Vacuum condition problem

[Chriss]

Hello all i just bought vacuum gauge Testo 552 and connect it to vacuum pump and Testo 550.

So when i start to pull the vacuum is ok, after that I close the valve on the Testo 550 to isolate the pump and I turn off the pump.

So all the measurements which i can see are from the vacuum between the Testo 550, ribber hoses and Testo 551

As you can see from the video which i took the vacuum is not stable and when i close the valve from the T550 vacuum level going more weak (rise up).

Here is the video
https://www.youtube.com/watch?v=bkkVvEiyw5o

PLease let me know why is that happen?

[RANGER1]

Chriss,
This may help as see that permeation occurs in hoses & fitting leak if not "0" ring type.

http://alltemp.ca/wp-content/uploads/2013/10/JB-Principles-of-Vacuum-Presention.pdf

[Grizzly]

Still not able to give you rep points Ranger.
An Interesting read all the same.
Thanks Grizzly

[monkey spanners]

I have seen similar vacuum rise, i think i read somewhere that is is because the volume of what you are measuring is so small (just the insides of the hoses) it should not behave the same way on a system. Also if they are new hoses they will give of fumes (new rubber smell) which will affect the vacuum reading until they have aged a bit.

[Grizzly]

I Quote from Rangers Link!
Read the last paragraph in particular.

  Always a good idea to attach a micron gauge to the vacuum pump to make sure the pump
pulls down to at least 50 microns.?
  If it doesn’t, your pump oil is contaminated and should be changed.?
 
Do not shut off the blank-off valve on the pump and expect the gauge to hold a
vacuum as the gauge will fall back to atmosphere.

(The sensor in the gauge is too close to the pump and does not have time to
equalize).

Grizzly

[chemi-cool]

When i vacuum a big unit, I use these two gauges to make sure it stays or leak.

1400714008

[RANGER1]

This is also interesting link, thanks for rep points ms.

https://www.youtube.com/watch?v=cI6pSBaskjc

[Grizzly]

Do you ever sleep:D
Grizzly

[RANGER1]

Do you ever sleep:D
Grizzly

Grizzly the second link is the one I was looking for in the first place, as thought it was pretty good.
I look at things on IPhone a lot so can look anywhere at anytime.
Had about 9 hrs last night��

[nike123]

The only connecting lines that are absolutely vacuum tight are soft copper tubing or flexible metal hose