Proper storage of spare gearboxes is critical for gearbox reliability. The following methods and illustrations are excerpts from Noria's Machinery Lubrication training course.
Method 1 – Lip Seals
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Spray shaft extensions with a suitable dry film or similar preservative. Some examples include Castrol Rustilo 181, ESSO Rust BAN 397 and Valvoline Tectyl 846.
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Pack grease around oil seals to prevent drying and cracking
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Fill the gearbox casing completely with oil and seal tightly. Label the gearbox as "FULL – not ready for service"
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Allow some space for thermal expansion
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Remove the breather and replace with an airtight plug.
Notes: While this method is simple and a relatively permanent solution it can be expensive for large gearboxes that require a lot of oil. It can also cause a hazard if the gearbox accidentally leaks.
Method 2 – Labyrinth Seals
Spray shaft extensions with a suitable dry film or similar preservative (examples given in method 1).
For gearboxes with non-contact labyrinth seals, use internal vapor-phase rust protective coating instead of complete oil fill. Both oil wet and non-oil wet surfaces are protected by vapor-phase rust inhibitors.
Consider using commercial vapor phase rust inhibitors such as Ashland Oil, Tectyl 859A or Cortec VP corrosion inhibitor. Typically, add 5 percent of the oil volume. Some inhibitors require the oil/inhibitor mixture to be heated and agitated in order to perform effectively.
Notes: This method may only be good for about six months and should be renewed if storage period is longer. Another disadvantage is that it may cause incompatibility and foaming problems when filled with the service oil. Flushing is recommended before putting the gearbox into service.
Method 3 – Oil Mist Method
As an alternative method for large gearboxes with lip or labyrinth seals, oil mist introduces a clean air/oil mixture (1 part oil to 200,000 parts air) into the headspace of the gearbox. Similar to fog, it keeps machine surfaces lightly lubricated to prevent corrosion. API-RP 686 3.2.1 recommends oil mist protection be used if equipment is stored for more than six months, especially if more than 10 pieces of equipment are stored at a time.
Notes: Additives in the oil mist protect gear and bearing surfaces. The low pressure keeps environmental contaminants like dirt and moisture out. It is safe, non-hazardous and will not support combustion. One system can provide oil mist to multiple gearboxes. This method is more expensive and difficult to implement.
Maintenance Issues During Storage:
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To distribute oil and prevent false brinelling and fretting corrosion, rotate the shafts at least once a month.
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Visual inspections – when rotating exposed machine surfaces, check to make sure applied protective coatings have not been removed.
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Do not store equipment on vibrating surfaces as this can also cause false brinelling and fretting corrosion.
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If possible, store gearboxes under constant temperature conditions.
