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. (Looking for previous posts? Find parts one, two and four.)

Last week, in part one, 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. (Already read part two? Read parts three and four.)

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 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.

The Dynamic Filtration Efficiency (DFE) Test is Hy-Pro's standard for testing filter elements. Throughout this four-part series  (find parts two, three and four) 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.

The Problem: Too Much Filter-Related Downtime

A paper machine was experiencing excessive downtime as maintenance personnel was frequently servicing a Brand X filter element installed on the lube system. The element would reach terminal ∆P and require replacement every 8.5 days on average.

Saves >$15,000,000 by removing water and particulate from common reservoir lube oil.

The Application

In boiler water feed pump applications, water often finds its way into the oil lubricating the pump’s bearings. This was the scenario at a paper manufacturing facility that turned to Hy-Pro for help.

The Problem

In this application, the boiler water feed pump bearing lube system was combined with the facility’s steam turbine lube oil system. The water and the particulate contamination it was bringing with it were decreasing the fluid’s ability to lubricate the bearings and causing premature wear on the bearings.

The facility was attempting to remove free water with water absorbing filters (changed weekly) but the rate of ingression was too high for the filters to be as effective as needed. And since absorbents only remove free water, the filter elements were unable to address the dissolved and emulsified water present in the oil. If the situation were to continue much longer, a premature replacement of the steam turbine and boiler feed pump bearings would be necessary outside of the scheduled maintenance periods. While possible, this solution would cost millions of dollars without addressing the root of the problem. 

Saves >$200K/year by reducing downtime, defective units, idle labor and oil costs.

The Application

During the manufacturing process of refrigerators, the organic compound isocyanate is hydraulically injected into the body of the appliance to improve insulation. After injection, the chemical transforms from liquid to foam, expanding to fill vacant areas completely. 

The Problem: Hydraulic Pump Failure 

Pumps are the heart of hydraulic systems. When the pump fails, the entire system is down until the pump is operational again. This poses a serious threat to any operation relying on hydraulic systems for productivity.

Recently, a hydraulic valve manufacturer was losing 25 pumps a year on their centralized hydraulic system at a cost of $2,440 each -- and that’s only the pump cost. When you account for maintenance resources, lost oil and lost production, each failure costs ~$25,320.

The Problem

Today’s oil suppliers are often required to provide fluid at or below a specified ISO Cleanliness Code. One such supplier was experiencing short filter element life (15 days) on the system (7 element multi-round housing) used to achieve the required ISO Cleanliness Code of 18/16/13 in a single pass as 15W-40 oil is transferred from their bulk storage tanks to tanker trucks for delivery.

The Application

An automotive stamping plant operating large presses to produce body panels was experiencing high surface finish defect scrap. Lubricating oil contamination was causing surface imperfections that would be visible after painting.

The Problem

The uncoiler/washer lube oil system was protected by an off-line filtration system fitted with CJC stacked disc cellulose media filter inserts (elements). Oil analysis revealed an operating ISO code of 23/19/11. Patch analysis showed cellulose fibers were shedding into the oil from the filter inserts downstream of the filtration system.

The Application

An Australian aluminum refinery was consistently performing premature gearbox lube oil changes on seven base drive units due to oil and particulate contamination.

With an average operating ISO code of 20/18/16 and average water levels of 4742ppm, the 360 liters / 90 gallons of ISO VG320 gear oil was being changed far too often. Cost per gearbox oil change (excluding crane, lost production, labor) is $17,962.60 which adds up to $125,738.20 for all seven units.