Hydraulic pumps are more common than you can imagine. They are very much present in your usual pumps and motors. If you have a lot of hydraulic equipment, you may already be spending a significant amount of time and money in running from one hydraulic cylinder or pump repair shop to another. Studies have indicated that 25% of total mechanical equipment failures are a result of design failures. This means it is possible that one out of four hydraulic cylinders may be inadequately designed to operate to their highest potential. Although poorly designed hydraulic cylinders may still do the job, they may not have an acceptable service life. Here are the four main ways that you can reduce the cylinder failures and save on the associated costs:
Insufficient rod diameter, inadequate material strength, abnormal cylinder mounting arrangement or a combination of all three can cause the cylinder rods to bend. In case of a bent rod, a deforming load happens to be placed on the rod-seal which ultimately increases leaks and premature seal failure. To avoid this, you can use the Euler formula and check the allowable rod loading for the cylinder.
Another critical reason for the cylinder to fail is the surface finish of a cylinder rod. The surface finish can have a significant effect on the rod seal’s longevity. A smooth surface results in a reduced seal life as it does not get adequate lubrication. On the contrary, if the surface roughness is too high, contaminant ingression is increased giving rise to an unacceptable level of leakage past the rod seal. To increase the cylinder’s service life, you can use some rod surface treatments that have better mechanical properties as compared to conventional hard-chrome plating. Using treatments such as nickel-chrome plating or high-velocity oxygen fuel (HVOF) metal spraying can help to increase the life expectancy of a rod and its seals. In some cases, you may also want to think about installing a shroud or bellows that will help to protect the rod surface from impact damage or contaminants, extending its functional lifespan.
One of the common issues associated with a cylinder is ballooning. Often ballooning is caused due to insufficiently thick walls or inadequate material strength of the tubes to support the cylinder’s operating pressure. The ballooning result in incorrect tolerance between the piston seal and the tube wall. This further allows high-pressure fluid to bypass the seal which goes on to erode the seal. Localized heating caused due to pressure drop can reduce the seal life significantly. This entire cycle causes premature failure of the piston seal, rendering your cylinder faulty.
Insufficient Bearing Area
One of the most critical aspects of the cylinder is the bearing (wear) band’s surface area in the gland and on the piston. If this area is not sufficient to provide ample support to the side thrust transferred to the cylinder, the rods and piston seals are overloaded, resulting in deformation of the seal and premature failure.
All hydraulic cylinders are not made equal. It can be difficult to gauge the underlying issues with hydraulic failure for your equipment based on generalization. If you have a piece of hydraulic equipment that is prone to frequent failure, speak to S&T Hydraulics to help you identify the issues and suitable recourse to reduce the instances of failure and improve the longevity of the equipment.