While most companies recognize the importance of routine maintenance for their industrial equipment, many risk permanent damage when they fail to take appropriate steps to mothball the equipment.
The risk is real: equipment that is not properly mothballed can quickly show signs of internal metal corrosion that will significantly reduce component life and cause startup problems when the equipment is brought back into service. (Without proper protection, water can enter through breathers and other openings, as illustrated. Proper mothballing can help significantly reduce water contamination.)
The three biggest threats to equipment that is taken out of service are:
- Moisture/water buildup inside the machine that can break down into acids that cause internal corrosion
- Vibration from external movement causing microwelding of contacting surfaces (better known as fretting corrosion)
- Foreign contaminants that can cause abrasive wear on rolling elements.
Approximately 24 to 48 hours prior to shutdown, machine operators should change filters, then add a system cleaner at a mix equal to some 5-10% of the existing lubricant. Once equipment is shut down, the mixture must be drained from the machine while still hot. After the equipment has been allowed to cool, it should be completely wiped down, using lint-free rags. The equipment''s filter elements should be replaced and all strainers cleaned. Next, the system should be refilled to capacity with a three-phase rust inhibitor lubricant. The operator should plug the system to prevent the release of any rust-inhibiting vapors.
To complete the mothballing process, the machine should be tagged with a prominent label (preferably red) stating, "This equipment has been mothballed. You must take necessary steps to prepare the system for restart."
Strong consideration should be given to listing the actual steps required for restart, as well as contact information for the machine operator who performed its shutdown.
For a mothballing case study, click here.