Basic knowledge of O-rings

Thread Content

Basic knowledge of O-rings – measuring them. An O-ring is a circular mechanical seal that prevents gases or liquids from passing through an opening. It can be said that this is an engineering miracle. However, they are not perfect; over time they may wear out and need to be replaced, so it is crucial to obtain the correct size. We have prepared some simple and easy-to-understand instructions to help you obtain the correct size for your work. Three D values for the O-ring: To obtain an O-ring with the perfect size for your application, you need three dimensions. They are the outer diameter (OD), inner diameter (ID), and most importantly, the cross-section (CS). It sounds simple, and to be honest, it is. All measurement values should be recorded in millimeters. First, place the ring on a flat and clean surface. · Outer diameter – Use a ruler or tape measure to determine the width from one outer edge to the other. ID – Repeat this process, but measure from one inner edge to the other. CS – Place the O-ring in a vernier caliper and gently close the jaws. The movements need to be very gentle; do not squeeze, record all three measurement values, and don’t forget to use millimeters as the unit – that’s all there is to it. I heard you say, “Ah, but I don’t have a caliper,” but that’s no problem. If you have both ID and OD, we can use a very simple formula to calculate CS. In fact, as long as you have two of these three dimensions, there is a convenient formula that can help you calculate the third one. O-ring – magical formula: the cross-sectional area is equal to the outer diameter minus the inner diameter, divided by two. Or use the equation CS=(OD-ID)÷2. The outer diameter equals the inner diameter plus twice the cross-sectional area, that is, OD = ID+(CS x 2). The inner diameter also equals the outer diameter minus twice the cross-sectional area, or ID = OD-(CS x 2). If your O-ring is cut or broken, we can still solve the problem. Measure the length and cross-section of the ring. Then divide the length by π (3.142), and this will give the perimeter. The inner diameter can be obtained by taking the cross-section from it. · Length ÷ π = Perimeter. Perimeter – CS = ID. Of course, if you don’t have a ruler, or if you really don’t want to try measuring it yourself, then just give it to us; our knowledgeable sales team will handle this task for you.