Machinery Lubrication

Machinery Lubrication March-April 2020

Machinery Lubrication magazine published by Noria Corporation

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Page 18 of 88

16 | March - April 2020 | www . Most hydraulic system failures can be classified as either a pressure problem or a volume problem. It normally is easy to tell which of these you are experiencing if you understand the difference between pressure and f low. This critical concept was covered in my recent Machinery Lubrication article titled "Hydraulic Pressure vs. Flow: Understanding the Difference." Armed with this knowledge, you can troubleshoot any system by simply eliminating the compo- nents that could not be causing the problem, isolating the components that could be causing the problem and then making checks of the possible culprits. In my experience, once a pres- sure problem is encountered, the f irst component to be changed is t he hyd rau lic pu mp. T h is frequently is a mistake. A common misconception is that pressure comes from the pump, thus making it the most likely suspect. Quite the contrary, while it is possible for the pump to be the cause of a pressure problem, it certainly isn't the most likely cause. Usually, something else is faulty. e fastest way to determine the rea l cause while protecting the system from further damage is to use the following four essential steps. 1. Gather Information is step is often skipped in the interest of saving time, but it is very important in troubleshooting. A lot of information can be gathered in a short period of time. e most critical piece of information is the system schematic. Use it to trace the flow through the system and deter- mine which of your components could be causing the problem. A typical schematic containing compo- nents common to most systems is shown on page 17. You also will need to have a good understanding of the symptoms. Was the system working fine and then suddenly lost pressure, or did it happen gradually? Was it accompanied by a strange noise or an increase in temperature? If so, where in the system did the sound or heat originate? 2. Isolate the Power Supply A well-designed system typi- cally will have some way to isolate the power supply from the rest of the machine. A manual valve is commonly used, but it may be neces- sary to plug a line. In the example schematic, there is a manual valve between the system relief valve and the directional valve. Close it and see what, if anything, changes. is often can cut your troubleshooting time in half. For instance, if the pressure is low and nothing moves, but when the manual valve is closed, the pressure builds and the relief valve begins to dump, you know the power supply is working fine and the problem is somewhere downstream. By the same token, if nothing changes, obviously the problem is in the power supply. 4 Steps to Diagnose Low System Pressure HYDRAULICS Jack Weeks | GPM Hydraulic Consulting You can troubleshoot any system by eliminating the components that could not be causing the problem, isolating the components that could be causing the problem and then making checks of the possible culprits.

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