Machinery Lubrication magazine published by Noria Corporation
Issue link: http://www.e-digitaleditions.com/i/1250226
22 | May - June 2020 | www . machinerylubrication.com Rarely do I encounter a hydraulic system that has never been modified in some way over the years. Usually modifications have been made either to make the system run faster or to add some functionality to the machine. Either way, more flow is normally required, which means the pump must be upgraded to a higher displacement. Unfor- tunately, the increased flow often exceeds the capability of at least some hydraulic lines. Hydraulic lines that are too small cause excessive heat and turbulence, ultimately resulting in system damage and fluid degradation. Whenever the system is upgraded to increase its flow, it is important to ensure that current line size is enough to handle the increase. Heat and turbulence caused by undersized lines is the result of excessive fluid velocity. Fluid velocity is inversely proportional to line size. Any increase in flow will lead to an increase in fluid velocity. is isn't much of a problem in a line that is straight. Imagine the fluid being on a molecular level. If all the molecules of the hydraulic fluid are traveling parallel to each other, you have a condition known as laminar flow. Laminar flow is the most effi- cient form of flow and the form that all flow seeks to become. Naturally, the fluid in the center of the line will move somewhat more rapidly than the fluid at the edges because of fric- tion with the walls, but the resulting temperature gain will be negligible in a line that is straight. e trouble comes when the fluid reaches a bend in the pipe, as illustrated to the right. The molecules then begin colliding with the sides of the pipe, causing the laminar flow to become turbulent flow, and heat is generated. It usually is quite easy to tell when the line diameter is too small by measuring the bends in the pipe with a thermal imaging camera. Hot spots at the bends are a dead giveaway. e schedule of the pipe influ- ences turbulence as well. Most systems require schedule 40 pipe for suction and return lines but schedule 80 or 160 pipes for pressure lines, Why You Shouldn't Overlook Hydraulic Pipe Size HYDRAULICS Jack Weeks | GPM Hydraulic Consulting Unfortunately, the increased flow often exceeds the capability of at least some hydraulic lines.