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  1. #16
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    Jan 2009
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    Thanks Neil.
    What size and brand/manufacturer is your pressure pot.
    In the aviation industry we concern ourselves re pressure cycles. Actually count them, to enable structural analysis and determine specific maintenance and inspections.
    Is your pressure pot up to Aust stds? What'd be your highest pressure and for how long? 40-60psi for 24 hours???
    Thanks for answering these questions, it is much appreciated.
    Lyle

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  3. #17
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    Apr 2005
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    Nerang Queensland
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    Quote Originally Posted by Lyle View Post
    Thanks Neil.
    What size and brand/manufacturer is your pressure pot.
    In the aviation industry we concern ourselves re pressure cycles. Actually count them, to enable structural analysis and determine specific maintenance and inspections.
    Is your pressure pot up to Aust stds? What'd be your highest pressure and for how long? 40-60psi for 24 hours???
    Thanks for answering these questions, it is much appreciated.
    Lyle
    I have a number of pots, an old 10 litre cast aluminium (that I do worry about fatigue, so rarely use these days), an old 20 litre steel pot made by a boiler maker (and definitely over designed), and a good quality 30 litre bought off Ebay. I run them within a closed shed for added safety. Generally they run for 24 hrs at a time at less than their design working capacity with safety valves I installed set for their safe working load. The aluminium runs at 50psi/60psi (because it's so old), the steel at 60psi/75psi and the new one 75psi/80psi (working pressure/safety valve).

    The cheap Chinese ones from Ebay/Super Cheap etc are ok but do have a limited life. Cheap ones have no seats for the hold down bolts and mark the lid steel. This is where they fail due to fatigue, so many put copper/brass/protector discs under the bolts so as to avoid stress concentrator points in the lid.
    Neil
    ____________________________________________
    Every day presents an opportunity to learn something new

  4. #18
    Join Date
    Feb 2014
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    Canberra, Australia
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    369

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    There's an Australian company that sells pressure pots for paint but does some modifications to make them suitable for resin casting including trimming the agitator. Don't know if they're ok with me posting name here so PM me.

  5. #19
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    Apr 2005
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    Quote Originally Posted by NathanaelBC View Post
    There's an Australian company that sells pressure pots for paint but does some modifications to make them suitable for resin casting including trimming the agitator. Don't know if they're ok with me posting name here so PM me.
    It's ok to put link here, saves you getting inundated with PMs too
    Neil
    ____________________________________________
    Every day presents an opportunity to learn something new

  6. #20
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    Feb 2006
    Location
    Perth
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    25,622

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    I've been watching a few vids on this top and a technical explanation for bubbles disappearing under pressure seems to be missing.

    I don't think the added pressure actually shrinks bubbles to invisibility because the pressure changes alone not large enough to do this.
    A 3 mm radius bubble under say 3x original pressure will only shrink the bubble to about 2mm in radius which would be easily visible.
    For it to become invisible the air must be dissolving into the resin.

    This is why soda water under pressure is transparent - the CO2 has been dissolved into the water. When the external pressure is release the CO2 no longer can stay in solution and so starts appearing as bubbles.

  7. #21
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    Aug 2017
    Location
    Canberra
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    Lyle can you give an example of what sort of voids you are wanting to fill?
    Maybe if they are open ones you can sand, shallow or you use coloured resin, you maybe not even need a pressure pot.

  8. #22
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    Apr 2005
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    Quote Originally Posted by BobL View Post
    I've been watching a few vids on this top and a technical explanation for bubbles disappearing under pressure seems to be missing.

    I don't think the added pressure actually shrinks bubbles to invisibility because the pressure changes alone not large enough to do this.
    A 3 mm radius bubble under say 3x original pressure will only shrink the bubble to about 2mm in radius which would be easily visible.
    For it to become invisible the air must be dissolving into the resin.

    This is why soda water under pressure is transparent - the CO2 has been dissolved into the water. When the external pressure is release the CO2 no longer can stay in solution and so starts appearing as bubbles.
    It's a mix of so small they are effectively invisible, but as you say, also dissolving into the resin. BTW big bubbles/voids often don't disappear, they just get smaller, it all comes down to the pressure
    Neil
    ____________________________________________
    Every day presents an opportunity to learn something new

  9. #23
    Join Date
    Feb 2014
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    Canberra, Australia
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    Quote Originally Posted by dai sensei View Post
    It's ok to put link here, saves you getting inundated with PMs too
    Yeah alright, this is the pot I got https://airless.com.au/paint-spray/c...-agitator.html

  10. #24
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    Apr 2005
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    Quote Originally Posted by NathanaelBC View Post
    Yeah alright, this is the pot I got https://airless.com.au/paint-spray/c...-agitator.html
    Nice, but not cheap
    Neil
    ____________________________________________
    Every day presents an opportunity to learn something new

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