Seals for flange fittings

Square section seals - flat o-rings

We offer NBR square section seals, also known as flat o-rings, designed for sealing connections of SFS, SFL flange fittings. Flat o-rings are available in NBR rubber as well as polyurethane versions ( more durable ). Only original flange seals ensure perfect tightness of flange fitting connections. These seals perform much better than standard o-rings.

Square o-ring – flange seal

What is a square o-ring ? A square o-ring, also called a Q-ring or a square-section seal- flat o-rings, is a specialized solution used in applications requiring exceptional sealing and mechanical resistance. Unlike classic o-rings with a circular cross-section, its geometric shape provides a larger contact surface. This makes the seal more stable, durable, and better suited for intensive use in hydraulic systems. HYDRON's offer includes flat o-rings made of high-quality polyurethane with a Shore A hardness of: 93–95. This chosen material is characterized by: resistance to abrasion and extrusion, minimal susceptibility to deformation under pressure, and a long service life even in difficult working conditions. These o-rings comply with the requirements of the SAE J 518 standard and are perfectly suited for hydraulic applications where operating pressure reaches up to 420 bar (≈ 42 MPa). 

Square section o-ring – what is it

A square section o-ring is a specialized technical seal that differs from a classic round o-ring in the shape of its cross-section. Instead of a circular profile, it has a square profile, which translates to a larger contact surface with the sealed elements. These types of flat o-rings are commonly used in flange connections where high tightness and seal stability under high mechanical and pressure loads are important.

Construction and material of square o-rings

Flat o-rings offered as standard NBR flange seals are made of NBR nitrile rubber. This material is characterized by good resistance to hydraulic oils, greases, fuels, and typical working media used in power hydraulics. NBR maintains flexibility over a wide temperature range, which contributes to long seal life and stable performance parameters even under intensive operation.

The square cross-section ensures that the seal does not roll in the groove during assembly, and pressure is distributed evenly across the entire contact surface. This is of great importance in flange connections, where precision and repeatability of sealing are essential for system safety.

Square section o-rings in flange connections

Flat o-rings are primarily used in flange fittings employed in power hydraulic systems. They are used in industrial installations, working machinery, high-pressure systems, and wherever a tight connection between two flat surfaces is required. The larger contact surface compared to round o-rings improves resistance to pressure pulsations and reduces the risk of leaks. These types of seals also perform well in spaces with limited mounting area, where a classic o-ring might not provide sufficient tightness or connection stability.

Advantages of NBR square o-rings for flanges

Square section o-rings provide high tightness, better fit to the groove, and greater resistance to deformation under pressure. Thanks to the use of NBR, they maintain good chemical and mechanical resistance, which translates into long-term and trouble-free operation of the hydraulic system. Stable positioning in the groove reduces the risk of seal damage during flange assembly and disassembly.

Flat o-rings in the Hydron offer

Hydron's offer includes standard NBR seals for flange fittings, including square section o-rings suited to popular solutions used in power hydraulics. A wide selection of sizes allows for easy matching of the seal to a specific type of flange and operating conditions. Thanks to Hydron's experience in the hydraulic industry and constant product availability, it is possible to quickly and safely replenish or service hydraulic installations while maintaining high quality standards.