What is the maximum operating pressure for this 20mm ID U-shaped sealing ring?

The maximum operating pressure is 250 bar when used with a proper gland and a gap of 0.3mm or less. The U-lip design is pressure-energized, meaning sealing force increases with system pressure. However, at pressures above 250 bar, the risk of extrusion increases, especially if the gap exceeds 0.3mm. For higher pressures, consider a back-up ring or a harder compound (e.g., 90 Shore A). Always ensure the bore and rod surfaces are within the recommended tolerance of H8/f7 and have a surface finish of Ra 0.4 μm or better to prevent leakage and extend seal life.

Can this U-shaped sealing ring be used in both hydraulic and pneumatic systems?

Yes, the NBR compound and U-lip design are suitable for both hydraulic and pneumatic applications. In hydraulics, it seals mineral oil-based fluids up to 250 bar. In pneumatics, it provides effective sealing at pressures up to 16 bar, with the added benefit of low friction due to the lip design. However, for pneumatic systems requiring very low breakout force, consider a lubricated version or a different profile. Always ensure the seal is compatible with the specific fluid: NBR is not recommended for phosphate esters or ketones. For air applications, a light film of grease during installation helps maintain lip lubrication.

How do I install this 20mm ID x 30mm OD x 7mm seal correctly?

Installation requires careful handling to avoid damaging the lip. First, clean the gland and rod, removing any burrs or debris. Lubricate the seal and gland with the system fluid or a compatible grease. Insert the seal into the groove with the U-lip facing the pressure side. Use a blunt tool to avoid cutting the lip. For blind grooves, use a sleeve or installation cone. After installation, cycle the system slowly to ensure the lip seats properly. Check for leakage during the first few cycles. Proper installation extends seal life by up to 50% compared to improper methods.

What is the expected service life of this sealing ring in a typical hydraulic cylinder?

In a clean hydraulic system with proper filtration (ISO 4406 18/16/13 or better) and operating conditions within the specified range, the seal typically lasts 1 to 3 years or 1 to 2 million cycles. Factors affecting life include fluid cleanliness, temperature, pressure cycles, and surface finish. In contaminated systems, life can be reduced by 50% or more. Regular maintenance, including fluid analysis and filter changes, helps maximize seal life. Bench tests at 160 bar and 80°C with 20mm rod showed over 1 million cycles before leakage exceeded acceptable limits.

U-Shaped Sealing Ring

U-shaped sealing ring 20mm ID x 30mm OD x 7mm height in NBR 70 Shore A for hydraulic and pneumatic systems

The U-shaped sealing ring is a precision-engineered elastomeric seal designed for dynamic applications in hydraulic and pneumatic cylinders. This specific model features a 20mm inner diameter, 30mm outer diameter, and 7mm height, molded from NBR (nitrile butadiene rubber) with a hardness of 70 Shore A.

Height

7mm

Material

NBR (Nitrile Butadiene Rubber)

Hardness

70 Shore A

Temperature Range

-30°C to +100°C

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How Does the 20mm ID U-Shaped Sealing Ring Perform in High-Pressure Hydraulic Systems?

The U-shaped sealing ring with a 20mm inner diameter, 30mm outer diameter, and 7mm height is a dynamic seal specifically engineered for reciprocating applications. Molded from NBR with a 70 Shore A hardness, it offers a balance of flexibility and mechanical strength. The U-shaped lip design creates a pressure-energized seal: as system pressure rises, the lip deflects against the mating surface, increasing sealing force. This self-energizing effect maintains integrity up to 250 bar in standard hydraulic circuits. The 7mm height provides sufficient radial stiffness to resist extrusion in gaps up to 0.3mm, while the 20mm ID ensures a snug fit on 20mm shafts or rods. The seal operates effectively within a temperature range of -30°C to +100°C, making it suitable for both mobile hydraulics and industrial power units.

Typical applications include hydraulic cylinders in construction equipment, pneumatic actuators in packaging machinery, and reciprocating pumps in chemical processing. In these systems, the seal addresses common pain points such as fluid leakage, air ingress, and premature wear due to side loading. The NBR compound resists swelling in mineral oils and greases, maintaining dimensional stability over extended service intervals. For instance, in a 20mm rod hydraulic cylinder operating at 160 bar and 80°C, the seal has demonstrated a wear life exceeding 1 million cycles in bench tests. Its compact 7mm height allows retrofitting into existing glands without modification, reducing downtime during maintenance.

Compared to O-rings or lip seals in the same size range, this U-shaped sealing ring offers superior performance in dynamic conditions. The 70 Shore A hardness provides better extrusion resistance than standard 70 Shore A O-rings, while the U-profile accommodates larger tolerances in bore and rod alignment. Unlike chevron packs, this single-piece design simplifies installation and reduces inventory costs. The 20mm ID variant is specifically optimized for small-bore cylinders where space is limited, delivering a higher sealing force per unit volume than larger cross-section seals. With a compression set of less than 25% after 24 hours at 100°C, it maintains elastic recovery even under continuous cycling.

Pressure-energized U-lip design maintains seal integrity up to 250 bar, reducing leakage in high-pressure hydraulic systems.
NBR compound with 70 Shore A hardness offers excellent oil resistance and a compression set below 25% after 24 hours at 100°C.
Compact 7mm height and 20mm ID fit standard glands, enabling retrofits without machining and cutting maintenance time by up to 30%.

Core Technical Features and Quantified Advantages

STEP 1

Pressure-Energized U-Lip Geometry for 250 bar Service

The U-shaped lip automatically increases contact force as system pressure rises, maintaining a tight seal up to 250 bar. This self-energizing effect reduces leakage by up to 40% compared to standard O-rings in dynamic applications. The 7mm height provides radial stability, preventing lip rollover during rapid pressure cycling. Ideal for hydraulic cylinders with 20mm rods operating at pressures up to 250 bar and temperatures up to 100°C.

STEP 2

NBR 70 Shore A Compound with Oil and Abrasion Resistance

The nitrile butadiene rubber compound is formulated for resistance to mineral oils, greases, and hydraulic fluids. With a hardness of 70 Shore A, it balances flexibility for easy installation with toughness to resist abrasion from contaminated fluids. Tested per ASTM D2000, the material exhibits a volume swell of less than 10% after 70 hours immersion in IRM 903 oil at 100°C, ensuring dimensional stability and long service life.

STEP 3

20mm ID x 30mm OD x 7mm Height for Standard Gland Fit

The precise dimensions of 20mm inner diameter, 30mm outer diameter, and 7mm height allow direct replacement of existing seals in standard hydraulic and pneumatic glands. The 7mm height fits common groove widths without modification, reducing downtime during maintenance. The 20mm ID ensures a snug fit on 20mm shafts, minimizing eccentric wear. This size is widely used in small-bore cylinders, offering a compact sealing solution with a 30% smaller footprint than comparable chevron packs.

STEP 4

Temperature Range -30°C to +100°C for Versatile Applications

The NBR compound operates reliably from -30°C to +100°C, covering most industrial hydraulic and pneumatic applications. At -30°C, the seal remains flexible enough to prevent cracking during cold starts, while at +100°C it retains sufficient elasticity to maintain sealing force. This wide range eliminates the need for special low-temperature or high-temperature seals in many systems, simplifying inventory and reducing costs. Suitable for outdoor equipment, food processing machinery, and automotive assembly lines.