Vacuum System question

[bob svoboda]

OK. I have just about acquired all the necessary parts. I just want to be sure I'm clear on how to assemble everything. I'm not concerned with the electrical, mounting etc, just the flow of the vacuum. Here's how I understand it (please set me straight if I'm off base)

Lathe adapter-----input filter-----relief valve (with filter)----gauge---pump---output filter-----silencer

Thanks for looking and helping me out. I will post pic's when all is complete.

[Steve Schlumpf]

Bob - looks like you got it straight. The output filter and silencer are optional.

Don't forget your vacuum chuck.

[bob svoboda]

Bob - looks like you got it straight. The output filter and silencer are optional.

Don't forget your vacuum chuck.

Thanks Steve. Yep, I have the vacuum hub from JT Turning Tools to help me with the chuck part. Appreciate the help!!

[Steve Schlumpf]

Looking forward to seeing photos of your system once it is completed!

[Thom Sturgill]

I'm also trying to figure this out.

It seems to me that the input filter is primarily to protect the pump. The closer to the pump the better for the pump, as it will catch anything sucked in at a leak. If it is downstream from the relief valve then a separate filter at the relief valve is redundant (except to protect the valve and possibly the gauge.)

I guess the first question is, does the gauge need the protection? That is, must the filter be upstream from the gauge? I wouldn't think so.

The other question is, does it matter whether the valve is upstream or downstream from the gauge? I believe I've seen systems where they both mount to a manifold, and that would probably be best, but not as easy to set up.

[Richard Madison]

There may be some pressure drop across the "input filter" (depending upon flowrate) which will increase with time (as the filter does its job). If so the gauge (at the location shown) will not be measuring the vacuum applied to the work. In practice the error may be negligible, as obviously many systems built as shown are working well. An alternative, however, would be; adapter, gauge, valve with filter, input filter, pump, etc. With this arrangement the valve would not require a filter, but still a good idea.

[Tom Steyer]

Bob,

Take a look at a simple system diagram available here - http://jtturningtools.com/files/Inst...%20Diagram.pdf
It may help you get set up. Let me know if I can help.

[Tim Rinehart]

Keeping gage just downstream of adapter will tell you what's happening at the workpiece, which is what matters.

If you have a spare gage, you could hook it up close to the pump...which would be an indication (looking at difference between gages) that your filter is getting clogged and restricting flow, and subsequently holding power.

I think most people just have the one gage, and mount immediately downstream of adapter.

Gages are 'dead-headed' devices, and aren't quite as susceptible to issues with regards to the dust as a device that has flow through it. I wouldn't be too concerned about it. Any need to 'filter' it's source pressure will only further isolate your knowing the pressure at the workpiece.

Have fun...I sure like having vacuum to clean bottoms of turnings.

[Greg Ketell]

I made one change to cheapen it up for me.

Lathe adapter --- relief valve --- input filter --- gauge --- pump --- output filter (as filter and silencer).

I never could understand why we needed two input filters.
GK

OK. I have just about acquired all the necessary parts. I just want to be sure I'm clear on how to assemble everything. I'm not concerned with the electrical, mounting etc, just the flow of the vacuum. Here's how I understand it (please set me straight if I'm off base)

Lathe adapter-----input filter-----relief valve (with filter)----gauge---pump---output filter-----silencer

Thanks for looking and helping me out. I will post pic's when all is complete.

[Greg Ketell]

Tim Rinehart had some good comments but didn't want to risk offending me so sent them to me privately.

Here's some thoughts on your comment though... For what it's worth, my background is controls engineering and working with powerplant equipment with hundreds of applications of devices like gauges, transmitters, etc...so I feel pretty good about what I'm going to say....though I've only been turning a little over a year.

If your filter gets clogged, pressure (vacuum) will drop at the workpiece, but you won't know it. The gauge is used to make sure you've got adequate pull at the workpiece and that you've sealed all leaks, AND that your input filter to the pump isn't clogged.

What happens downstream of the input filter is of no consequence, as long as workpiece vacuum pressure is still healthy.

As to location of relief valve...I don't see a big difference on mounting before or after the gauge...but again, since I'm most interested in monitoring what the vacuum in my workpiece looks like, I place that relief valve downstream towards the pump.

A little more flexibility with placement of relief is OK.but not the gauge.

Regards,
Tim

OK, I get that and it makes perfect sense. So maybe a change is in order for my setup.

Gauge
|
filter
|

Lathe-adapter ------- relief valve ---- input filter -------- pump ------- output filter (silencer)

This has the gauge closest to the lathe-adapter but still protected by a filter. And since the filter has no air-flow through it other then initial turn on and final turn off (both of which happen when there is no dust) it should never get dirty so the gauge should always remain accurate.

(I suppose that by the same argument you could say the gauge filter is not necessary but I over-engineer everything.)

Thoughts?

[Thom Sturgill]

Gauge
|
filter
|

Lathe-adapter ------- relief valve ---- input filter -------- pump ------- output filter (silencer)

This has the gauge closest to the lathe-adapter but still protected by a filter. And since the filter has no air-flow through it other then initial turn on and final turn off (both of which happen when there is no dust) it should never get dirty so the gauge should always remain accurate.

(I suppose that by the same argument you could say the gauge filter is not necessary but I over-engineer everything.)

Thoughts?

Actually the filter by the gauge could be a problem as there will be a pressure drop across it giving a low reading if I understand correctly.
My parts will be in tonight. What I'm building will be:

Rotary adapter - tee - tee - filter- pump - filter - silencer

with the gauge at the first tee and the relief valve at the second. (I could not get that to format right).