Replies

1. 
   user-83153 | Mar 31, 2007 03:01am | #1

   wisfarm,

     If you ONLY spray waterborne finishes then you don't need to worry about an explosion proof fan. The finish itself is explosion proof.

                   Rob

2. 
   frenchy | Mar 31, 2007 03:14am | #2

   wisfarm,

     What standard to you need to conform to?  EE or EX rated fans are expensive and required to conform to many community requirements,  In addition insurance requirements may call for them.. However I've seen an awful lot of plain old fans  doing the job and have been doing the job for decades..

     Most finishes used in wood working aren't that volatile.  If you are carefull about the placement of the fan, start it before the fumes are present and leave it running untill all the fumes are cleared out before you switch it off, there is darn little chance of problems..

    Can one cause an explosion? Sure but I've seen painter smoking in the booth without any problem. The floor of the paint booth is littered with butts and he pauses spraying only long enough to light the cigeratte.

    When I asked him about his practice, he shrugged and replied that nothing has happened to him in 60 years and he wasn't about to get excited now..

    Confession time, I use a regular fan whenever I set up a temp spray booth.  spraying cars as I have done is far more volitile than any time I spray wood work..

     

   
   

   ---

   Edited 3/30/2007 8:16 pm ET by frenchy

1. 
   Quickstep | Mar 31, 2007 03:36pm | #4

   Frenchy, You said

   "Most finishes used in wood working aren't that volatile.  If you are carefull about the placement of the fan, start it before the fumes are present and leave it running untill all the fumes are cleared out before you switch it off, there is darn little chance of problems."

   Do you believe this to be true for shellac? I know you're a shellac guy, but I didn't know if you spray it. I love a sprayed shellac finish, but I have heard that shellac overspray can be volatile. Knowing your expertise with shellac, I'd appreciate your thoughts.

    

    

1. 
   frenchy | Apr 03, 2007 02:12am | #6

   Quickstep,  

    Let me start out with a statement that eliminates me as an expert on the volatility or explosiveness of any item. 

    I started out spraying shellac in my basement. In the past whenever I sprayed I used to enclose everything in poly and suck the fumes out with a box fan. I was careful to start the fan prior to creating any fumes and shut it off long after all the fumes were removed.. I've sprayed mainly lacquer, which in my humble opinion is far more volatile than the alcohol used in shellac. (especially on humid days)  Now I've sprayed an awful lot of lacquer, Barrels full, not just gallons..

    The first time I sprayed shellac I was, well "in a MOOD" Normally I protect all my tools and cars carefully because of overspray.This time I simply pulled two of my 7 cars out and went at it.  I sprayed a lot! I had panels all over and danced between sawhorses spraying..

     Even with my HVLP guns there is enough overspay in the air to coat things.. not with shellac! The overspray behaved itself very nicely not only staying off my collector cars but off my tools and everything..  Since then I spray shellac without my usual "spray"   booth and don't worry about it..

     MY background is a little more complex than spraying.. I was trained as a firefighter.. In fact I even became a Navy fire fighting instructor.   Training others to fight fires..  I've been in closed steel rooms with 1000 gallons of jet fuel spilled, a handful of young kids and a hose and kept them from panicking while I helped them put out their first roaring fire close up.  (You want to feel like a minor god?  Try that sometime!)     As far as expolosive goes alcohol is way down on my list and since just a little water will dilute it enough to put it below the flash point (at Indy the fire fighting equipment in the pits is lead off with buckets of water, plain old water)  Fire and shellac is not something that holds me in much fear..

    On a humid day I wonder if it would be possible to generate enough fumes to create an expolsive enviornment.  Remember water dilutes alcohol and drops it below it's normal flashpoint.  If you are concerned, keep a bucket of water handy.  Me, I spray away.. (but with my over thinned technique I find I can brush faster than I can spray (except the celings or upside down)..

1. 
   Kevin | Apr 03, 2007 03:31am | #7

   Good advice and a great story about the spilled jet fuel!!

3. 
   ring | Mar 31, 2007 09:23am | #3

   If you use water-borne finishes you are 100% OK.   Unless you are a business that has to meet the "explosion proof" requirement for its insurance coverage, you can forget about it.

    

   David Ring

   http://www.touchwood.co.il/?id=1&lang=e

4. 
   dukeone | Mar 31, 2007 04:32pm | #5

   Wisfarm: Not only does the motor have to be explosion proof but the electric boxes, connectors, switch etc. all have to be rated the same and properly setup. It is one of the more complex parts of electric work. In many cases the parts and pieces have to be rated for the specific chemicals involved, maximum surface temperature of motors, light fixtures: it gets wild. Ask any electrician who works in a oil refinery or similar place.

   Duke

   Support the Troops, Support your Country

   Support Western Civilization:

   Fight Islamofascism

5. 
   wardprobst | Apr 06, 2007 05:12am | #8

   I was reading Jeff Jewitt's book Great Wood Finishes which has a good description of a knock down spray booth. He says "I always recommend an explosion-proof motor, even if you'll be spraying only nonflammable, water-based finishes. Fine dust that accumulates around the discharge opening and motor is a potential source of ignition."
   Guess I believe that cause I dropped $600 on a Dayton explosion proof fan today. Cheaper than a trip to the emergency room or the burn ward.
   DP

1. 
   JohnWW | Apr 06, 2007 06:10pm | #9

   With due respect to Jeff Jewett, his advice was overly cautious and you are buying a motor that won't be any safer than a conventional totally enclosed fan cooled motor. 

