FAQ: Vacuum line diagram v2.0

If you have a question about this topic, the answer is probably in here!
Tom McCarthy
Posts: 404
Joined: Wed May 08, 2013 7:36 pm
Real name: Tom McCarthy
Location: Ireland
Contact:

FAQ: Vacuum line diagram v2.0

Post by Tom McCarthy » Mon Jun 17, 2013 1:38 pm

This is the new diagram for the vacuum line, I've added a colour coding identification method and made the whole thing a bit easier to read and nicer to look at.
You can thank Rich Feldman for this version as it's from his tips that these improvements have come!

Also, I hope that the outlet/Inlet locations for the diffusion or turbo-pump are right. Feel free to tell me if that's wrong or anything else isn't right, any tips or things that could be added are appreciated.
Gas line diagram v1 soon to come.
v2.1: Added T-junction for ball valve/roughing pump/Bellows sealed valve connection.
Screen Shot 2013-06-17 at 21.20.17.jpg
Vacuum line diagram v2.1
Screen Shot 2013-06-17 at 2.53.52 PM.png
Vacuum line diagram v2
Screen Shot 2013-06-17 at 2.52.24 PM.png
Vacuum line diagram v1
Tom

Due to the fine work done here, I have edited the title to be a FAQ. R.H.
Last edited by Tom McCarthy on Mon Jun 17, 2013 8:21 pm, edited 1 time in total.

Tom McCarthy
Posts: 404
Joined: Wed May 08, 2013 7:36 pm
Real name: Tom McCarthy
Location: Ireland
Contact:

Re: FAQ: Vacuum line diagram v2.0

Post by Tom McCarthy » Mon Jun 17, 2013 7:09 pm

...That well and truly filled me with a feeling of joy after reading your edit Richard. Again, most of it is down to Rich's help and corrections for v1 to bring it to what it is.

Also, after your reply on the Mechanical pump - Diffusion pump FAQ today, I've realized that he foreline should be split from the start with the bellows sealed valve one way and the ball valve the other, I'll fix it as son as possible and get it up on this post.

Tom

User avatar
Rich Feldman
Posts: 1121
Joined: Mon Dec 21, 2009 11:59 pm
Real name: Rich Feldman
Location: Santa Clara County, CA, USA

Re: FAQ: Vacuum line diagram v2.0

Post by Rich Feldman » Mon Jun 17, 2013 10:02 pm

Got tired of holding my breath waiting for someone else to respond.

The T fittings you added in v2.1 (by editing your v2.0 original post) are a step in the right direction, but you can install a trap in the foreline without using any tees. Hint: label the "foreline". Or search this forum (as I have not searched) for fusor vacuum system diagrams drawn by others.

Now how do you admit air to the intake port of mechanical pump, when it's valved off from the HV pump?
(It's bad practice to leave the mechanical pump turned off with its inlet under vacuum.)
Richard Hull told you a solution today, in another thread:
The ball valve is mounted in a "T" fitting in the foreline and not inline within the foreline, such that when opened it will act as an "up to air valve", This valve and "T" are cheap and can be found at any good hardware store. This valve is forever left closed. The only time it is ever opened is to release all vacuum from the foreline and forepump body. All this assumes that all other valves are locked closed before doing this.
Even if you do it by momentarily opening a quick-connect pipe fitting (Richard's "KF" trick -- look up KF), that fitting needs to be there. You don't want to be unscrewing a threaded joint or pulling a hose/tube off of a barb fitting.

What would be a good sequence to release the vacuum from the fusor chamber before, for example, taking it apart?

I also think the mechanical pump's exhaust port should be shown. [ edit -- I see that it is now! ]
They all have one.
People using industrial rotary-vane vacuum pumps generally put an oil mist eliminator on the exhaust.
One example is at the bottom of first picture here:
viewtopic.php?f=10&t=3977&p=25528&hilit ... ron#p25528
Some have reported using a hose to carry the oil mist somewhere else.
Mike echo oscar whisky! I repeat! Mike echo oscar whisky, how do you copy? Over.

Tom McCarthy
Posts: 404
Joined: Wed May 08, 2013 7:36 pm
Real name: Tom McCarthy
Location: Ireland
Contact:

Re: FAQ: Vacuum line diagram v2.0

Post by Tom McCarthy » Tue Jun 18, 2013 2:45 pm

Just finished adding a few small things for v2.2, I've added two vents - One for the foreline and one for the chamber.
Took in what you said Rich, hope this addresses most of the issues. I also found a diagram literally a minute ago while searching the net, that is excellent. I'll attach it below.
And again, if there's anything else that can be added/fixed/labelled do tell!
Screen Shot 2013-06-18 at 3.41.19 PM.png
Vacuum line diagram v2.2
Screen Shot 2013-06-18 at 3.45.01 PM.png
Diagram found on net
Tom

Dan Tibbets
Posts: 578
Joined: Thu Apr 17, 2008 5:29 am
Real name:

Re: FAQ: Vacuum line diagram v2.0

Post by Dan Tibbets » Tue Jun 18, 2013 3:26 pm

Regarding relieving fore line vacuum. I have relied on unscrewing the connection - admittedly not an elegant solution. But, I also rely on the ballast valve built into the roughing pump to gradually drain the fore line vacuum (over several minutes?). Is this adequate? Any additional valve introduces the potential for leaks, so it is not without some compromise.

