Vac leak Problems

[bstern]

Decided to upgrade my vac system when I moved my shop. Upgraded to a Becker VTLF250 from a 10hp Fuji. I cut 3/4 melamine almost exclusively.The fuji had done great at about 7"mg and degradation to about 5.5" after cuts on most sheets. The only problems I had was on very small pieces, ie 12"X3.5" toe-kicks.

The problem I am having now is very quick loss of vacuum. All plumed up and cutoff valve closed I get 24". With a full sheet of melamine loaded it drops to 8". I have 4 zones. If I open only 1 zone I can maybe get to 10".

The worst part is when cutting vac drops rapidly.

I know that I must have some serious leaks. I have resealed the edges of the spoil board with caulk.
I have gone around with burning incense (saying all sorts of incantations) and seeing no major leaks.

How much should I normally see with a full sheet?
(On the fuji the relief valve kicks in.)

How much should it degrade with cutting?

Any notorious places to look?

BTW my plenum is made of Azak so sealing there should not be a problem. Spoilboard is caulked to the plenum.

Thanks
Bob

[carlcnc]

BOb
I just went thru this with my new table
first you want to isolate if it is plumbing or plenum/spoilbd
I would tape some visqueen over entire table,
plain masking tape works well.
then see what you get with all valves open,no valves. work your way thru opening and closing each valve/zone. If each zone by itself gives you the same reading[low] then it has to be connection at the azek. or around whatever you used to fasten azek to machine.??
vacuum leaks are a pain to hear over other noises,.
Carl

[terryd]

I had this problem when the vacuum release valve would kick open to protect the pump and then bounce continuously. Resetting the pump (valve)with a corrected guage eliminated the problem.....Took a lot of beer and staring at the 'bot' to get to root of the problem

[Brady Watson]

Bob,
What is your vacuum Hg" reading with the bleeder board completely uncovered & all zones open - as if you had a 4X8 on the table? If your bleeder is not bleeding enough, this would be the culprit.

-B

[ken_rychlik]

In my previous life as a mechanic, I would take a piece of old garden hose about 3 ft long and use it to find vac leaks on engines. Hold one end right up against your ear and take the other end of the hose and "hunt" for the leak. It gets loud in your ear when you get close. You can find leaks even with the engine running and background noise, so I think it will work fine for a vac leack on a table also.

Kenneth

[rb99]

Why not go around the areas in question with a lit cigarette? If there are no drafts it should show the leaks...

RB

[rb99]

Why not go around the areas in question with a lit cigarette? If there are no drafts in the room it should show the leaks...

RB

[dubliner]

I think that what the incense was for...

[rb99]

I am incensed I did not read more carefully...

RB

[bstern]

The incantations were no help either!

OK - I removed the old spoilboard and put a cap on each zone at the plenum holes.
got about 20" hg at each hole. (the relief valve is set at 23". So there is some loss.

After installing a new spoilboard and carefully sealing all edges (2 times) I am up to 14" with all valves open.

With only 1 valve open I get 18" open 2 it goes to 15.5 open 3 14.5" and all 4 14".
Seems to be the same no matter what order I open the valves in.

We are going to a test cut in the morning and see what it drops to.