Temporary Idling & Preservation of Gearboxes, Bearings, Hydraulic and other Lube Oil Reservoirs
It is very important to protect oil lubricated equipment against corrosion and oxidation while the equipment is idled. Therefore, it is important to take proper steps to ensure the equipment is idled and stored properly. The equipment must be ready to be restarted safely and quickly- and operate reliably as it did, if not more so, before it was idled.
If it is possible to plan ahead, while the equipment is running and the oil is at operating temperature and condition, collect an oil sample, then filter the lubricant with the correct dedicated filter cart for that system. Remove as much solid particulate contamination and entrained moisture as possible. If the equipment is already shut down, use portable (dedicated to system/oil type) kidney loop filtration if it is practical to do so. To test for leakage consider adding a UV dye to the system during a final shift before outage. Inspect with a UV (black-light) and fluorescence-enhancing glasses to help detect and document system leak points. This could be an opportunity to plan and perform proactive maintenance and repairs (e.g. fixing leaks) that are normally difficult or impossible to schedule during regular operation.
Steps to Consider Before Your Equipment Down Shutting Down:
1. Create an equipment work list including tags based on a tagging checklist system for each piece of equipment to be temporarily idled.
2. Remember to lockout and tag out (LOTO) equipment to be worked on, and any related equipment. Follow all safety procedures.
3. Similar to periodic startups of assets like standby power engines/gensets, determine if larger systems with pressure circulating lube systems can be easily and safely started up periodically and operated under no or light load conditions
- For hydraulic systems or gearboxes with an independently controlled lube oil pump, consider weekly or monthly startups (or more frequent) to allow oil to circulate through the system
- For large circulating systems equipped with KP or LP Pushbutton sampling valves, samples can be collected on these periodic startups to ensure each system is remaining free of excessive moisture and other contaminants
After Shutting Down:
1. Drain a portion of the sump to remove any sediment and demulsified free water that may have shed from the oil after shut down, and replace with top-up oil
- For most industrial formulation mineral and also Group IV synthetic based gear/bearing and hydraulic oils, most free water will have settled to the bottom within 24 hours or less, or after cooling/resting overnight
- A BS&W (Bottom Sediment & Water) sight glass can help with this procedure
2. Top-up the sump with the correct fresh oil to at least the recommended oil level (pre-determined/marked on sight glass or level gauge)
- If topping up beyond the recommended high point/non-operating level mark, make sure to indicate that on the tag
- Remember to include any special notes that will assist with safe restarting of the equipment in the future at the proper oil level
3. For larger equipment, remove moisture from the airspace of gearboxes (for shafts sealed by lip seals) and reservoirs by removing the desiccant breather/vent and sealing with a bushing and run tee adapter that includes a vacuum gauge (with thread sealant) and elastomerically sealed valve
- Checkfluid’s L16-GVAC breather adapter is designed for this purpose
- Use a vacuum pump, the valve and probe adapter to remove moisture/humidity and create a very low vacuum [-2 psi] in the headspace
- Check the vacuum gauge. Note: creating a higher vacuum could compromise seals. However if purposely overfilling past the normal oil level (ie so that that entire shaft/seals are immersed in oil) then a higher vacuum pressure in the headspace is not an issue, as long the only air entry/seal point is the Checkfluid L16-GVAC adapter
- Use the gauge to periodically monitor for any loss of vacuum (through unplugged air sources above the oil level) and therefore the potential for moisture or particulate ingress
- With the system now sealed vacuum tight against air/oxygen that can accelerate corrosion, place the removed desiccant breather into a clear Ziploc/airtight sealed bag and tape it to the top of the reservoir to be installed prior to restarting the equipment
- As a bonus, if there are any slow drips or leaks below the oil level, for example a leaky plug or shaft seal, the vacuum in the headspace will eliminate these leaks (ie. prevent the gradual and/or steady loss of lubricant during the outage)
4. If not already equipped with an Oil Mist Coalescer, consider an adapter with a vacuum gauge indicator between the reservoir and desiccant breather
- The purpose is to ensure the breather is working effectively to control humidity in the headspace especially for equipment located outdoors or indoor areas subject to variations in daytime and overnight temperatures
