Small pressure chamber made from rated NPT components... Safety questions. - Page 4
Close
Login to Your Account
Page 4 of 5 FirstFirst ... 2345 LastLast
Results 61 to 80 of 89
  1. #61
    Join Date
    Dec 2008
    Location
    Vt USA
    Posts
    9,478
    Post Thanks / Like
    Likes (Given)
    1666
    Likes (Received)
    3453

    Default

    Quote Originally Posted by digger doug View Post
    I'm sure you can regulate it down....

    Of course, an air leak can be used to soften the vacuum. That risks carrying away the lubricating and sealing oil.
    Too large a flow through such a pump will literally burn the oil. Go ahead, Turn one on disconnected from anything. observe the smoke produced at the exit pipe. IIRC the compression ratio is over 10,000 :1

    I keep just such a pump, out of a small window A/C unit. I use it to draw down auto A/C units after they have been open. Or I use the Robinair 15600. For degassing, I prefer the little Gast diaphram pump. It's the right tool for the task.

    If an oil sealed mechanical pump is used for epoxy degassing, I suggest a closed volume evacuated for a very short period of time, (seconds) with repeated cycles as necessary. Too long at too hard a vacuum, and "fizzy bubbles"* will form. (* that a sophisticated techno-term used at the optics assembly bench ;-) or a lesser pump and you don't need to monitor or worry about the potential problems

  2. #62
    Join Date
    Nov 2010
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    154
    Post Thanks / Like
    Likes (Given)
    224
    Likes (Received)
    46

    Default

    Quote Originally Posted by jim rozen View Post
    Looks good.

    Looks good.

    Looks good.

    (blooorp!!)

    AAAAAAHhh!!!!

    (stycast all over the inside the vacuum jar)
    LOL

    I've had it foam up over the top of the specimen holders, but never very dramatically. But, looking at the inside of every single system I've worked with, your description seems to happen pretty often!

  3. Likes CalG liked this post
  4. #63
    Join Date
    Feb 2004
    Location
    peekskill, NY
    Posts
    27,271
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    6347

    Default

    Quote Originally Posted by CalG View Post
    Of course, an air leak can be used to soften the vacuum. That risks carrying away the lubricating and sealing oil.
    Too large a flow through such a pump will literally burn the oil. Go ahead, Turn one on disconnected from anything. observe the smoke produced at the exit pipe. IIRC the compression ratio is over 10,000 :1
    ..
    Nothing's burning there, that's just oil mist from the pumped vapor bubbling out through the oil in the pump. As long as the oil doesn't get too low, there's no harm to the pump. Lab occupants however can get oil pneumonia - so we hook oil-based pumps up to an exhaust when pumping at high inlet pressures for an extended time.

    On systems where we know it will be operated that way (high inlet pressure) constantly, there's a way to put an oil trap in the outlet, and a return line from the trap into the pump's gas ballast line, so most of the oil gets back where it belongs.

  5. Likes aarongough liked this post
  6. #64
    Join Date
    Oct 2005
    Country
    UNITED STATES
    State/Province
    Pennsylvania
    Posts
    22,351
    Post Thanks / Like

    Default

    Quote Originally Posted by CalG View Post
    Of course, an air leak can be used to soften the vacuum. That risks carrying away the lubricating and sealing oil.
    Too large a flow through such a pump will literally burn the oil. Go ahead, Turn one on disconnected from anything. observe the smoke produced at the exit pipe. IIRC the compression ratio is over 10,000 :1
    Uhm....yeah.

    I have used them for just such purposes.
    I'm not advocating a 1000 hour solution, simply a quick way to get started, as cheaply as possible.

    I have no idea what you going on about " the compression ratio is over 10,000 :1".....

  7. Likes aarongough liked this post
  8. #65
    Join Date
    Jan 2007
    Location
    wales.uk
    Posts
    1,844
    Post Thanks / Like
    Likes (Given)
    412
    Likes (Received)
    432

    Default

    Recently bought a Makita cordless vacuum pump locally, mrs uses it for canning, but it’s intended for air con installation, not cheap at 140 pounds but certainly as good as big pumps, I’ve done some experiments with gluelam seems quite satisfactory.
    Mark

  9. Likes CalG liked this post
  10. #66
    Join Date
    Dec 2008
    Location
    Vt USA
    Posts
    9,478
    Post Thanks / Like
    Likes (Given)
    1666
    Likes (Received)
    3453

    Default

    Quote Originally Posted by digger doug View Post
    Uhm....yeah.

