[slammedxonair]

Does anybody know if this will work? I have been emailing the guy about it, he didnt know the CFM rating but gave me a part number that I cant seem to find online anywhere. http://sandusky.craigslist.org/for/1400234965.html Model # 4C639A

[LeonD]

I generally am pretty fried by the end of a day so I don't often get to these forums BUT.. tonight I was curious. Some ANSWERS for you.

1 FANS - The downdraft air table was designed based on area. A 4x8 table requires 3500 CFM @ 2" static pressure. A 5x10 table requires a 4500CFM fan @ 2" static pressure. Best choice for efficiency (smallest motor) is a backward inclined fan. This type will be quiet and lowest amperage.
For a 4x8 A Grainger model 7H165 or equivalent is needed. (2 HP)
For a 5x10 A Grainger model 7H166 or equivalent is needed. (3 HP)

If you find a used backward inclined centrifugal blower with a 15 to 20 inch wheel, it should work. Call me however to size the drive for proper RPM.

2- THC crashes. This is most often a problem of too low of a voltage setpoint. If it just randomly "jumps' then we have a problem with electrical static getting into the voltage line. This can usually be filtered out easily. Call me for instructions. It's a $2 fix.

Leon - Dynatorch Inc. Tech line

[slammedxonair]

well that blower for my 4x8 table won't work. I don't have 3 phase electric....

[LeonD]

That part number was just an example. However any fan used to move that volume of air will have to be 3 HP. Basic laws of physics and efficiency levels of fans. You may find a 3HP motor in single phase and just buy a fan without the motor. Then get pulleys and a belt to run the fan the required RPM. Otherwise, use a phase converter to get 3 phase from your single phase for the fan.

[Hi-Vac]

I was just wondering has anyone ever attempted installing a close meshed electromagnetic field under the cutting slats that can be turned on during the cutting process to collect the "plasma dust" while cutting steel. I realize this would not work with stainless or aluminum, but if it helped 90% of the time it might be worth a shot.

[Med-Pac]

Hey slammedonair,

Slow day in the shop, I came across your thread while I was trying to look busy. Here's a couple of pics of our set-up. We have a 4x8 table running a 1000 hypertherm. I regularly cut thicker pcs. up to .50 thk, every once in a while I've had to cut .75. It works, but you have to play with the settings to make it work.

The table is a downdraft witha pull out drawer for the slag. Not sure what the exact specs on the fan are. If you need them I can search around for them. Pretty sure we picked it up at Grainger, and if memory serves I told them I needed a big "barn fan". It moves enough cfm's to suck all the heat out of our 140' x 60' shop though. THe duct work is 24" x 24", and we mounted the fan inside the duct. Easier to work on if we ever have a problem....especially in the winter.

hope this helps ya
Mike

[Med-Pac]

Forgot to finish typing!!

The fan is mounted in the darker steel box you see in pic 2. My advice on the fan choice is to go with the biggest possibility that you have power for. If it doesn't perform the way you need.......get 3phase or open the door!

Mike

[WSS]

Water table-

No electric bill
No 3ph
No ducting
No heat loss in building
No warping

No, No, No...........

Just a thought!

WSS

[slammedxonair]

Yea I wish I would have known all of this before I got my downdraft table... off Dynatorche's web site "Uses a low volume customer supplied vacuum source (exhaust fan)."
I wouldn't call a 3 phase 3500 cfm blower a low volume exhaust fan....

[slammedxonair]

what is static pressure and why does it need to be 2" ?

[LeonD]

All fans are rated by CFM and Static pressure. Both must be specified as the fan has a performance curve. As static pressure (back pressure or suction pressure) is increased, air flow volume decreases. Maximum pressure (or suction) is acheved at zero CFM (blocked inlet or discharge). On the other end of the scale, maxiumum flow CFM is acheved at zero static pressure. The air table system has a small amount of static pressure loss that must be overcome. This is the 2" water gauge pressure. Low pressures are rated at inches of water column. That is the pressure required to lift water in a tube by X inches.