Is there any legal requirement to have regular leakage tests done on
microwave ovens in an office environment?
I understand that portable appliance tests PAT need to be conducted at
regular intervals depending on the type of equipment and the
environment they're in, but do leakage tests need to be conducted?
I appreciate that if any equipment is suspected of damage then it
should be tested for safety before using again - however it's unclear
in our case if the equipment is indeed damaged.
We have a microwave oven that has some small paint chips inside the
oven under the turntable. We're not sure if this constitutes damage or
not (it appears to be bare metal beneath the paint and I always thought
that was a bad thing for microwaves but I could be wrong). It still
cooks fine and doesn't appear to spark or anything during use.

At a cost of around £35 I suspect that it may be cheaper just to
replace the oven itself rather than go down the qualified tester route
- but I could do with some advice on whether this is necessary for the
situation. It'd be a shame to throw out a perfectly good oven if it's
unlikely that small paint chips are likely to affect the safe operation
of the equipment.
Has anyone any experience of this? What would be the legal position?
Could a small paint chip affect the safe operation of a microwave oven?


Your advice would be greatly appreciated.
N

On 9 May 2006 04:10:38 -0700, Norbet
wrote in . com:

We have a microwave oven that has some small paint chips inside the
oven under the turntable. We're not sure if this constitutes damage or
not (it appears to be bare metal beneath the paint and I always thought
that was a bad thing for microwaves but I could be wrong). It still
cooks fine and doesn't appear to spark or anything during use.

Could a small paint chip affect the safe operation of a microwave oven?

No. The paint is only a cosmetic covering over the metal cavity
of the microwave oven. There should be no risk of sparking as the cavity
walls are nulls in the standing-wave pattern. The only place you should
normally be concerned with leakage of a microwave is at the door seal --
assuming no-one has been silly enough to interfere with the magnetron
feeding the cavity. Dirt on the seal or damage could allow leakage but
given that the wavelength is about (3x10^10/2.45x10^9)=12.2 cm, you need
a fairly large gap to get any significant leakage -- consider the size of
the holes in the door-screen which allow you to see into the oven but do not
let any microwaves escape.

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. ] Room 40-1-B12, CERN
KotPT -- "for stupidity above and beyond the call of duty".

Norbet wrote:
Is there any legal requirement to have regular leakage tests done on
microwave ovens in an office environment?

Not as such

I understand that portable appliance tests PAT need to be conducted at
regular intervals depending on the type of equipment and the
environment they're in, but do leakage tests need to be conducted?
I appreciate that if any equipment is suspected of damage then it
should be tested for safety before using again - however it's unclear
in our case if the equipment is indeed damaged.
We have a microwave oven that has some small paint chips inside the
oven under the turntable. We're not sure if this constitutes damage or
not (it appears to be bare metal beneath the paint and I always thought
that was a bad thing for microwaves but I could be wrong). It still
cooks fine and doesn't appear to spark or anything during use.

At a cost of around £35 I suspect that it may be cheaper just to
replace the oven itself rather than go down the qualified tester route
- but I could do with some advice on whether this is necessary for the
situation. It'd be a shame to throw out a perfectly good oven if it's
unlikely that small paint chips are likely to affect the safe operation
of the equipment.
Has anyone any experience of this? What would be the legal position?
Could a small paint chip affect the safe operation of a microwave oven?


Your advice would be greatly appreciated.

Invest four quid in a leakage detector from Maplins
http://www.maplin.co.uk/module.aspx?...=SEO&U=Strat15

Meanwhile, keep your distance from the machine if it is in use, and
don't have your workstation next to it.

Thankyou kindly for your advice - much appreciated!

"Dr Ivan D. Reid" wrote in message
...
On 9 May 2006 04:10:38 -0700, Norbet
wrote in . com:

We have a microwave oven that has some small paint chips inside the
oven under the turntable. We're not sure if this constitutes damage or
not (it appears to be bare metal beneath the paint and I always thought
that was a bad thing for microwaves but I could be wrong). It still
cooks fine and doesn't appear to spark or anything during use.

