Connecting Multiple Vacuum pumps? Potential damage?

Help Support and Requests
1

I am curious if there is a right and a wrong way to hook two rotary vein vacuum pumps together. One of our new welch crv pro 16 and an aging Edwards 28 were hooked together, simply, with a barbed T fitting. A one foot section of hose coming off each inlet to each pump was hooked to a simple barbed T fitting and then to an SPD system in hopes of getting “better vacuum”. Upon seeing this it made me a little nervous. The ultimate vacuum test on the Welch pump was in the high teens, low 20’s.

  1. Does hooking them together in the way described above risk damaging either pump?

  2. What would be the correct way to stack vacuum pumps to achieve greater vacuum or capacity to remove solvent?

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2

The pumps must have close deep vacuum endpoints
No more than 100 micron
If You are able to use a Y fitting would be beter than a T
If possible each pump schould have a valve
If not both pumps must be turned off and on simultaniosly
For one pump sucks out the oil from the other otherwise
I do iT often but valved

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3

Would there be better vacuum pressure with 2 pumps? I thought the total would be equal to the max pressure of the most efficient of the two pumps.

4

No the vacuum reached If the diffrence between pumps is not to big is 20% lower than the average of the two
So 100 micron pump and a 200 micron pump give a vacuum of aprox 165 micron

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5

But de cfm is the Sum of the 2

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6

What makes the Y more efficient than the T. Jw.

7

Every thing likes the road of least resistance in a t the shorter path is the next pump in a straight line so iT places more vacuum effort on the pump then on the glasswear

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8

Also flow wise 45 degree angels are more favorable than 90 degree angels

9

I’m glad I asked but I feel like that should’ve been obvious to me :joy::joy::joy:

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10

Keep a valve on each pump so if you turn one off for some reason you can close off that pump completely. I learned the hard way and sucked vacuum oil from one pump to another because of my neglectful error

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11

Is anyone using something like these but suitable for high vacuum? The cracking pressure is the required pressure differential, which is is too large for our purposes (0.6" Hg = 15.24 mm Hg).