How to Select a Rotary Joint: 5 Key Parameters
Most early rotary joint failures trace back to a mismatch between the joint and the real duty, not to product quality: the wrong seal material for the media, speeds beyond the bearing limit, or underestimated pressure causing leakage. Confirming five parameters before ordering prevents most of this rework.
1. Bore size: flow and connection
Bore (DN or mm) determines flow capacity. Quote the actual pipe bore to the manufacturer instead of rounding it yourself; oversized or undersized bores both hurt flow velocity and pressure loss. Standard single-passage joints cover DN6-DN100, and large pipeline joints reach DN350.
2. Speed: the duty cycle matters more than the maximum
Catalog maximums such as 3,000 RPM or 30,000 RPM are limits, not continuous ratings - leave margin for continuous running. CNC spindle coolant duty cares about dynamic balance and seal temperature rise at speed; slow, high-torque duty cares about bearing load.
3. Pressure: static and pulsating are different
Besides system pressure, confirm whether the circuit pulses or shocks. Hydraulic fixture duty typically runs 16-25 MPa; high-pressure washing and oilfield fracturing reach 70-138 MPa, with completely different seal structures and face materials.
4. Temperature: media and ambient both count
Heat transfer oil duty often runs 180-320 C and needs high-temperature seals with cooling structure; cooling water duty needs to consider ambient low temperature and condensation.
5. Media: it decides the seals and the body material
Water, hydraulic oil, heat transfer oil, steam, water-glycol and slurry each demand different seal materials; for mixed media, always state the proportions.
Which series fits which duty
For a single medium, start with the single passage rotary joint; two independent circuits suit the dual passage rotary joint; CNC spindle cooling calls for the spindle coolant rotary joint; rotary tables and fixtures use the multi-station rotary joint; excavators and cranes use the central rotary joint.
Practical advice
Send these five parameters together with the installation envelope and connection type, and you will receive a model recommendation with 2D/3D drawings. When the duty is unusual, ask for a trial sample before volume ordering.
