Basic Protection for a Slip Ring Assembly

Posted on Thursday, November 19, 2015 in UEA Blog

UEA slip rings are mounted in various types of applications where falling liquids or foreign objects may try to enter the enclosure.  A very common assembly for construction applications places a slip ring underneath a hydraulic swivel or next to a gear box.  In either case it is realistic to think that either hydraulic fluid or oil may fall on to the slip ring assembly during typical operation.  For this type of protection, Engineering will need to know the mounting orientation of the slip ring assembly in order to seal against falling fluids and to allow any penetration to drain away underneath.    Each test has a specified water flow rate and duration of testing.  The test apparatus for the falling water tests is shown in figure 1.1.

figure 1


One of the most common protection ratings for slip rings is IP54.  This applies in nearly every application that uses slip rings, including wind turbines, construction equipment and irrigation equipment.  The “5” stands for dust protection.  In order to ensure the design is properly sealed the product is placed within a dust chamber while talcum powder is agitated to become airborne. Next, the product is covered in fine dust as shown in Figure 1.2.  The “4” relates to water being sprayed from all applications, shown in figure 1.3.

figure 1.2

Figure 1.2

Figure 1.3

Figure 1.3

IP65 and IP66

The next step up for sealing is IP65 testing.  In many ways this dust protection testing is similar to IP54, however, in IP6X testing the dust is forced into the product by spraying sealing points or by applying a vacuum to the internal slip ring assembly. Stepping up to IP66 requires the same dust protection techniques with even more powerful water jets.  The biggest challenge with IP65 or IP66 testing for slip ring applications is the balance of keeping water and dust out while still allowing air in.  Our tests have shown when a slip ring contact is completely sealed during rotation, a noticeable increase in wear can be observed.  For applications this isn't an issue.  However, when a product is expected to last 200 million-plus revolutions, engineering needs to pay special attention to the sealing methods.

Immersion Protection

IP6X is the highest classification for dust testing, but liquid protection also includes IPX7 and IPX8.  These include the product being fully immersed in a liquid.   Testing for IPX7 includes a 30 minute immersion of the DUT in water up to 1m with the highest point being at least 150mm below the surface.  IPX8 doesn't have a specific depth of immersion or a set amount of time as this is defined by the product specification. The slip ring needs to be properly sealed from every angle.

Overall, a better sealed slip ring isn't always a better option and sealing should be done to properly represent the actual operating environment to maximize performance.  If any of these applications fit your demand, please contact UEA for your slip ring ingress protection needs.

Kyle Riegel
Design Engeneer