There are many factors that drive the design and manufacturing of hydraulic swivels. We have outlined the factors below and how they are determined in regards to the overall design.
If a center through hole is necessary, the diameter is determined by the size of the wiring harness of the slip ring. The size of the wiring harness is governed by the number of circuits and their function.
When selecting material for the housing and spool, tensile and/or fatigue strength need to be considered. A safety factor of 4:1 is applied to the tensile and fatigue strength of each material. The length of the swivel is determined by the number of ports and the width of the flow grooves, along with the number of seals including: excluder, u-cup, wear ring, high-pressure cap seals, and o-rings. The operating pressure, size, and the number of ports all have an effect on the bore of the swivel.
In considering ports, the wall thickness of each port is determined by the operating pressure, material strength at safety factor, and port deep drill diameter. Ports may also need to be located around the head of the spool, which also has as an effect on the length of the swivel.
As one can see, these factors make up the lion's share of the overall design and envelope size of a hydraulic swivel.
Thomas Van Veldhuizen