The other issue is that (at least in version 2.0) I see no way of roughing down the vacuum chamber without going through the high vacuum pump. If you open the chamber for any purpose you have to make sure the high vacuum diffusion pump has cooled, you cannot by pass it.

Dan Tibbets

User avatar
Chris Bradley
Posts: 2931
Joined: Fri May 02, 2008 11:05 am
Real name:

Re: FAQ: Vacuum line diagram v2.0

Post by Chris Bradley » Tue Jun 18, 2013 5:09 pm

Rich Feldman wrote:Now how do you admit air to the intake port of mechanical pump, when it's valved off from the HV pump?
(It's bad practice to leave the mechanical pump turned off with its inlet under vacuum.)
I don't see any reason for wanting to admit air at that point, if it is valved off?


Usually, what [I've always thought!!!] is to be done is to have a trap right on top of the intake port of the mechanical pump, and then a valve straight after that (which then leads to the molecular pump).

In this way, when you shut that valve, the vacuum is held in the intake port of the mechanical pump AND the trap. If you go opening that up, you contaminate the trap. To de-contaminate it, you run the mechanical pump with that valve closed.

The intake port is designed to hold a vacuum. If it didn't, it wouldn't pump??!!!

FWIW, I use an electromechanical valve between the trap and the molecular pump, with a 24V 'open' and a 5V 'sustain' operation. In this way, if there is an electrical interruption in the mains (which is not at all unknown where I am - rubbish power grid) then the valve shuts and remains closed, thus protecting the molecular pump from being exposed to the mechanical pump while it is not pumping during that electrical interruption. If one were to have the ballast valve open and the valve in the foreline fixed open (viz., a manual valve), and the mechanical pump stops momentarily (for whatever reason, mech or electrical failure) whilst it is backing a turbo, the turbo will be history.
Last edited by Chris Bradley on Tue Jun 18, 2013 5:24 pm, edited 2 times in total.

User avatar
Richard Hull
Moderator
Posts: 11427
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: FAQ: Vacuum line diagram v2.0

Post by Richard Hull » Tue Jun 18, 2013 5:10 pm

The net based diagram shows a roughing line. Absolutely not needed or important at all for any fusor work. You can rough through the diff pump.

How to open to air the chamber? Answer....

1.Close all valves
2. Temporarily remove small gas line.... or.... simply unbolt your chamber conflats and give a light pry up with a screwdriver at the seams. Usually, unbolting will create such a leak that by the time you are finished unbolting, the thing comes apart. Meanwhile, the diff pump is still under vacuum.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

User avatar
Chris Bradley
Posts: 2931
Joined: Fri May 02, 2008 11:05 am
Real name:

Re: FAQ: Vacuum line diagram v2.0

Post by Chris Bradley » Tue Jun 18, 2013 5:13 pm

Dan Tibbets wrote:Regarding relieving fore line vacuum. I have relied on unscrewing the connection - admittedly not an elegant solution. But, I also rely on the ballast valve built into the roughing pump to gradually drain the fore line vacuum (over several minutes?). Is this adequate?
I just don't see any reason to do this. I suppose it'd work, if you really want to vent the intake port [I still don't get why] but risks pushing vapours/oil droplets sitting above the pump oil back into the trap and everywhere that you don't want it.

One word of warning: Never shut off the pump with the ballast open.

User avatar
Chris Bradley
Posts: 2931
Joined: Fri May 02, 2008 11:05 am
Real name:

Re: FAQ: Vacuum line diagram v2.0

Post by Chris Bradley » Tue Jun 18, 2013 5:15 pm

Cheapest way to install an up-to-air vent.

Works perfectly.

---> viewtopic.php?f=25&t=3952&p=25258#p25258

User avatar
Rich Feldman
Posts: 1121
Joined: Mon Dec 21, 2009 11:59 pm
Real name: Rich Feldman
Location: Santa Clara County, CA, USA

Re: FAQ: Vacuum line diagram v2.0

Post by Rich Feldman » Tue Jun 18, 2013 6:35 pm

Chris, I love your tape-over-hole trick for venting foreline.
Other inexpensive alternatives come to mind that will not lose stickyness, but can still wear out:
a tiny rubber stopper in a tapered hole, or a short bit of gum rubber tubing with a pinch clamp.

I was taught not to leave mechanical pumps turned off with inlet under vacuum, even if valved off from trap and/or foreline.
The pump chambers will slowly fill with oil, via the clearances provided for lubrication.
That creates the risk of overpressure or even hydraulic lock when the pump is restarted, especially if the two pump stages have different displacements or phases. It's been known to make press-fitted part connections slip. One design remedy is an overpressure relief valve. I got one retrofitted for free, by the factory service tech who re-pressed a rotor in my DV-85 pump.

Another practical note, to which I can personally attest:
When a mechanical pump is not right-side-up, then running the motor for even a second can discharge a full load of oil through the exhaust port.

Tom: re. the diagram "found on the net" which you re-posted. I encourage all re-posters of Internet content to carry along the attribution, or at least a source link. It's the respectful thing to do, even if original content did not have a copyright label.
Last edited by Rich Feldman on Tue Jun 18, 2013 7:02 pm, edited 3 times in total.
Mike echo oscar whisky! I repeat! Mike echo oscar whisky, how do you copy? Over.

Post Reply