Sealing Solutions for Fluid Power Applications | Trelleborg

Sealing Solutions for Fluid Power Applications

Delivering reliable, long-lasting performance

Hydraulic applications are challenging for seals. Not only must the hydraulic seals prevent leakage of fluid from the cylinder, but they must also withstand high pressures, extreme temperatures and transverse forces within the application. The function of hydraulic seals goes far beyond preventing fluid leakage.

At Trelleborg Sealing Solutions, we are experts in fluid power sealing. Our engineers partner with customers to design sealing solutions to meet your unique application needs.

Hydraulic Cylinders

Hydraulic cylinders are sealed using a combination of specialized products:

  • Hydraulic rod seals prevent leakage of fluid from within the cylinder to the outside
  • Hydraulic piston seals prevent fluid from flowing across the cylinder head, which allows pressure build up on one side of the piston, making the cylinder extend or retract
  • Wear rings guide the piston and piston rod within the hydraulic cylinder, absorbing transverse forces, preventing metal-to-metal contact
  • Scrapers or wipers scrape dirt, foreign particles, chips or moisture from the piston rods as they retract into the cylinder, preventing contamination

Application examples

Rotary Actuators

Rotary actuators can be hydraulically, pneumatically or electrically powered and have a range of sizes, powers, and speeds. Rotary seals are critical for keeping oil and grease in the system while excluding dust and other debris from the internal bearings. Static seals prevent ingress of contamination through joints or other locations that are possibly exposed to the environment.

Application examples

  • Hydraulic manifolds
  • Steering systems
  • Oil distributor in machine tools
  • Rotary joint in a lathe
  • Extruder on filament winding machine
  • Swivel Joints

Motors & Pumps

Both motors and pumps use rotation to create fluid flow and/or linear movement. Different types of seals play different roles in the component:

  • Rotary seals are commonly seen at multiple locations to prevent leakage of oil and grease
  • Piston seals prevent fluid flow between internal pump sections
  • Rod seals prevent leakage on linear components
  • Wear rings are used to centralize both rotating and linear components and prevent metal-to-metal contact
  • Static seals prevent environmental contamination ingress, which helps prevent particles that may cause wear from entering the motor or pump.

Application example: Axle motors, Axial piston pump on forklift


Valves regulate, direct and control the flow of a fluid through various passageways from areas of higher pressure to lower pressure. There are numerous valve configurations that involve both rotary and linear movement.


  • Piston Seals prevent leakage across internal portions of the valve
  • Rod Seals prevent leakage into the environment across the valve shaft
  • Rotary seals are sometimes required based on the configuration
  • V-Rings are used to prevent contamination from entering along axial faces
  • Static Seals prevent leakage at joints and other connections
  • Custom molded parts such as diaphragms can direct fluid flow within the valve itself


  • Ball valves
  • Cartridge valves
  • Check valves
  • Direct control valve
  • Poppet valves
  • Proportional valves (directional, flow, shut-off/seal valves)
  • Relief valves
  • Sandwich plate valves
  • Servo valves
  • Solenoid valves

Drivetrain Components

The drivetrain of a vehicle comprises the transmission and the axles with the intention of delivering power to the wheels or tracks that will ultimately move the vehicle.

  • Rotary seals are needed in the transmission, which contains numerous rotating components, to protect internal bearings and prevent oil and grease from leaking into the system
  • Static seals prevent contamination from getting into the system and causing premature wear on the moving components
  • Custom molded parts are used for unique sealing needs.
  • Cassette seals are used on the axle in situations where the equipment’s surface is not controlled or where the seal needs additional protection from debris.
  • Mechanical face seals protect roller bearings and other sensitive components where the equipment is subject to heavy contamination
Application examples: Axle-wheel hub, brake system, gearbox and steering system on forklift

Fittings & Connectors

Hydraulic fittings and connectors require a variety of static seals to keep fluid contained within the hydraulic system and prevent environmental contamination from entering. These seals can be standard industry profiles or custom molded parts for complex geometries or unique requirements.



Engines & Controls

The engine delivers power to drivetrain components thus forming the powertrain of the vehicle. Engines can have a variety of configurations, but most involve rotary seals for keeping oil and grease within the system.

Static seals and custom molded parts are found throughout and provide multiple functions such as preventing contamination ingress or separating fluids. The V-Ring is typically used to prevent contamination from entering the engine components through axial faces.


Application examples: Distributors, Emissions Controls, Idlers


Accumulators are used for storing energy within a hydraulic system via compressed fluid. In many instances, this involves the separation of hydraulic fluid and nitrogen gas thus requiring leak-tight piston seals to ensure fluid separation. Wear rings are used for centralization while static seals keep both the hydraulic fluid and gas contained within the accumulator to prevent energy loss.



Filters are critical components within a hydraulic system as they help remove particulates from the hydraulic fluid, which can keep the system from getting clogged and losing efficiency.

Both standard static seals and custom molded parts keep external contamination from entering into the system through these filters.


Power Units

Hydraulic power units comprise of multiple elements such as motors or engines, pumps, and valves. Together they form the primary component of a hydraulic circuit and thus contain numerous types of seals.



  • Doors
  • Drives
  • Drives – Fans
  • Heating Units
  • Reservoirs
  • Rollers
  • Sensors
  • Sheaves
  • Shock Absorbers
  • Suspension Systems
  • Switches
  • Tools