By Fred K. Geitner
In the early nineties, a decommissioned and subsequently mothballed fertilizer plant located in the United States was purchased, dismantled, and reconstructed at a location half way around the world. When I visited this plant about 10 years after it was restarted at its new location, it was producing fertilizer at a fraction of the investment cost of a brand new plant. This attested to good storage protection because the plant had sat idle for a considerable time before it was relocated. This is just one example demonstrating that long-term storage protection of sensitive machinery such as compressors, pumps, and associated drivers saves money.
Appropriate procedures for the preservation or corrosion inhibiting of inactive process machinery depend on the type of equipment, expected length of inactivity, and the amount of time required to restore the equipment to service. Leading companies in the process industries develop their mothballing standards to consider these criteria. One typical mothballing program for indefinite storage was planned and executed as follows and forms the basis for our recommendations.
The probability of equipment failure is high following commissioning of equipment, whether for initial operation or following a rebuild. Machines can often sit at a new industrial site for months while the slow process of site construction progresses. Unless the buyer clearly specifies storage measures in the technical purchase specification, it is likely that machinery would be shipped without adequate provision for storage. Onsite storage preparation for the three to twelve months that machinery may sit idle at a construction site before commissioning usually entails a preventive maintenance (PM) program. Adequate storage protection plans would typically look like the following (assuming a northern, dry climate):
Rotate all equipment such as motors, turbines, gears, and compressors every two weeks.
When rotating exposed machined surfaces, check shafts and couplings to confirm that a protective coating has been applied and has not been removed. Reapply coating if needed.
Check all lubricating lines to see if any tubing, piping, tank or sump covers have been removed. Retape ends and cover as needed. If flanges are open on machinery connections, notify the pipe fitter first line supervisors or other designated personnel to reinstall the covers.
Draining of Condensate
Drain condensation from all bearing housings, sumps, and oil reservoirs on a once-per-month schedule. If excessive condensation is found, recheck once a week, or at two-week intervals, depending on the amount of condensate present.
Fill all bearing housings that are oil-lubricated but not force-fed with rust preventive concentrate, bringing the oil level up to the bottom of the shaft. For force-fed bearings, the upper bearing cap and bearing must be removed. A coat of heavy, inhibited oil can be applied to the journal and bearing surfaces. This should be reapplied as needed.
Electric motors with greased bearings need not be lubricated. If received with a grease fitting, it should be removed and plugged or capped.
Spot-check turbines by removing the upper half of the turbine casing and visually inspect. Plan to open a sampling of these turbines, selecting from the first preserved and those in the worst condition. This should be done on a three-month schedule. Other turbines may be inspected by the manufacturer’s field service engineer on his monthly visits through the opening in the top casing as the rotor is being rotated. This should be done on a three-month schedule.
Fog the interior of housings with rust-preventive concentrate. Coat tooth contact points with an inhibited grease or heavy, tacky oil. Remove inspection plates and visually inspect interiors on a three-month schedule.
Manufacturers’ representatives should inspect the compressors during monthly visits. Any preservatives needed can be applied under their supervision. Fog centrifugal compressors, and consider placing desiccant bags in these machines. Inspect these compressors on a two-month schedule. Inspect high-speed air compressors on a three-month schedule. Inspect and fog axial compressors on a three-month schedule.
In a warm, high-precipitation climate, it is wise to look for other solutions to the problem of field storage during construction and prior to start-up. If oil-mist lubrication is not already part of the original design, it should be seriously considered, because in many cases it provides the best protection against contaminant ingression.
Practical Machinery Management for Process Plants: Volume 4;
Major Process Equipment Maintenance and Repair, Second Edition by H.P.
Bloch and F.K. Geitner, ISBN 0-8841-5663-X, 1997,
Pipeline and Gas Technology Magazine, June 2007