"Cleaning" an electric motor ??
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  1. #1
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    Default "Cleaning" an electric motor ??

    I have a couple of ald machines. One is a Do All bandsaw and the other is a DiAcro 6/8 power bender. The bandsaw looks like once upon a time it had been used w/oil for cutting fluid. The lower cabinet was kind of slimy. Is there any way to clean out the accumulated sooty looking dust out of the motor? If i take it to a motor shop is there anything short of rewinding? Can it be cleaned out with LOW pressure air or a shop vac? Any and all help is appreciated.

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    My old L&S motor had been apparently used on a dirt floor cutting cast iron most of its life. The motor was full of a brown magnetic dust/sludge. A wise old guy I used to work with at the museum (who was a power company steam plant engineer) suggested I wash it out with mineral spirits, as that was what they cleaned their big generators with.

    HF sells a pressure washer like thing that attaches to your air compressor, which you can run mineral spirits through. Take the motor completely apart so you cna get into the coils. Just hit it like you were pressure washing it and give it a day or so out in the summer sun to dry.

    DO NOT use a water pressure washer. The rewind shop I work at does this and it works fine, but you have to bake the motor for several hours at 250degrees or so to get the water out, or risk frying the windings.

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    I have a 55 year old 5Hp motor in my lathe in a similar condition, I pulled it apart and replaced the worn bearings and left the rest of it alone as from past experience it's better to leave sleeping dogs lie, besides it megged at +10 Meg Ohm per phase to earth at 1000V anyway. If it megs out fine and you don't know if it has a modern solvent proof wire coating, I'd let it be as no matter how much a coating of crud bothers me: it's cheaper than a rewind.

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    I had the pleasure of working in a motor repair shop about a gazillion years ago down in Cocoa Beach Florida. The motors we got in were full of sand, salt, or JP4 jet fuel or a combination of all three. We would wash them out with high pressure water and bake them dry. Mike C. is correct to a point. If you can cob up an oven out of sheet metal then you can bake them dry no problem. I have done it many, many times without any problems. If you can get your hands on a Megar meter then the process is even more sure fired. A megar meter is nothing but a high voltage ohmeter. The Radio Shack variety of ohmeter uses a small battery to supply the voltage. My Megar has a hand crank on the side that uses big horseshoe magnets like in the old telephones. You hook up the meter between the windings and ground and crank away on the handle. The meter lets you know how much resistance there is between the windings and ground. If it reads high then it is back in the oven. Water really doesn't hurt motors if you get it out before you energize the motor.

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    Instead of an oven, better to put full load current through the windings..... at a low voltage. You can usually do that because the back EMF won't be there if the motor isn't turning. DC can work too.

    Start lower and work up, if you want.

    That bakes it from the inside out, and seems to do at least as good a job as an oven.

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    Default Use caution with old windings

    It's usually best to avoid any high pressure when cleaning old windings.... unless you have the ability to re-dip them. Inspect the winding insulation carefully, if they have started to flake almost any cleaning will make things worse. Clean very gently with a soft brush. If re dipping isn't an option, winding varnish is available in rattle cans.
    Solid, intact winding insulation can be cleaned more aggressively.
    Check the winding leads for insulation damage also. Glass fiber sleeves or heat shrink tubes work well here.

    Old motors are always worth saving, good luck
    -Tom

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    The electric shop in my alma mater had a very complete motor shop. They could rewind anything from slot car motors to 10,000 HP propulsion motors. Their motor stator and armature cleaning operation was very simple: they used a steam cleaner with non-ionic detergent followed by a bake-out, then a dip and another bake. Very seldom did they fail to restore a marginal motor to one that high-potted to 500 meg ohms or more, even one submerged for months in salt water.

