What are the common oil seals used in hydraulic systems?

In hydraulic systems, the common oil seals include O-rings and Quad rings. O-rings are widely utilized due to their versatility, effectiveness in sealing against leaks in both static and dynamic applications, and ability to conform to various shapes and sizes. Quad rings, also known as X-rings, offer similar sealing properties but provide a distinct advantage due to their design, which reduces friction and wear and enhances sealing performance in high-pressure applications.

These seals are essential for maintaining hydraulic fluid integrity and preventing contamination, which is crucial for system performance and longevity. Their selection often depends on the specific hydraulic application and operating conditions, such as temperature and pressure. While other types of seals, like mechanical seals and V-rings, do play roles in different contexts, O-rings and Quad rings are more common in typical hydraulic systems. Thus, their prominence makes the choice of O-rings and Quad rings the correct answer for this question.