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    Centrifugal Pump Overloading

    Uploaded by

    Abdul Alim
    Centrifugal pumps can become overloaded when they draw excess current, consuming more power than normal. This overloading has several potential causes: 1) operating at too high of a speed, which increases power consumption proportionally to the cube of the speed; 2) pumping a liquid that is more viscous than designed for; and 3) using an impeller that is too large for the system and motor. Other causes include operating at a higher or lower total head than anticipated, misalignment between the pump and driver, wear/damage to bearings, excessive pressure from a mechanical seal, a bent shaft, or operating too far from the pump's best efficiency point on its head-capacity curve.

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    Centrifugal Pump Overloading

    Uploaded by

    Abdul Alim
    158 views2 pages
    Centrifugal pumps can become overloaded when they draw excess current, consuming more power than normal. This overloading has several potential causes: 1) operating at too high of a speed, which increases power consumption proportionally to the cube of the speed; 2) pumping a liquid that is more viscous than designed for; and 3) using an impeller that is too large for the system and motor. Other causes include operating at a higher or lower total head than anticipated, misalignment between the pump and driver, wear/damage to bearings, excessive pressure from a mechanical seal, a bent shaft, or operating too far from the pump's best efficiency point on its head-capacity curve.

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    Centrifugal Pump Overloading

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    Centrifugal pumps can become overloaded when they draw excess current, consuming more power than normal. This overloading has several potential causes: 1) operating at too high of a speed, which increases power consumption proportionally to the cube of the speed; 2) pumping a liquid that is more viscous than designed for; and 3) using an impeller that is too large for the system and motor. Other causes include operating at a higher or lower total head than anticipated, misalignment between the pump and driver, wear/damage to bearings, excessive pressure from a mechanical seal, a bent shaft, or operating too far from the pump's best efficiency point on its head-capacity curve.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    158 views2 pages

    Centrifugal Pump Overloading

    Uploaded by

    Abdul Alim
    Centrifugal pumps can become overloaded when they draw excess current, consuming more power than normal. This overloading has several potential causes: 1) operating at too high of a speed, which increases power consumption proportionally to the cube of the speed; 2) pumping a liquid that is more viscous than designed for; and 3) using an impeller that is too large for the system and motor. Other causes include operating at a higher or lower total head than anticipated, misalignment between the pump and driver, wear/damage to bearings, excessive pressure from a mechanical seal, a bent shaft, or operating too far from the pump's best efficiency point on its head-capacity curve.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    of 2

    Centrifugal Pump Overloading

    Centrifugal pumps are said to be overloaded when the driving motor draws excess current
    resulting in excess then normal power consumption. This overloading of the pumps can be
    caused by various reasons as discussed below.

    Causes of pump overloading


    Centrifugal pump may draw high ampere due to the following reasons:-

    1. Speed too high: - When speed increases the power consumption and current drawn increases,
    as changes in power is direct proportion to the cube of the speed N. (P α N3)

    To avoid overload, control the speed of the primover of the pump to meet the design specific
    speed.

    2. Higher viscosity of pumped liquid:- When the viscosity of the pumped liquid increases the
    brake horse power increases PH(K.w.)=(Q*g*H*γ)/(3.6x106).

    Control the temperature of the fluid to be maintained at its working temperature, lower
    temperatures normally lead to higher viscosity.

    3. Oversized impeller installed:- As flow rate is proportional to diameter of impeller then if an


    over sized impeller installed the pump power will increase (Q2/Q1)=(D2/D1).

    Check impeller size and do all necessary actions to maintain the impeller size to its original size.
    If impeller size is increased, check the motor adequacy to handle new load.

    4. Total head of system either higher or lower than anticipated.

    Check piping installation and system design.

    5. Misalignment between pump and driver: - Misalignment is the main reason for pump damage
    and trip as it can cause damage to stuffing box, failure of mechanical seal, bearing premature and
    pump over heat or seize. Typically angular shaft misalignment can be up to 1° and parallel
    misalignment up to 0.015 in.

    Check pump and motor alignment and double check motor soft foot.

    6. Rotating parts in contact with stationary parts: - this will cause an increase in the friction
    force and of curse increase the power needed to rotate pump

    Stop the pump and check shaft endplay.


    Check bearing condition.

    Check motor and pump alignment.

    7. Worn or damaged bearings: - Damaged bearing will cause misalignment between pump and
    motor also it will increase the friction force which may lead to compelete pump seizer.

    Dismantle the pump bearing and replace the damaged bearing with new one.

    8.Mechanical seal exerts excessive pressure on seat:- this will cause an increase in the friction
    force between face and seat in the mechanical seal and increase the power needed to rotate pump

    Slightly loosen the bolts of mechanical seal.

    9. Bent shaft: - This produces a reversal of stresses in the shaft in each revolution that could lead
    to fatigue cracking and an eventual breakage of shaft, the most important reason is that some of
    the rotating parts maybe exposed to the stationary parts. Stainless steel parts will gall as soon as
    rubbing contact is made that results in motor overload.

    Dismantle the pump and check shaft run out if it’s fond that readings are out of range send the
    shaft for balancing if the problem remains replace the shaft with a new one.

    10. Pump operating too far out on head-capacity curve.

    Control the flow of the pump by slightly close the discharge valve till the pump operate at its
    best efficiency point.

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