Increasing object exposure time under UVC when rotated?

  • Thread starter joniverson
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  • #1
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Main Question or Discussion Point

I use UVC to sanitize. However, since I sometimes use HID lights, when it comes time to flip over or change the angle of objects and the light is deactivated, there is a 10-15 min cooldown period before the light will reignite. I have been thinking of using a rotating platform that would have a one minute rotation period for any object placed on top of it. I've normally been using 15 min per side before manually changing object orientation or flipping, but since the rotation would now be continuous and automatic, how would this affect exposure time? Thank you.
 

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  • #2
jim mcnamara
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We need help:
1. have you have tested/verified the outcomes of sanitizing using your current single turn method method? How do you test?
2. what shape (cylindrical or whatever) objects has the old method worked on?
3. can we assume the UVC lamp "works" in an enclosed space, and the walls of the space are able to reflect UVC effectively?
 
  • #3
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Sorry, I don't think I was clear.

Basically, I want to know the information regarding the formula:

UV dose μWs/cm2 = UV intensity μW/cm2 × exposure time (seconds)

Currently, for a non-rotating square object, it takes 15 minutes per side to attain the necessary 2,500 μW·s/cm2.

Now, if the object is automatically rotated, and takes one minute to complete a rotation, how does this effect dose? What about the fact that no side of the object is under the light constantly... is a constant UV exposure needed, or can individual dosages be added to achieve the required total?

Thanks again.
 
  • #4
jim mcnamara
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Thanks that helps.
The UV dose is the product of UV intensity (expressed as energy per unit surface area) and residence time.
So, this means that for a flat surface (like a box) the angle of incidence changes and reduces the energy per surface are large.

So the answer depends item shape, but in most cases I can think of I would say yes, definitely a lot longer. This is why I asked about testing.

Take a box - the DNI (direct normal irradiance, fancy term for beam intensity) is usually given for a 90° angle of incidence. Rotation takes the item surfaces out of 90° for most of the time. I do not trust myself to work out times calculations for you. Without sterility testing for certification available, the calculation could have bad results.

And I do not know of a reference, offhand. But I'll bet @Dale and @Choppy do have better background than I do.

And as a guess, your times will work out to be greater than your current 4*15 minutes + 4*10 minutes, but I don't know for sure.
 
  • #5
berkeman
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since I sometimes use HID lights, when it comes time to flip over or change the angle of objects and the light is deactivated, there is a 10-15 min cooldown period before the light will reignite. I have been thinking of using a rotating platform that would have a one minute rotation period for any object placed on top of it. I've normally been using 15 min per side before manually changing object orientation or flipping
I guess I don't understand the setup very well (maybe post a couple pictures?), but can't you just temporarily cover the light(s) while you flip the object? Or wear enough protection so that you don't need to turn off the lights to do the flipping?
 
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  • #6
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Due to lack of available information, I have decided against a rotating platform and will use extra illumination for the shadow sides. Thanks again to those who replied.
 
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