Remote Vacuum Pumps

[robinsoncr@naxs.net]

Hi,

I'm getting ready to re-install the 15hp Cascade vacuum pump. I have to redo the pvc plenums because we added the two middle legs and this is where the main inlet was originally located.

I have the pump on a equipment dolly and under the table right now. If on the floor, it would bearly clear the plenums. Then I have to locate the filtering bag (expansion chamber). The bottom horizontal brace for the middle legs interferes with it's installation.

This brings me to the question about a remote location for the vacuum pump assembly.

The center of the table is 30' away from our warehouse. Once you add in the distance to the ceiling, we're talking about 54 lineal feet of pipe.

What would this do to our vacuum holding efficiency?

If we can't/shouldn't relocate the pump that far away, then I'll either have to get creative on the under-table assembly or rethink the location of the Shopbot. Which means I'd better stop with the setup until I figure this all out!

Thanks,

Chris R

[gerald_d]

Q: What would this do to our vacuum holding efficiency?

A: Not much if your pipe diam. is big enough.

All that length and diameter gives you volume, that some guys even think is desirable.

[robinsoncr@naxs.net]

Gerald,

That was exactly what I was thinking.

I could run it at the same diameter as the main plenum without alot of trouble.

Thanks,

Chris

[gerald_d]

I personally don't believe that all that volume is beneficial, unless one has a "pre-evacuation" system involving some valves. If you don't plan on "pre-evacuating" then the extra volume simply means that you will take longer to create the initial hold-down - it has to suck all that air out of all those pipes first.

However, if you put a big valve near the SB, you can leave that closed while the pump pre-evacuates the pipes. Then quickly open the valve and you get a surge of "vacuum" into all the volume of the sucked-out pipes, and the sheet is snatched down onto the table surface, sealing most of the leaks, and making it easier to maintain a vacuum after that.

[robinsoncr@naxs.net]

Gerald,

I was going to install a main valve at the front of the table to cut off vacuum while removing or loading the materials. So, it should work fine.

Thanks,

Chris

[elcruisr]

Remember that you need to be able to move enough air through that pipe run to maintain your vacuum on anything that dosn't cover the whole surface of your table. That means a larger diameter pipe. The pre evacuation is also important. Another shop in our area does this with their 25 hp vacuum pump. I think it's about a 30 foot run to their pump. The best thing to do is call the tech department at the pump manufacturer and let them check out your idea and they can tell you the diameter you'll need for the length of run you're planning.

Eric

[gerald_d]

"you need to be able to move enough air through that pipe run to maintain your vacuum on anything that dosn't cover the whole surface of your table"

Or, throw a sheet of plastic over the unused table.

Or, divide your plenums into zones with separate valves

But, Eric is correct, if you want to get the full benefit of that MONSTEROUS vacuum pump, make sure the pipes are big enough, like I said before.

[elcruisr]

You also can lose alot of air through cuts when doing sheets full of small parts no matter how well you mask. We run 100s of sheets of small parts for one customer of ours. Each 4x8 sheet has over 40 parts on it. No matter how well you mask off unused parts of zones by the end of the cuts we are losing alot of air through those tool paths and see a definate vacuum drop because of it.

Eric