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UPS Battery Capacity and Aging The function of an Uninterrupted Power Supply, or UPS, is to provide clean back-up power supply for essential and critical systems. These systems include the general alarm, navigational, telecommunications, power plant, station keeping capabilities, and BOP control systems, in the event of a power failure of the primary power source(s). Accordingly, irregularities with the UPS systems could result in system failures with devastating consequences. On a recent assessment, WEST found the preventive maintenance program did not specify periodic replacement of these critical batteries. Battery capacity is regulated by regulatory bodies such as ABS, DNV, Lloyds, API, IEEE and others. These organizations require minimum times for retention of nominal voltage after charger or line power failure. DNV, for example, specifies periodic testing to ensure sufficient capacity is provided for 30 minutes of operation with batteries. Additionally, there were no alarms installed to alert personnel to system failures as recommended by these standards.
Best oilfield practice suggests batteries in every UPS should be regularly replaced, depending on battery type, to ensure adequate power for backup of critical systems in case of a power loss. For gel type batteries, commonly used offshore today, replacement should occur biannually. The particular rig referenced above was nearing two years of age, and battery replacement had not been scheduled. Also
on the topic of batteries, all systems using batteries should include
periodic replacement in their preventative maintenance program.
This is most critical in systems where such batteries provide backup
functions and dead or weak batteries cannot be identified until
the system fails as a result. Most PLCs have a Lithium battery to
reload the program code from the EPROM on reinstatement of power.
However, if the battery fails, you have no program! |