    In the home shop, hot water, non-ionic detergent, and a plastic bristled brush will go a long ways towards cleaning up a sludgy motor. After a general de-gunking with putty knife and a shop vac, I use a mineral spirits wash down to remove the oily residue. Then I bake it for a full day to flash off the mineral spirits residue. I use Joy dishwashing liquid, hot water, and a bristle brush for the final cleaning followed with another 48 hour bake. If the motor seems to warrant it, I'll take the stator to the local motor shop for a dip and a bake. This seals up all the little cracks leading into the motor windings locking out moisture intrusion.

    If the motor will not fit in the family oven a welder connected to the leads and cranked up to motor full load current provides the heat source. Some batt house insulation packed around it keeps the heat in. A long stem thermometer allows you to monitor temperature. Keep it below 250 degrees F.

    It takes a couple of days to do all this because of the long baking cycles. I don't know of anyway to hurry the process.

    Here's a relavent link: http://www.reliance.com/prodserv/motgen/h7000ch1.htm

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    If you are careful you can dry the windings by connecting a battery charger across the moter leads.
    This it a low voltage high current power source.
    keep the charger amps below the full load amps of the motor for single phase motors and below 2/3s full load amps for three phase.

    This was the way we dried motors and generators in place on Navy ships.
    Almost all navy ships had a very good fixed battery charging system that were variable from 6 volts to 120volts DC. and currents loads from 2 amp to about 100 amps.

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    A lot of the big companies are using cryogenic cleaning.

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    Mineral Spirits.

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    300hp_dc_electric_motor_cleaning_in_parts_washer-s.jpgarmature_before_after_stingray_parts_washer-s.jpg
    Better late than never: Electric motors are cleaned daily in aqueous parts washers in 100's of motor shops all around the world. The machines use a low conductivity alkaline washing detergent running in the range or 175 deg F at 80 to 150 psi. Every kind of motor & generator from traction motors in a diesel locomotive to the speciality motors from a Zomboni ice resurfacing machine is cleaned. Both AC & DC motors are cleaned. After the cleaning the motors are dried by hot air, in a bake oven or in a vacuum drier for those that are in a hurry. Large traction motors are dried in less than an hour in a vacuum dryer. I know this because I work at StingRay Parts Washer and we make parts washers to do this work.
    Last edited by Matr; 06-08-2017 at 03:48 AM. Reason: spelling correction

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    My wife took a class in bubbles as a teacher. She learned that Dawn dishwashing liquid soap is the best for grease and oil removal.
    Bill D.

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    Quote Originally Posted by welderboyjk View Post
    Is there any way to clean out the accumulated sooty looking dust out of the motor? If i take it to a motor shop is there anything short of rewinding? Can it be cleaned out with LOW pressure air or a shop vac? Any and all help is appreciated.
    The only way I have done this is to remove the end caps and stand the motor housing on end with a few blocks of wood. Then spray a mild solution simple green or some other degreaser at the top. All the crud drips off at the bottom. Follow with water. Then compressed air. Sometimes I have used mineral spirits. If its a warm sunny day then all the better.

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    Quote Originally Posted by Matr View Post
    300hp_dc_electric_motor_cleaning_in_parts_washer-s.jpgarmature_before_after_stingray_parts_washer-s.jpg
    Better late than never: Electric motors are cleaned daily in aqueous parts washers in 100's of motor shops all around the world. The machines use a low conductivity alkaline washing detergent running in the range or 175 deg F at 80 to 150 psi. Every kind of motor & generator from traction motors in a diesel locomotive to the speciality motors from a Zomboni ice resurfacing machine is cleaned. Both AC & DC motors are cleaned. After the cleaning the motors are dried by hot air, in a bake oven or in a vacuum drier for those that are in a hurry. Large traction motors are dried in less than an hour in a vacuum dryer. I know this because I work at StingRay Parts Washer and we make parts washers to do this work.
    Why thank you dredging up this old post and adding exactly ZERO help to the O.P.

    They are not going to be going out an purchasing your specialized wash tank for a one off job.