- Alternatively you can overfill the sump with fresh oil to maximize contact with surfaces that could corrode and leave the desiccant breather in place. Inspect the breather periodically to ensure it has not become saturated (via color change), and is still working to remove humidity from the headspace during day-to-day and season-to-season fluctuation in ambient temperatures
5. For all systems, including both lip sealed as well as labyrinth/non-contact shaft seals in gearboxes and bearing housings, consider adding a vapour-forming rust and oxidation inhibitor/preservation oil to the system lubricating oil
- Preservation oils are available from most major lubricant manufacturers
- Added to gearboxes and reservoirs, these oils are designed to be volatile within the headspace of the reservoir to protect non-oil-immersed surfaces
- They are designed to form a lubricating vapour in the headspace to help protect exposed surfaces above the oil level from corrosion
- For reservoirs that have been drained and are empty, consider adding preservation oil exclusively
- This is especially useful for longer-term storage, to preserve internal exposed metal surfaces
- Check with your lubricant supplier for the optimum recommended product, amount/concentration to add
It is generally recommended, before restarting equipment containing system oil that has been treated with a preservative formulation oil, to perform a complete oil change prior to restarting the equipment. Although depending on the type of system, viscosity of the oil and type and concentration of the preservation oil, this is not always required. In either scenario, ensure there is a safe and reliable way to collect oil representative oil samples immediately after the equipment is restarted, and at the appropriate sample interval subsequently. Aside from monitoring the health of the equipment, this will help with identification and planning for which assets may need an oil change sooner than later after start up back to regular operation.
6. This is an often overlooked step - remember to manually turn the shaft at least 1¼ turn (3 to 4 times each month, or as recommended), to lubricate the bearings but also critically to help prevent false brinelling of the bearings as they sit unused in a static load condition.
- Vibration absorbing blocks should also be considered where applicable.
- Consult the equipment service manual for more information on these and other recommended procedures and best practices.
For The Temporary Idling of Grease-Lubricated Electric Motors:
1. Purge and regrease all grease points with the correct grease, avoiding under or over greasing that may damage the bearings and/or windings
2. Airtight (shrink) wrap and seal all motors not installed or where possible/practical, installed motors
- For outdoor installed motors, use airtight and weatherproof covers
- Storage of spare motors should be indoors (clean and dry; temperature controlled room if possible)
Long-Term Storage Reminders and Tips:
For long-term storage (months to years) the use of preservation formulations (rust inhibiting/preventative/vaporizing) type oils should be considered best practice. Consult your lubricants supplier for recommended products and procedures.
Consider indoor storage on vibration absorbing material. Large presses and railway traffic are obvious sources of vibration, however unobservable vibration sources can cause permanent bearing damage as well, such as the brinelling of rolling element and raceway surfaces. This can result in premature and/or rapid failure of equipment when it is needed most following recommissioning and start up. Consult OEM and manuals for additional recommendations specific to each type of equipment.
Prioritize internal component preservation and protection, but don’t forget unpainted/treated or vulnerable external metal or other surfaces on equipment. For example, external shafts, housings, slides, belts, chains, conveyors and wire ropes etc that normally receive lubrication at scheduled intervals. Wipe, brush or spray the appropriate type and amount of rust preventive oil or grease to reduce and prevent external corrosion and reapply as necessary. Pay particular attention to equipment/areas where rust formation could lead to a future safety or reliability issue.
For large and/or critical equipment in preservation during outage collect oil samples periodically, at least annually, to check for viscosity or moisture changes in the oil and replace when necessary.
Last but not least, remember to collect oil samples for analysis immediately before, and also immediately after restarting equipment. Even if the oil has been completely changed prior to restarting, but also (and especially) for equipment that did not have the luxury of getting a full oil change before restarting- collecting a live operating temperature sample within the first hour of resumed operation is critical. Check visually and send immediately/same day to the lab for analysis.
Special thanks to Rick Schrama for his advice to help us come through these difficult times