Techno Vacuum Table Help

[Dave's_Not_Here]

Gauge should arrive with the meter tomorrow.

[ericscottf]

Any info yet?

Eric

[Dave's_Not_Here]

Parts were supposed to arrive today, but Amazon Prime, as usual, is a day late and a dollar short. Supposed to be here Thursday. . . most likely end of the day.

I will try to get the gauge installed by Friday. Remind me where you want it installed? Before the main electric ball valve by the blower or after the main electric ball valve toward the plenum?

[ericscottf]

Close to the pump. So you can progressively shut off valves and see what effect they have on the pressure.

Anything between the valve and pump can't be tested.

[Dave's_Not_Here]

Close to the pump. So you can progressively shut off valves and see what effect they have on the pressure.

Anything between the valve and pump can't be tested.

I have been fighting a bad clod and flu for several days, so I am a little confused. I have to put the gauge close to the pump but anything between the valve and pump can't be tested?

In this photo, I have a small area just behind the ball valve, between the coupling and the 90° elbow, where I can put the gauge. Will that work? I can keep the main electric ball valve open and manually turn off the other 10 zones one at a time.

[ericscottf]

I meant to say gage, not valve. Anything between gage and pump can't be tested.

[Dave's_Not_Here]

Okay. Makes sense.

Send me a list of tests you want me to do.

Also send me instructions on how you want me to use the clamp meter on the blower.

As soon as everything arrives and gets installed, I will work on the tests and post the results.

[ericscottf]

First test, close all valves, read gage. Clamp meter around 1 hot leg of the pump, read ac amps.
Second, open all valves, read gage. Read meter.
Cover table with material and open valves for material, read valve and gage.

We will go from there.

[Dave's_Not_Here]

First test, close all valves, read gage. Clamp meter around 1 hot leg of the pump, read ac amps.
Second, open all valves, read gage. Read meter.
Cover table with material and open valves for material, read valve and gage.

We will go from there.

Open the box on the blower and check the hot leg? I will most likely have to disconnect and strip the wire some more, as the legs are barely short enough to make the internal connections.

[ericscottf]

Hold off on anything with the meter and power measuring for now please. Just do the gage stuff.

[Dave's_Not_Here]

Here is what I got so far:

1.
All valves closed.
All zone holes plugged.
Blower only; 9.5-10 Hg

2.
All valves open.
All zone hole plugs removed.
2.5 Hg

I have to get some sheet goods to do the material test. Hopefully tomorrow.

[ericscottf]

OK, next up, material on top of the table, all appropriate valves open, what reading do you get.

Eric

[Dave's_Not_Here]

Yeah, I will see how much I can get done Saturday.

I asked the rep from the company that supplies various vacuum applications for different industries, and supplied me with parts for my blower upgrade, about why the sheets of plywood and acrylic would not maintain vacuum, regardless of hole sizes and counts, once the full vacuum had been pulled. Here is his reply:

"Regarding the question about number of holes, this statement may be true if you were pulling an absolute vacuum, but you’re not doing this. The vacuum is static, but is being held by continuous air flow being pulled through the blower via the vacuum booster to allow the compressor to operate within its standard range. Also, this statement has a given of holding totally non-porous material, which is something that you stated is not always the case. In addition, air flows like water to seek least path of resistance and the further away the holes the more likely the vacuum would be weaker or experience pressure losses.

One more thing to consider is that your application is introducing stress/force perpendicular to the vacuum hold that can tend to dislodge or break the vacuum at its worst, and create movement of the piece being held at the least, most likely starting at the point that the vacuum is the weakest."

[ericscottf]

With a sheet of material on the table, the difference between valves completely open (material being held down however well) and valves completely closed (material loose) is a function of how much leakage you're seeing around and thru your material.

In a perfect setup, a sheet of acrylic that's directly atop well-laid gasketing will pull the same vacuum as all valves closed. any difference between those two numbers is leakage in your hardware or gasketing.

[Dave's_Not_Here]

Well, Disappointing results. I didn't have a full sheet so I used 4 1/4 sheets an d overlapped the seams with three more 1/4 sheets.
I checked the gauge and it was pulling 5 Hg; About a 50% reduction.
It pulled a vacuum pretty quick, however, I could feel/hear air movement at the far edge.
I checked the 10 ball-valves coming from the plenum and I believe I need to double check the sealing. I don't think the PVC Glue is doing a very good job, so I am going to put some silicone around all the joints.
I am also going to check the table strips. I am not sure the double stick adhesive strips are sealing adequately, so more silicone adhesive along the perimeter edges of the strips.
I am also going to pull off the extrusion end-caps and reseal all 20 again, with fresh silicone .
I replaced the questionable areas of the gasketing and made good butt joints. I am confident the gasket isn't leaking.

After doing all these adjustments, I will pull another vacuum and see how much improvement I have.

[Dave's_Not_Here]

Ball valves are not leaking.
End-caps are not leaking.
That leaves the table strips. . . If I have to pull them off, they might as well stay off and I can part out the vacuum system.

[ericscottf]

You're sure it isn't leaking through the gasketing or material? The way you describe sealing the top with 1/4 sheets sounds like there may be room for air ingress.

Can you plug the drilled holes with rubber plugs and check pressure that way?

[Dave's_Not_Here]

I have a couple of sample plugs on the way already. Should be here end of the week. After that I order the size that fits. Another week. Then I can run the test.

[Dave's_Not_Here]

Got the sample plugs. Will work perfectly. Had to order minimums - so 400 plugs on order. Should be here next week.

[Dave's_Not_Here]

Received the 400 plugs and installed 190 into the table.

I turned on the blower and got the usual 10 Hg with the ball valves closed.

I opened the ball valves and it dropped to 8 Hg with all the plugs in.

Using the discs to close off the holes with all ball valves open, I got 10 Hg., so the plugs don't seem to do as good as the discs.

Still doesn't tell me what's happening when sheet are put on the whole table and it drops to 5 Hg.

Closing all the ball valves, generates 10 Hg, about what's expected for the blower.
Using the Silicone and Rubber Plugs with the ball valves open, bypass the gaskets and take them out of play. I get 8 Hg, - 2 Hg below closed ball valves.
Using the Disc Plugs with the ball valves open, bypass the gaskets and take them out of play. I get 10 Hg, the same reading with all ball valves closed.

The discs show that the ball valves are not leaking.
The discs show that the table tape under the strips are not leaking, or that the discs seal 100% and the table strip tape leaks at the same rate as when the ball valves are all closed.
The plugs show that they do not seal as well as the discs.

I am ready to toss in the towel on chasing down the black magic vacuum issues and spending more money needlessly. I am starting to wonder if everyone who did the Techno Isel vacuum table setup, have gotten the same results and are afraid to admit it or there is something missing ion the instructions I got regarding the installation.