WorldWide Drilling Resource

29 WorldWide Drilling Resource ® JANUARY 2015 Hydraulic Training by J. Eric Freimuth Hydraulic Training associates Revisiting System Cleanliness Part 3 Beta Ratio of Filters Filtration devices are used to filter particles out of the system’s fluid. A fil- ter’s efficiency is rated with a beta ratio. The unknown or often neglected fact is, many operators do not know the differ- ence between filter’s beta ratios. What makes up the different ratios is the material used to manufacture the filter. Often, companies use paper or card- board as mediums for filtration. The better the material, such as fiberglass, the more optimum your filter’s beta ratio will be. The beta ratio is the number of particles upstream from the filter which are larger than the filter’s micron rating divided by the number of particles downstream larg- er than the filter’s micron rating. In our example, there are 200 par- ticles upstream which are larger than 3 micron. These flow up to, and through the filters. A filter which allows more particles through, or in other words one that is less efficient, has a low beta ratio. The filter at the top allowed 100 particles through. The filter on the bottom allowed only 1 particle through. If we apply these numbers to the beta ratio formula, we can see the filter at the top has a lower or less efficient beta ratio, and the filter at the bottom has a higher or more effi- cient beta ratio. ISO Code So how is the cleanliness of the oil specified? Oil sampling is a must for every piece of equipment in operation. Sending your oil samples in to be tested will give you an idea of what is happen- ing in the system in real time. A major disaster can be averted if proper sam- pling is done on a regular basis. To specify the cleanliness level of a given volume of fluid, we refer to what is known as an ISO code, or ISO solid contamination code. This code, which applies to all types of fluid, provides a universal expression of relative cleanli- ness between suppliers and users of hydraulic fluid. Based on 1 milliliter of fluid, a par- ticle count is analyzed using specific sizes of particles: 4-micron, 6-micron, and 14-micron. These three sizes were selected because it gives an accurate assessment of the amount of silt from 4-micron particles and 6-micron parti- cles, while the number of particles above 14 micron reflects the amount of wear type particles in the fluid. In our next issue, we will interpret the meaning of these numbers for you, and continue with the understanding of keeping our systems clean. Eric Eric Freimuth may be contacted via e-mail at michele@ worldwidedrillingresource.com