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Old 12-18-2012, 02:21 PM   #1
fiberpro

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Exclamation Vacuum pump proper pressure

Short question to you guys,





How this 0,05mBAR reffers to -30HG or-1Bar?? ( ideal for infuse)

I want to buy pump and have to know how strong the vacuum is..
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Old 12-18-2012, 10:44 PM   #2
herman

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0,05 mbar is -0,99995 bar.

Some remarks:
-good pump for infusion
-smokes when not reaching a very low vacuum, so make sure you are working without leaks
-the oil usually is supplied in a bottle, not in the pump. Fill the pump with oil before starting. (sounds stupid, but you are amazed on how many people forget that.)
-do not expect an enormous life expectancy. 1 or 2 years heavy use and you wear it out. (composite vanes instead of cast metal vanes)
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Old 12-19-2012, 01:06 AM   #3
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I cannot understand this.. pressure conversion table shows that 1 bar is 0.001mBar
Herman I have pump now, its dry pump , it is said it has ultimate vacuum 150mBar
But conversion tables are telling 150mBar is equal 0,150 Bar...

disaster..

How did you get this value of -0,99995 ?
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Old 12-19-2012, 02:00 AM   #4
Halto

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Hi,

your confussion comes from mixing the terms relative pressure and absolute pressure.
Conversion tables do not take this into account!!!

Absolute pressure have it's reference point at 0 mbar (100% full vacuum)
It gives a value of the "rest-pressure" within the vaccuum.

Relative pressure have it's reference point at atmosphere pressure (0% vacuum).
Relative pressure shows the difference of your vacuum level to the atmosphere pressure.
Atmosphere pressure have an absolute pressure of ~1000 mbar.
(Value is idealised, in relality the atmospheric pressure varies a lot depending of your geographic location above sealevel and the actual weather)

To indicate that a value is given relative pressure the value is writen negative.
Most of the time this "-" is not given, you can only guess by the value if it is relative or absolute:

A vaccum pump which creates a relative pressure of 150mbar would be quiet lame. So it must be a absolute pressure.
An absolute pressure of 150 mbar is a relative pressure of 1000 mbar - 150 mbar = -850 mbar equal to -0,85 bar. The "-" sign indicates that its a relative pressure.

This -0,99995 bar comes the following:
Maximum vaccum for the VP115 pump in absolute pressure is 5 Pa, equal 0,05 mbar equal to 0,00005 bar.
The relative pressure is 1000 mbar - 0,00005 mbar = -999,95 mbar equal to -0,99995 bar.
Again the minus sign is given to indicate relative pressure sothat it comes to Hermans number.

Hope that helps
Halto.
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Old 12-19-2012, 11:57 AM   #5
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And one other thing: 1 bar = 1000 mbar, not 0,001 mbar
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Old 12-20-2012, 03:47 AM   #6
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Thanks very much Halto , now i get to the proper point.

Apart from that.. If my pump is 150mbar and (you clarify) is equal -0,85bar, shows -0,2 Bar on gauge it means pump is broken
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Old 12-20-2012, 03:51 AM   #7
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hi fiberpro, are you going to buy this pump? For my hobby I have a 70 L/min....this pump with 42 L/min is small in my opinion...you have difficult to degas resin (like volume of degassing chamber)and you can do only small pieces.
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Old 12-20-2012, 05:12 AM   #8
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Hey GAB981, Im asking about pumps cause my pump "suck" only to -0,2 Bar...
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Old 12-20-2012, 05:38 AM   #9
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Quote:
Originally Posted by fiberpro View Post
Thanks very much Halto , now i get to the proper point.

Apart from that.. If my pump is 150mbar and (you clarify) is equal -0,85bar, shows -0,2 Bar on gauge it means pump is broken
Hi fiberpro,

I see 3 possible reasons:
1. you have a major leak in your setup
2. the gauge is not working correctly
3. pump is broken

If you can sort out the first two reasons then most likely your pump is broken...
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Old 12-20-2012, 06:18 AM   #10
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I didnt mention i plug gauge directly into pump, its brand new.
Such pumps can be restored by replacing some parts?
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