O-rings are a type of hydraulic seal that is made of a resilient material, such as rubber or silicone. O-rings are typically used in hydraulic systems to seal between two surfaces.

O-rings are available in a variety of different materials, including:

• Nitrile rubber: Nitrile rubber is the most common material used for O-rings. It is a durable material that is resistant to oil, grease, and other chemicals.
• EPDM rubber: EPDM rubber is a good choice for O-rings that will be exposed to ozone, sunlight, or weathering.
• Silicone rubber: Silicone rubber is a good choice for O-rings that will be exposed to high temperatures or extreme chemicals.
• Fluorocarbon rubber: Fluorocarbon rubber is a good choice for O-rings that will be exposed to aggressive chemicals or high temperatures.

O-rings are also available in a variety of different hardness ratings. The hardness of an O-ring is measured on the Shore A scale. The higher the Shore A rating, the harder the O-ring.

70 Shore O-rings are relatively soft and are often used in applications where a high level of sealing is required. 70 Shore O-rings are also good for applications where the O-ring will be subjected to shock or vibration.

90 Shore O-rings are harder and are often used in applications where the O-ring will be subjected to high pressures or temperatures. 90 Shore O-rings are also good for applications where the O-ring will be exposed to chemicals or other harsh environments.

The best type of O-ring to use in a particular application depends on a number of factors, including the operating pressure, temperature, speed, fluid type, and the amount of compression that the O-ring will be subjected to.

Here are some examples of how O-rings are used in hydraulic systems for construction machinery:

• Hydraulic cylinders: O-rings are used in hydraulic cylinders to seal the piston rod and the end caps.
• Hydraulic pumps: O-rings are used in hydraulic pumps to seal the rotating shaft and the moving parts.
• Hydraulic motors: O-rings are used in hydraulic motors to seal the rotating shaft and the moving parts.
• Hydraulic valves: O-rings are used in hydraulic valves to seal the moving parts.