Wet/Dry vacuum back blowouts while grinding concrete

[Andrew LB]

Has anyone enountered this? I bought a diamond-cup wheel to grind down the raised concrete just outside my garage door because a tree had lifted it years ago, and after a good amount of grinding I notice the suction going away so I turn the thing off and here are the results...





What a mess.

My shop vac is a 6 horsepower 14 gallon Ridgid, equipped with the level 5 filter and instead of using the **** ridgid bags, I use the bags made for drywall dust for the Craftsman version of this same vacuum. Both bags blew out on the back end, at the farthest point away from the opening. And pretty much destroyed my filter which I'm now going to replace with a Gore/Cleanstream Hepa filter since it's washable and much better.

My first theory was that my grinder shroud was too restrictive, which strained the motor and eventually blowing out the bag itself. This is just a theory but after looking at professionally made grinder shrouds, they all seem to have a series of holes on the TOP which would definitely allow more air into the vacuum when the shroud is so close to the surface you're grinding.

It's not like either bag was anywhere close to being full. The first one was about 20% full at the time of self-destruction, and the second bag was brand new and I had only been grinding about 30 minutes. Also, both bags were not clogged with concrete dust because the vacuum's exhaust while warmer than normal, was blowing pretty hard prior to the rupture.

Lemme go get a photo of the grinder shroud. I made it myself and it does an outstanding job on concrete dust collection. as long as it's flat on the surface, I see ZERO dust escaping.

If anyone has insight into this problem, i'd really appreciate it.

 

[Andrew LB]

Here is the shroud. I made it out of an old vacuum attachment and from the lip from the plastic filter retainer from shop-vac brand vacuums. Epoxied the ring to the modified vac attachment, which then attaches to the guard on my milwaukee grinder with two T-15 screws. The guard's quick-adjust system is held together with 6 screws, two of which I removed in order to use them to attach the vac-shroud.

 

[Andrew LB]

Also, has anyone tried these bags? They're made from cloth and guarantee they wont blow-out, rip, and many other claims. If they work only half as good as they claim, i'm sold... http://www.icscompany.net/airflow_bag.htm

edit:

On the topic of vacuum bags, I just came across these "Herky" bags which are non-woven felt, re-usable, supposedly they filter ash and fine dust, and have a 1 year warranty. interesting... http://www.herkyfilters.com/Herky_vac_bags.htm

and a youtube video:

 

[Armorpoxy]

Hi
You should not use a shop vac when grinding larger areas of concrete since the fine dust will plug so quick virtually any vacuum not designed for this. The result is fast loss of suction, accumulation of dust in the tools, and leaving too much dust on the floor.

For this reason a self cleaning vac should be used. We carry one as a convenience item. The technology is really neat there are 3 filters, not one inside. While one is 'sucking' the other two air pulses into them in reverse popping the dust off them into the canister. The vacuum then switches filters every minute or so so you get zero loss of suction. Other companies offer similar technology.

This is why grinding or shot blasting is often left to professionals who have this not inexpensive equipment, since it's hard to find to rent.

http://www.armorpoxy.com/mm5/mercha...A&Product_Code=COM-ARM1050&Category_Code=FREP

 

[LegacyIndustrial]

A self-cleaning vac is a great item when you make your living doing this.
If you are an occasional user, add a dust-deputy to your existing vac and solve your problem.

Link: http://www.oneida-air.com/homepage.asp

The best part is this will work with concrete and wood dust.

 

[jake00]

Water trap http://www.routerforums.com/tools-woodworking/19587-shop-vac-water-filter.html

 

[OldNeons]

Dust deputy looks slick for a DIY job, never seen that before. We have not had any similar problems using drywall bags. They worked great on the small 7" grinder and the big 220v floor grinder. I think you do need some air intake holes on top of shroud, especially if your shroud fits fairly snug to floor.

 

[JimVonBaden]

I have little clue on this, but how about adding a bit of water to the bottom of your vacuum? Like the old rainbow vacuums?

Jim

 

[Shea]

I had only been grinding about 30 minutes

In my experience helping people out who have been successful using a standard shop vac, the biggest thing by far that needs to be done is stop very frequently to clean the filter. About every 10 to 15 minutes. Chances are your filter was already clogging up from dust escaping the bags before they blew out.

I'm a believer in the Dust-Deputy. It's cheap and I know installers who use it as a backup to their self-cleaning vacs or as an extra when they are doing a large area with an extra grinder. You don't need to stop frequently to clean the filter either.

