how to prevent electrical erosion in bearings pumps
Bearing Handbook for Electric Motors
11 Find the cause of bearing failures Bearings are built to last so frequent failures may point to an installation or lubrication problem QIBR bearing analysis experts can identify the cause of bearing failure and help you prevent it in the future 12 The contact between the bearing ring and a
Bearing Protection
During virtually every VFD switching cycle induced shaft voltage discharges from the motor shaft to the frame via the bearings leaving a small fusion crater (fret) in the bearing race When this event happens temperatures are hot enough to melt bearing steel and severely damage the bearing lubrication
ABB drives
Apr 27 2011This is known as electrical discharge machining or EDM The effect of a single pulse is insignificant but a tiny EDM pit is an incontinuity that will collect more pulses and expand into a typi-cal EDM crater The switching frequency of modern AC drives is very high and the vast number of pulses causes the erosion to quickly accumulate
Electrical pitting
To prevent electrical erosion of bearings and other issues generator manufacturers incorporate a slip ring and brush system to provide a low resistance path to ground for any charge that may build on the rotor shaft This grounding system may degrade over time if the ground ring becomes oxidized the brushes become worn or the brush holder
How to Control Erosion (with Pictures)
Jan 18 2020A channel is a spot where running water cuts into the soil and forms a rut By filling the channel with compost or manure you will help prevent further erosion If a channel increases in size with each rain it can eventually form a gully which is harder to address Stop a channel before it turns into a gully by using a hoe to break it up
Preventing VFD/AC Drive Induced Electrical Damage to AC
As demonstrated above electrical damage to VFD/ac motor bearings begins at startup and grows progressively worse As a result of this damage the bearings eventually fail To prevent such damage in the first place the induced shaft current must be diverted from the bearings by insulation and/or an alternate path to ground
The use of protective coatings on pump components
Pump shaft bearing journals Pump shafts often incorporate oil or product lubricated bearing surfaces that are integral to the shaft or are in the form of a shaft sleeve These bearing surfaces are often subject to an unexpected amount of wear even in the presence of 'clean' oil or process medium
Preventive maintenance checklist for centrifugal pumps
Jul 17 2017For pumps equipped with re-greaseable bearings avoid mixing greases of differing consistencies or types Also note that the shields must be located toward the interior of the bearing frame When re-greasing confirm that the bearing fittings are absolutely clean to prevent contamination which can decrease bearing life
12 Reasons Why Bearings Fail
Prevent electrical currents from flowing through the bearing by grounding or using insulated bearings 8 Fatigue (Spalling) Spalling is often the result of overloading an excessive preload tight inner-ring fits and using the bearing beyond its calculated fatigue life What to Look for
Understanding Journal Bearings
Bearings are used to prevent friction between parts during relative movement In machinery they fall into two primary categories: anti-friction or rolling element bearings and hydrodynamic journal bearings The primary function of a bearing is to carry load between a rotor and the case with as little wear as possible
How to Determine Root Cause of Excessive Pump Vibration
Pumps with high suction energy and low NPSH margins especially when operated in the suction recirculation flow range (see June 2010 column) may experience noise vibration and/or minor cavitation erosion damage with impeller materials that have low cavitation resistance such as cast iron or
Protecting Thrust Bearings in Deepwell Submersible Pumps
Apr 17 2013Most deepwell submersible pumps use fluid film thrust bearings instead of ball and roller bearings used in most surface mounted pumps The unique thing about this type of bearing is that there are no moving parts within the bearing so if the motor is
Bearing Protection
During virtually every VFD switching cycle induced shaft voltage discharges from the motor shaft to the frame via the bearings leaving a small fusion crater (fret) in the bearing race When this event happens temperatures are hot enough to melt bearing steel and severely damage the bearing lubrication
Preventing Damage to Motor Bearings
As demonstrated previously electrical damage to VFD/AC-motor bearings begins at startup and grows progressively worse As a result of this damage the bearings eventually fail To prevent such damage in the first place the induced shaft current must be diverted from the bearings by insulation and/or an alternate path to ground Insulation
How To Find And Prevent Pitting Crevice Corrosion
Mar 12 2013These lower-profile corrosion types are dangerous and deserve your attention By Gerald O 'Jerry' Davis P E Davis Materials Mechanical Engineering Inc Pitting and its closely related form crevice corrosion cause significant problems across industry yet don't receive the attention they deserve Maintenance professionals often focus on other types of corrosion such as stress
