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REAL Canned Air and your camera

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  • REAL Canned Air and your camera

    Save your camera. Use real canned air. The cans of Dust Off etc contain HFC-154A refrigerant. It can damage lens coatings and first surface mirrors. Most especially it can cause damage to the exposed image sensor in a digital SLR. If any of the liquid refrigerant manages to spray on these items it can cause permanent clouding.

    To avoid this take a used up can and provide a schrader bulkhead valve for refilling with clean filtered dry air. Do a nice job of soldering in a brass fitting using low melting silver bearing flux core solder. DO NOT USE SOFT SOLDER. Ensure all parts to be soldered are bare clean metal. Pre tin both parts and reflow them together. Remove the valve stem before soldering and replace after it cools.



    The soldering should look like this.



    The can will easily withstand over 150 psi air as the original product has a vapor pressure of about 86 psi at room temperature and double that in a hot car in the sun. The can will take over 300 psi when the safety margin is included.

    A charge of 100 psi air will produce a couple of dozen good squirts and a bunch of feebler ones.

    All that is left to do is to relabel the can.

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  • #2
    Do you still leave the little ball bearing in ?

    .
    .

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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    • #3
      Ball? Bearing

      It's been one ling time since I have seen a ball bearing in a spray can. I get nothing but cheap glass marbles, undersize ones at that.

      It may be I'm buying my products from the wrong place.....
      Norm'
      Member C.A.L.S. Balt'
      If it's not broken, why do I keep trying to fix it....

      Comment


      • #4
        Shudder... be sure to read and follow Evan's discalimer. All steel cans are not created equal. Evan has apparently carefully evaluated the quality and wall thickness of his can and deemed it suitable.

        While I agree with the idea of a refillable air can, I would perfer to see a stronger solder joint. Perhaps a turned brass bushing with a more generous lap flange - more surface area for the solder joint. Indeed, somewhat difficult to closely fit the radius of the cylinder, but do-able. Thread the Schrader into that. Such an arrangement would be less susceptible to weakening or damage if the can were dropped or the stem were bumped.

        As with any pressure vessel, a proof test at higher pressure than you will normally use is necessary - then have the discipline to never exceed your reduced working pressure.
        Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
        ~Practitioner of the Electromechanical Arts~

        Comment


        • #5
          Originally posted by John Stevenson
          Do you still leave the little ball bearing in ?
          -No mixer in canned air, since there's nothing to mix.

          But Evan's right on the typical canned airs. The photography buffs have been warning against using it since the early days of digital SLRs. One of the first things I read when I started looking at an SLR back in late 2004, was an account by a fellow that had gotten the refrigerant (technically, it's a trace of lubricant in the "freon") all over his sensor, and had to send it in to get it properly cleaned off.

          I don't think it can "permanantly" smudge or stain the sensor (technically a cover over the sensor, either an IR filter or just the antialias layer) but the lube is supposed to be a bugger to remove- at least without resorting to solvent that can, themselves, smudge or cloud the sensor/cover.

          Me, I just take the lens off and remove the battery, and give the whole camera a good soak in a sinkful of hot, soapy water, and a rigorous scrub with a toothbrush and Brillo to get those stubborn stains off.

          Doc.
          Doc's Machine. (Probably not what you expect.)

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          • #6
            Sigh. It isn't going to blow up. I suppose I should mention that I turned the threads off the soldered end of the fitting leaving a wide land under the hex. Even if I hadn't the fitting wouldn't fail in a dangerous manner. It would crack and leak out the pressure. A container that size doesn't hold much relative to it's surface area.

            Spray cans can withstand much more pressure than you might think. The hoop stress of a cylindrical pressure vessel is directly related to the diameter. Pressure containers under 4" diameter are not regulated as pressure vessels because they are not subject to the same failure modes as larger vessels.

            You are concerned about the pressure in a can made of steel. What about a simple aluminum soda can? Now there is a bomb waiting to go off. A can of Coke Classic is under 55 psi at room temperature and the wall thickness is less than .005". Yet they do not explode like fire crackers even when dropped. The most that happens is a leak forms. The steel can I used is perhap an order of magnitude stronger.

            Basically, you can't make a steel can that size that wouldn't hold the pressure with a generous safety margin. The simple geometry of such a tight radius container combined with the minimum practical wall thickness that can be manufactured makes it impossible to make a weak steel can that size. The bursting pressure for any common thin wall steel container with that diameter will be above 300 psi. Even if it does burst it won't tend to throw shrapnel. It will tend to fail at a seam and develop a split at that point, releasing the pressure.

            You cannot translate the requirements of a larger pressure vessel to such a small diameter vessel. They are not the same mechanically.
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            • #7
              wouldn't it be easier to use straight from the compressor with a long spiral hose they have a good reach this seems dangerous to me sorry Evan I wouldn't trust this.Alistair
              Please excuse my typing as I have a form of parkinsons disease

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              • #8
                Originally posted by Evan
                I suppose I should mention that I turned the threads off the soldered end of the fitting leaving a wide land under the hex.
                Indeed. Would have gone a long way in minimizing doubts.
                Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
                ~Practitioner of the Electromechanical Arts~

                Comment


                • #9
                  I assume that you have a VERY effective means of removing all oil and water from the compressed air before it goes into the can.

