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Industrial X-ray machine - will it work?

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Mates

Wed Oct 08 2008, 08:45PM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

Harry wrote ...

Drying of transformer insulation using zeolite

That's great Harry! I have few kg of Zeolite, I was using it for removing water from ethanol few years ago... I'll give a try.
Btw: Any chance to get the complete paper?

Proud Mary

Wed Oct 08 2008, 08:56PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Zeolite is an excellent molecular sieve, but I'm sorry I don't have access to the full paper. You'll need to ask someone with access to a university library system to get it for you.

...

Wed Oct 08 2008, 10:09PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

I am not sure about the legal implications of posting the article off ieee, but if you e-mail me (see profile) I can get it you. Just if anyone asks I totally thought that was my english paper.

Proud Mary

Wed Oct 08 2008, 11:03PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

I have thought about your problem, Mates, and given the high value of your transformer if it can be salvaged would suggest the following approach.

1. Do not drain the oil below the level of the transformer, as your problems will be very much less if it can be salvaged without letting air into the windings.

2. Take a sample of the oil, and test with a colour-indicating dessicant. Use whatever means you have to determine (a) free water (b) emulsified water (c) water in solution.

3. Using a centrifuge if you have one, spin down a litre of the oil and examine for micro-particulates.

4. Test for the presence of colloidal metals and acetylene (indicative of arcing in oil) if you can.

5. Using a high voltage megohm meter measure the resistance between primary and secondary. If you do not have such a meter, then connect 10kV DC to the secondary and measure the leakage current into the primary. Good insulation shows a gradually climbing resistance over a period of five or ten minutes, but insulation contaminated by moisture will cause leakage currents sufficient to mask the dielectric absorption effect, and the leakage current will remain fairly constant (the so-called time-resistance insulation test)

6. If the winding is sound, and the water content is low, then I would suggest using cartridges filled with zeolite to desscicate the remaining oil in the transformer, so you will not be faced with the problem of air bubbles forming in the windings, and all the vacuum pumping needed to get rid of them.

LutzH

Thu Oct 09 2008, 01:21AM

Registered Member #1721 Joined: Sat Sept 27 2008, 08:44PM
Location:
Posts: 136

Hello:

Well it looks like you have your work cut out for you. Reference the H2O problem I would try the following after having first confirmed that you do not have huge amounts of H2O:

Most HV tanks like this seal very well, I would heat up the entire tank overnight to about 30-40C, with heating blankets, or a space heaters etc, in order to raise the vapor pressure of the H20. Then pull a vacuum on the tank with a refrigeration vacuum pump. This is what we did for large medical systems after removing all "visible" water. The pump was left on for up to a day depending on how bad it was.

If the oil is clear, to amber, with no free carbon, and you re-dry it as above it should be just fine.
An old arc welder transformer makes a nice inductive current control unit if you are going to use it at a set KV/MA.

I would seriously consider selling/ trashing the tank, and going with a single phase one, or even using a second hand fluoroscopic HV unit to run your tube head instead, if these items are available in your area. -Or- Convert this one to run on single phase, leaving you with plenty of spare parts. This would simplify the control and "feeding" aspect of your project. At 1.5KW, single phase should be enough.

I would be interested at some point in seeing a picture of one of the XR tubes, then I can maybe help you with the cooling aspect, like if to use H20, or Vertrel XF cooling fluid etc.

Aloha.....

Mates

Thu Oct 09 2008, 07:13PM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

Here are the promised pictures...

One of the six water cooled tubes I have. This one has Cr anode. The other anodes are Cu, Co,Ni, Fe.

This is the HV plugin together with HV switch removed form the oil tank... I want to make some maintanance on it

The holder of the tube is equiped by specialized filters from different materials...It has mechanical control unit for switching between the filters...

plazmatron

Fri Oct 10 2008, 01:17AM

Registered Member #1134 Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351

Those are X-ray Diffraction tubes. I have one myself, and ex-Russian tube rated for 24kV.
Cooling is a walk in the park, since these are run with a grounded anode. the heated cathode is at, in your case -60kV

You can take advantage of the fact that those tubes have 4 Beryllium windows, thus emitting 4 beams, simultaneously.

Very nice collection of stuff!

