DFE - Testing Filters Under Real-Life Conditions, Part 4 of 4

Posted by Jim Harlan on Tue, Jul. 18, 2017

Throughout the first three entries in this series we've discussed the difference in two filter element testing methods, ISO16889 and DFE. We've also illustrated how many elements fall short of their stated beta ratio under dynamic flow conditions. Today we'll wrap it up with simulated cold start tests.

DFE Multi-Pass: Cold Start Contamination Retention

Once the element has captured enough contaminant to reach approximately 90% of the terminal ΔP (dirty filter indicator setting), the main flow goes to zero and the injection system is turned off for a short dwell period. Then main flow goes to maximum element rated flow accompanied by real time particle count to measure retention efficiency of the contaminant loaded element. The dynamic duty cycle is repeated to further monitor the retention efficiency of the filter element after a restart.

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Topics: hydraulic fluid, ISO 16889, ISO Fluid Cleanliness Codes

DFE - Testing Filters Under Real-Life Conditions, Part 3 of 4

Posted by Jim Harlan on Tue, Jul. 11, 2017

Last week we covered the differences between the ISO16889 Filter Test Procedure and the DFE Filter Test Procedure. This week we illustrate the difference between elements engineered to retain particles during dynamic flow conditions and those that are engineered only to pass the ISO16889 test.

Quantifying Contaminant Capture and Retention

Figure 2 compares the performance of two identical high efficiency glass media filter elements, one tested to ISO16889 multi-pass and the other to the DFE multi-pass method. The graph expresses the actual number of particles 6μ[c] and larger counted downstream of the filter element from several data points during the tests.

Filter A2 was tested at a constant flow rate and maintained a steady efficiency throughout the test. Filter A1 was cycled between max rated flow rate and half of rated flow with a duty cycle consistent with that of a hydraulic system. The downstream counts for Filter A1 varied and were highest during changes from low flow to high flow. The peaks represent counts taken during flow change and the valleys represent counts taken after each flow change. The alternating high peaks represent counts taken during changes from low flow to high flow. As the amount of contaminant captured by Filter A1 increased, the downstream counts increased most dramatically during the flow changes from low to high. Filter element A1, not properly designed to retain previously captured contaminant during dynamic system conditions, can become a dangerous source of contamination as it captures and then releases concentrated clouds of contaminated fluid.

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Topics: hydraulic fluid, ISO 16889, ISO Fluid Cleanliness Codes

DFE - Testing Filters Under Real-Life Conditions, Part 2 of 4

Posted by Jim Harlan on Tue, Jun. 27, 2017

Last week we briefly discussed how filter elements are rated by manufacturers. This week we're discussing the industry standard ISO16889 multi-pass test and Hy-Pro's standard, the DFE test.

Current Filter Performance Testing Methods

To understand the need for DFE it is important to understand how filters are currently tested and validated. Manufacturers use the industry standard ISO16889 multi-pass test to rate filter efficiency and dirt holding capacity of filter elements under ideal lab conditions.

Figure 1 depicts the test circuit where hydraulic fluid is circulated at a constant flow rate in a closed loop system with and on-line particle counters before and after the test filter. Contaminated fluid is added to the system at a constant rate. Small amounts of fluid are removed before and after the filter for particle counting to calculate the filter efficiency (capture). The capture efficiency is expressed as the Filtration Ratio (Beta) which is the relationship between the number of particles greater than and equal to a specified size (Xμ[c]) counted before and after the filter. In real world terms this test is the equivalent of testing a filter in an off-line kidney loop rather than replicating an actual hydraulic or lube system. It’s basically a filter cart test.

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Topics: hydraulic fluid, ISO 16889, ISO Fluid Cleanliness Codes

DFE - Testing Filters Under Real-Life Conditions, Part 1 of 4

Posted by Jim Harlan on Tue, Jun. 20, 2017

The Dynamic Filtration Efficiency (DFE) Test is Hy-Pro's standard for testing filter elements. Throughout this 4 part series we'll discuss what it is, why it matters and why elements engineered with this test in mind outperform others in real-life applications.

First, let's start with the basics...

Why are filters used? How are they rated?

All hydraulic and lube systems have a critical contamination tolerance level that is often defined by, but not limited to, the most sensitive system component such as servo valves or high speed journal bearings. Defining the ISO fluid cleanliness code upper limit is a function of component sensitivity, safety, system criticality and ultimately getting the most out of hydraulic and lube assets.

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Topics: hydraulic fluid, ISO 16889, ISO Fluid Cleanliness Codes

Video: Your Lab Reports Are Probably Wrong - Here's How To Save Them

Posted by Scott Howard on Tue, Aug. 16, 2016
When looking at a lab report it is assumed the information on the report is accurate. A certified lab will not usually make an error in the report, but if so it is obvious and easily fixed. Ever hear the saying "By the time the lab gets the report the error has already been made?" For the most part this is true. Where people are led off course is believing the particle count on the lab report is the gospel. This is natural, but unfortunately not always the case with a bottle sample unless you already employ the techniques listed in the video below.
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Topics: hydraulic fluid, fluid cleanliness, dirt, hydraulic filters, ISO 16889, iso cleanliness codes, ISO Fluid Cleanliness Codes, diesel, ISO 4406, fluid samples, filtration

[Video] How big is a micron?

Posted by Jim Harlan on Mon, Aug. 26, 2013

If you’ve been following our blog you probably have a pretty solid understanding of ISO fluid cleanliness codes (if not, click here). You know that ISO codes quantify levels of particulate contamination at three different micron sizes (4m/6m/14m), but how big is a 4m particle?  Watch the video below for a brief explanation.

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Topics: contamination, fluid cleanliness, dirt, hydraulic filters, ISO 16889, iso cleanliness codes, ISO Fluid Cleanliness Codes, maintenance, new oil

Glass or Cellulose: Which hydraulic filter media is best?

Posted by Aaron Hoeg on Mon, Sep. 17, 2012

There are several distinct differences between glass and cellulose media. Media selection should be based upon the required cleanliness and other unique needs of the system. Evaluate the Beta ratio (efficiency), dirt holding capacity, flow versus pressure drop characteristics, etc. A hydraulic filter supplier should be able to supply more detailed test information in addition to what is supplied in the literature.

Normally, wire mesh and cellulose media elements are nominally rated which means that they might be only 50% efficient at the rated micron size.

Most glass media elements are considered to be “absolute” rated which means that they are 99.5% efficient at the rated micron size. Check the Beta ratio before selecting the media as all “10 micron” filter elements do not filter with the same efficiency. Glass media has superior fluid compatibility versus cellulose with hydraulic fluids, synthetics, solvents, and high water based fluids. 

Elements of different media with the same “micron rating” can have substantially different filtration efficiency. The graphic below provides a visual representation of the difference between absolute and nominal filter efficiency.

The illustrated glass element would typically deliver an ISO Fluid Cleanliness Code of 18/15/8 to 15/13/9 or better depending upon the system conditions and ingression rate. The cellulose element would typically achieve a code no better than 22/20/17.

Runaway contamination levels at 4μ[c] and 6μ[c] are very common when cellulose media is applied where a high population of fine particles exponentially generate more particles in a chain reaction of internally generated contaminate.

Inorganic glass fibers are much more uniform in diameter and are smaller than cellulose fibers. Organic cellulose fibers can be unpredictable in size and effective useful life. Smaller fiber size means more fibers and more void volume space to capture and retain contaminate. 

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Topics: contamination, hydraulic filters, ISO 16889, hydraulic and lubrication filter types