-approach entiy section has made practical the recirculation of slurries. Various forms of adjustable throats, which may be under manual or automatic control. 

Two-way analysis of variance (and higher classifications) leads to the presence of interactions. If, for example, an additive A is added to a lube oil stock to improve its resistance to oxidation and another additive, B, is added to inhibit corrosion by the stock under load or stress, it is entirely possible that the performance of the lube oil in a standard ball-and-socket wear test will be different from that expected if only one additive has present. In other words, the presence of one additive may adversely or helpfully affect the action of the other additive in modifying the properties of the lube oil. The same phenomenon is clearly evident in a composite rocket propellant where the catalyst effect on burning rate of the propellant drastically depends on the influence of fine oxidizer particles. These are termed antagonistic and synergistic effects, respectively. It is important to consider the presence of such interactions in any treatment of multiply classified data. To do this, the two-way analysis of variance table is set up as shown in Table 1.24. 

Unfortunately, calibration standards prepared with actual wear metal particles at various sizes and concentrations are not available. Also, even if they were available, shelf-life, particle settling, and the actual distribution of particle sizes could be problematic. Thus, in order to provide the basis for benchmarking RFS calibration and to assure that data are consistent, spectrometers are calibrated with certified commercial or military metallo-organic calibration standards. This insures the spectrometer has the same response over time and permits trending of wear metals and contaminant particles. It is important to note that RFS data is therefore not in true parts per million (ppm), but in scalar units that the spectrometer can reproduce over time. 

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