Rotary joints must not only be able to withstand high-speed operation, but also be able to withstand gaowen, so it has technical content in design and scientific research. Rotary joints usually have three oil ports to connect with workshop pipes. Three of these ports are statically connected to the rotary joint and the housing of the joint. The swivel housing and uncoiler or winder remain relatively non-rotating. For example, the diameter of the mandrel inside is smaller than the diameter of the housing, and the gap is equivalent to the gap between the cylinder and the piston of a general hydraulic cylinder. Can not withstand excessive pressure, generally does not exceed 3bar, but it has tightness under low pressure and high speed conditions, its role is to seal the leaking oil from the rotary joint rotary seal. There are other leaking oils that are drained back into the tank at very low pressures to protect the oil seals from damage. Be careful not to install a filter on the leaking oil pipe.