Vacuum Line question

[westhillsugarmaker]

We're loosing vacuum due to friction in the line caused by long runs up mainlines. We have a wet/dry line system, 2 releasers. I've seen a little bit on here about expansion tanks before the releaser to help gather the vacuum before you use it again, do these work? Any other ideas would be much appreciated.

[Haynes Forest Products]

This is what I know in my system. There is very little friction in a vacuum line under high vacuum. In reality its the high pressure air rushing in to fill the void that slows down the process. The tank will help by allowing the air to rush into the larger area. Its like a packed hall way full of kids entering a large auditorium.

Yes if your vacuum line to your releaser is undersized the best fix is to have a tank as close to the manifold as possible with a good size transfer line.

[JoeJ]

What size is your wet/dry lines and how far are you running to your releaser?

Joe

[westhillsugarmaker]

We have 2 releasers, one is maybe 100' from the vacuum with a 2" line. When that releaser is deadheaded we can get 27.5" of vacuum. From that releaser the line runs a long ways, maybe 3000' to the next releaser, we loose .5" by the time the vacuum gets there. We have a lot of mainline and we use manifolds at all the junctions. We were told that a booster wouldn't help the situation. I know we probably need bigger mains but that's obviously not going to happen soon since this system has only been in the woods for a year. Just trying to figure out what we can do in the meantime.

[maple flats]

My best suggestion is two-fold. First add a large tank (3-4x the volume of the releaser) close to the second releaser (that way there will be a "stash" of extra vacuum when the releaser trips), then order Steve Childs' Tubing Handbook and read it fully. It will give you all of the answers.
For one thing, regardless of the pump, if the transfer line for that vacuum is under sized you get no more vacuum out 3000' than if you had a much smaller pump. That notebook will give you the sizes you need to get the vacuum out 3000'. That large vacuum tank will help but will not be a cure, the only cure is to use the right size vacuum line.
After the sugar season you could also hire a tubing installer, they will know what size pipe you need, it may be 2.5", maybe 3" maybe more.

[westhillsugarmaker]

My best suggestion is two-fold. First add a large tank (3-4x the volume of the releaser) close to the second releaser (that way there will be a "stash" of extra vacuum when the releaser trips), then order Steve Childs' Tubing Handbook and read it fully. It will give you all of the answers.
For one thing, regardless of the pump, if the transfer line for that vacuum is under sized you get no more vacuum out 3000' than if you had a much smaller pump. That notebook will give you the sizes you need to get the vacuum out 3000'. That large vacuum tank will help but will not be a cure, the only cure is to use the right size vacuum line.
After the sugar season you could also hire a tubing installer, they will know what size pipe you need, it may be 2.5", maybe 3" maybe more.
All the mains/vacuum lines were run by a tubing installer, both this year and last. . . .

[GeneralStark]

You could run an additional line to the further releaser to increase the cfm capacity. What size is that line?

[westhillsugarmaker]

You could run an additional line to the further releaser to increase the cfm capacity. What size is that line?
That's what we have been told to do, 2".

[JoeJ]

How many taps at 3,000' and how many CFM is your pump?

Joe

[westhillsugarmaker]

2400 taps, not sure of the cfm honesty. It's a new vacuum that CDL sells. We put in a Y connection before the first relearer today and changed out the union hoping to cause a little less friction. We'll see what happens....

[maple flats]

Another thing is that you say you loose vacuum going up the long mains. How long and how many taps are you talking. For 3/4" I think the max is supposed to be 1000' and I personally think 750' but that's just my opinion. There is also a max number of taps but I forget what that is, someone will chime in on that. If you use 1" mains you can go farther, but I don't have the tubing notebook at hand so I'm not sure how far of how many taps.

[Chris_In_Vermont]

A 2" line for 3000' and 2400 taps isn't enough? I don't get it... We can get the same vacuum at the releaser as we do at the top of a sub-conductor that is 15,000 feet from the vacuum pump, going through 7000' of 4", 2000' of 3", 1500' of 2", 1500' of 1.5", 1000' 1.25", and 2000' of 1", reducing down all along the way and picking up 10 other sub conductors, each over 2500' long and starting out 1.5", 30,000 odd taps. This is just the vacuum lines, in general we go down one size for liquid lines. I know because we were checking vacuum last week and the boss wanted to know what the vacuum level was at the top manifold of one of our furthest back conductors, and once we got leaks fixed up it was the same as what the gauge on the releaser at the pump station was reading. That's my experience anyways...
Not sure why overbuilding systems is pushed so much...

[JoeJ]

The Cornell vacuum book shows that you get 20 CFM from a 30 CFM vacuum pump at 3,000' with a dry line capacity of about 2,030 taps. If the pump is 60 CFM, then you get 25 CFM with a dry line capacity of 2,500.
They recommend 1 cfm per 100 taps to properly transfer the vacuum and overcome small leaks.

Joe