When a hydraulic cylinder seal fails, it always leaves behind telltale clues that will offer valuable insight into the underlying causes that led to the failure. In the same way that a detective examines a crime scene for clues, a hydraulic cylinder repair technician looks for evidence such as glazing, cracking, fracturing and swelling to track down the culprit responsible for putting your cylinder out of action.
This information can be used to make the necessary changes to ensure the failure doesn’t reoccur. So, with this in mind, let’s look at the top types of hydraulic cylinder seal failures - and what causes them. Thus, extending the service life of your cylinder and reducing the instance of unplanned maintenance downtime.
Deterioration occurs when the cylinder seal has lost all of its elasticity and begins to break apart. It has a cracked and crumbling appearance. This usually occurs due to high operating temperatures and prolonged exposure to sunlight and or ozone.
Extrusion happens when the inner (dynamic) face of the seal begins to push out and break apart. What is happening is that the seal is unable to deal with the internal pressure. Sometimes this is due to excessive internal pressure, but it can also be caused by mating surfaces worn out of spec. So when encountering extrusion, disassemble the cylinder and measure all mating surfaces, bearings guide rings and measure to ensure tolerances are within acceptable limits.
Grooving presents as linear cuts or grooves worn into dynamic seal side in the direction of rod travel. This is usually caused by internal contamination - whereby hard or sharp foreign debris has found its way under the seal and worn it into the characteristic groove. In this case, the system must be flushed and the hydraulic fluid replaced to prevent a reoccurrence.
Fracturing is a sign of significant issues. This problem is signified by chunks of seal material that have broken off, seal surfaces may appear burned and long cracks or splits may appear. Causes for this include excessive backpressure, increased friction, or bad hydraulic fluid. A qualified hydraulic cylinder service technician will be able to visually inspect the seal to tell you what conditions lead to failure.
When hardening occurs, the seal appears glazed, cracked and brittle. The material loses its elasticity and splits easily when pulled apart. This condition commonly occurs due to excessive operating temperature and can result from higher-than-recommended stroke speed and / or poor quality hydraulic fluid. In some cases, the seal material may not be suitable for the application or the type of hydraulic fluid in use.
Scarring is any form of cut, dent or scratches on the dynamic face of the seal. This is sometimes caused by improper installation of the seal (in which case the seal will almost invariably leak immediately). More commonly, scarring is caused by damage to the cylinder rod due to external impact or contamination leading to sharp-edged marring of the rod surface. When the seal runs over these spots, the soft material easily becomes cut or damaged.
In the case of swelling, the seal material becomes deformed and mishapen. This is usually a result of hydraulic fluid that is incompatible with the seal material. In some cases, water in the fluid or external chemical exposure may also produce similar results. Ask your hydraulic service provider to advise you on the correct seal type for the application and the fluid in use.
Extreme wearing can appear as a glassy, mirror-like shine on the dynamic face of the sea. It is usually caused by insufficient lubrication. In some cases, the seal may be worn inconsistently - with one side or both sides of the seal face exhibiting excessive wear. If this is the case, then you should suspect excessive lateral loading has taken place or a cylinder that is out of alignment.
For every hydraulic seal failure, there is an explanation. And every seal that comes out of a cylinder tells a story about the life it has endured and the condition of the component and the system itself. A qualified technician can read hydraulic seals, identify the clues and diagnose the cause of failure so that you can take steps to prevent costly reoccurrence and unscheduled downtime. A reputable hydraulic cylinder repair center should provide you with a report on the cylinder condition which will prove invaluable to preventing problems down the line.