Could a small paint chip affect the safe operation of a microwave oven?

No. The paint is only a cosmetic covering over the metal cavity
of the microwave oven. There should be no risk of sparking as the cavity
walls are nulls in the standing-wave pattern. The only place you should
normally be concerned with leakage of a microwave is at the door seal --
assuming no-one has been silly enough to interfere with the magnetron
feeding the cavity. Dirt on the seal or damage could allow leakage but
given that the wavelength is about (3x10^10/2.45x10^9)=12.2 cm, you need
a fairly large gap to get any significant leakage -- consider the size of
the holes in the door-screen which allow you to see into the oven but do
not
let any microwaves escape.

Huuummm, interesting, Ivan; is it possible to pad the cavity out so altering
its resonant frequency, and furthermore is it also possible to give some
idea what kind of modulation transformer would be needed so that one could
use the oven as a source on 23 cms for EME? ;-}

Dave Doubleyew. ( G3F**.)

On Tue, 9 May 2006 15:29:56 +0100, Dave Doubleyew~ waifs.strays@org
wrote in :

"Dr Ivan D. Reid" wrote in message
...
On 9 May 2006 04:10:38 -0700, Norbet
wrote in . com:

Could a small paint chip affect the safe operation of a microwave oven?

No. The paint is only a cosmetic covering over the metal cavity
of the microwave oven. There should be no risk of sparking as the cavity
walls are nulls in the standing-wave pattern. The only place you should
normally be concerned with leakage of a microwave is at the door seal --
assuming no-one has been silly enough to interfere with the magnetron
feeding the cavity. Dirt on the seal or damage could allow leakage but
given that the wavelength is about (3x10^10/2.45x10^9)=12.2 cm, you need
a fairly large gap to get any significant leakage -- consider the size of
the holes in the door-screen which allow you to see into the oven but do
not
let any microwaves escape.

Huuummm, interesting, Ivan; is it possible to pad the cavity out so altering
its resonant frequency, and furthermore is it also possible to give some
idea what kind of modulation transformer would be needed so that one could
use the oven as a source on 23 cms for EME? ;-}

Well, you're starting to get beyond my area of expertise. As a
licenced ham you're probably better equipped to judge (I was just 2nd
operator on VK0KC in 1980...) I'm not sure it's necessarily a
_resonant_ cavity, but by definition the nulls had better be at the
walls. I assume it's something else that sets the actual 2.45 GHz
operating frequency -- I've had much more experience with thyratrons
than magnetrons. :-0!

Dave Doubleyew. ( G3F**.)

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. ] Room 40-1-B12, CERN
KotPT -- "for stupidity above and beyond the call of duty".

Dr Ivan D. Reid wrote:
On 9 May 2006 04:10:38 -0700, Norbet
wrote in . com:


We have a microwave oven that has some small paint chips inside the
oven under the turntable. We're not sure if this constitutes damage or
not (it appears to be bare metal beneath the paint and I always thought
that was a bad thing for microwaves but I could be wrong). It still
cooks fine and doesn't appear to spark or anything during use.


Could a small paint chip affect the safe operation of a microwave oven?


No. The paint is only a cosmetic covering over the metal cavity
of the microwave oven. There should be no risk of sparking as the cavity
walls are nulls in the standing-wave pattern. The only place you should
normally be concerned with leakage of a microwave is at the door seal --
assuming no-one has been silly enough to interfere with the magnetron
feeding the cavity. Dirt on the seal or damage could allow leakage but
given that the wavelength is about (3x10^10/2.45x10^9)=12.2 cm, you need
a fairly large gap to get any significant leakage -- consider the size of
the holes in the door-screen which allow you to see into the oven but do not
let any microwaves escape.


