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Post Time: 14/10/2007 15:06:15 |
Rbarker
Total Forum Posts: 2 |
could someone tell me whether there is an effective may of screeing the emfs and particularly the magnetic field generated by a lift generator. The small grey box is in a small seperate room withing a basement flat which i would very much like to buy. Is there some form of lead casing, panelling that would do the job. There are companies out there (Aaronia Magnoshield) that provide magnetic screening products...are these genuine industrial products. Bottom line is: is there a genuine way of screening magnetic fileds or is it impossible. Help. |
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Post Time: 16/10/2007 05:17:12 |
alasdairP
Total Forum Posts: 173 |
It is not clear what the "small grey box" is. It may be a transformer or a switch control box, though these are normally in the lift-room at the top of the building. Where are the lift motors located? If it is a control switch-gear box then it will have significant power cables running in and out of it and they will almost certainly give off high(ish) magnetic fields. Such fields are difficult to screen without enclosing then in a long sttel and preferably mu-metal trucking box.
The first thing to do is to actually measure the magnetic fields btoh in the flat and close to the grey box. Once produced, power-frequency magnetic fields are almost impossible to shield without re-constructing the source of the problem. Basically, either you (i.e. all your rooms) have to be thick steel boxes with few sized openings or the source has to be enclosed in a similar box. Panelling is not normally at all effective (I have tried it several times where it was possible to do more).
Mumetal based products such as the Aaronia Magnashield Dur plates certainly have a place and cab be effective. They are not cheap (800 Euro for a piece 0.7m x 2m for the 0.5mm thickness - and you may need double that in your case), they are very heavy to transport and you need to handle them with great care. If the are "banged" or "bent around a shart (e.g. 90 degree) corner, they need re-annealing at a high temperature in a hydrogen atmosphere - very specialist job. Een cutting has to be done gently and by hand if reannealing is not the be carried out.
So, the first thing for you to do is to survey the magnetic fields with the lift running (and not running) and to try to identify (i) how wide-spread the fields are (ii) where they are coming from (iii) are they at levels that are concerningly high (abouve, say, 0.4 microtesla). EMFields (or sister company) hires out EMFields Pro meters by the week at a reasonable cost just for this purpose. We also sell a cheaper Gigahertz Solutions 3030 model if you are like to want to take readings over an extended time frame.
If the fields are high, then you will specialist engineering advice to have a hope of designing a screening system that will be properly effective. That will add significantly to the cost of the project
I hope this helps, even if it is more complex that I expect you hoped.
I certainly recommend making the measurements - the problem may be small.
Alasdairp |
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Post Time: 18/10/2007 15:54:24 |
Rbarker
Total Forum Posts: 2 |
alasdair. thank you very much. I bought your meter and measured the magnetic levels. Very high at the 'grey box' which i think is a transformer - - went off the meter. Levels in one bedroom read around 150 - - at the pillow. ambient level of flat even far away from box was around 80 ( big flat) I had a chat with the guys in the online shop and they felt that seemed high. It seems that around 40-50 is 'normal' from doing other tests in friends flats. Spoke to metal workers about creating Mu metal box. Can be done, but as you said Verrrry expensive. Is my interpretation of these readings correct do you think? |
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Post Time: 28/10/2007 04:25:08 |
alasdairP
Total Forum Posts: 173 |
Sorry about the delay. Yes, the readings and you interpreation sound right. They are significanlt higher than normal. 150 on pillow is higher that I would want to see, certainly not for a young child, even though the doubling in child leukaemia does not appear until betwee 0.3 to 0.4 microtesla (300 to 400). 40 is most common with 20-30 in well spaced out deteched homed to 30-60 in semis and terraces to 0.1 or abouve in some flats. I have also see flates at 30 nT!
You really can't screen effectively at a reasonable cost. I think you just have to live with it or find somewhere else.
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