Ventilation for a Manufacturing Facility

[Fugeguy]

We build large custom manufactured horse trailers.

We moved into a new 50,000 ft^2 facility this spring.

Winter is coming and the facility is closed up. All summer we had the doors open and that provided excellant ventilation. We perform a variety of operations including welding of aluminum and steel, plasma arc cutting, gluing operations with DAP,cleaning of the finished aluminum with acid and cutting of FRP. None of these are that bad on their own, however as we have closed the facility doors, we now have a dustcloud in the afternoon.

Since our activites and locations vary each day, we are planning on getting some industrial floor fans to push fumes and dust from the work areas. In addition, we are going to put large industrial fans in each end of the building.

If you go to ASHRAE Standard 62-1999, table 2.1, there are not any recommendations for manufacturing facilities. As noted, we generate a relatively small volume of dust and fumes so my thought was to size the fans based on the .3 cfm/ ft^2 recommendation or about 15,000 cfm. The plan would be to put a 7,500 cfm reversible fan in each end of the building.

Does this seem a reasonable approach?

 

[quark]

The number of air changes per hour coming out to be less than 1.5. (assuming a room height of 15 feet)

As a general idea 5 would be ok, but then the fans will become too huge. How about localised ventillation near equipment?

For my information where did you get that 0.3cfm/ft^2 recommendation?

I hope somebody else will give you better advice.

Regards,

 

[KenRad]

If you have relatively few point sources of dust/fumes as compared with your overall facility size, local ventilation would probably be your best bet for the following reasons:

1. Most likely, your outside air requirements will be less, reducing your heating bill. As an example, if your outside air is 40F, every 1000 CFM of outside air will take about 32,000 BTU/HR to heat.

2. Removing the contaminants at the source is more effective, since they don't have a chance to get dispersed throughout the room.

You said your locations for the different operations vary each day, which might create some challenges. But I would definitely run the numbers on local ventilation before settling for a large volume of general ventilation.

---KenRad

 

[Fugeguy]

The .3 number comes from ASHRAE Standard 62-1999, table 2.1. The problem with this standard is that it concentrates on office and retail spaces. I selected that number because it was the most severe (not the best logic I realize).

I had considered localized venting, however the quantity and size of trailers we build varies greatly, so our locations change on a weekly basis. We will probably be in a position to standardize some of our operations in the future, but for now, we need a short term fix. Plus long term we need ventilation at the peak of the building so it was not wasted effort.

Thank you for your thoughts.

 

[janners]

Fugeguy,
Nederman at 1-905-795-0632 (sorry its in canada) do excellent local ventilation systems for welding and other highly fumy occupations. I have used them mostly in UK & western europe and they've not let me down yet.
These items can be made portable or with giant hose tails such as I've used in Auto testing stations.
Also you do need ventilation, but as you said you are in a large warehousey type structure I dont think you should worry too much on the exact air change rate. You will get a huge air VOLUME change, not rate, from leakage in the structure. And if its windy, more than you want!
I Suggest a heat exchanging system with a bypass on the HX, on CO2 sensors if you're worried about ventilation overall rate.
BUT, Caustic fumes from acid etching and welding fluxes and the glues, are a definite cause for concern. Either one will cause major respiratory problems. Other possible solutions would be to containerise local areas and give them, (the etching and welding) a very high volumetric air change rate. This would minimise your heat losses and also chances of breathing problems.
Hope that adds a few more arrows to your belt.
On a last note, you build structures therefore you can build a mobile fume extraction system. Bits of flexible duct such as I use for HVAC work, a circular turbo type extractor fan would be good to whip the fumes away to outside!
Good luck
Janners

 

[quark]

Here is a good reference.

http://www.roofunitsltd.co.uk/sharing/design-what-size.asp

Follow that site and you will get very good data. Low limit of ACPH stated will suffice the requirement as far as my experience is concerned.

Regards,

Repetition is the foundation of technology