Interesting, wouldn't the microwaves actually penetrate the screen
with an intensity which falls off exponentially with distance? The
quantum analogy here being a particle in a finite potential well. (A
solid door screen being analogous to an infinite potential well). -
Just a thought that crossed my mind.

In message , Dr Ivan D. Reid
writes

Huuummm, interesting, Ivan; is it possible to pad the cavity out so altering
its resonant frequency, and furthermore is it also possible to give some
idea what kind of modulation transformer would be needed so that one could
use the oven as a source on 23 cms for EME? ;-}

Well, you're starting to get beyond my area of expertise. As a
licenced ham you're probably better equipped to judge (I was just 2nd
operator on VK0KC in 1980...) I'm not sure it's necessarily a
_resonant_ cavity, but by definition the nulls had better be at the
walls. I assume it's something else that sets the actual 2.45 GHz
operating frequency -- I've had much more experience with thyratrons
than magnetrons. :-0!

Ivan and his toys in Geneva ...

--
geoff

"Guy King" wrote in message
...
The message . com
from "Norbet" contains these words:

e have a microwave oven that has some small paint chips inside the
oven under the turntable. We're not sure if this constitutes damage or
not (it appears to be bare metal beneath the paint and I always thought
that was a bad thing for microwaves but I could be wrong). It still
cooks fine and doesn't appear to spark or anything during use.

White-inside microwaves often do this. It's not leaking deadly rays all
over the place at you, don't worry.

As for bare metal - the internal casings of microwaves are made
(usually) of metal. Indeed, if they weren't the microwave wouldn't work
properly as it relies on the metal (or other conductive material, for
the pedants) to bounce the radiation around till it meets the meat (or
other succulent comestible, for the pedants). Many microwave instruction
manuals even suggest you cover parts of somethings, like the tips of
poultry limbs, with tin foil to reflect the radiation away.

It would only be an issue if it had rusted right through and left a
hole, and (even then the hole would have to be over a certain size to
allow the particular wavelength through, for the pedants).

Now think on about the third, fifth and seventh harmonics of the fundamental
frequency generated. Then consider the wavelength they produce including the
half-waves and the minimum escape apertures from within the cavity for those
frequencies. At this point gentlemen anytime we enter a kitchen with a
microwave we should don lead aprons. Also note the old penny size sticker on
the door of the oven with point 2 sized print that reads "If you can read
this then you are sterile!" :-)

Dave Doubleyew. (G3F**)

Norbet wrote:

Is there any legal requirement to have regular leakage tests done on
microwave ovens in an office environment?

There presumably would be if the unit has suffered significant damage, etc.

A jewellers shop owner suffered multiple false alarms. A technician
discovered that a microwave in a fast food across the road had the door
interlock defeated. When staff opened the door the waves triggered the
jeweller's alarm.

Norbet wrote:
Is there any legal requirement to have regular leakage tests done on
microwave ovens in an office environment?
I understand that portable appliance tests PAT need to be conducted at
regular intervals depending on the type of equipment and the
environment they're in, but do leakage tests need to be conducted?
I appreciate that if any equipment is suspected of damage then it
should be tested for safety before using again - however it's unclear
in our case if the equipment is indeed damaged.
We have a microwave oven that has some small paint chips inside the
oven under the turntable. We're not sure if this constitutes damage or
not (it appears to be bare metal beneath the paint and I always thought
that was a bad thing for microwaves but I could be wrong). It still
cooks fine and doesn't appear to spark or anything during use.

At a cost of around £35 I suspect that it may be cheaper just to
replace the oven itself rather than go down the qualified tester route
- but I could do with some advice on whether this is necessary for the
situation. It'd be a shame to throw out a perfectly good oven if it's
unlikely that small paint chips are likely to affect the safe operation
of the equipment.
Has anyone any experience of this? What would be the legal position?
Could a small paint chip affect the safe operation of a microwave oven?


