More on exhaust system

[AMALGAM]

I have been thinking about making a fume exhauster. Then, I got inspired by Scott S’ idea, technically helped by Franz (he answered a thread of mine), and finally scared by Davesisk's math. So, I decided to ask. I work in a three car garage I do not know exactly the dimensions (and I am too lazy to take the tape right now), but when an Expedition and a Toyota Highlander are together inside of it, you can barely open the doors. I am occupying the third car space. When I weld, I do it with the two-car side door completely open. However, I still can feel the fumes around me (I am a little apprehensive about inhaling contaminants). So, watching Scott’s idea I decided to copy the same system that he built. Following Franz recommendation I bought a dryer machine blower. The motor specifications are – HP 1/3 SPL, 115/60, 5.9 A – My question to you guys is what technical considerations should I pay close attention when building and positioning the exhauster to optimize its use? By the way that 115/60 means 115 volts/ 60 hertz right?
Thank you very much
Alfredo

[Scott S]

You want to limit the amount of bends and the length of the duct to reduce the friction loss of the airflow. Try to center the hood portion directly over your work area. I used flex on the tail end to give some movment as needed.( Plus it won't hurt as much if you bang you head into it...LOL)

[Franz]

This page should give you a pretty good idea of how fume exhaust units are constructed. You can simply downsize to your fan unit by using 4" flexible drier vent hose. A simple sheet metal funnel that is about 8" across the mouth and necks down to the vent hose will work well for the inlet.

http://www.engwald.com/weld/weld_page5.html

[echo8287]

Yes on the 115volts/60 htz and the 5.9 is the amperage draw of the motor at that voltage.David

[AMALGAM]

Thank you guys for yur answers. Does the position in which I install the blower affect the airflow? Would the motor work well in any position? Also, for what I read the closer the blower is to the hood, the better the suction power is, is it not?

Thank you again
Alfredo

[Radar Hendrex]

fumes

I just bought a house with 2-2 car garages. One of them is a shop already and has an A/C unit. Will that help the fumes disperse or just re cycle them?

[echo8287]

AMALGAM
I would answer yes to all your questions.The more pipe you have attached the more friction loss in the pipe,plus the more bends and turns the same thing happens. Depends on the blower motor you have too. I've got an old squirrell cage fan out of a furnace that we take with us in the summer time for coolings purposes, if you hooked that thing up for ventilation purpose you'd have to have a door open for intake air and it would suck all the shielding gas away in a small space.
Radar the heating unit will re-circulate the fumes in the area of the garage.
David

[AMALGAM]

Reading another thread about the same subject somebody mentioned the need to let in as much fresh air as you are exhausting to maintain efficiency. As I said before I work in a three car garage with the two car area door completely open. So, there will be a lot much more fresh air coming in than going out. Would this affect efficiency too?
Alfredo

[Scott S]

Depending on where your exhaust duct vents, it could be drawn back in through those doors.

[AMALGAM]

Hi Scott,
The exhaust duct will vent far away from the doors. But what I meant was will the high volume of fresh air coming in through those doors overcome or limit the suction power of the exhaust fan?
Thank you
Alfredo

[Franz]

Originally posted by AMALGAM
Hi Scott,
The exhaust duct will vent far away from the doors. But what I meant was will the volume of fresh air coming in through those doors overcome or limit the suction power of the exhaust fan?
Thank you
Alfredo

The amount of fresh air coming thru an open door will always overcome the CFM a blower can exhaust, but that isn't a concern since the suction hose will be located near the weld, and will be removing the smoke product.
The concern in a smoke exhaust system comes into play when your blower turns the room into a negative pressure situation. Any exhaust system must have at least equal CFM of intake or makeup air to avoid negative pressure.
With TIG and MIG processes, it sometimes becomes a problem of exhausting too much and sucking the cover gas away from the molten pool. In your situation, you can avoid that by adjusting the door opening so you don't wind up creating a wind tunnel at the immediate weld area.

[RBryant]

Follow up question on venting fumes

Does anyone have an opinion or experience on whether or not an exterior-mounted fan vent such as this 900CFM unit: http://www.ventingdirect.com/Product...ProductId=332H would adequately vent welding fumes if mounted in conjunction with a range hood that was approx. 3' over a welding table?

Let's assume no open doors so draft from doors would not be an issue. I had my shop wired so that I could position my welding table very near to my shop's garage door, so once it is open there should be lots of fresh air, but I'm considering the range vent and exterior fan mentioned above for when the door is closed (like these days when it is below freezing outside but still 60 F in the shop.

Thanks,

Regie

[Scott S]

Regie, I am sure that it would work fine, but I don't think you need to spend that much money on it. You can do it alot cheaper and still get the results you are looking for.

[RBryant]

Scott,

OK, I'm all for not spending the money, but how then would you suggest getting to a safe venting situation?

Maybe what I was really asking in the first place is this--at what CFM would an ordinary range hood be useful?

Yes, I referenced a nice one (but you can go to 1500CFM with them), but are you saying a 160CFM cheapo hood vent would be adequate? http://www.ventingdirect.com/Product...oductId=402101

Thank you for any feedback.

Regie

[Aaron]

I'm afraid that the 160 CFM unit will not perform well enough for your needs. Are you able to fabricate your own hood? If so you can buy a higher CFM fan and just run 10" duct to it.