Operation & Maintenance Process Equipments

Operation and Maintenance of Pumps

Cavitation in centrifugal pumps- Pump cavitation is the formation and subsequent collapse or implosion of vapor bubbles in a pump.Causes of pump cavitation-Reason for pump cavitation lies in operation of the pump which deviates from design conditions such as low suction pressure, high liquid temperature etc.Damages from pump cavitation - Pump cavitation in centrifugal pumps can damage various pump parts.How to prevent pump cavitation - Different types of pump cavitation and basic guidelines to prevent them are discussed.
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Centrifugal Pump Maintenance - Centrifugal Pump operating problems that may cause damage to the centrifugal pump can be either hydraulic or mechanical. Certain precautions which can be taken to avoid pump damage are discussed along with different inspection schedules and pump maintenance schedules. Tasks to be performed during scheduled inspection and pump maintenance are briefly discussed.
Internal recirculation in centrifugal pumps - A pump operating at lower capacity than design limits can suffer from recirculation which occurs internally in the pumps. This recirculation is different than the minimum recirculation flow required for centrifugal flow and can be a source of serious problems.
Overloading of centrifugal pumps - Centrifugal pumps are said to be overloaded when the driving motor draws excess current resulting in excess then normal powerconsumption.Causes of pump overloading- Various deviations in pump operations from normal conditions can lead to overloading of centrifugal pumps.Effect of pump overloading - Frequent operation of pumps under overload can damage some parts of the pump.
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Pump Performance Test - The purpose of pump performance test is to ensure that the actual performance of a pump is close to that predicted by supplier. Typical steps to be followed to conduct a pump performance test are outlined. Pump performance tests are performed to plot the pump performance curves and compare them to curve supplied by the pump manufacturer.  
Pump Priming - Pump priming reduces the risk of pump damage during start-up by preventing dry running. For reliable operation, pumps  must first be primed by removing air or gases from the suction and impeller eye areaand replaced with liquid.How to prime centrifugal pumps - Brief guideline / pointers for priming the centrifugal pumpsSelf Priming Pumps - Brief description of how the self priming pumps work.
 Pump vibration limits as per international standards - Pumps being rotating equipments, normally vibrate to some extent. Hence, instead of worrying about whether or not a pump vibrates, the engineers and operators should rather examine if the amplitude of pump vibrations is high enough to cause damage to the pump parts and if the observed pump vibration in a symptom of other more worrying phenomena such as pump cavitation.  
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Reliability coefficient for pumps - Many factors influence pump operation and pump reliability such as poor initial installation may cause premature failure due to misalignment, excessive piping strain, improper lubrication, etc. A pump reliability coefficient value of 0.00 means absence of reliability where as reliability coefficient value of 1.00 means perfect reliability. An acceptable reliability coefficient must not be less than 0.90, as less than this value indicates inadequate reliability of pumps. For instance, r =0.95 on a test means that 95% of the test score is accurate while the remaining 5% consists of error.
Troubleshooting for pumps - Problems with pumping equipments cause not only inconvenience, but can also contribute to loss of production. The table in this post lists problems that often occur with pumps with probable symptoms and the possible causes pertaining to them. Crossectional view in pump
Typical Pump Start-up procedures - Typical start-up procedures to be followed for start-up of different types of pumps are given on following links.

Vibration Analysis Charts for Pumps - Vibration monitoring for pumps is the best known and most publicized technique, and the most powerful for rotating machines such as pumps. Well-aligned and smoother running machines use less energy and in general also cost less to maintain, balancing is a common solution, temporary or permanent, to high vibration. Vibration instrumentation can also be used for balancing, but simpler methods are sometimes possible and acceptable.

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