Tips for safe battery inspection, maintenance, testing

As he approached the podium, Michael O’Brien, technical services manager of Nolan Power Group LLC, asked attendees at CTOTF’s Spring 2015 Generators/High-Voltage Electrical/I&C Roundtable, “Can your turbine or generating plant survive an unplanned or emergency trip without sustaining major damage?” This session, chaired by Moh Saleh, engineering O&M manager at SRP’s Desert Basin Generating Station, is responsible for station batteries within the CTOTF organization and O’Brien’s goal was to help users ensure their DC systems would operate if and when called upon.

Virtually everyone in the room was aware that major damage to critical equipment was likely if station batteries and the associated direct-current (dc) system failed to adequately support the emergency lube-oil and seal-oil pumps and associated equipment following a trip.

O’Brien began with brief descriptions of vented lead-acid (VLA) and valve-regulated lead-acid (VRLA) batteries, the two types typically found in powerplants. He then discussed safety, maintenance practices, inspection goals, and testing.

Users can access the speaker’s presentation in CTOTF’s robust Presentations Library.

The safety portion of the presentation included a well-received perspective on the hazards plant personnel should be aware of before tackling any battery tasks. Here are some bullet points:

      • Stationary batteries can pose an electrocution hazard. Voltages may range from 24 to more than 600 Vdc, short-circuit currents from about 1500 to more than 40,000 amps.

      • Most, but not all, stationary batteries are intentionally isolated from earth ground. Communication systems and some high-voltage (HV) UPS batteries are grounded.

      • The electrolytes used in lead-acid and NiCad batteries is corrosive and will attack human tissue. Eyes and mucus membranes can suffer permanent catastrophic damage when exposed to electrolyte. First aid following exposure: Immediately flush the affected area with clear water for at least 15 minutes; then seek medical attention. Skin exposed to electrolyte should be flushed with clear water.

      • All flooded cells (lead-acid and NiCad) produce a highly explosive mixture of hydrogen and oxygen. Always consider the air space inside a cell to have an explosive atmosphere. Functional flame arresters should be installed in stationary batteries. Avoid vent manifolds because they link the explosive air spaces in each of the cells served by the manifold and one ignition source can cause all cells to explode.

      • Most injuries associated with batteries are weight-related. Be sure to use proper lifting techniques and equipment in good repair. Best practice: Restrain cells during movement.

Maintenance. O’Brien identified the applicable IEEE/ANSI standards at the beginning of his segment on battery maintenance programs: VLA, 450-2010; VRLA, 1188-2005; NiCad, 1106-2005. He explained that these standards reflect the minimum recommended practices and stressed the need to have knowledgeable personnel schooled in safe work practices performing the maintenance. O’Brien said proper maintenance will prolong battery life and help assure the battery can satisfy its design requirements.

His “Golden Rule” for success: Maintenance must be regular, be consistent, follow standard procedures, be well-documented, and address the specific needs of the battery installed; all data obtained must be corrected to standard industry references. Additional points made:

      • All inspections should be made under normal float conditions.

      • Specific-gravity measurements are not meaningful during recharge or following the addition of water; also, they must be corrected for electrolyte temperature and level. The true level correction factor varies with each different model cell and must be obtained from the battery manufacturer.

Inspection. O’Brien offered the following guidelines for a general inspection of station batteries:

      • Conduct monthly or more frequently.

      • Measure float voltage at the battery terminals with a calibrated digital voltmeter.

      • Check the battery, rack, and battery area for cleanliness and general appearance.

      • Measure charger output current and voltage.

      • Check electrolyte levels.

      • Verify there is no electrolyte leakage and there are no cracks in cell jars/covers.

      • Check for evidence of corrosion.

      • Obtain pilot-cell specific gravity, electrolyte temperature and cell float voltage.

      • Record ambient temperature and check the condition of ventilation equipment.

      • Measure the float current of VRLA if installed.

The speaker went on to provide checklists for quarterly and annual inspections by battery type. You can obtain these by accessing O’Brien’s presentation in the CTOTF Presentations Library. The final segment of the presentation provided a roadmap for capacity testing.

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