    I have used them for just such purposes.
    I'm not advocating a 1000 hour solution, simply a quick way to get started, as cheaply as possible.

    I have no idea what you going on about " the compression ratio is over 10,000 :1".....
    Do the maths

    An oil sealed pump can usually achieve 10-4 atmospheres and still push gas out the exhaust.

  11. #67
    Join Date
    Sep 2010
    Location
    Oklahoma City, OK
    Posts
    5,585
    Post Thanks / Like
    Likes (Given)
    1081
    Likes (Received)
    2435

    Default

    I see nothing physically wrong with your design, but here's what I'd change.

    For background, I have 10 years in the nat gas pipeline world. I've dealt with DOT regulated lines and their design criteria as well as ASME BPVC section 8.

    I'd make it from seamless pipe, but ERW is fine for this service with a cap welded on the end. At 12:00 I'd weld on (2) thread-o-lets for instrument ports. On the other end I'd use a Huber-Yale Figure 500 knock-off cap. These are meant to be removed and reinstalled repeatedly, with a hammer. Dead simple cap with acme threads that seals via o-ring. If I was feeling very fancy, I'd use an isolator (basically a double blind hydraulic cylinder) between the gauge and vessel to insure the gauge's tube never experienced anything but clean oil.

    Grade B line pipe has a minimum yield strength of 35ksi. With Sch40 pipe of this class and a safety factor of 2 you'll have a MAOP north of 2000psi. This is determined using the Barlow Equation, it's basically hoop stress plus some de-rate factors pertinent to pipelines.

    For hydrotest, fill it with water and use a grease gun to achieve 1.5x your desired max. If this was a pipeline that'd be an 8hr test, however I feel that it's closer to a vessel and 6" and under isn't classified in Section so no test reqd.

  12. Likes aarongough liked this post
  13. #68
    Join Date
    Sep 2008
    Country
    UNITED STATES
    State/Province
    California
    Posts
    2,630
    Post Thanks / Like
    Likes (Given)
    1963
    Likes (Received)
    1637

    Default

    At 120psi it wouldn't have even occurred to me to hydro test the setup up in post #1.

    But as pointed out you need a vacuum. I did work for somebody who encapsulated electronic components in epoxy and that was his method. Flat piece of 6061, sheet of silicone rubber, and a half dome made of perspex. The vacuum required to pull out the bubbles wasn't very high. He used a venturi vacuum pump and varied the air flow to vary the vacuum.

  14. #69
    Join Date
    Oct 2017
    Country
    UNITED STATES
    State/Province
    California
    Posts
    1,334
    Post Thanks / Like
    Likes (Given)
    428
    Likes (Received)
    451

    Default

    Pressure pots for paint sprayers are rated to around 110psi often. I have two and they are very convenient.

    A cheap diaphragm pump can pull 20 in hg and may be adequate. Otherwise I would use an aspirator. They are simple and contamination resistant, and oil free.

  15. #70
    Join Date
    Oct 2014
    Country
    CANADA
    State/Province
    Ontario
    Posts
    1,644
    Post Thanks / Like
    Likes (Given)
    1292
    Likes (Received)
    1405

    Default

    Just as a follow up:
    1) I bought a grease gun as suggested and will be hydro testing this vessel to 1.5x working pressure, as well as testing some smaller similar vessels to failure to see what the 'real' safety margin is... Hoop stress calculations for this 'vessel' indicate that at 125psi the safety factor is over 40x so overall I'm not super worried about the pipe, as others have stated I'm sure the end caps would be the first failure point at higher pressures.

    The reason I want to hydro test some smaller 'scale replica' vessels to failure is because there has been such a huge variety of feedback on the safety of this system that I want to get some real-world results to see how they stack up to the feedback and to the specs on the pipe and fittings. I will make a video for my YouTube channel and will post it here when it's finished!

