Shaped like a doughnut, O rings are arguably the most common type of seals found in systems flowing with fluids. Once in place, O rings create zero clearance. This helps keep fluids within a system, consequently preventing leakages, which in most cases are responsible for system failures. While O rings are designed to function correctly for a time, it is vital to keep in mind that they are not intended to last forever. As such, you should keep an eye out for signs that an O ring is nearing its usefulness and replace it immediately. This article highlights common O ring wear signs you should watch out for.
Abrasions — Routine inspection of an engine system is necessary to ensure all parts, including O rings, are in excellent condition. Therefore, if you see tiny abrasions on the surface of an O ring, then that should be enough to indicate impending failure. Abrasions on the upper surface of an O ring can be caused by various factors, the most common being rough glands. For instance, if you don't lubricate joints well enough, the glands will dry out, and as the part keeps moving, the roughness will create abrasions on the O ring. Another reason for O ring abrasions is fluid contamination by abrasive particles that rub against the surface of the seal. Therefore, ensure that you lubricate all O rings adequately and also replace filters to prevent breach by contaminants.
Cracking — Something can only crack once it is hardened, and this is precisely what happens to O rings that have cracks on the surface. Usually, O rings are designed to be partially supple to deform slightly when the gland is tightened to create a perfect seal. However, if temperatures are extremely high, then the O ring might begin to harden. Over time, hardened O rings will start to develop cracks since they are no longer flexible enough to sustain sudden movements. Additionally, extreme temperatures often lead to plasticiser evaporation, thereby ridding the O ring of its suppleness. You can prevent O rings from hardening and eventually cracking by lowering operating temperatures.
Nibbling — If you have ever seen a doughnut that has been nibbled all around, then you should have a good idea of what a nibbled O ring looks like. The small bites on the surface are difficult to miss during inspections. O ring nibbling is caused by different factors such as sharp edges on the gland and the use of soft materials. Excessive system pressure can also eat away tiny chunks of the O ring slowly. For this reason, it is crucial to inspect the gland for improper machining to avoid future O ring failure.