Rotary unions manufactured by United Equipment Accessories (UEA) go into a wide array of machinery. Each application that we design for is different from the next. While there are usually some similarities in form, fit, and function, extra care is needed during initial design discussions to ensure that the rotary union is properly mounted.
The initial discussion of mounting the rotary union typically revolves around not only the mounting but also the torquing. Our rotary unions can be mounted in nearly any position or orientation. But depending on how it’s mounted, the torquing or rotational retention will need to be closely considered with its orientation.
The swivel can be considered to have two primary pieces, the rotor and stator. The rotor and stator are terms used to say that one part is rotating, the rotor, and the other part is stationary, the stator. In simple terms, the goal is to rigidly mount the stator, allowing the rotor to be retained in rotation only. The rotor does not have to be the spool, and the stator doesn’t have to be the housing. Depending on how the swivel is packaged into the larger assembly, they can switch around.
Rigidly mounting refers to mounting it solidly. Solid mounting requires no relative movement between itself and the pieces it attaches to. This usually involves using multiple high-grade bolts, washers, and nuts that are screwed down tight. The clamping force of the bolts stops any relative motion from occurring.
The rotor is retained in rotation, allowing it to find a floating center. This requirement is accomplished in a few different ways. The most common method is a torque arm connected to the rotor, which engages in the customer’s machine. Allowing the rotor to find a floating center means having clearances that accommodate the swivel slightly off the center axis of rotation. As the machine ages, the slew bearing will naturally cause eccentric rotation and place the swivel slightly off the center axis of rotation. Anticipating this eventual wear of the slew bearing and allowing for it is key to the long-term performance of the rotary union.
If the rotor and stator are both solidly mounted, one of two things will happen. Due to the inevitable eccentric rotation, the swivel will bind up, or one side of the mounting will eventually loosen up and allow relative movement. These are not desirable outcomes and will reduce the life of the rotary union.
Proper mounting of the stator and rotational retention of the rotor are essential to the longevity of the rotary union. Contact us today to work with one of UEA’s engineers to design a rotary union for your application.
