Extraction System problem- Bags sucked up into Hopper

[kayak23]

Hi,

I was wondering if anyone may be able to help us with a problem we are having with our extraction system.

Most places I have worked, the bags on the extraction unit seem to blow out and inflate when the unit is in operation. Our unit however seems to actually suck the plastic extraction bags up into the hopper when in operation.

It is quite a large unit (UMA 750v) as its services the large workshops here at the college where I am the technician and I believe it used to have large, heavy woven collection bags.
We have recently had all the filters changed and the performance of the unit has increased significantly. The bags continue to be sucked up into the machine though and they often split because of this.

Can anyone suggest a likelt cause or remedy for this?

Any help greatly appreciated.

Oliver

 

[OPJ]

Hi and welcome to the forum.

Is this happening when the bags fitted? Perhaps it would help to 'manually' put some shavings and sawdust in the bottom to give the bag some weight?

 

[big soft moose]

i think its fairly usual for the bag to get sucked up - mine always does - eventually the weight of the shaving pushes it back down.

the filter bag on the blower side of the fan inflates but clearly a collection back on the suck side isnt going to

if this is causing the backs to split - at the end of the day you need stronger bags

 

[Harbo]

I have a Record DX5000 which always sucks up the bag especially with both motors working. It is fitted with a metal cage which prevents total suck up
I also use two bags - one top of the other which prevents splits - I empty and reuse them so do not have to replace too often.

Rod

 

[p111dom]

Same here too on my DX5000 clone. Sometimes with new filters and and empty bag the bag can rip. Have been meaning to come up with a sloution to this for a while now.

 

[kayak23]

Yes, even with a bucketful of shavings, the bags still get sucked up into the machine.

It is a massive system, much bigger than most fitted in many workshops and services about 11 machines, many with extraction gates left open.Its about as tall as a first floor window (its sited outside obviously) with two filter boxes on top, then has a big hopper beneath, at the base of which is another fan which I think spins at a slow RPM and 'scatters' the shavings into the twin collector hopper at the base, to which two heavy duty refuse sacks are fitted.

We tried to stay away from the super-thick clear bags you can buy as the cost implications are quite large throwing these away as we have to dispose of all dust waste in sealed bags.

I think the wire mesh idea may be a good one which could perhaps be fitted just inside the twin collector 'hopper-rings'....

An extraction company I briefly spoke to suggested that many units get fitted with a hose kit which runs from the base-hopper up to the filter units and equalises the pressure in some way preventing suck-back.
I guess I was really looking for a low-cost option....

I suppose many bags fitted tend to be felt or canvas and so naturally 'breathe' a little, something a plastic bag cannot do. As the waste needs to be sealed before disposal, this isn't really an option. Plus the older style canvas bags are so heavy and dusty...

 

[TheTiddles]

I don't know if it's feasible in such a large machine but you could put the bags in a bin then seal the lid on, attach the vacuum to the bin then off the bin onto the bag, this creates a very slight differential pressure and will hold the bag open, the same thing is done on hospital suction vessels

Aidan

 

[Russell]

Record do a pressure release kit part DX100PR for the Dx5000 type extractor to regulate airflow and stop "suck up splitting" but reducing the suck will cause a drop off in efficiency