Gearboxes that are not in use for extended periods of time should be properly cared for to ensure their trouble-free operation once they are put in to service. A great reference document is also provided by CTI’s Engineering Standard Guideline ESG 138 (Long Term Storage Procedures for Cooling Towers). There are two different considerations when preparing your gearbox for long-term storage. They are when the gearbox is out of the cooling tower and when it is in the cooling tower (in-situ).
Gearbox Long Term Storage Not in a Cooling Tower:
It is imperative that your fan drive gearbox is stored in a warehouse, out of the weather. A climate-controlled environment is recommended, but not required. If the gearbox is not new you should drain the old oil and replace it with new Amarillo Gear approved lubricant. It is best to fill the gearbox with oil to the top of the gear case within about 1 inch (25.4mm) to allow for expansion and contraction with temperature variations. The best spot for filling in this case is the vent hole located on the top gear case cover. This ensures all bearings, gears, and internal surfaces are being coated and protected. Once completely filled, reinstall the vent plug. Note on the new GEN II Series of fan drives, they cannot be filled above operating level due to leakage through the non-lip bearing isolators. In this case, the gearboxes should be ordered from the factory with a vapor phase rust inhibitor in the oil that will coat and protect the inside components. If you have questions prior to order, please contact the factory. Now is the time to attach a warning tag that states the gearbox is completely full of lubricant and must be drained to the proper operating level prior to operation in a cooling tower. All external shaft extensions should be coated with a rust inhibitor grease such as CORTEC VCI-368 or equivalent.
The input shaft does not need to be rotated in this situation since there is no loading on the bearings and false brinelling will not occur unless the gearbox is exposed to external floor vibration. In this case, contact the factory for recommended enhanced long-term storage procedures.
Long Term Storage “In-Situ” in the Cooling Tower:
An in-situ gearbox should have the old lubricant removed (warning: imperative that the external sight glass on the fan deck must be removed and plugged prior to overfilling to prevent oil spillage on the fan deck outside the fan stack). Next, completely fill the gearbox with new Amarillo Gear approved oil through the vent hole in the gear case cover to within 1” (25.4mm) of the top. Reinstall the vent plug and apply warning tags as needed stating the gearbox has been overfilled and should be drained down to operating level prior to starting. If the gearbox is the new Amarillo GEN II, then after draining the old oil and installing new Amarillo approve oil, an Amarillo factory-approved vapor phase rust inhibitor should be installed with the oil and the gearbox allowed to run at full speed for at least 5 minutes so all internal components can be coated with the rust inhibitor. After the 5-minute run, plug all ports into the atmosphere so the vapor phase rust inhibitor cannot escape.
All exposed machined services such as shaft extensions should be coated with a rust inhibitor such as CORTEC VCI-368 or equivalent.
Allow the gearbox to rotate freely from windmilling. This allows loaded bearings to rotate and prevent possible false brinelling of the bearings between the rollers and race. If the gearbox has a non-reverse backstop, contact the factory. Disengaging may be required but varies by applications.
Commissioning a Gearbox into Service:
Prior to starting the gearbox for operation, the oil needs to be drained back to the operating level. If it has been overfilled in an “in-situ” condition, after lowering the oil level to operating level, the external fan deck sight gauge needs to be reinstalled. If your gearbox is the new Amarillo GEN II that had vapor phase rust inhibitor added and plugged, unplug the vent hole and drain a portion of oil out of the drain port to remove any water build-up from condensation. Replace makeup oil back to the proper operating level. Inspect vent lines for any debris blockage and check all fill and drain lines & connections for leakage. Rotate the gearbox by hand making sure it rotates freely and smoothly before energizing the electric motor.