{GarbageCan} [UPDATE#2 - Getting Swagelok sealing right]
The {GarbageCan} is shaping up nicely
It is designed to characterise pressure and evolved gasses.
On January 2nd, our experiment at HUG in Minnesota showed for the first time publicly what kind of pressure profiles can occur in a Ni + LiAlH4 system. Dr. Parkhomov added more evidence on the 18th March. We hope for the raw data following the up and coming report on his first long run experiment.
Understanding pressure is critical to moving forward and so Bob Higgins has designed an experiment based on our earlier work that will be used to add a lot of clarity to the LiAlH4 and, perhaps other alkali hydride systems.
Built literally in a garbage can, the experiment is designed to overcome the entrained water questions raised against Dr. Parkhomov's original experiment by focussing on the rate of temperature rise in a large insulated volume of water.
The experiment has 3 other key features
1. Active cooling, to add control
2. Minimal 'shielding' window for looking for any radiation
3. A sample bottle
Feature 3 has the potential to add extremely important data, if for instance we were to find Helium in significant quantities, we would know it can't be from D+D but might be from another reaction, see this sheet for potential possibilities.
The apparatus has a rack on on which the reactor is placed. At one end is the power connectors and at the other, the pressure sensor, sample bottle and some zero displacement volume (ZDV) fittings.
An important milestone in its manufacture was achieved today when Bob managed to solder on the main ZDV tube from the Swagelok that will attach to the reactor ceramic. This took a number of attempts and there is some great learning to share on that.
UPDATE#1 - pressure test of the ZDV plumbing
1st April 2015
Bob Higgins finished pressure testing his micro-plumbing platform to 450 PSIG using He. It worked just as expected with pressure sensor reading the pressure and with gas sampling in the cylinder and with bleed to atmosphere.
The tiny capillary tubing behaves as (expected) as a flow resistor, slowing the release of gas. This is convenient, in particular for doing gas sampling, or a bleed to atmosphere, as it prevents sudden pressure surges. Pressure shocks can damage the pressure sensor.
See images in Gallery
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UPDATE#2 - Getting Swagelok sealing right
It is not as easy to get a Swagelok to seal nicely on some ceramics as Bob Higgins has been finding out as he readies his {GarbageCan} for experiments. Here, in his own words.
"Well, I have had many tries (>10) to seal the aluminum ferrules to the high purity alumina closed-one-tubes. I tried lapping them to insure they were round. I machined a close fitting steel insert to go inside the tube to support the alumina from the inside. Every time, the alumina tube broke off as a ring right at the small end of the main aluminum ferrule as it began to seal. What I haven't tried yet is annealing the ferrules to about 350°C and then cooling them quickly to soften them. Perhaps these high purity tubes are particularly brittle.
To get on with experiment preparation, I have decided to try another approach. I found that of the readily available materials, mild steel provides the closest temperature coefficient match to alumina (actually titanium would be nearly a perfect match). I machined a mild steel adapter that slips over the alumina tube and then is turned down to 3/8" on the end to accept a 3/8" ferrule - even SS ferrules could be used. I will use a thin layer of epoxy to seal the alumina to the steel adapter. As the pressure rises, the forces will be radial outward on the alumina so as to compress the seal - and thus improve the sealing. When/if a vacuum is present, the forces will be much less to break the seal because even a perfect vacuum is only 1 bar. The thin layer of epoxy should be a good seal as long as it stays under about 120°C. It was an easy machining job."
Below are some pictures of his approach.
Comments
What would you recommend in regards to your
post that you just made some days in the past?
Any positive?
Another thought. You have the T-Piece in the middle as an inspection port for the Geiger counter? That copper pipe is going to have some hefty IR coming down it straight into the sensor when the tube is running at high temperatures. Perhaps consider putting a small bit of foil between the sensor and the tube outlet. The foil should have no effect on gamma and will hopefully block the IR and prevent the sensor from cooking. Another possibility is to use a small mirror at a 45 deg angle with the sensor just behind it inline. The gamma will go straight through the mirror to the sensor while the IR should be deflected to some degree. You might even be able to face a camera at the mirror so you can monitor the coil tube visually without getting in the way of the gamma sensing.
From Bob Higgins
"For dead space filler, I am using SS rod because it is available in more sizes and more accurate diameters than alumina. The SS has about the same thermal conductivity as alumina. AP has shown that the SS doesn't affect the ability of the reaction to work. In my case, there are two solid pieces of SS rod that are machined to fit (loosely) into the SS fuel tube. The rod pieces will be linked together using short 4-40 screw studs screwed into the adjoining spaces. The rod is broken into segments so it and wiggle a little to accommodate the slight bending in the alumina tube. The machined insertion of the the rods to go into the tube are loose enough for gas to readily escape. I think there is little danger of the H2 not being able to get out - it will blow its way out through some path in the gap between the tube and the machined section of rod. When I go to fill it, I will have one section of rod inserted, fill with a tiny funnel, then put the other segments together and slide the assembly into the alumina reactor tube. When I am done, I will pull it out (I am using a closed-one-tube initially, so I cannot push it out)."
"I think what you are referring to are the insulation plugs and/or baffle plates to keep heat from leaking out the ends of the tube. The copper tube will be at the same temperature as the water. So, even if air is baffled so that it must flow along the pipe to move around, the heat will be extracted. The ends will probably have insulation, but the inner part will probably have SS baffles which will be circular disks that will e attached to the rail and slide into the copper tube right along with the reactor."
Also I see 4 shaded areas in the diagram of the t-piece / reactor tube assembly. Are these some kind of bearing to mount the reactor tube in the t-piece?
You can see more images here
bit.ly/1KAVMF2
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