   Explosion proof motors are designed to prevent a vapor explosion inside of the motor from spreading outside of the motor and lighting off a larger explosion of the surrounding fumes.  An explosion proof motor doesn't offer any additional protection to your set up, if there aren't actual flammable vapors, which you are saying there won't be.

   John White, Shop Manager, Fine Woodworking Magazine   

1. 
   wisfarm | Apr 06, 2007 06:23pm | #10

   John,
   So what your saying is that I should be relatively safe if I use a exhaust fan that is driven with a motor that drives the blade and not mounted inside the fan it self? Again, I an only planning on using water base finishes.
   Thanks for all the help on this. I am all so building a knock down booth and didn't quite understand the need for the expensive fan. Mark

1. 
   JohnWW | Apr 06, 2007 06:52pm | #11

   I would use a sealed motor, mostly to prevent damage to the motor itself from blocked air passages, and a good filter to prevent overspray from building up on the motor, the fan, and the housing.  The motor could be directly in the air steam it wouldn't have to be a belt drive. 

   Occasionally wiping down or vacuuming out the fan unit to prevent dust and overspray build up would also be good maintenance, it is on any air mover, but there is no great risk of fire from spraying water based finishes that requires extensive safety precautions in a small non-commercial shop. 

   Wood dust getting into the motors and blowers in your shop would certainly be as great, or probably a greater fire risk, and nobody is using explosion proof or especially fire safe equipment there.

   John W.

2. 
   wardprobst | Apr 07, 2007 03:57am | #12

   John,
   Thanks for the information- with due respect, I'm happy I got the explosion proof. I _will_ spray some hazardous finishes occasionally and the extra cost is worth it to me. I'll take risks somewhere else where I can control the parameters a little better. I do have metal ductwork on my dust collection and use iron pipe for compressed air. I've got friends that use PVC for both and that's okay. I'll take my risks elsewhere but thanks again for the information.
   Dale
   http://www.wardprobst.com

1. 
   user-83153 | Apr 07, 2007 09:51am | #13

   Dale,

     I see that you refinish pianos. Do you use mostly waterborne finishes? If so, what products do you usually use? If this is info you would rather not give I understand.

              Rob

1. 
   wardprobst | Apr 07, 2007 11:52pm | #14

   Currently we do traditional nitrocellulose lacquer(Gemini) but we will be doing water based finishes as soon as we can transition to them. The water based lacquers on the market have really improved and we will probably be using Target or Enduro that Homestead Finishing carries. Just have to get some time in with them to see what will work for us and our schedule.
   Dale
   http://www.wardprobst.com

2. 
   user-83153 | Apr 08, 2007 12:01am | #15

   Dale,

     Thanks for the reply. I would be very interested to know what your testing reveals and what you choose to use. I would love to use waterborne finishes but am not convinced that they are on par with solvent finishes. If you would post your results in the finishing forum or e-mail me when you have completed your testing it would be much appreciated. I know in your business the finish is extremely important so I trust your judgement.

                Rob

2. 
   JohnWW | Apr 09, 2007 09:07pm | #20

   An explosion proof motor by itself is not sufficient for safety.  If you are going to worry about a fire hazard then the wiring, the lights, and the switches also need to be rated for use in areas with flammable vapors.  In fact the lights and switches present a much higher risk of lighting off vapors.

   John W.

1. 
   frenchy | Apr 10, 2007 05:03am | #21

   JohnWW

      well said!

2. 
   JohnWW | Apr 10, 2007 05:32pm | #22

   Thanks,

   John W.

6. 
   HowardAcheson | Apr 08, 2007 08:31pm | #16

   One way to get around having an explosion proof fan is to have the air being blown INTO the booth. That way no fumes or overspray passes the motor. Just have a filter on the exhaust side to keep the overspray contained.

   Howie.........
1. 
   frenchy | Apr 09, 2007 05:29am | #17

   HowardAcheson,

    the trouble with that approach is it violates the basic  airflow rule with regard to spraying, thou shalt not risk kicking up dust on what you spray..

1. 
   ring | Apr 09, 2007 09:04am | #18

   FYI,Just a few months ago I got a state of the art spraying room installed in our shop. (Made by Saima of Italy). There is no exhaust fan, only a baffle at the bottom of one wall before it is ducted out. The huge fan unit forces air INTO the room from above - the entire ceiling is an air filter. The air flow created, flowing from above to the exit baffle below, makes spraying a joy. We've been doing 100% glossy lacquers and dust is no longer an issue. I realize that this is irrelevant to the OP's question, but the system of forcing air into an enclosure and letting it just escape is perfectly viable. The pressure inside the room has the added advantage that when one opens a door to enter, the air rushes out, and never allows contamination (dust) to enter the room while the fans are working.David Ring

   http://www.touchwood.co.il/?id=1&lang=e

1. 
   frenchy | Apr 09, 2007 05:39pm | #19

   David,

    I've seen booths like that.  (heck on rare occasions I've even used them) They are wonderful but terribly expensive to design and engineer, far beyond the typical put up some poly and suck out the fumes that most of us use..