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The Weartrap Filter Traps 10-Micron and Larger Particles That Can Later Be Analyzed Microscopically Using the Same Methods Employed in Ferrographic Analysis
Oil analysis serves a pivotal role in a machine condition-monitoring program in the area of wear debris analysis. Specifically, tests such as ferrous density analysis and analytical ferrography provide vital information (both pre- and post-failure) about the machine’s health. This information allows the educated analyst to diagnose the problem, identify its root cause, make an informed decision and schedule appropriate corrective action. However, to effectively use these tests, it is imperative that sample test points be correctly located on the system. For circulating oil systems, the best sampling location is immediately downstream of the component of interest. Likewise, to ensure that the sample is an accurate representation of the oil’s condition, it is equally important to use the correct equipment and flush the appropriate amount of dead volume. Although, depending on the nature and severity of the problem, there may be an insufficient number of particles present in the sample to allow an accurate diagnosis of the root cause of the problem.
How the Weartrap is Deployed in a Typical Installation:
Install the unit (which is left in place) as shown in Figure 2.
One solution to this dilemma is the Weartrap™ large particle assessment module, developed by The Fluid Life Corporation. The Weartrap unit has a nickel-plated aluminum housing with a standard sample valve, pressure gauge and a small, 10-micron pleated paper filter similar to an automotive fuel line filter (Figure 1). Rated to 250 psi (1,724 kPa) and 250°F (121°C), the unit is typically installed in a slip stream on either the supply or return line of a pressurized lube system with a small portion of the oil passing through it (Figure 2). Weartrap’s sample valve allows a representative sample to be collected to test the condition of the lubricant (e.g., viscosity, AN, etc.). The Weartrap filter traps 10-micron and larger particles that can later be analyzed microscopically using the same methods commonly employed in ferrographic analysis.
The success of this unit lies in the subtle difference between those particles typically present in an oil sample and those collected and analyzed from the Weartrap filter. When a sample is correctly obtained, it may contain particles that represent a snapshot of the machine condition on that specific day and time. In contrast, debris collected in the Weartrap filter provides historical data from all wear particles and debris that have passed through the Weartrap unit since the filter was last replaced. In certain circumstances, when the amount of wear debris generated is small or is produced slowly over a long period of time, the unit may be the only method that can provide a sufficient concentration of particles to allow accurate root cause diagnosis.
From experience, the simplest way to remove particles from the Weartrap filter is to immerse the complete filter in a toluene bath and agitate using either a paint shaker or lab shaker. The toluene/particle mixture is then passed through an 8-micron filter patch and washed with more toluene to create a filtergram. The filtergram can then be analyzed using a microscope to identify the type, shape and morphology of the particles. In many cases, this allows the root cause of the problem to be quickly and accurately diagnosed.
The Fluid Life Corporation
9321 48 Street
Edmonton, AB T6B 2R4