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Compressor justification?

Discussion in 'Scenery, Props, and Rigging' started by Charc, Feb 20, 2008.

  1. Charc

    Charc Well-Known Member

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    So the TD turned on the compressor during a work call on Saturday, and left it on. Evidently to test it to "see if it works" because "it won't hold air". So he left it on for the 6 or so hours during the work call. I came in Tuesday afternoon. (72 hours later, compressor still cycling to maintain pressure [unused{for months} since it was charged, but still charged since Saturday]). I figured why wear down the equipment, waste power, and leave condensation in the tank? So I switched it off, and opened the release valves. I left a note to the TD informing him of the change of status. He sorta jokingly sorta angrily brought it up, and mentioned he was still testing it by leaving it running...? I don't know much of anything about compressor maintenance besides switching 'em off and opening valves at the end of the day, so I'd like to know some of your thoughts on the situation.
     
  2. thelightingmancan

    thelightingmancan Member

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    I have a compressor in my wood shop, and I have it on a timer, so it runs once a day when I am not using it. Since it is at my house, I do use it for lots of small things. It is a 20 gallon tank, so it takes a while to charge but, if you have a smaller tank this might not matter to you. In my opinion, and I'm no expert either, but leaving the tank at pressure reduces stress on the metal, and makes life easy.
     
  3. Charc

    Charc Well-Known Member

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    Just to clarify, it wasn't left on to use (at all) just to "test". And for a small tank, it takes what, 5 minutes to charge? (As you can tell, I'm not familiar with it, we've used it once in 18 months... 18 months ago.)
     
  4. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    My 2.5gal compressor is on a timer also, but only so it won't annoy the neighbors. When I remember, I switch it to "off," but usually it sits at 90psi for months between uses. Takes 2.0 minutes to go from zero to fully charged.
     
  5. icewolf08

    icewolf08 CBMod CB Mods

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    If the compressor motor was just running without stopping for all that time, then you did the right thing turning it off. If the motor never stopped running then you have a pretty serious leak in the system somewhere. The motor should run until you reach operation pressure, then shut off. When the pressure drops below a certain point the motor should kick on again. From the way you tell the story, it sounds like your compressor, or whatever it was connected to has quite the leak.

    We leave our compressor powered almost all the time. We turn it off during shows, and if we remember at the end of the work day (and any time that it just starts driving us nuts and is not being used). There are a few small leaks in the system, so the motor kicks on every couple hours if no one is actually using any pneumatic tools. When people are using tools it kicks on more frequently.
     
  6. Charc

    Charc Well-Known Member

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    Thanks Derek and Alex, both are interesting responses.

    Derek, you leave yours pressurized? So you don't buy in to the tank corrosion from water? Also, if it takes 120 seconds, why not just open the release valve for the couple month hiatus?

    I'm sorry if my original post wasn't clear, but there was no apparent serious leak with the tank, not even an audible hiss. The motor did run every once in awhile (annoying), but not enough to raise any eyebrows.

    Learning from observation (and hands on), at my internship there were two compressors. A 60 gallon unit in the shop, and a smaller portable unit for use in the theaters. Both of these units were powered off and had pressure released at the end of the day.

    The reason why it was being run is the TD thought there was a serious leak issue, and apparently was monitoring the compressor by leaving it on through the work day. I don't see how an extra 72 hours would prove anything, especially because with the compressor on, it's just going to keep shoving more air in.
     
  7. thelightingmancan

    thelightingmancan Member

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    My compressor runs about every 15-18 hours, so it drove my parents nuts. They would wake up, but I sleep right through it, but I got the timer out of it, which has all of my shop equipment on it so someone can't accidentally start something. I know it sounds strange, but our neighbors always think I'm in there and want to borrow something, or talk, but a little kid neighbor could go in while I have the garage open and mess with stuff, cutting fingers off or something. It's a small community, nobody really locks anything, and they all leave cars unlocked.

    I still think filling and draining puts undue stress on the metal, and I do drain the water valve once a month, but nothing really comes out.
     
    Last edited: Feb 20, 2008
  8. Charc

    Charc Well-Known Member

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    That interesting, I've felt noticeable spitting and wetness when draining tanks, not to mention what seemed to have been a chunk of ice inside a tank, clogging up the valve.
     
