for maintenance without the need to drain down the system . With only two rotating parts , there is little to break in the pump . They can be configured for applications with low & high temperatures , high system pressures , Atex certification , self-priming ability , and with air motor drives . Due to the drive mechanism being through the magnetic coupling rather than fixed directly to the shaft , close coupled magdrives can generally operate at higher temperatures as it removes the possibility of heat conduction along the pump shaft to the motor .
Dry running :
Running dry is the main cause of mag-drive pump failures . This is when the impeller / gear / rotor of a pump rotates without any lubrication between it and the shaft that it runs on . A lack of lubrication results in excessive heat being generated on the surfaces of the mating bearing sections . This heat will damage the shaft and the bearing element and will eventually cause the pump to seize and fail . Plastic / epoxy materials will fail faster than metal / carbon / ceramic parts .
As science and technology progresses with time , modern materials options are continuously evolving and improving the life span of mag-drive pumps . Latest sleeve bearings offer very low coefficients of friction . Depending on the materials of construction , some mag-drive pumps can run dry for limited time periods . However , this should not be a regular occurrence .
Operational monitoring :
For increased Life Cycle and reduced downtime , mag-drive pump monitoring should be done by using a power monitor to prevent the pump from dry running . A level up would be to also monitor the temperature of the containment shell or the fluid leaving the containment shell . This will give an indication of the condition of the pump ’ s inner bearing condition .
Advantages of magnetic drive pumps : Very low risk of fluid emissions from the pump Low maintenance seal less design No mechanical seal materials selection choices No expensive seal support systems No pump to motor alignment problems
Magnetic coupling means no damages to the motor if pump gets jammed
Quick wet end service replacement Low customer Life Cycle Costs
Positive attribute in an Organization ’ s Safety , Health and Environment activities
Disadvantages of magnetic drive pumps :
Not suitable for liquids with solids and / or metallic particles in suspension
Easily damaged if operated incorrectly Limited in torque transmission capacity due to strength of magnets
Typically require higher motor power than mechanically sealed pumps for the same duty
Minimum Flow requirements : a ) stable minimum flow rate to ensure the pump operates reliably , and b ) thermal minimum flow rate to ensure heat generated in driven magnet / bearing section is dissipated
Conclusion :
With only two rotating parts , there is little to break in the pump . The simpler the pump , the less chance there is for failure . Some manufacturers now even offer pumps that can handle liquids with up to 3 % of solids in suspension .
It is important to understand that mag-drive pumps are not a cure for all difficult liquid applications . Improper selection will cause more problems than they were intended to solve and will cost a plant dearly . Pump users are advised to make use of the technical expertise of the pump manufacturers and their appointed sales distributors . The popularity of mag-drives can only increase .
Telephone : + 44 ( 0 ) 1480 214444 Email : sales @ marchmay . co . uk Visit : www . marchmay . co . uk twitter : @ surfaceworldmag NOVEMBER 2021
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