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                  • #10
                    Doc,

                    First a correction, the refrigerant is 152A, not 154A. It will directly attack many common plastics as it is strong solvent. Quite a few cameras have plastic lenses and other plastic optical components as well as the usual plastic materials. The plastics most susceptible to attack are the fluorocarbon based plastics.

                    While it won't directly attack glass elements it can attack optical coatings, in particular magnesium fluoride which is widely used as an anti reflection coating on optics including the infrared filter over the sensor of a digital camera.
                    Free software for calculating bolt circles and similar: Click Here

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                    • #11
                      Scrubbers

                      Originally posted by Doc Nickel

                      (Snip/ped)...........
                      ............................

                      Me, I just take the lens off and remove the battery, and give the whole camera a good soak in a sinkful of hot, soapy water, and a rigorous scrub with a toothbrush and Brillo to get those stubborn stains off.

                      Doc.
                      That's the truth Doc.

                      Ask John Stevenson.

                      He knows all about vigorous activity with hot old scrubbers.
                      Last edited by oldtiffie; 12-07-2007, 09:16 AM.

                      Comment


                      • #12
                        Originally posted by Evan
                        Sigh. It isn't going to blow up. I suppose I should mention that I turned the threads off the soldered end of the fitting leaving a wide land under the hex. Even if I hadn't the fitting wouldn't fail in a dangerous manner. It would crack and leak out the pressure. A container that size doesn't hold much relative to it's surface area.

                        Spray cans can withstand much more pressure than you might think. The hoop stress of a cylindrical pressure vessel is directly related to the diameter. Pressure containers under 4" diameter are not regulated as pressure vessels because they are not subject to the same failure modes as larger vessels.

                        You are concerned about the pressure in a can made of steel. What about a simple aluminum soda can? Now there is a bomb waiting to go off. A can of Coke Classic is under 55 psi at room temperature and the wall thickness is less than .005". Yet they do not explode like fire crackers even when dropped. The most that happens is a leak forms. The steel can I used is perhap an order of magnitude stronger.

                        Basically, you can't make a steel can that size that wouldn't hold the pressure with a generous safety margin. The simple geometry of such a tight radius container combined with the minimum practical wall thickness that can be manufactured makes it impossible to make a weak steel can that size. The bursting pressure for any common thin wall steel container with that diameter will be above 300 psi. Even if it does burst it won't tend to throw shrapnel. It will tend to fail at a seam and develop a split at that point, releasing the pressure.

                        You cannot translate the requirements of a larger pressure vessel to such a small diameter vessel. They are not the same mechanically.
                        I found (but cant now bl**dy internet, things keep moving) An article which showed how dangerous it was to refil the disposable mig cylinders, the little ones which are 3" or so diameter. Basically the metal is not treated / the correct metal for cyclic pressure stresses, and fatigue cracks / catastroptically fails. I dont know about disposable air duster cans, but I would guess that they are made from the cheapest steel they can be, with the minimum of post weld annealing / heat treatment. 2 reasons for this:
                        1 they are disposable, so have to be cheap, and
                        2 they only ever see 1 pressure cycle, (usually) a diminishing one as the contents get used up.
                        I personally would not do what you have done AT ALL. YMMV, but I'd rather know the can Ive got in my hand hasnt been fatigued into a potential hand maimer.

                        Dave
                        Just south of Sudspumpwater UK

                        Comment


                        • #13
                          Mig helium is at several thousand psi. There is a world of difference between that and 100 psi.

                          they only ever see 1 pressure cycle, (usually) a diminishing one as the contents get used up.
                          Not so. As the temperature changes in storage the pressure changes, especially with a freon type compound. If the storage conditions vary between freezing and a warm day then a complete full pressure cycle can occur once per day. The container must be and is designed to withstand that.
                          Free software for calculating bolt circles and similar: Click Here

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                          • #14
                            Originally posted by Wes1
                            Shudder... be sure to read and follow Evan's discalimer. All steel cans are not created equal. Evan has apparently carefully evaluated the quality and wall thickness of his can and deemed it suitable.
                            Wusses!

                            Great tip, Evan!
                            Probably a good idea to use a moisture trap or some filter, when filling this up.

                            The faint-hearted can buy this .


                            .
                            Thomas

                            Problems worthy of attack prove their worth by hitting back
                            - Piet Hein

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                            • #15
                              At the shop I used to work at my friend used to use re-usable cans -- they were very beefy and also had an unscrewable top so that you could fill with whatever you wanted --- He used to buy bulk brake cleaner and carb cleaner at a fraction of the cost, I suppose you could fill them with air but like someone stated thats what air hoses attached to tanks are for


                              Evan, tell us about your label

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