Hydraulic Seal Designs

Best Metal Products partners with leading hydraulic seal manufacturers to identify and develop the most effective and reliable seal options for each application of its world class hydraulic cylinders.

In each case, we consider a broad range of structural and service-related factors in deciding which seals will provide superior long-term performance at the most reasonable cost. These factors include:

Hydraulic Seal DesignsFriction:

Friction is a function of the radial force exerted by a hydraulic seal and the coefficient of friction between the seal material and the dynamic sealing surface.  It is largely determined by the characteristics of the seal and the counterface, the range of working pressure, the type of hydraulic oil used, and the seal materials.  High friction is undesirable because of heat generation. This will wear seals and reduce system efficiency. Best Metals has all the resources to select the correct seal to optimize performance and protect against detrimental side effects of friction for any given application.


Pressure spikes, the duration of pressure cycles and changes in pressure direction during work all need to be considered. The interplay of pressure and cold temperatures makes sealing more difficult at low or zero-pressure, as seals become less elastic and oil properties change. Pressure at higher temperatures can also lead to seal extrusion.  Selecting the correct material to withstand the system's pressures and temperatures is critical.  Best Metals has all the resources to select the hydraulic seal that can withstand pressures for any given application.

Surface Properties of the Cylinder Tube:

This greatly impacts the performance and life of the hydraulic seal. A smooth surface allows a seal to stay in productive service longer than one with sharp details or a rough surface. Understanding and applying the benefits of appropriate surface finish can dramatically affect the longevity and effectiveness of a sealing system.  In a dynamic surface, microscopic variations form recesses which hold an oil film between the seal and surface.  It is possible that the sealing surface can be too rough, or too smooth. Too smooth can lead to higher friction and increased wear, too rough will create leak paths and accelerate wear. Best Metals has all the resources to suggest the correct surface properties for any given application.

Speed of Travel:

Rapid stroke movement and rapid change in direction need to be considered when selecting a hydraulic seal.

Resistance to Drift:

Leak-free / low leakage specifications can be difficult. The viscosity of the hydraulic oil as well as the ability to seal securely during "rest" intervals need to be considered.


Wear rings, and increasing the bearing length of both the piston and head can go a long way toward alleviating the damage that can be caused by sideload. Increased seal life, not to mention overall cylinder longevity, is a direct result of properly accounting for sufficient bearing length.

Work Environment:

Many other conditions, including heat, oxidation, weathering, aggressive chemicals, and resistance to compression set should be considered.
Our commitment to material integrity:  Each hydraulic seal used in a Best hydraulic cylinder is manufactured from high-performance elastomers, fluoroelastomers (FKM/Viton), HNBR and PTFE, Polyurethane, and nitrile rubbers.  We never permit the use of cheap, imitation seal materials.

In the case of fluoroelastomers, there are "commercial" or "industrial grades" that are not 100% virgin fluoroelastomer, but rather, FKM, adulterated with hydrocarbon elastomers, such as ethylene-propylene, chloroprene or acrylic rubbers.  For the mission-critical mobile hydraulic cylinders that are our specialty, these knock-offs present a high risk of failure, are always inappropriate, and are never used.*

* Many hydrocarbon rubbers can be (and typically are) blended to take advantage of specific features inherent in the individual rubbers. Fluoroelastomers in general cannot be blended with any hydrocarbon rubber without significantly degrading the resistance of the resulting vulcanizates to heat, fluids and compression set.