WorldWide Drilling Resource

17 WorldWide Drilling Resource ® JUNE 2013 Hydraulic Training by J. Eric Freimuth Hydraulic Training Associates How Does Force Play a Role in Sizing a Cylinder? How many pounds of force will be developed on the extension stroke of a 3¼-inch bore cylinder operating at 1500 psi? If the same cylinder had a 1¾-inch rod diameter, how much force will be developed on the retraction part of the stroke? The answer can be found by refer- ring to the cylinder force chart. You will see it shows 12,444 pounds for a 3¼- inch bore cylinder. A solution can be obtained by using the piston area of 8.296 as the power factor and multiply- ing it times the pressure of 1500 psi. On the retraction stroke, the amount of force developed on the 2.41 rod area must be subtracted. 12,444 - 3608 = 8836 pounds What psi gauge pressure is required for retractions of a 50,000-pound load with an 8-inch bore cylinder on a 4-inch rod? The solution is net piston area must be found. This is the full piston area minus the rod area. 50.27 (piston area) - 12.57 (rod area) This equals 37.7 square inches. psi is 50,000 divided by 37.7 which equals 1326 The actual pressure will be slightly greater due to friction of the piston and the barrel. The proper way to define this is determining FORCE - PRESSURE - AREA and calculate accordingly. If you want to find Force, you mul- tiply Pressure and Area. If you want to find Pressure, you divide Force from Area. If you want to find Area, you divide Force from Pressure. Staying educated and up to date on the information about hydraulics will help in becoming a better troubleshoot- er. Our goal is not to make experts of mechanics, rather to assist them in troubleshooting and giving knowledge that will guide them in their efforts. In the next issue, we will be dis- cussing the relationship of speed to flow with cylinders. Eric admin@ worldwidedrillingresource.com