Part of a piston or cylinder’s sealing system, U-cup seals have a distinct U-shaped profile that helps safeguard the hydraulic cylinder.
Designed primarily to seal at low pressures, they can also handle high pressures and extreme temperatures.
Factors and elements to consider when choosing the right sealing solution, which the team at SSP explores in more detail throughout this post, include the application’s surface finish, whether the O-ring is loaded, inner and outer diameters, the tensile strength of the materials, and more.
What are u-cup seals?
A U-cup seal features a U-shaped profile and consists of an inner lip that is movable and an outer lip that is static.
Typically made of polyurethane (although there are subtypes and various patterns of U-cups available, such as Nitrile (oil-resistant), Viton (chemical-resistant), and EPDM), this particular seal resembles O-rings.
However, a urethane U-cup is also durable, easy to install, and, if required, can be removed with ease while also withstanding high pressure.
U-cup seals are designed to prevent fluid leaks, maintain pressure, and ensure optimal performance in hydraulic and pneumatic applications, as well as in industrial machinery and automotive components.
Able to withstand up to 5000 psi pressure and temperature ranges from -40 degrees Celsius to 200 degrees Celsius, this U-shaped seal is suitable for both dynamic and static applications.
Definition of U-cup seals
Loaded U-cups – designed primarily for hydraulic applications, loaded U-cups (can also be known as PolyPaks) are loaded in their grooves with a suitable O-ring that is typically constructed from the material polyurethane.
Standard U-cup seals definition – with a distinct U-shaped to set them apart, these U-cup seals ensure a secure seal suitable for a range of varying conditions. Adapting to the contours of the cylinder, the edge of the U-cup will adapt to provide a robust sealing solution and prevent leaks. It distributes stress evenly to prevent uneven wear which, in turn, increases the seal’s lifespan.
Types of U-cup seals
Loaded U-cups – here, the U-cup is loaded with an O-ring, providing a tight seal in low-pressure applications. Great for low-pressure rods and pistons.
Unloaded U-cups – this seal has no O-ring and is suitable for heavy-duty sealing applications.
Spring energised u-cups – specially engineered, this type of u-cup includes a metallic spring instead of an O-ring. This makes it more suitable for dynamic applications as it offers great compression.
Homogeneous u-cups help reduce friction, minimise wear, and ensure a smooth seal. This type of U-cup is suitable for friction-sensitive pneumatic applications.
Z-seal u-cups – suitable for applications involving very heavy rods.
You will also find available:
Square straight loaded – offering a height dimension that is equal, the cross-section of the square means this O-ring offers a more balanced seal. Suitable for dynamic applications.
Bevel loaded – the square dimensions of this seal provide a sharp sealing edge due to its bevelled lip. Suitable for pressure applications.
Deep loaded straight – asymmetrical in its design, here the cross-section is exceeded by the height and features a straight lip. This seal provides enhanced sealing where height is critical to the application.
Bevel loaded (deep) – asymmetrical with a beveled lip, this seal is suitable when you require a strong seal as this type can withstand varying pressures.
In essence, a U-cup with a straight lip will be more suitable for applications operating at high-pressures, such as applications operating with static seals. Note: This type of seal does accelerate wear due to an increase in friction.
Those U-cups with a bevel lip are more suitable for dynamic applications and high-speed operations. However, they aren’t so robust in low-pressure, and they can move (unwanted move) if not installed properly.
Applications of u-cup seals
Before diving in and buying any type of U-Cup, you must make sure:
- Seal material is compatible with the application
- Seal won’t react to the fluid inside the application
- Seal is resistant to abrasion, moisture, and any chemical properties of the fluid
- Check surface finishes, tolerances, configurations, and cross-section sizes
- You will also need to consider the average lifespan of the seal, the value and availability.
U-cup seals can be found in:
- Hydraulic and pneumatic applications such as:
- Water treatment
- Oil and gas
- Petrochemical applications
- Heavy engineering
- Automotive parts
- Pipelines
- Agricultural equipment
- And more.
Offering a superior sealing performance that is designed for high pressure and dynamic systems, make sure you choose the right seal for your application.
O-ring supplier
An essential element across various sectors, the U-cup seal helps to ensure the efficient operation and longevity of diverse applications.
If you’re looking for an o ring manufacturer who can provide you with a vast range of seals and gaskets to suit diverse applications, all of high quality, and meeting industry standards, look no further.
At SSP, we stock a range of seals and gaskets to meet all requirements.
Call us today on 01535 274 776 to find out more.
