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Thread: Back to Line Shafts?

  1. #1

    Back to Line Shafts?

    I was reading an interesting article the other day regarding effeciency in the work place. An interesting statistic was this...

    75% of all electrical costs are used by electric motors in industry.


    That got me to thinking, wouldn't it make sense that if that much energy is used to operate industrialization, that companies could gain effeciency by going back to line shafts?

    I mean there is some benefits. A shop that has one or two big motors turning 100% of the time would be far more efficient then say 30-50 smaller electrical motors running intermittently. That is because the start-up factor, and the fact that one or two big motors have rotating mass, and as we all know, a body in motion likes to stay in motion. I would think that would easily make up for the extra friction losses a line shaft system would cause. Besides modern bearing and lubricants are pretty high tech now making friction almost a non-issue.

    Going a step further, what would a line shaft operation be like in say a woodworking shop. I have seen them too where you step into the door, flip on one switch, then moving clutches engages the tools you want to use one at a time. No multiple motors to deal with, no starting and stopping, no noise either as in this shop the motor running everything was outside.

    I am not sure I will run out and convert my shop to a single 10 hp electrical motor and line shafts, but would that reduce my energy consumption? Would it be better? What advantages and disadvantages would it have? Should we all be gravitating towards line shafts in our shop to conserve electricity and thus energy? Just curious as to what you guys and gals think?
    I have no intention of traveling from birth to the grave in a manicured and well preserved body; but rather I will skid in sideways, totally beat up, completely worn out, utterly exhausted and jump off my tractor and loudly yell, "Wow, this is what it took to feed a nation!"

  2. #2
    Join Date
    Oct 2006
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    ozarks
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    what about power loss due to friction? how about having to run a motor rated for the largest anticipated draw continuously?
    when line/jack shafts where popular they where usually powered by water.... when the old mills started switching to `lectricity they quickly discovered what a drain all those shafts-n-belts produced....
    i suppose if you have either a free or afordable source of power for the shaft that it would be a good idea.... but by and large industry doesn`t make stupid mistakes for very long or their competetors would eat their lunch, and industry has long since abandoned lineshafts..
    [SIZE="1"] associated with several importers and manufacturers.[/SIZE]

  3. #3
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    One of my customers estimates that 50% of their energy cost goes to compressed air. Since they blowmold they use a LOT of compressed air. They are currently doing studies to match their air production capacity at a given moment in time to their air consumption at that time. They've been putting meters on everything and I'm writing reports that show their energy use. Running the compressors on demand does help reduce their consumption.

    Now this is a little different than the situation you are talking about, but still, the evidence that I'm seeing is that running just what you need right now is more efficient.

  4. #4
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    Manistique, Michigan
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    We ran a line shaft for years at our paper mill to drive the paper machine. The line shaft was driven by a steam turbine. The issue is that each consectutive section of the machine has to run faster than the previous because the paper stretches as it dries and as you pull it unsupported off one roll to the next section - we call this an open draw. Each section has a gearbox and a series of belts to run each section the proper speed. The system was a mechanical nightmare and caused more down time that it is worth. Each 1% of operating efficiency means a lot to the bottom line. We gained about 10% efficiency due to the elimination of the line shaft. We always had gearboxes to rebuild, couplings and bearings would fail on the line shaft, belts were a big issue and it was difficult to tend the drive side of the machine. The electronic drive is very easy and safe to adjust speeds and tune. The range of adjustability is much larger as well. Our machine runs between 2400 fpm to 4700 fpm.

    What would really be great is if FERC would let us use our flume and dam to produce hydro power. We use to produce 25% of the power we needed by using two hydro generators - wood grinders that ran an electric generator when we did not use them for grinding wood. The structure would have to be rebuilt in order for FERC to let us use it and it would cost more than the papermill is worth to rebuild the structure.
    Rich (the Yooper)

    "To the world, you may be one person, but to one person, you may be the world."

    "Common sense is not so common."

  5. #5
    Join Date
    Dec 2006
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    Portland, OR
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    There was just this week an article in one of the cabinet shop trade mags regarding the cost of electricity.

    They addressed the idea that if a machine is not going to be used for more than 30 minutes, it is less expensive to shut it down and restart...and less time than that and the demand draw for startup was higher.

    Further more, I found it interesting that the production of compressed air is considerable higher to run the air tools than electric...I really liked my air sanders until I read this. Also, it is less expensive to run several small compressor's than one large one, shutting down the small ones that are not being used during the day..again, looking at the 30 minute factor. Also stated that is is less expensive to produce compressed air in the winter (for us colder states) than in the summer, and further more, best if we draw air from the outside.

  6. #6
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    What would really work good is, if someone could make a modern motor that is more energy efficent. If they can do that for a vacuum motor, then why not on a larger scale? Yes, I think it would be cool to see if a flat belt system vs. motors which one could do the better job.

  7. #7
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    Small electric motors as are found on most woodworking tools (say less than 10HP) come up to speed in a couple of seconds. Power is measured in killowatt hours (using 1,000 watts for an hour) so the cost to start up a small motor is pretty small. Rounded, one HP is about 750 watts (maybe 800-850 since the motor is not 100% efficient). So based on common electricity rates, running a one HP motor at full load for an hour costs you about 15 cents (maybe less, depending on your rates).

    A big motor is more efficient than a small motor but not by a lot and the efficiency measurements are almost always made at full load - and few motors in woodworking are run continuously at full load. Also running shafts continuously means you're paying for the friction all the time, not just when the tool is being used.

    I think we're going to see more motors rather than less (rather than one big motor). With the electronic controls on motors you can change the speed easily to adapt it to the work. And more motors means that you aren't put out of business when you have a motor failure. Since the motor is designed specifically for the task of the tool, you get the best efficiency.

    Regarding making motors more efficient, if you purchase a high efficiency motor, it's going to be in the 90's percent efficient at full load. There's not a lot of room to make improvement.

    Mike

    [PS - you can't just look at the voltage and current into the motor to figure efficiency - you also have to consider power factor. Only current that is in phase with the voltage creates power (watts) and you only get charged for that power. The out of phase current can cause waste in resistance heating but that's pretty small.]
    Ancora imparo
    Go into the world and do well. But more importantly, go into the world and do good.

  8. #8
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    This is just motor trivia but I found it interesting. I have a friend who does electrical design at the ports here in the LA area - which means he works with BIG motors.

    One problem with motors is that they look like inductors to the power company - which in turn means that the current is not in phase with the voltage. Current that's not in phase with the voltage does not produce power and the power company would not get paid for it, even though they have to generate and distribute it. So the power companies measure the power factor and charge companies a fee if their power factor falls too low. That fee keeps getting bigger and bigger every year.

    So what the motor people have started doing is putting some electronics between the power source and the motor. That electronics first converts the electricity to direct current (and does it with a 100% power factor), then it reconverts it to AC to feed the motor. That way, any power factor problems are between the motor and the electronics and is never reflected into the power grid. So the power company gets paid for all the electricity they supply, and the motor user gets a more efficient motor, with speed control (if they want speed control) and other advanced features (electric brake is one used on hoists).

    Mike
    Ancora imparo
    Go into the world and do well. But more importantly, go into the world and do good.

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