PUMPS


Well location and water demands are major factors in dry-running problems. In certain geographical areas, water table levels are dropping due to reduced aquifer recharge and heavy usage. This can result in well loss, a measurement of diminishing static water level or yield. As well loss increases, pumps previously sized for higher well yields may produce large drawdowns, resulting in partial dry-running. Over time external conditions may cause the water level to drop below the functional limits of the well.


Things to consider: When a well is no longer functional due to low water levels, further drilling and deeper pump setting may be required. Alterations to the well will result in changes to the system’s total dynamic head and required pump performance. It is important to ensure that system equipment is resized to determine if it’s compatible with the operation requirements of the re-drilled well. Pump protectors can also be installed to monitor the electrical conditions of a submersible motor. When low amp draw (load) is detected, the motor protector will shut the pump down for a given period to protect the system and allow for well recharge. The protector will not eliminate the problem of reduced yield; however, it will guard against costly motor replacements due to dry-running.


CAVITATION Commonly arising during partial dry- run conditions, cavitation occurs when


pressure on the suction side of the submersible pump drops below the vapor pressure of the liquid, resulting in the formation of small vapor bubbles. When the pressure rises during pump operation, these bubbles collapse or implode and release shock waves, damaging the impeller.


Pit marks left by cavitation reduce pump efficiency and decrease flow and head, resulting in a reduction in overall pump performance. Furthermore, cavitation can increase operation noise and vibration, which can damage bearings, seals and welds, resulting in a shorter pump lifespan.


Things to consider: Since cavitation often occurs during partial dry-run or conditions with excessive entrained air, a pump protection unit can be used to help eliminate the risk.


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Symptoms of cavitation include decreases in pump yield and irregular noise during operation; however, cavitation cannot be confirmed until the pump is disassembled.


CORROSION Stainless steel is naturally corrosion- resistant, but it is not fully immune


to rust. While it is less susceptible than conventional steels, exposure to chlorides or other chemicals can speed up reactions and break down stainless steel over time. Extended periods of exposure to heat can also act as a catalyst in chemical reactions, speeding up corrosion.


Narrow openings and spaces between surfaces on the pump typically have stagnant conditions that make them particularly vulnerable. Crevices, such as those found at flange joints or at threaded connections, are thus often the most likely spots for rust formation and corrosion.


Corrosion causes degradation in the shape and integrity of pump components, leading to seizing, slipping, deformation and component failure.


Things to consider: Corrosion will occur naturally over time on almost all metal materials. To ensure that you get the longest life possible from your pump, it is important to understand the chemical makeup of the liquids you are pumping and select products for these characteristics. It is also important to consider how heat and abrasives affect your application. If these factors are also present, it may be best to invest in higher-quality alloys.


POWER There are several aspects of power quality as well as unexpected power


events that can severely hamper the operation of a submersible motor:


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Dry running can cause bearing failure wear and tear between the impeller and chamber. Well location and water demands are major factors in dry-running problems.


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