vacuum relief valve

[balloonguy]

I am not sure if this should be here or in equipment... I just broke the glass on my exposure unit. I am getting it replaced shortly. In order to prevent this happening again I an thinking a relief valve may help. Can anyone tell me if this is the right item?
Thanks,
Matt

https://smile.amazon.com/Control-Devices-Brass-Vacuum-Relief/dp/B0081TJQ52/ref=sr_1_7?ie=UTF8&qid=1485995724&sr=8-7&keywords=vacuum++relief+valve

[Admiral]

I've never heard of using those...

What actually broke the glass though? Was the screen not flat and put more pressure on one corner? Some debris on the screen on the glass?

Back when we used glass it happened about 3x over 3 years it randomly broke but we were able to replace it same day luckily.

[balloonguy]

I just replaced the blanket and added a new seal. I think the vacuum is just too strong. I had small bleed hose to keep the vacuum from being too strong. I did not realize that it fell out. I want to get a permanent solution. I am thinking I can set the vacuum strength from being enough to break the glass.

[tonypep]

Should be a regulator/adjustment knob fir vacum pressure..no more than 27psi. And yes, relief valves very common on most brands of vacum exposure units.

[Sbrem]

Should be a regulator/adjustment knob fir vacum pressure..no more than 27psi. And yes, relief valves very common on most brands of vacum exposure units.

I remember one breaking about 30 years ago on a smaller Polycop. No bleed valve on those though, never happened again. It was pretty odd...

Steve

[Inkworks]

Nuarc flip-topss come with a vacuum dump, basically a "T" in the line that lets you bleed outside air into the draw-tube. I have some funky screens for rotary printing ceramic coffee mugs and broke the glass with full draw-down once, now I let 'er bleed a little and it's all good.

[balloonguy]

Thanks for the replies. I will try it out and update you next week.
Have a great weekend!
Matt

[markdhl]

If you are using a good blanket we suggest a max vacuum of 18. Contact and vacuum are not the same thing.  All our units come standard with a bleeder valve to keep vacuum down and less wear and tear on the blanket.  With our blanket the less vacuum gives faster contact (newton rings).

However, I agree biggest reason was probably a screen that was not sitting flat on the glass.

Mark Diehl
Douthitt Corporation
313 515 8635

[ScreenFoo]

Should be a regulator/adjustment knob fir vacum pressure..no more than 27psi. And yes, relief valves very common on most brands of vacum exposure units.

Normally I never even briefly question your replies, but I think you missed some math there.
I can pull around 23-24 inches of mercury, (stupid altitude ) and that translates to a little over 11 PSI.

18 inches of pull sounds about right to me, as does the idea that the frame was warped or not flat on the glass...

[tonypep]

Quite possibly. Don't use film now so a bit rusty on that math....in any case yes its best to use manufacturers recommendations of course. Sorry if that was misleading

[balloonguy]

Just a quick update. I added the valve and it seems to work perfectly. It has a screw in valve that adjusts the vacuum pressure. I do have to make slight adjustments for different frame sizes. It beats broken glass though!