Termografia Sistema Hidráulico

Reducing Hydraulic System Temperatures Deborah Hays Dmax Ltd.

ABSTRACT The predictive technology team at DMAX, Ltd. consists of a mechanical technician and an electrical technician. We primarily use the IR camera camera to run predictive routes on electrical panels, buss buss plugs, and motors. Occasionally, we are called to the plant floor to help troubleshoot troubleshoot a problem. This paper discusses a trouble call on a hydraulic system that supports one of our larger machines. INTRODUCTION DMAX, Ltd. builds the Duramax Duramax Diesel engine for use in General Motors Motors heavy duty trucks. At our facility the engine block, head, crank, and connecting rod are machined. These parts are used in our assembly area where we build and test the engine. The problem occurred on a cylinder block line line transfer machine that is 54’ x 30’ consisting of 5 cutting stations, 2 rotate stations, a gage station, check station and 5 idle stations. Most of the cutting stations have a left and right right side. Each cutting station either bores, chamfers, chamfers, or mills the cylinder block. After each station finishes a cycle, the machine machine then transfers the cylinder block to the next station. Hydraulic cylinders are used to transfer transfer the blocks as well as rotate them and clamp the part when when it is being machined. Hydraulic cylinders are also used in in several stations to assist the large cutting heads as they rise and lower. lower. This hydraulic system system has a 600 liter reservoir reservoir of hydraulic fluid. fluid. The OEM has stated that the maximum system temperature should be no higher than 120 F (49 C) when running at a normal pressure of 1200 psig. The system has a high temperature fault that that is set at 117 F (47 C). The OEM used yellow zinc dichromate heavy walled steel tubing to distribute the hydraulic fluid to the desired components on the machine. There are several supply and return lines lines running to each station as well as to the large cylinders used to transfer the blocks as they are machined. ˚

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PROBLEM Electricians from the cylinder block line had been called to this operation numerous times to reset high temperature faults on the hydraulic hydraulic system. The electricians asked the mechanics to check the system for any abnormalities. All pressures and flows flows were found to be within OEM specification. The electricians also also wanted to verify that the actual temperature temperature in the hydraulic system matched the thermal thermal couple reading. We checked the temperature using our FLIR P65 and determined that the thermal couples where operating correctly (Fig. 1). The electricians did not want to spend their their day resetting temperature temperature faults. We needed a solution.

Figure 1. Thermogram/photo pair showing hydraulic system.

InfraMation 2008 Proceedings

ITC 126 A 2008-05-14

TEMPORARY FIX The electricians were advised not to adjust the temperature upper limit to eliminate the fault. Running the hydraulic unit with excessive heat would cause the hydraulic oil to deteriorate at a rapid rate possibly causing failures to the hydraulic pump, cylinders or valves. The machine was needed to meet production schedules so there was little time for a formal root cause analysis. We needed a quick solution or what we like to call a “band-aid” (Fig 2.).

Figure 2. The fastest and easiest way to cool something down, THE FAN!

ROOT CAUSE ANALYSIS  As we analyzed the root cause it was discovered that the hydraulic system was slightly undersized for this particular application. An additional gage station had been added to the machine which increased the load on the system. A second contributing factor was the temperature inside the plant on this summer day. The DMAX plant has a chiller system that is designed to keep the plant at a constant 76 F. The cylinder block line can reach the 90 F mark in the middle of summer. It was decided not to spend the money to upsize the hydraulic system that worked fine 10 months out of the year. The purchase of an additional chiller unit was also not approved. Even the fan was not keeping the unit as cool as it needed to be and temperature faults quickly returned. We needed an inexpensive permanent solution. ˚

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SOLUTION We remembered our IR level I class. Instructors Bernie Lyon and Bob Rogers were telling the class about a presentation at the 2004 InfraMation conference. An electrician from a Coors Brewing plant was having problems with a stainless steel motor over heating. He had created an IR route to check it but found it difficult to find the taped spot during his route. He had placed electrical tape on the motor due to the reflectivity of the stainless steel and he decided to paint the entire motor so the routes could go faster. Much to his surprise, this stopped the motor from over heating by allowing the heat to dissipate instead of being trapped in by the reflective steel. We thought if it can work on a stainless steel motor it could work on yellow zinc dichromate tubing. Remembering E+R+T=1 and low emissivity, we put electrical tape on two of the hydraulic lines and checked the temperature difference between the taped surface and the steel surface (Fig. 3). We found a 4 degree C temperature change and we decided to paint the tubing in the hopes it would radiate enough heat to keep the unit running below the OEM set point year round (Fig. 4).

InfraMation 2008 Proceedings

ITC 126 A 2008-05-14

REFLECTIVITY

Object Parameter Emissivity Object Distance Reflected Temperature Label Sp1 Sp2 Sp3 Sp4 Dt1: [ana.Sp1.temp] [ana.Sp2.temp] Dt2: [ana.Sp3.temp] [ana.Sp4.temp]

Value 0.96 1.9 m 22.4 °C Value 36.9 °C 33.1 °C 35.0 °C 31.8 °C 3.7 °C 3.3 °C

Figure 3. Thermogram/photo/chart showing reflectivity of steel tubing.

RESULTS

Figure 4. Photo before and after painting.

Twelve cans of flat white spray paint and a week later, we reshot the hydraulic unit. The overall system temperature went from 117 F to 107 F. We were able to reduce system temperature by 10 F, which was enough to keep the unit running even on the hottest days (Fig. 5). ˚

InfraMation 2008 Proceedings

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ITC 126 A 2008-05-14

Figure 5. Thermograms before and after painting hydraulic lines.

SUMMARY  After a week of painting, we realized this operation had several more feet of hydraulic tubing than we had first realized. We believe this is why we were able to achieve a ten degree temperature reduction. We have since changed the new equipment specification and require any future purchases of hydraulic systems to have the hydraulic lines painted flat white. Ten degrees F may not sound like much, but sometimes it is just enough. REFERENCES Voitl, John C.; Predictive Maintenance Technician; Coors Brewing Company; 2004 InfraMation Conference; October 2004 ACKNOWLEDGEMENTS The authors wish to thank the Infrared Training Center and specifically instructors Bernie Lyon and Bob Rogers. We would also like to thank DMAX Ltd. maintenance personnel and management for allowing us to experiment with this operation. ABOUT THE AUTHOR Deborah Hays is a Level II Thermographer and has been a mechanical service technician for the last 15 years. She has been assigned as a predictive technologies technician for the past 5 years. She utilizes infrared, vibration analysis, motor circuit analysis, and ultrasound technologies at her plant.

InfraMation 2008 Proceedings

ITC 126 A 2008-05-14