what are differences between Hydraulic Rotary Unions and pneumatic rotary unions?

Hydraulic rotary unions and pneumatic rotary unions are both devices used to transfer fluid or gas between stationary and rotating parts of a machine, but they differ in their application, construction, and operational characteristics:

Fluid Type:

Hydraulic rotary unions are designed to transfer hydraulic fluid, which is typically oil-based and used in applications requiring high pressure and force, such as heavy machinery, construction equipment, and hydraulic systems.

On the other hand, pneumatic rotary unions are used for transferring gases, typically compressed air or other gases like nitrogen. They are common in pneumatic systems used in manufacturing, packaging, and automation.

Pressure and Flow Rate:

Hydraulic systems generally operate at much higher pressures than pneumatic systems. Hydraulic rotary unions are built to withstand high pressures often reaching several thousand PSI (pounds per square inch) and to handle high flow rates.

Pneumatic systems typically operate at lower pressures compared to hydraulic systems. Pneumatic rotary unions are designed to handle lower pressure ranges usually up to a few hundred PSI and moderate flow rates.

Sealing and Construction:

Hydraulic rotary unions require durable seals and construction materials to prevent leakage and withstand the high pressures encountered in hydraulic systems. They often use seals made of materials like rubber, polyurethane, or PTFE (polytetrafluoroethylene) and are constructed from materials such as stainless steel or hardened steel.

Pneumatic rotary unions also require effective sealing, but they operate at lower pressures, so the seals and construction materials may not need to be as heavy-duty. Common seal materials for pneumatic applications include rubber, NBR (nitrile butadiene rubber), and PTFE. Pneumatic rotary unions may be constructed from materials like aluminum, brass, or stainless steel.

Application:

Hydraulic rotary unions are primarily used in applications where high force or torque transmission is required, such as hydraulic machinery, industrial presses, and heavy equipment.

Pneumatic rotary unions find application in industries where compressed air or gases are used for actuation, control, or powering tools and equipment, such as in manufacturing,

packaging, and automation systems."