Water pump question.

Discussion in 'Water Fed Pole Cleaning' started by Diwrnach, Jul 27, 2015.

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  1. Diwrnach

    Diwrnach Grand Master
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    Quick question, if they run out of water and are left running for any length of time do they overheat? and if so how long does it take?

    Cheers
     
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  2. Jake

    Jake Grand Master
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    Yeah it would overheat, even at very high outdoor temps (38-40c) they can over heat if left running for long enough...

    Without water on a standard summers day, I'd guess within a few minutes it would shut down/overheat, but I don't know for sure, only guys that have tested it would perhaps know for sure...

    I think they have a heat protection switch anyway?
     
  3. Diwrnach

    Diwrnach Grand Master
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    No idea, wasn't sure if they used the water to cool themselves or not.
     
  4. spruce

    spruce Grand Master
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    #4 spruce, Jul 27, 2015
    Last edited: Jul 27, 2015
    A Shurflo pump is a diaphragm pump and the makers say it can run dry. But I haven't seen anything written to say how long for though.

    A Shurflo pump doesn't have a thermal overload and it doesn't rely on the water pumped to cool the motor. It isn't designed to be run continuously. The motor housing does get warm to the touch during day to day on/off work but we have never had an issue with them. If you are having an overheating issue then it could be a bearing or armature (rotor) failure. It was a good few years ago when I took one apart, but if memory serves me they use a sintered bush (absorbs oil like a sponge) on one end and a needle roller bearing on the other - but please don't hold me to that.

    Over the years, I estimate that we have a 50/50 working cycle on residential. So a 6 hour working day translates in 3 hours of pump time. One of the Shurflo's on the van that works daily is now 9 years old.

    We don't do a lot of commercial, but what we do changes that quite dramatically for what we do. I estimate that we have an 75/25 working cycle, especially when we are doing long stretches without moving the van.

    About 40 years ago, we used to sell the American Devilbiss range of both high and low pressure sprayguns. They also used to make a low pressure (40psi max) diaphragm compressor called a 'Tuffy' which lasted for many years. The crankshaft was driven by a small 1/3hp motor and all the bearings, including the conrod bearing were self greased sealed roller bearings.)

    Gosh! They are still around.
    http://www.ebay.co.uk/itm/Devilbiss...674?pt=LH_DefaultDomain_3&hash=item3aadfe2af2
     
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  5. Jake

    Jake Grand Master
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    I've inly heard of the odd Pearson who's had it running for about 45mins continuously who said it cut off due to heat build up, so guess they can fail from heat spruce? Also I would have thought the water would have some cooling effect on the motor?
     
  6. spruce

    spruce Grand Master
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    I suppose Jake that it could in a minute (very small) way. The motor is separated from the pump with a diaphragm in a hard 'plastic' housing. The casing of the motor is metal with 4 magnetic 'blocks'. It called a Permanent Magnetic DC motor or PMDC motor for short. This casing will be what the motor uses to dissipate any heat build up. If these magnets where replaced with a coil (field coil) made from copper wire then they would generate more heat. To run the motor as efficiently as possible (our batteries aren't a never ending power source) the motor must remain as cool as possible. Any heat generated in the motor is wasted power from the battery.

    There are motors that do rely on water to cool them though. Electric bore hole pumps were very popular in South Africa and they relied on the water in the borehole to cool the outer housing of the motor. Continuously running for many hours will create heat which has to be disposed of. High frequency electrically driven poker vibrators used in the building industry that are used to vibrate the air pockets from poured concrete rely on the wet concrete for cooling as well.

    So when Diwrnach asked if the water would help cool the pump motor, I thought of these examples, hence my answer. :)

    Quite why someone would want to run a pump dry for 45 minutes is beyond me. On the couple of occasions we have sucked the tank dry the pump has maybe run for 30 seconds; the time it took to get back to the van to switch the pump off.
     
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  7. Jake

    Jake Grand Master
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    No it wasn't run dry, just continuously for 45 minutes...
     
  8. Diwrnach

    Diwrnach Grand Master
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    I am in the process of switching over to van mount, but was looking at running a pump box I make myself in the back of the pick up running off barrels until I get a water tank, which is why I asked.

    Wanted to make sure I didn't run it dry and overheat it in the time it takes to get back to the van and switch barrels.
     
  9. You want a fancy remote?
    I do.
    I use to design diaphragms for pumps (polymer r n d) and the most common failure was the bond between the central screw and the rubber. Nowt to do with lack of water.
    Although we were pumping other liquids.
     
  10. Diwrnach

    Diwrnach Grand Master
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    Not sure about remote, I like the idea but I worry it will be unreliable and just add an extra layer of faff (and expense) and not entirely sure how well they would work when directly behind a building.
     
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