    2) I have been using the vessel at lower pressure while enclosed in the steel base cabinet for my lathe, figured that was a good safety measure in the short term. No issues at all so far, though reliably sealing the threaded end cap is a total pain and I will be replacing it with a flanged adapter and cap as suggested to make opening/closing the vessel easier.

    3) PRESSURE CASTING WORKS GREAT!!!

    Pressure casting is a pretty well proven process which is why I went this route... Everyone who has said you 'need vacuum' is off base here. If I was to use vacuum degassing I'd have to babysit the resin to make sure it doesn't overflow, then be extremely careful while pouring it to make sure I don't entrap any air-bubbles, and agitating the mixture to make sure the powder stays suspended in the resin would obviously cause huge problems with creating new bubbles...

    With pressure casting I have been mixing the powder and epoxy mixture by hand with no care not to create bubbles, pouring it directly into the mold and then curing it in the pressure pot. The reason bubbles are potentially such a huge issue for me is because I am cutting into the casting and so I would expose any bubbles inside. I have cast and machined several blocks of material so far using the pressure method with ZERO issues, and no voids or bubbles found.

    This is what the material looks like when cured at ambient pressure, full of bubbles and voids:


    This is what it looks like when cured at 60psi, the texture makes the details a bit hard to see but there are ZERO bubbles:


    The final result:




    This is Strontium Aluminate glow in the dark powder mixed with casting epoxy at basically 100% fill along with pigments to get the daytime color correct, then cast in place inside the G10 composite handle scales for my knives. It's then machined so the glow powder shows up as a liner next to the opaque black G10.

    It's been a pain to work this process out, lots of failed attempts precede the move to pressure casting, but it seems to be working great now! This stuff is BRIGHT, easily visible in a dark room after 10 hours.

    I will report back once I have the hydro test results for the various vessels.

    -Aaron

  16. #71
    Join Date
    Jun 2002
    Country
    CANADA
    State/Province
    British Columbia
    Posts
    3,206
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    3137

    Default

    Hi Aaron:
    Thanks for showing us the result of your experiments...it's always really nice to get follow-up from someone who's asked a question on the forum.
    Way too often it just all floats away, never to be seen again and no one knows how it actually worked out.

    On another note, that's one fine looking knife...you make good stuff!!

    On a last note...be sure you don't over stress the grease gun using it to hydro test your vessels...it'd be a real drag to have the gun blow up and bonk you on the nose before a vessel blows up.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

  17. Likes TeachMePlease, aarongough, cyanidekid liked this post
  18. #72
    Join Date
    Mar 2014
    Country
    UNITED STATES
    State/Province
    California
    Posts
    264
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    110

    Default

    This thread has gone past being ridiculous. Whether you are pressurizing at 120 PSI or using a vacuum, You could probably use room temperature butter for the cylinder and be safe.

    So you have more to be worried about, a bottle of club soda from the grocery store at room temperature is about 65 PSI (beer is usually around 25 PSI). At 100 degrees the pressure will be about double. So if it's summer you now have a 120 PSI club soda bomb waiting to kill you and your beer is now 50 PSI and warm and not worth drinking!

    My 92 year old father is watching over my shoulder as I type this(PHD mechanical engineering) and designed the fuel pumps on the Apollo rocket engines. He also thinks you are way over thinking this. We are talking about 120 PSI not 1200 PSI.

    By the way, the knife looks good.

  19. Likes Yan Wo liked this post
  20. #73
    Join Date
    Oct 2014
    Country
    CANADA
    State/Province
    Ontario
    Posts
    1,644
    Post Thanks / Like
    Likes (Given)
    1292
    Likes (Received)
    1405

    Default

    Quote Originally Posted by Laverda View Post
    This thread has gone past being ridiculous. Whether you are pressurizing at 120 PSI or using a vacuum, You could probably use room temperature butter for the cylinder and be safe.
    To be honest that was exactly how I was thinking about this originally, but I posted a picture of the setup on Instagram and a petro-chem engineer reached out to me and told me what I was doing was 'very unsafe'... I didn't want to ignore the warning regarding something that is definitely dangerous if it was to go wrong, so I started the thread here.

    It's been very interesting to see the variety of different responses regarding this, I would have thought there would be a single answer, but I was wrong!