Your advice would be greatly appreciated.
N


A paint chip has no effect on the safe and proper working of a nuke.

There is no reason nor need to leakage test modern microwave ovens. A
leakage check consists of visually checking the cooking cavity hasnt
rusted through, bent out of shape, or had some wally cut a hole in it,
and that the door closes ok.

Microwaves do not have door seals, and have not for decades. If you
have a 1970s one that does, get rid of it.

Microwave leakage detectors are junk products.


NT, qualified

On Tue, 09 May 2006 21:54:32 GMT, raden
wrote in :
In message , Dr Ivan D. Reid
writes

I assume it's something else that sets the actual 2.45 GHz
operating frequency -- I've had much more experience with thyratrons
than magnetrons. :-0!

Ivan and his toys in Geneva ...

heh! Actually, the thyratrons were for my thesis in 1974 et seq...
Aust. J. Phys. 33, 215 (1980).

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. ] Room 40-1-B12, CERN
GSX600F, RG250WD "You Porsche. Me pass!" DoD #484 JKLO#003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".

On Tue, 09 May 2006 20:37:32 +0100, Scott
wrote in :

Interesting, wouldn't the microwaves actually penetrate the screen
with an intensity which falls off exponentially with distance? The
quantum analogy here being a particle in a finite potential well. (A
solid door screen being analogous to an infinite potential well). -
Just a thought that crossed my mind.

Probably, to first order. Now, put a 6.1 cm wavelength over a 1.5
mm hole, and exponentiate that! (I get 10E-18.)

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. ] Room 40-1-B12, CERN
KotPT -- "for stupidity above and beyond the call of duty".

In article . com,
"Norbet" writes:
Is there any legal requirement to have regular leakage tests done on
microwave ovens in an office environment?
I understand that portable appliance tests PAT need to be conducted at
regular intervals depending on the type of equipment and the
environment they're in, but do leakage tests need to be conducted?

A PAT test on a microwave should include an inspection for
damage which could cause microwave leaks, but no leak detector
is required (and the cheap ones you could buy were useless;
they were far too sensitive). The inspection should check for
correct operation of the door interlock, damage to the casing,
door, and hinges, etc. Rusting of the internal cavity metal
liner is also a cause for PAT failure, as it can result in
leakage. This commonly seems to happen in the corners and
under the turntable.

I appreciate that if any equipment is suspected of damage then it
should be tested for safety before using again - however it's unclear
in our case if the equipment is indeed damaged.
We have a microwave oven that has some small paint chips inside the
oven under the turntable. We're not sure if this constitutes damage or
not (it appears to be bare metal beneath the paint and I always thought
that was a bad thing for microwaves but I could be wrong). It still
cooks fine and doesn't appear to spark or anything during use.

As others said, paint chips alone are not an issue. However, if
the paint has come off because the underlying metal is rusting,
that would be a PAT test failure.

At a cost of around £35 I suspect that it may be cheaper just to
replace the oven itself rather than go down the qualified tester route
- but I could do with some advice on whether this is necessary for the
situation. It'd be a shame to throw out a perfectly good oven if it's
unlikely that small paint chips are likely to affect the safe operation
of the equipment.
Has anyone any experience of this? What would be the legal position?

In theory, if you are having it PAT inspected/tested as part of
your routine office saftey procedures, this should get picked up.
Unfortunately, most PAT testing which is performed is a complete
waste of time and money as the electricians who do it have never
been trained in doing so, and have no idea what they are supposed
to be doing. (Also, many companies PAT test far too often.)

--
Andrew Gabriel

Andrew Gabriel wrote:
In article . com,
"Norbet" writes:
Is there any legal requirement to have regular leakage tests done on
microwave ovens in an office environment?
I understand that portable appliance tests PAT need to be conducted at
regular intervals depending on the type of equipment and the
environment they're in, but do leakage tests need to be conducted?