    And if I need a cleaning tank, your spamming here has just taken your company
    OFF my list of possible suppliers.

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    My ex neighbor, a retired electrical enginner, had the job of drying out some big generators that were flooded by a river. He said they washed the mud out and then put them in a sealed tank. I assume they were pulled apart first? In the tank were electric heating elements. The tank had a vacuum pulled and then the heat was turned onto low and they were left to dry for about a year. He was tasked with doing the same when he came to California because his method worked well.
    These were huge generators for a TVA power plant so they would have taken longer to have them custom made then to dry them out. The California ones were,I think, smaller.
    Bill D

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    White spirit (mineral spirit) will do the job, but does tend to soften oil based varnishes that were used in old motors, although if it is hot where you are right now, a day out in the sun will evaporate it all away. In the UK today the recomended wash out for electrical equipment is now Anhydrous Isopropyl alcohol. It is considered less dangerous vapour and fume wise than mineral spirit, and generally does not soften the varnish. It IS a good idea to keep the internals of the motor really clean, as dust and dirt becomes conductive very quickly, especially in damp weather.
    Phil

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    Interesting post. The obvious consensus is yes you can wash them out. We just washed out a 20hp Fadal spindle motor using just hot water and compressed air. There was probably a solid 1/2” of gooey sticky residue built up that cold water wouldn’t even soften. Full straight on hot water that is hot enough it was uncomfortable to hold the sprayer melted it off and flushed it out the bottom side vents taking the metal chips with it. There was so much build up the fan on top couldn’t spin. The early 90 Fadal motors are not that great a design far as keeping swarf out. Thankfully they’re open enough designs there is a 3/4” gap between the case and the windings so that space can be used to flush crud out and away. I also noticed they had built in drainage runs so they likely figured this would happen and designed the motor at the time to be flushed and cleaned without removal. Thinking about it if water was going to hurt it then why would they stick it where coolant splashed in and down through it. Obviously not the case for every motor and you want to get it relatively dry but we didn’t bake or heat it. Just simple compressed air and let to sit 24 hours was enough. This likely saved and added life to the motor. Originally it was so dirty I don’t think it would’ve lasted another week if left it dirty. Knowing this I don’t think I’d ever try soap or any chemicals.

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    If you dont want to get it wet and baked dry, clean it with napha and air dry outside..Keep in mind any type of cleaning will degrade the insulation and the winding should be redipped in electric motor varnish, but only if the winding's are clean and checked with a magger....Phil

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    My lathe motor the fan was so caked with crud it looked like it had truck liner sprayed onto it. Could not be good for balance. I scrapped it with a putty knife and soaked it in hot soapy water. It cleaned up nicely. I used a soapy rag and paint brush to wash down the windings inside the motor. Good rinse with clean water. Air dry in the sun in summer for a few days. Probably over 120 degrees F in the litlte box I made for it most of the day.
    Bill D

    It has been fine for 2-3 years now, since before this necro post started.
    Last edited by Bill D; 04-24-2020 at 10:01 PM.

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    I wait for a nice warm August/September day, break out the pressure washer and a can of engine degreaser. I hit the nastiest with degreaser, give it a few minutes, then blast it. I follow with the engine-driven leaf blower, then air hose and a long wand, then put several pumps of grease in the bearings, and apply limited power, get it up to about 1/4 speed. They dry out quick. If it doesn't survive that, then it'd go to the rewind shop for a full rehab anyway... but of the hundreds of motors, welders, and machine tools I've dragged out of mud, fires, floods, and outside storage, I've only had a few motors that were unuseable as-is, and it was ALWAYS because there was some OTHER form of damage.

    This being said, I usually do this to clean them up PRIOR to bringing them into the shop to pull off the end-bells for inspection and bearing replacement. I've had many that I didn't feel needed it, and they turned out fine, but the key is to get them dried out, and relubricated swiftly.


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