Announcement

Collapse
No announcement yet.

I need a pressure vessel

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • I need a pressure vessel

    I need to make or buy a pressure vessel to the following specifications:

    max operating pressure = 60 psi.

    Cavity size = apprx 8" by 6" by 4"

    Door must be able to be rapidly opened/closed

    maintain pressurized state for 1 to 3 hours

    The purpose is to pressurize plastic cast materials as they cure. Since the pot life of the plastic once it is mixed is very low (a few minutes), the door must operate quickly and the vessel pressurized before the cure stage reaches maturity.

    Any ideas?

    Marv

  • #2
    Marv,

    Would the tanks used for industrial paint application would work for your application? They have a gasketed top that is secured with swing away clamps with large knobs that can be quickly tightened.

    The other option is to build one. We use a shop made unit that is a heavy square steel plate with a heavy steel cylinder welded to it. The top is a turned steel plate that is recessed to fit into the cylinder. The cylinder then has two heavy steel ears welded to it that project up above the top of the cylinder a couple inches at 180 degrees. The ears have a hole bored in each. There is a shaft with a "T" handle about 1 1/4-1 1/2" diameter that slides across the top of the lid through the holes in the ears. The shaft is turned down offset in two spots that line up with the holes to provide a cam action. When the shaft is turned in the holes, the cam action forces the fatter section of the shaft against the top of the lid securing it. The center of the turned lid has a raised portion in the center so that the shaft will have a bearing surface to clamp against rather than relying on resting against the entire top surface of the lid. The lid is about 3/4" thick material.

    My brother-in-law used to be a denturist and he used a pressure cooker for curing resin for dental work, however I don't know what pressures he was working at. I know the pressure cookers are not normally rated that high.

    Hope this long winded reply helps. If I was at work today, I would take a digital photo and post it for you.

    Bernard

    Comment


    • #3
      Thanks. Some good ideas. I will look into the paint tank idea. Should be easy to see what pressure they are rated at.

      Your idea sounds similar to what I was thinking. I was considering 1/2" plate aluminum, but the door could swing inward. On the contact surface between the door and wall I would line with a rubber gasket. I was thinking that the compressed air would keep the door sealed since it would press the door into the seal at pressure.

      Instead of welding I was considering bolts so I could assemble the container with the door in place.

      I am not sure that this would be mechanically sound or not. The last thing I would want is the box to burst! If it doesn't cause bodily harm, it sure would cause a mess upon rapid decompression!!!

      Marv

      Comment


      • #4
        Marv,

        If you build such a chamber I suggest you design a pressure actuated safety interlock that will not permit the door to be opened while the vessel is under pressure.

        [This message has been edited by Evan (edited 10-04-2003).]
        Free software for calculating bolt circles and similar: Click Here

        Comment


        • #5
          Try a local SCUBA dive shop for a condemned 80 cu.ft aluminum cylinder they are 8 1/4 in. dia. and 3/4" wall.The dive shop or fire exstinguisher test places dispose of them when they crack at the neck or fail hydro test at 3000 P.S.I.! The remaining tank is great for adaptation to small pressure vessel.We sawed one off at 10" high and made a quick close door out of 4 pieces of laminated polycarbonate to pressurize dive computers to 100 p.s.i. to test for leaks. A single tank will yield all the material for the parts except for the flat plate/window for the top.And the best part is they will give them to you FREE or scrap price.Being designed for 3000 p.s.i. they will easily hold 100-200 psi for pressure vessels.I have a pressurized coolant tank for my mill made from one holds about three gallons and fills with air from shop compressor.Check your phone book for dive shops and go visit,They will usually be greatful to get rid of the "junk" tanks as long as you don't try to fix or fill them.

          Comment


          • #6
            Don't know if they are good to your design pressure, but what came to my mind is a kitchen pressure cooker.

            Comment


            • #7
              If the vessel were round, how big would the inside diameter have to be, and how deep would it have to be?
              Any products mentioned in my posts have been endorsed by their manufacturer.

              Comment


              • #8
                I use an old pressure cooker that has 6 thumb screws on the top and an air conditioner gauge set up for both vacuumming out any air bulbs and then switch over to high pressure to stop any gassing of the material for final cure. I pretested the cooker to over 75 lbs. outside and covered with a tarp to maintain it could handle the regulated 60 lbs pressure used. The arrangement is set up so the vacuum pump is on the low side of the A/C gauge and regulated 60lbs pressure is on the high side and the center hose goes to the cooker. I start out by placing the item in the cooker and at the same time start the vacuum pump which helps to seal the top as I draw down the thumb screws, as soon as I get to about 28 inches of vacuum I shut off the vacuum valve and open the pressure valve. These steps take only seconds to go from one to the other. I have also used a 2 gallon painting vessel but it can't take the bigger pieces I was doing.

                Comment


                • #9
                  I just checked my storage room and I have a pressure tank made by EFB company. It is about 6.5" ID x 7.5" deep. It has 4 swing toggles that hold an O ring sealed lid. It has a pressure pop off valve and a pressure regulator with pressure gauge. It has removable plastic liner. It made of cast aluminum is rated for 100psi. It appears to be in new unused condition. Send me some email if you want it for $100 plus shipping.

                  Comment


                  • #10
                    The pressure cooker sounds like a possibility. I have one I use for vacuum, but I wasn't sure if it would handle that much pressure. It has a screw type lid and is made by Ultrex.

                    I don't know what max pressure they are designed for. A clue might be what pressure the relief valve goes at. Might look around on the internet.

                    Marv

                    Comment


                    • #11
                      From what I could find, it looks like pressure cookers are used up to 15 psi. Even with a generous safety margin in the design, using one at 60 psi seems a bit risky.
                      Any products mentioned in my posts have been endorsed by their manufacturer.

                      Comment


                      • #12
                        I used a pressure cooker pot all the time in dentistry to stop porosity when curing plastic. Buy a standard pressure cooking pot take of the valve that goes with it put on a pressure gauge, then a standard tyre valve fitting preferably a metal one with screw fitting as opposed to the pull through type, then a standard washing machine water valve to release the pressure this can all be done quite safely. Just drill or elongate the holes already there and fit the new parts it should work fine, releases in an instant Alistair
                        Please excuse my typing as I have a form of parkinsons disease

                        Comment


                        • #13
                          I forgot to add put some warm (not hot) water in the pot even immersing the plastic this should help speed up the cure time .Alistair
                          Please excuse my typing as I have a form of parkinsons disease

                          Comment


                          • #14
                            A friend of mine recently took a bunch of aluminum cylinders for Self Contained Breathing Apparatus to the recycler. He got them at an auction where Fire Department equipment was being sold, they went for $1 each, he being the only bidder. They normally hold 2216 PSI working pressure and had a flat bottom that could be modified to install a door. There was a valve on the other end that the high pressure hose is connected to for the breathing apparatus that could be used to pressurize and later bleed off pressure.
                            You might keep an eye out at city/county auctions for similar cylinders.

                            Comment


                            • #15
                              Hey,
                              Dentists used to vulcanize dentures , when the denture bases were made of rubber. They used vessels about a foot tall and 6-8 inches in diameter. These were filled with water and the dentures were placed inside and then the top was put in. The top had a guage attached and the pressure was applied. Pressure pots are used daily in the dental field to cure the acrylics used to make denture, partial denture, temporaries and the like.

                              Comment

                              Working...
                              X