By Charles G. Stolberg
Life cycle costing is a major issue in the wastewater industry today. One way to control costs and insure long lasting submersible sewage pumping system operation is to conduct periodic checks and inspections.
Regular inspection and preventative maintenance of submersible sewage pumping stations will ensure continued, reliable operation of the entire system. The major components in all stations should be inspected at least once a year and more frequently under severe operating conditions. One of the major advantages of a submersible station is the ability of the service technician to handle most maintenance and service onsite, without entering the wet well. All equipment in the station should be backed by manufacturers service manuals. This material should be carefully read, filed and consulted whenever servicing is required.
Weekly station checks should be performed and data recorded in the Station Log Book. Certain visual inspections should be made, amperage readings should be taken and recorded, and megohmmeter checks should be made.
In conducting regular inspections and preventative maintenance, be sure to follow the manufacturer's recommendations (pump, control panels, valves, etc.) as well as appropriate safety precautions to minimize the risk of accidents.
Before starting work, make sure the pump and the control panel are isolated from the power supply and that neither can be energized.
In making station checks and visual inspections, when taking amperage readings, and in making megohmmeter checks, follow these basic steps:
Conduct weekly performance checks by recording the running time of each pump in the Log Book (if hour meters are provided). This will allow analysis comparing relative time of operation and possible increased pump wear or station inflow changes. In a station with multiple pumps designed for all pumps to be run evenly, pump hour meters can be used to detect system problems, specifically when uneven run times are recorded. Time to pump down should be measured and recorded for each pump. All pump down times should be equal, at equal amperage loads. If not, determine the cause and correct the deficiency. If the impeller and pump housing are not excessively worn, the reason could be as simple as a partially clogged impeller or rotation in the wrong direction. Worn parts cause the run time per cycle to increase from month to month. Once wear starts affecting performance, the operating cost increases.
Making Visual Inspections: If the pump connection is worn or is not sealing properly, leakage at the discharge connection will cause the wet well to become agitated each time the pump runs. When this happens, the pump causing the agitation should be removed and inspected. If the pump checks out satisfactorily, then the discharge connection could be the problem. Correcting a problem with the discharge connection should never be done with the station in service. The station should be removed from service, bypassed, and entered only by qualified individuals following all confined space entry requirements and regulations. (See Occupational Safety and Health Standards for General Industry 29 CFR PART 1910.120(b)(4)(ii)(i)(c)(3), Confined Spaces, Hazardous Work).
Taking amperage readings: Weekly amperage readings recorded in the Station Log Book can identify changes in pump performance due to clogging and wear. The amperage readings could go down or up with a partially clogged impeller. The readings could increase if a restriction is wedged between the impeller and casing components causing drag on the impeller. The readings could decrease due to a restriction of full flow through the pump, which does not drag on the casing or impeller. As the flow is reduced, the work that the motor must do is reduced which, in turn, lowers the amperage reading.
Making megohmmeter checks: In general, the temperature compensated megohmmeter values should not change very much from month to month. These can easily be compared when recorded in the Station Log Book. Meg values vary with design characteristics and among motor manufacturers. (Contact your manufacturer for acceptable megohmmeter values.) If moisture gains access to the inside of a pump motor or pump power leads, the readings will start declining and then fall drastically with a totally damp interior. The pump motor will continue to run with very low readings. Time until failure will be very short. If the pump motor is removed and serviced prior to total failure of the windings, it is likely that the situation can be corrected by baking the stator and replacing the components which allowed the water to gain access to the inside of the pump. If the pump continues to operate until total failure, then a complete rebuild will be necessary. For service information, contact the pump manufacturer for specific recommendations.
Station Log Book and Log Book Forms
It is recommended that a Station Log Book be created based on the needs and specifics of the individual station. There is no universally accepted format for a Station Log Book and no pre-formatted forms for recording station data.
Whatever format is used, it is recommended that the Station Log Book be kept at the station in the control panel.
A daily planner type book, available in most office supply stores, offers an ideal format for a Station Log Book. For most stations, a standard, wirebound book, 4-7/8" x 8" page size, dated for a full year, with one weekday per page, Saturday and Sunday combined, is sufficient.
This format and size is ideal to use for recording station information and maintaining a record of periodic maintenance done on the station. The lined format allows space for comments about the station's operation which need to be noted. This might not be easily accomplished on a pre-formatted form.
The value of the Station Log is in consistently utilizing the book and noting all important information so it can be used for analysis and comparison.
For additional information on Operation and Maintenance, including a "Troubleshooting Checklist" of common problems and their probable causes, consult Submersible Sewage Pumping Systems (SWPA) Handbook, Third Edition, published by the Submersible Wastewater Pump Association (SWPA).
About the Author: Charles G. Stolberg is Executive Director of the Submersible Wastewater Pump Association (SWPA). For more information about the association, its programs and activities, and its technical resources, visit the SWPA Web Site at www.swpa.org.