Filter RatingsWhen considering filtration choices don’t be fooled by the advertising. Filter manufacturers have one goal, to sell their filters! Salesmen are not commonly concerned about which brand of filter is best for your application; they are determined to convince you that their brand of filters are the best thing since apple pie and baseball. Be careful when looking at filter specifications. Some filter manufacturer’s rate filter performance with a simple micron rating, like “3 microns”. A rating such as this actually tells the consumer very little about how the filter will perform in a real life application. Another ploy in advertising is to advertise an efficiency rating in percent of efficiency at a certain micron. The better quality filters are commonly advertised with a Beta Ratio rating.
Beta RatioThe beta ratio rating of a filter is be expressed something like this “β3µ=1000” which means the beta ratio for 3 micron sized particles is 100. What this is saying is that for every 1000 particles 3 microns in size, that enter the filter, only 1 will pass through. Likewise, if a filter is rated β3µ=200, for every 200 particles 3 microns in size, that enter the filter, only 1 of those particles will pass through the element. Below is a visual representation of beta ratio that effectively illustrates the meaning.
(Courtesy of HY-PRO)The test for beta ratio ratings is effectively standardized, but not absolute; what I mean to say is that the test cannot emulate the varying operating conditions a filter will encounter in real life applications, but it does provide a standard for comparison. To illustrate the significance of beta ration ratings, the following case study is provided: The test was conducted on a 300 gallon rolling oil system that is used to flood work rolls as material is passed through a cold rolling mill. The oil drains into an open sump and is returned to the reservoir by a transfer pump. The particle count was conducted in house, through a minimess port, with an on sight particle counter. Both test were taken under similar operating conditions and are representative of the average from several test that were conducted. The first test report represents the performance of a name brand filter element with an advertised performance rating of β3=75 and the second test was taken after replacing the original element with one that has a rating of β3=1000. (The particle count represents the number of particles per milliliter of fluid) Thinking back to when I started my career as a maintenance lubricator I did not fully understand the significance of filter ratings and in no way would not have expected such a difference between two filters with the same micron rating. Obviously the results identify significant disparities in the single pass efficiency of the two filters. This presents a common problem for many trained lubricant professionals when it comes time to order filters through the purchasing department of their companies. If the call out is for a 3 micron filter, the purchaser will first look for a 3 micron filter rating and then (commonly from pressure to reduce cost) look for the cheapest 3 micron rated filter they can find. The problem is that you commonly get what you pay for! In the above case study, the β3=75 filters cost about $50 each and the machine takes 6 filter elements per change out, for a total change out cost of $300. The elements were changed semi annually, on a scheduled PM work request, for a yearly total of $600. The β3=1000 filter elements cost around $130 each and are changed out 3 times year (change out intervals were modified as determined through condition based monitoring) for a total annual cost of $2340.00. So what is the company gaining for the extra annual expense of $1740.00? Within 6 weeks of implementing the filtration system upgrade, the department engineer approached the lubricators and asked if we had implemented the proposed upgrade yet? Management was seeing a 10% product yield increase through final inspection due to surface quality improvement, but could not identify where it was coming from. It was from improved lubricant cleanliness and saves the $100,000.00 a year! As an added benefit, the bearings that support the work rolls are also lubricated by the rolling oil. Work roll bearings have customarily been changed out at six month intervals, the current set of bearings have exceeded twice the life expectancy and are still going strong. If this pattern of increased bearing life repeats, there will be a verifiable reliability improvement with a cost savings of $140,000.00 a year. That is a total savings of $240,000 a year!! In a nut shell, the purchasing agent can save the company $1740.00 a year by buying cheaper filters, but a pro active lubrication strategy saved the company just under a quarter million dollars a year by identifying an opportunity for improvement and spending a little more on filtration. The above case study is not an isolated occurrence or the largest realized savings we have seen from employing a proactive approach to lubrication. We have realized significant decreases in mean time between failures, increases in equipment uptime due to improved reliability and in some instances product improvement due to better responsiveness from the machines controls. When initiating a lubrication improvement, please take every opportunity to measure the fluid condition before and after the modification. Document the gains, work with production, engineering, purchasing and management to document, implement and measure the improvements. If you can’t show a gain, you will not invoke the support of your company and there will likely be no opportunity to prove and advance proactive lubrication practices in your facility. The value of proactive lubrication practices is largely overlooked and until you can document gains, management will not be able to realize the value added.