Servo valves are a tiny but essential component of manufacturing processes. However, as you will see in the video case study below, servo valves can fall victim to failure due to excessive fluid contamination. Watch the video below to see how a tire plant in the south diagnosed and dealt with a servo valve problem that would have resulted in thousands of dollars of damage.
The Problem: Oil with MPC Values of 250
A coal-fired power plant in the Philippines has a scheduled shutdown. Upon shutdown, it is revealed that the turbine lube oil, Shell Turbo 32, in the system has suddenly darkened. After conducting MPC and ISO code testing, it is determined that the oil’s current state is unusable with MPC values as high as 250 and ISO codes at 20/17/10.
Large paper mills rely on continuous production to be profitable, thus unplanned down time is a huge financial burden. When unplanned downtime does occur and equipment must also be either repaired or replaced, the damages can feel exponential.
Throughout the first three entries in this series (find parts one, two and three), 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 the 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.
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
The Dynamic Filtration Efficiency (DFE) Test is Hy-Pro's standard for testing filter elements. Throughout this four-part
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.
Saves >$15,000,000 by removing water and particulate from common reservoir lube oil.
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.
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.
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.
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.