  9. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    This is Las Vegas in the desert, where average relative humidity is around 6%. A friend with a 30gal tank, opens his once per year, and rarely gets more than a few drops, if that.
     
  10. Van

    Van CBMod CB Mods Premium Member

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    ******* Danger Warning Danger Will Robinson*******
    A Compressor is technically referred to in most OSHA type safety manuals as a "Charged Battery" Most states safety regs requires you to relieve the pressure form the tank every night. When not in use a compressor should be de-pressureized. Metal fatigue is not a valid excuse for storing a pressurized vassel. A compressor should be drained weekly if not daily. Now Derek, in Vegas, is right that he can go for much longer given the average relative humidity, but those of us living in more hospitable climes need to be much more vigilant in compressor maintenance.
    I don't think it's worth getting into a heated discussion with your TD about though. But if he was checking for leaks that shouldn't take more than an hour. Charge it up. Turn it off. Come back in an hour and see how mor pressure drop there is.
     
  11. porkchop

    porkchop Well-Known Member

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    From my experience working on cars in a variety or garages most people that drain there tank (and aren't just doing it cause they're told to) are doing so to remove water from the tank, not because of corrosion but because of the water going through the lines. In your other thread about dimmer failure there was a lot of talk about oil coming through your lines, thats a constant (usually) but its also a very small amount. Older compressor motors, or ones running high compressor and/or in high humidity will get enough moisture in the lines that you can really notice it. I had to drain my portable compressor when it was outside during winter (Wyoming winter = snow) after just 4 hours cause my hands got soaked every time I used an air tool.
    In theory the water could corrode the bottom of the tank and cause pressure loss. I have worked with at least 10 compressors all with varying ages (25 y/o - brand new) and all kinds of ideas about maintenance never heard of it happening. though, if it's really a concern they sell air filtration systems for compressors, and they do work.

    If your TD is worried about a leak in your system I would check the air lines and EVERY connection. Just cause you can't hear it doesn't mean it isn't leaking. Use a spray bottle full of water on every connection, get it nice and wet and look for bubbles. It's tedious but it's the best way to find the most common leaks.
     
  12. porkchop

    porkchop Well-Known Member

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    exactly 4.

    First time I've seen your signature.
     
  13. Van

    Van CBMod CB Mods Premium Member

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    :grin:
    I've been waiting for someone to yell at me about the Doughnuts pun, I've begun to wonder if anybody gets it?
    /end hijack
     
  14. porkchop

    porkchop Well-Known Member

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    i didn't until you said something. I actually read it and went well that really doesn't make sense but oh well
     
  15. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Unlike my friend in the desert, I live in a very wet environment. I keep my personal 2.5 gal compressor empty and with the drain valve open. Having my compressor running just a few hours for an afternoon project typically results in one or two ounces of condensation.

    As for the reducing stress on the metal theory, I don't buy it. While I don't claim to be a compressor expert, I did used to have a boiler license and spent several years working with boilers and expansion tanks so I know something about pressure vessels. With the safety factors that I assume are used in designing these tanks, (they are there on other pressure vessles) having air in or not in the tank really shouldn't matter. Would you want to have a compressor in your house that actually feels the strain of adding and removing pressure (I sure wouldn't). Those thanks should be so strong that it takes 10 times (or more) the amount of pressure for the tank to even notice. Or you could think about it this way. I ran a boiler that was 60 years old and it was shut down every night loosing all it's pressure only to be repressurized the next morning, then shut off for 3 months in the summer. No scientific data there but I wouldn't worry about it.
     
  16. Charc

    Charc Well-Known Member

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    Thanks for the input. Yea, I don't think it was a huge deal for him, he just seemed crabby about it... however, I think I've determined why.
     
  17. thelightingmancan

    thelightingmancan Member

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    I checked up on the stress thing, and it does have an effect, but not on a large enough scale to matter. I live in a moist environment, but my compressor is in an enclosed space, so it still doesn't get much in the way of moisture collection.

    Porkchop, I missed the cubits and priate thing too, even though I was a member when it happened.

    Van, I love the coffe and Donates comment, it is pretty awesome.
     

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