Analysis on the hidden dangers of using lubricating grease in electric slip rings

Many slip ring manufacturers promote the advantages of using lubricating grease in slip rings: Lubricating grease could not only reduce the wear of slip ring contact materials, thereby prolonging the its life, but also increase theelectrical and thermal conductivity, inertness, excellent oxidation resistance, and waterproof, anti-corrosion effect. Misleading that only high-quality slip rings are the ones that use lubricating grease.

After investigation and verification, it is not difficult to find that they are based on a product introduction on a certain lubricating grease website, and that they are exclusively used on power switches and electrical connectors. “High-voltage power switches can be used, and low-voltage conductive slip rings can also be used.” The professional article was “naturally” misled, but never consider that this misleading would bring serious problems to electric slip rings.

Let’s first analyze the conductivity of the lubricating grease applied on the slip ring.

Lubricating grease is mainly used in the bearing and contact parts (signal loop, brush wire or electric brush) of the slip ring. Moreover, generally only slip rings with ultra-long life and low speed will use lubricating grease on the contacts, and slip rings with high speed will not use lubricating grease. Because, in the process of use, the lubricating grease with good adhesion will be thrown off by the centrifugal force generated by high speed; no matter how inert it is, it is easy to be melted, evaporated, or even volatilized by the heat generated by the high-speed rotation and friction of the contact parts. It is also easy to wear due to the high speed and long-term friction of the contact parts, which becomes a source of internal pollution in the slip ring. If the slip ring uses conductive lubricating grease, it will easily cause a short circuit. Not only is it easy to cause a short circuit between the slip ring tracks during rotation, but because the slip ring contacts are very precise, a little more lubricating grease during the production and assembly process can easily lead to hidden dangers.

Therefore, in order to avoid the hidden danger of causing short circuits, the lubricating grease used in the slip ring must be insulated. Moreover, lubricating grease will only reduce the electrical conductivity of the slip ring contacts, and will never increase the electrical conductivity.

Everyone may disagree with this conclusion: Since it is an insulating grease, how can slip rings conduct signal transmission? As we all know, the insulation and conductivity we often say are relative, and the state performance will be changed by many influencing factors.

After soaking or spraying or brushing lubricating grease on the slip ring contacts, it will form a lubricating film layer with a thickness of only a few microns after drying. Although this thickness of insulating grease will increase the resistance value and reduce certain transmission performance, it is not enough to block affects the normal transmission of current and signal. However, in the slip ring production process, the thickness uniformity and conductive stability of the lubricating grease cannot be accurately controlled, which increases the dynamic resistance fluctuation value of the slip ring contacts, thereby reducing the stability and reliability of the slip ring. This is determined by its own characteristics. In addition, the volatilization of grease, dust pollution, abrasion and even corrosion after thermal denaturation will directly affect the normal use of slip rings, and even cause safety hazards such as short circuits.It should be particularly pointed out here that the volatility of grease has a serious impact on the optical transmission device in the optical slip ring and optical fiber slip ring. This discovery has benefited from 3KM LINK years of experience in R&D and production of optical transmission devices, tested and verified from a large number of long quality control cases.

In order to completely eliminate the safety hazards of lubricating grease, 3KM LINK team has achieved the same effect without using lubricating oil by improving the contact technology and adopting high-quality bearings. The slip ring contact materials are treated with unique wear-resistant and corrosion-resistant three-level super hard gold technology, and the hardness, strength, wear resistance and electrical conductivity are better than the international military standard specifications (MIL) for connector contacts, making the contacts’ surface is very smooth, with a roughness of 0.2~0.5μm, which avoids the flashing phenomenon of the brush wires, greatly reduces the phenomenon of early powder accumulation, and the fluctuation resistance value is also significantly reduced, as low as 0.001Ω, which effectively extends the conductive slip ring life span.

In other words, unlike electric slip rings, when conductive lubricating grease is used on power switches and electrical plug-in parts, the current and voltage are high, but there is no centrifugal force, volatile pollution, long-term wear, high-temperature heating and other conditions or environments. So there is no security hazard mentioned above.

Post time: Nov-27-2021