Leslie

LutzH

Tue Oct 14 2008, 02:07AM

Registered Member #1721 Joined: Sat Sept 27 2008, 08:44PM
Location:
Posts: 136

WoW :)

Nice collection of diffraction tubes, since the efficiency of x-ray production depends on the atomic number of the element, the higher the atomic number, the higher your output. In the case of the tubes that you have the Cu, and the Ni tubes are going to give you the highest, and hardest output, with the Cr tube being the lowest. When your input KV is well in excess of the K-edge line of the element, you will have a continous brems spectrum above the K-line also.

So in a nutshell: I would use the Cu tube, and keep the Ni as a backup to start with if you cannot locate one of the tubes below. A far better solution for your application would be to obtain a Mo, or W anode tube with a beryllium window. This would give you a far greater output, and far more penetration to achieve a much more uniform dose to your cultures. At the wavelength of your tubes even air absorbtion is a major factor, and dose uniformity, and even measurment will be a big problem.

Check around your area to see if you can get a Mo anode Mammography tube, these are now being changed out for Rhodium anode tubes, so many good tubes are available. Some of these come with oil cooling connections already in place. A second even better bet would be any large focal spot industrial tube, or a rotating Tungsten anode medical tube.

The absolute ideal for your application would be a CT scanner tube, these are rated in the Million heat units + range, and these are designed to be run at multi 10s of KW levels all day long!!! with oil / water cooling in a grounded anode configuration. They normaly change these out way before the tube is shot.

Running such a tube with your power supply is no problem, you could even put a voltage doubler circuit into the tank with a couple of caps for 120KV if you get a CT, or regular W anode medical tube, now you are cranking some serious rads. You can rotate the anodes in the medical tubes just fine with 110-220V and a 10-30mfd capacitor. I used a 100W mecury vapor lamp ballast to current limit the rotor circuit, and a capacitor to run the rotor in a grid controled tube I had.

If you get one and have trouble with the filament isolation voltage requirment with the higher KV Tungsten medical tubes, I may be able to help you out, with one that I have. To close I would seriously attempt to locate one of these tubes, its not as hard as you may think. Many medical tubes are changed because only one filament is open, or because the anode bearings are a little noisy. With a Mammography tube you will be able to use your existing filament transformer with a simple resistor etc. Also the operating values of these tubes is available on line easy, to help you set up your power supply.

Good luck, let me know if you ever want to get rid of the Fe, or Co anode tube, I do not have anything that soft in energy :)

Mates

Tue Oct 14 2008, 07:23AM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

Hello,
Thanks a lot for your help guys. I have only few comments to your suggestions. There is a huge difference in designing a device which will be used in your home (private) conditions and in case it will be installed as part of University research facility. I mentioned in the beginning that the device will need an approval from the atom law authorities before is operated so all suggestion like DIY voltage doublers and incompatible tubes substitutions are out, despite are possible and would increased the performance.
The photon distribution and problems with the energy of the light will have to be solved using a rotating platform (microwave oven based). I will stick to the heavier anodes for sure. Recently I run into interesting publications dedicated to the research of low energy (soft gamma) X-rays DNA damage induction and it really seems there will be no need for voltages over 60KV for my routine work. For special cases when hard gamma would be needed I have access to Cs and Co radioisotopes (the only problem is it that the sources are not in the same building as my lab is and its use is a bit restricted).

Small update of my work on the X-ray device:
This weekend I cleaned the cables, all the mechanical switches and plug-ins (my hands look like Iâ€™m a car mechanic and not a scientist

). I redesigned the tube holder (all the filters are removed now and made the main window for the beam much bigger). Iâ€™m also designing the shielded box, I already ordered the lead and found a guy (company) who will make the box. Wish me good luck and Iâ€™ll keep you updated.

mikeselectricstuff

Sun Oct 19 2008, 07:08PM

Registered Member #311 Joined: Sun Mar 12 2006, 08:28PM
Location:
Posts: 253

LutzH wrote ...

Most HV tanks like this seal very well, I would heat up the entire tank overnight to about 30-40C, with heating blankets, o

It would be more efficient & easier to use the windings as a heater. You can also determine internal temperature by measuring the change in resistance.
Either use DC or short the secondary & current-limit the input to avoid any HV which might introduce breakdown.

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