Cutting marine ply gingerbread

[edp]

For the third time in as many years, my 15hp vacuum system bought from ShopBot has jammed. I have not yet pulled it down to fix it, but from past experience, there will be a small(very small) chip of aluminum from one of the turbine blades(?) caught between a blade tip and the walls of the case as has happened previously. Has anyone else had this problem and if so, how did you cure it?
All intake filters are in place and clean, piping to the vacuum table is not leaking and mdf spoil board in good shape.
Many thanks.

[Brady Watson]

EF,
The 15HP Cascade pumps have very close tolerances, and as a result, they do not like to be 'hot started'.

Here's a few tips that will help you avoid the condition that you have posted:

1: Never start and stop the pump more than 3X in one hour. Tolerances are tight and from what I have heard, damage can result if you frequently turn the pump on and off at a higher frequency than what is recommended. This may be what those AL chips are...If they are coming off of the impeller and jamming it you know how tight the tolerances are...

2: When you do start the pump, lift the bleeder board to reduce the amount of load on the blower and make sure that ALL of your zones are open.

3: When it is time to swap out material, LEAVE THE PUMP RUNNING and open the 5th valve which will open the pump up (before the filter) to free air...and close off your table zones. This will reduce the vacuum draw on the table, allow you to swap out material and keep the pump running. If you don't have a 5th valve installed ~ put one in there.

Give those things a try...

-Brady

[bob_lofthouse]

Hi Brady,

I didn't know about the above problems.

Your solutions are ok but will slow production down.

My vacuum goes on and off upto 15 times an hour.

[Brady Watson]

Robert,
If you have a 5th valve and release the vacuum, that shouldn't add any significant time to your current routine. Just a flick of the wrist


I wouldn't really classify what I posted as being problems...more along the lines of proper care and feeding of your vacuum system. This is typical for most regenerative blower-type vacuum systems out there...they are not meant to be cycled on and off...rather, the vacuum is meant to be bled off while material is being changed, and then re-applied under load. Starting and stopping some of the larger systems can be really hard on the unit in addition to high-demand on your electrical system. It is not uncommon for some of these motors to draw 100 to 200A for a second or two when starting.

-Brady

[elcruisr]

We run the FPZ 15 hp system and they call for a vacuum relief valve just before the filter that is set for release at max reccomended vacuum. It would be pretty easy to install one in a system and they are adjustable. just install it with a master valve and you would only have one to close and open. I have to admit to cycling the FPZ fairly often on some runs and it's been flawless for almost 4 years.

Eric

[edp]

Many thanks for the responses. Just to set the record a bit straighter, We do not cycle the blower often at all, certainly not 3 times per hour and usually use other hold down options for everything other than sheet goods. This problem has always popped up on the first start of a day. I do have the relief valve installed but do not have a manual relief valve. Unit is always started with all four table zones on. I am well aware of the huge draw on start-up - we have a 25 kw 3 phase diesel generator for standby use and nearly bogged it down completely when we tried to use the vac with it running. Fortunately our power is very reliable, but being a wood shop in the hurricane zone we need a backup for worst case scenarios.

Once again, many thanks for the inputs.

[kr_fitz]

I'm confused (or my browser is); what does this thread have to do with

[dhunt]

E.F.P.,
Now we've been cutting 7-9 sheets of marine ply a day for the last 3 wks. or so...
those full-sheet .sbp cut files are taking about 34 mins. per file, at 1.2 ins. per sec.
I turn the vac.pump off within 5 secs of end of the file, and re-start it after cleaning the spoil board of dust and repositioning a new sheet of ply(6-8 mins.?)
- let's say, every 45 mins.
5 days a week,now, for 3 wks. not bad.
Funny how the personal experiences and suggestions range from the nonchalant
(a mere 15 times an hour) to the overly cautious
( leave it ON, use a dump valve between sheets,then close valve to resume vac.)!!