Understanding Bearing Housing Protection and Reliable
An increasing gas temperature (usually air or an air-oil mixture) in the bearing housing (A in Fig 2) tends to elevate pressure in the bearing housing This elevated pressure drives down the oil level in the housing (arrows in Fig 2) increases the oil level in the narrow annular space above the tip of the wing nut and can result in
How to Determine Root Cause of Excessive Pump Vibration
Pumps with high suction energy and low NPSH margins especially when operated in the suction recirculation flow range (see June 2010 column) may experience noise vibration and/or minor cavitation erosion damage with impeller materials that have low cavitation resistance such as cast iron or
Demagnetizing motor shafts to prevent bearing failures
The most likely culprit is electric current through the motor and shaft either from internal dissymmetry welding or from a variable frequency drive It can also be caused by electrical faults in the system or even a lightning strike We of course know that shaft voltages and the associated currents can cause bearings
3 Ways to Prevent Metals from Corroding
Mar 26 2020How to Prevent Metals from Corroding Corrosion is a natural process that happens to all metals but it can be slowed down greatly with a few different treatments It is caused by the presence of oxidizing agents in the environment like
How to Determine Root Cause of Excessive Pump Vibration
Pumps with high suction energy and low NPSH margins especially when operated in the suction recirculation flow range (see June 2010 column) may experience noise vibration and/or minor cavitation erosion damage with impeller materials that have low cavitation resistance such as cast iron or
Protection against Wave
Protection against Wavebased Erosion The guidelines below address the elements of shore structure design common to nearly all erosion control structures subject to direct wave action and run-up 1 Minimize the extent waterward Erosion control structures should be designed with the smallest waterward footprint possible
How to prevent false brinelling in rolling
Jan 20 2015The average motion within each bearing is non-zero promoting movement of the lubricant within the rolling elements One caveat: This design doesn't resolve issues from assemblies that lie motionless for substantial periods of time between uses — on spare electric motors for example This needs oscillatory motion of a magnitude large
Preventing VFD/AC Drive Induced Electrical Damage to AC
As demonstrated above electrical damage to VFD/ac motor bearings begins at startup and grows progressively worse As a result of this damage the bearings eventually fail To prevent such damage in the first place the induced shaft current must be diverted from the bearings by insulation and/or an alternate path to ground
Preventive maintenance checklist for centrifugal pumps
Jul 17 2017For pumps equipped with re-greaseable bearings avoid mixing greases of differing consistencies or types Also note that the shields must be located toward the interior of the bearing frame When re-greasing confirm that the bearing fittings are absolutely clean to prevent contamination which can decrease bearing life
Electrical discharge machining
Electrical discharge machining (EDM) also known as spark machining spark eroding die sinking wire burning or wire erosion is a metal fabrication process whereby a desired shape is obtained by using electrical discharges (sparks) Material is removed from the work piece by a series of rapidly recurring current discharges between two electrodes separated by a dielectric liquid and subject
White Paper: Detection of electrical discharges in bearings
Finally electrical erosion can cause lubricant decomposition and degradation Blackened grease is a common sign of advanced electrical erosion as high temperature peaks locally cause the thickener base oil and additives to react See figure 9 Figure 5: micro crater of a few um in diameter Figure 7: Fluting on the outer ring raceway of a bearing
Lubricating And Troubleshooting Centrifugal Pumps
Jun 01 2012There are two types of oil-mist: pure and purge Pure mist is applicable to ball bearings in pumps and electric motors Purge mist is suited to any type of bearing As with motors oil-mist lubrication of pumps offers a number of benefits: Bearings running significantly cooler (15-30 degrees F) Clean once-through lubrication
Protection against Wave
Protection against Wavebased Erosion The guidelines below address the elements of shore structure design common to nearly all erosion control structures subject to direct wave action and run-up 1 Minimize the extent waterward Erosion control structures should be designed with the smallest waterward footprint possible
How to prevent false brinelling in rolling
Jan 20 2015The average motion within each bearing is non-zero promoting movement of the lubricant within the rolling elements One caveat: This design doesn't resolve issues from assemblies that lie motionless for substantial periods of time between uses — on spare electric motors for example This needs oscillatory motion of a magnitude large







