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Cooling Down period before moving HMI


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#1 Jordan-Rhys Jenkins

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Posted 03 April 2014 - 10:47 PM

Hi,

 

I'm wanting to know, whats the cooling down period for HMI before it's safe to move it?

Suggestions?

 

Thanks


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#2 Mark Kenfield

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Posted 04 April 2014 - 02:22 AM

Depends on the size, design and wattage of the fixture as well as the ambient temperature. When packing down HMI fresnels I generally open the lid of the fixture to let the hot air out faster, and when shooting with PARs I'll try and remove the lens if I can to facilitate the same accelerated cooling.

 

Bug lights like the Profoto HMIs or the Joker Bugs have a very different design and the bodies of those fixtures don't get anywhere near as hot as conventional fixtures (just the reflectors you add on to them).


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#3 timHealy

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Posted 04 April 2014 - 07:40 AM

Hi,

 

I'm wanting to know, whats the cooling down period for HMI before it's safe to move it?

Suggestions?

 

Thanks

There is no real cooling down time to move an HMI. I even move them when they are on if there is enough header to get it to it's next position. An HMI does not have a filament like a tungsten lamp that is fragile especially when it is hot.

 

In fact some of the bigger heads have so much trouble with hot re-strikes its preferable to leave them on. Experienced electricians know when a DP says turn something off you just pan it away. Unless they say "no really that one can be turned off". Experienced DP's will know to ask to pan an hot HMI off too once they have been burned by that.

 

The only time we open a lens is during a hot re-strike situation and hopefully it will come back on given a few minutes, and before someone panics and says get another head.

 

As far as par lenses go it seems to help to take scrims out of a lamp before you turn it off to help facilitate cooling of the lens. If you leave scrims in the par lens itself (not the UV glass) seems to easily crack and break.

 

Best

 

Tim


Edited by timHealy, 04 April 2014 - 07:41 AM.

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