A PAT test on a microwave should include an inspection for
damage which could cause microwave leaks, but no leak detector
is required (and the cheap ones you could buy were useless;
they were far too sensitive). The inspection should check for
correct operation of the door interlock, damage to the casing,
door, and hinges, etc. Rusting of the internal cavity metal
liner is also a cause for PAT failure, as it can result in
leakage. This commonly seems to happen in the corners and
under the turntable.

I appreciate that if any equipment is suspected of damage then it
should be tested for safety before using again - however it's unclear
in our case if the equipment is indeed damaged.
We have a microwave oven that has some small paint chips inside the
oven under the turntable. We're not sure if this constitutes damage or
not (it appears to be bare metal beneath the paint and I always thought
that was a bad thing for microwaves but I could be wrong). It still
cooks fine and doesn't appear to spark or anything during use.

As others said, paint chips alone are not an issue. However, if
the paint has come off because the underlying metal is rusting,
that would be a PAT test failure.

At a cost of around £35 I suspect that it may be cheaper just to
replace the oven itself rather than go down the qualified tester route
- but I could do with some advice on whether this is necessary for the
situation. It'd be a shame to throw out a perfectly good oven if it's
unlikely that small paint chips are likely to affect the safe operation
of the equipment.
Has anyone any experience of this? What would be the legal position?

In theory, if you are having it PAT inspected/tested as part of
your routine office saftey procedures, this should get picked up.
Unfortunately, most PAT testing which is performed is a complete
waste of time and money as the electricians who do it have never
been trained in doing so, and have no idea what they are supposed
to be doing. (Also, many companies PAT test far too often.)

--
Andrew Gabriel

Its when rust has compromised the integrity of the steel cooking cavity
that it is a problem, ie severe rust. I know many failures are declared
following surface rust, but its a position that would be hard to
defend.


NT

On Tue, 9 May 2006 15:29:56 +0100, "Dave Doubleyew~"
waifs.strays@org wrote:

Huuummm, interesting, Ivan; is it possible to pad the cavity out so altering
its resonant frequency,

No, the frequency is a function of the magnetron design and has
nothing to do with the microwave oven cavity (which is *not*
resonant).

and furthermore is it also possible to give some
idea what kind of modulation transformer would be needed so that one could
use the oven as a source on 23 cms for EME? ;-}

You would need to filter the power supply to provide clean DC to the
magnetron. Microwave ovens use an unfiltered supply (providing
rectified AC to the magnetron).

The anode of the magnetron in a microwave oven is connected to common
ground, and the cathode (which is also the heater filament) is fed
from the negative output of the HV rectifier.

AM and FM modulation of a magnetron is extremely problematic, and so
the usual modulation used is pulse modulation. It should not be too
difficult to arrange the HV to the magnetron to be switched by a PCM
or PWM circuit. I have no idea how fast you can switch a magnetron.
A bonus would be that you could increase the peak power considerably.
Used in conjunction with a large parabolic dish, I should think that
its signals could be readily detected on Earth after being bounced off
the Moon.

I have done a limited amount of experimentation with a microwave oven
magnetron. If you plan on operating it outside the oven, be *very*
aware of the dangers of high voltages (the mains transformer in the
oven provides about 5000V IIRC and is *very* lethal), and also the
danger of high intensity microwaves. Apart from the possibility of
causing physical damage to yourself, you can fry electronic equipment
from quite a distance away (as I discovered during my brief bout of
experimentation).

There are lots of fascinating things you can do with an intact
microwave oven. Try putting an old CD or DVD in the oven for a light
show. Next time a lightbulb burns out, put the dud bulb in the oven
to see it light up again (also works with non-dud bulbs). Be prepared
to clean broken glass from the oven as the bulbs will sometimes
shatter. A lit birthday cake candle also looks good in a microwave as
the radiation hits the ionised flame. Be prepared to spend time
cleaning the oven before the wife finds out.

--
Cynic