 

[Edger]

The reason your dust bag blew out is because concrete dust is much heavier than drywall dust and it clogs bags faster. Once your bag got a film of dust inside there was pressure inside the bag which, together with the weight of the concrete dust building up in one area caused the end to blow out. Once that happened the dust immediately clogged your filter.

You probably would have succeeded if you stopped after 10 mins maximum and renewed the bag.

The dust deputy is the best diy answer, or hire a proper concrete dust vacuum with filter cleaning.

 

[Andrew LB]

Water trap http://www.routerforums.com/tools-woodworking/19587-shop-vac-water-filter.html

PURE GENIUS!!! And I have modification for this to reduce the loud bubbling noise as well as the splashing. A little trick I learned back in my weed smoking days.

On the end of the intake pipe that is submerged in water, you drill tons of holes. These holes break up the incoming dirty air which not only reduces the noise and splashing, but it also drastically increases the surface area of bubbles which comes in contact with water, and should remove more dust making the whole water filtration more efficient. I think a larger volume of water should be able to be used, making changes less frequent.

I'm going to build one of these when i get a chance tomorrow and report back.

In my experience helping people out who have been successful using a standard shop vac, the biggest thing by far that needs to be done is stop very frequently to clean the filter. About every 10 to 15 minutes. Chances are your filter was already clogging up from dust escaping the bags before they blew out.

Well... I bought some different bags yesterday. The ones that screwed up were the yellow shop=vac drywall bags, so I went with the white Ridgid "High Effienency" ones, and has much better luck this time around.

This is a photo after 1 hour of grinding. Every 15 minutes or so I'd bang the bucket up and down a few times to knock the dust to the bottom of the bag, then start up again. Even before doing this, the flow of air out the back of the motor was not very restricted.

As you can see, the filter itself is in great shape. The only dust in the canister and on the filter was already in the bucket because I didn't wash it out when replacing the blown out bag.

edit: Oh yeah, I also used super sticky packing tape on these new filters to reinforce the edges where the material is folded and glued. That may have been why these bags are surviving.

Hi
You should not use a shop vac when grinding larger areas of concrete since the fine dust will plug so quick virtually any vacuum not designed for this. The result is fast loss of suction, accumulation of dust in the tools, and leaving too much dust on the floor.

For this reason a self cleaning vac should be used. We carry one as a convenience item. The technology is really neat there are 3 filters, not one inside. While one is 'sucking' the other two air pulses into them in reverse popping the dust off them into the canister. The vacuum then switches filters every minute or so so you get zero loss of suction. Other companies offer similar technology.

This is why grinding or shot blasting is often left to professionals who have this not inexpensive equipment, since it's hard to find to rent.

http://www.armorpoxy.com/mm5/merchan...gory_Code=FREP

I know you're in the business selling these "self cleaning" vacuums but even if I was a professional... price is INSANE. And I'd much rather buy a Nilfisk Attix 30 with HEPA for 1/3 the price, which comes with a 2 year warranty, showing me the manufacturer has confidence in their product rather than lip service.

Rudeness on my part aside... I will compliment your company on fantastic floor coatings. I know many people whose garages and businesses here in SoCal use your epoxy and have nothing but good things to say about it.

 

[Andrew LB]

Hi
You should not use a shop vac when grinding larger areas of concrete since the fine dust will plug so quick virtually any vacuum not designed for this. The result is fast loss of suction, accumulation of dust in the tools, and leaving too much dust on the floor.

I wanted to add that now that i have different bags, and taped up the seams with packing tape so they don't rip, everything is working great with little to no dust in the main filter, and as a test I took a piece of wet black cloth to see how much dust was coming out of the exhaust, and there was none. Also, my tools have been dust free since i built my shroud and fixed the bag problem. As for the floor, there is a little dust, but nothing I can't fix by blowing out the garage with 160psi of air from my compressor.

 

[atfulldraw]

I had the same experience.....

 

[Andrew LB]

Well, yesterday I threw together a water pre-filter from a home depot bucket, 3 ft of 2" PVC, 2ft of 4" PVC, a few assorted PVC parts, a couple shop vac parts, and some epoxy. And it works GREAT. The only thing I need to add is even though I have not had any water leave the bucket, the bubbling does get some splashing up the bucket sides and underside of the lid. So i'm going to make a splash-guard that will keep the water where it belongs while at the same time not restricting airflow.

As for the holes in the bottom of the intake tube... they work perfectly. I cannot even hear the bubbling over the sound of the vacuum, and while there is some splashing, I believe they also reduce the amount of strain on the vacuum's motor compared to just having a solid pipe that's submerged 2" under the water surface.

some pics: