Plant Services - July 2008 - (Page 40)

Power Transmission Reliability Now for the system PS0807_TelTru.pdf 7/2/08 11:43:55 AM Good things take time Heat exchangers need flushing and cleaning. Flush the tubes in a water-type cooler (item 12 in Figure 1) periodically to remove deposits. A mild alkaline solution such as Oakite or a 1.5% solution of sodium hydroxide or nitric acid can be used. If your system uses an air cooler, verify 1. Before Flushing 3. After 4 hours 2. After 1 hour 4. After 16 hours that the fan turns on when the oil temperature reaches Figure 3. In round terms, the longer about 118°F. Use combs to you can permit the hydraulic fluid straighten the fins on the to circulate during the flushing operation, the cleaner it will become. unit if necessary. Don’t forget pump testing. If you use a variable-volume pump, check the flow out of Looking for wear the case drain line by porting it into a container and using a stopwatch to measure the flow. Make this test with the outlet pressure at maximum. Don’t risk safety by holding the line by hand during this test. Instead, secure it to the container before starting the pump. The normal case flow is 1% to 5% of the maximum pump volume. Vane pumps usually bypass more than Figure 4. A bucket and a stopwatch piston pumps. If 10% of the can reveal whether a fixedmaximum volume flows out displacement pump has worn internals. of the case drain line, replace the pump. Test fixed-displacement pumps by checking the flow through the relief valve. Turn the pump on and measure the flow rate coming from the relief valve tank line for one minute (Figure 4). Then reduce the relief valve setting to its minimum. There should be less than 10% difference in flow rates between the two tests. If a pump is badly worn, the flow will be considerably less at the highest pressure. Test accumulators if your hydraulic system uses piston accumulators, install the charging rig and bleed the oil off the top of the piston (Figure 5). With the pump on and the bleed valve open, there should be little or no flow exiting the bleed valve. If the flow is continuous, the piston seals or barrel are badly worn. If the flow ceases, recharge the accumulator to the proper pressure using dry nitrogen. Test bladder-type accumulators by installing the charging rig on the valve stem. Osmotic pressure forces dry nitrogen through the bladder over a long period of time. If necessary, precharge to the recommended pressure. 1 2 3 4 40 www.PLANTSERVICES.com July 2008 http://www.rydlyme.com http://www.rydlyme.com http://www.teltru.com http://www.teltru.com http://www.PLANTSERVICES.com

Table of Contents Feed for the Digital Edition of Plant Services - July 2008

Plant Services - July 2008 Contents From the Editor Letters The PS Files Up and Running Crisis Corner Asset Manager Technology Toolbox Cover Story Compressors Power Transmission Flooring Web Hunter In the Trenches Product Picks Classifieds Energy Expert

Plant Services - July 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.