    At this point I personally feel like the chamber is safe, but I will be doing some further testing as I mentioned, mainly just for my own education!

    -Aaron

  21. #74
    Join Date
    Aug 2019
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    108
    Post Thanks / Like
    Likes (Given)
    2
    Likes (Received)
    109

    Default

    I'm pretty sure my wife wants one of those knives...

  22. Likes aarongough liked this post
  23. #75
    Join Date
    Jun 2006
    Location
    Near Seattle
    Posts
    5,316
    Post Thanks / Like
    Likes (Given)
    3945
    Likes (Received)
    1642

    Default

    Aaron - I *forbid* you to make wharncliffe blade folders with that treatment (since I'll go broke buying them if you do...)

    Actually, I should learn to do that, and make scales like that for my folding knives - make them easier to find in a power outage, really, it's a safety thing.... (Sort of project that might actually keep me out of trouble for while....)

  24. Likes aarongough liked this post
  25. #76
    Join Date
    Oct 2014
    Country
    CANADA
    State/Province
    Ontario
    Posts
    1,644
    Post Thanks / Like
    Likes (Given)
    1292
    Likes (Received)
    1405

    Default

    Quote Originally Posted by wp6529 View Post
    I'm pretty sure my wife wants one of those knives...
    I'm glad she likes them! I'm actively working on adding a kitchen knife to my lineup as well, should be ready within a couple of months... More temptation!

  26. Likes BugRobotics liked this post
  27. #77
    Join Date
    Oct 2014
    Country
    CANADA
    State/Province
    Ontario
    Posts
    1,644
    Post Thanks / Like
    Likes (Given)
    1292
    Likes (Received)
    1405

    Default

    Quote Originally Posted by bryan_machine View Post
    Aaron - I *forbid* you to make wharncliffe blade folders with that treatment (since I'll go broke buying them if you do...)

    Actually, I should learn to do that, and make scales like that for my folding knives - make them easier to find in a power outage, really, it's a safety thing.... (Sort of project that might actually keep me out of trouble for while....)
    I have initial design work done on a button-lock folder actually! Initial design has a tanto blade, but it would be easy to clip it to make it into a wharncliffe!

    I'm curious to see how the initial prototypes of the folder turn out, the handle is solid 17-4 stainless with a H900 heat-treat. To keep the weight down the entire inside of the handle is skeletonized with an Isogrid pattern, should be pretty cool if it works out!

    I'll have to see about adding some glow to it!

  28. Likes TeachMePlease, bryan_machine liked this post
  29. #78
    Join Date
    Feb 2014
    Location
    FL
    Posts
    4,492
    Post Thanks / Like
    Likes (Given)
    13835
    Likes (Received)
    5469

    Default

    Quote Originally Posted by aarongough View Post
    I have initial design work done on a button-lock folder actually! Initial design has a tanto blade, but it would be easy to clip it to make it into a wharncliffe!

    I'm curious to see how the initial prototypes of the folder turn out, the handle is solid 17-4 stainless with a H900 heat-treat. To keep the weight down the entire inside of the handle is skeletonized with an Isogrid pattern, should be pretty cool if it works out!

    I'll have to see about adding some glow to it!

    *drools in tanto folder...*

    Let me know if you need beta testers.

  30. Likes aarongough liked this post
  31. #79
    Join Date
    Aug 2019
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    108
    Post Thanks / Like
    Likes (Given)
    2
    Likes (Received)
    109

    Default

    Do you have a web site? (I see you do in your profile) For kitchen knives I'm rather a fan of the inexpensive commercial ones from Sam's, they work well and I don't worry about them when butchering a critter.

  32. #80
    Join Date
    Nov 2018
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    794
    Post Thanks / Like
    Likes (Given)
    429
    Likes (Received)
    533

    Default

    Quote Originally Posted by TeachMePlease View Post
    *drools in tanto folder...*

    Let me know if you need beta testers.
    Thing about early stage testing is... The more people that do it, more and better feedback you get!

    I've been daydreaming for years about building myself a custom handmade folding knife, but hearing that you're getting into it simultaneously makes me rejoice and despair.

  33. Likes aarongough liked this post

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •