Operation & Maintenance Process Equipment

Pump operations

Pump operations refer to the procedures and activities involved in operating a pump, which is a device used to transfer fluids or gases from one location to another. Pump operations can include the start-up procedure, monitoring, maintenance, shutdown procedures and troubleshooting. Effective pump operations require careful attention to all these points.

Typical pump start-up procedures 

Pump start-up procedures are the steps that must be followed to properly start and operate a pump. Starting a pump involves a series of steps to ensure that the pump is functioning correctly and efficiently, and that it is not at risk of damage or failure. These procedures may vary depending on the type of pump and the specific application.

Typical start-up procedures to be followed for start-up of different types of pumps are given on following links.

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 area and replaced with liquid.

How to prime centrifugal pumps - Brief guideline / pointers for priming the centrifugal pumps.

Self Priming Pumps - Brief description of how the self priming pumps work.

Pump vibration limits as per international standards

Pumps being rotating equipment, 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.

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.

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.

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.

Pump Maintenance

Pump operating problems that may cause damage to the 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.

Overloading of centrifugal pumps

Centrifugal pumps are said to be overloaded when the driving motor draws excess current resulting in excess then normal power consumption.

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.

Internal recirculation in centrifugal pumps

Internal recirculation in pumps refers to the phenomenon where a portion of the fluid being pumped recirculates back into the impeller instead of being discharged. This can occur when the flow rate is too low, causing the pressure at the impeller inlet to drop below the vapor pressure of the fluid.

When this happens, some of the fluid vaporizes and forms bubbles, which can collapse and cause damage to the impeller and other pump components. This recirculation is different than the minimum recirculation flow required for centrifugal flow and can be a source of serious problems.

Cavitation in pumps

Pump cavitation is the formation and subsequent collapse or implosion of vapor bubbles in a pump. Reason for pump cavitation lies in operation of the pump which deviates from design conditions such as low suction pressure, high liquid temperature etc. Pump cavitation in centrifugal pumps can damage various pump parts. Different types of pump cavitation and basic guidelines to prevent them are discussed.

Troubleshooting for pumps

Crossectional view in pump

Problems with pumping equipment cause not only inconvenience, but can also contribute to loss of production. This post lists problems that often occur with pumps with probable symptoms and the possible causes pertaining to them.

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