So far, we’ve mainly covered what rust is and how to prevent it when preserving equipment. This article discusses what can happen when equipment isn’t preserved correctly and what the corresponding impacts are.
What is a common occurrence when equipment is mothballed improperly? Rotating equipment and parts are designed to be moving. Too often, equipment that is idle “freezes up”, not just from general rust and corrosion, but from fretting corrosion. Failed bearings with roller spaced marks generally fail due to a condition called false brinnelling that occurs when balls or rollers vibrate and break through the lubricant film. Nearby operating equipment, trucks, trains, and other equipment cause tiny vibrations that create small movements in the bearings when they are not operating. If there is enough downward pressure, the balls or the rollers displace the lubricant and start to wear into the race causing roller-spaced marks. When false brinnelling occurs, bearings fail, and when looking across all idled assets, costs add up in terms of direct part replacement, production, and manpower.
Tip- when inspecting failed bearings, if the marks are roller-spaced - the damage most likely occurred when the equipment was stopped.
Picture of false brinnelling
There are two ways to prevent false brinnelling. First is to rotate the equipment periodically. Second is to support the shaft on blocks or on a vibration-dampening material.
This foundational understanding of rust prevention should help you and your company either build on your existing rust prevention program or give you some guidance on how to start one. If there are plans to begin mothballing equipment soon, remember that any lubricated equipment or parts that are to be idled should be part of your rust prevention plan. These short-term steps and measures that are needed to execute your rust prevention plan can pay off big in the long-run in several different ways:
ExxonMobil has equipment-specific corrosion protection guidelines, and our Mobil Serv℠ field engineers have helped customers build and tailor rust prevention programs to their specific needs. If you want to learn more about how to properly mothball and preserve your equipment, you can contact one of our engineers at our Technical Helpdesk, 1-800-MOBIL-25 (or visit us at https://www.mobil.com/en/lubricants/for-businesses/industrial/contact-us).