Welding Fume Exhaust Systems
The following is a helpful guide in helping design an efficient and reliable welding fume exhaust system. Our design criteria follows that of The American Conference of Governmental Industrial Hygienists and some of the following are excerpts from the ACGIH Manual of Recommended Practice 22nd Edition as well as clips from various Welding Journal magazine articles.
Engwald is proud to be a member of the newly formed N.A.O.V.E.R.M. National Association of Vehicle Exhaust Removal Manufacturers, which has as one of its goals, the development of standards and specifications for the industry and to present them to other national organizations such as BOCA and ASHRAE.
Studies have compared the lungs of heavy duty welders without proper ventilation, to lungs of people who smoke. The findings were that these welders had the lungs of people who smoke about 25 Cigarettes a day.
A common problem with general ventilation systems in regards to welding fumes is that welding smoke particles stay in the air a lot longer than grinding particles (therefore, a larger spread throughout the workplace). For example, it takes 4 hrs. for a welding smoke particle to hit the floor from a height of 3 ft. whereas, it takes only 3 min. for a grinding particle from the same height.
All of Engwalds' fume exhaust systems are based on the principal of Source Capture, in other words, capturing the contaminant as close to its source as possible, thereby not allowing it to get into the general atmosphere where the worker can breath it in. The main objective is to keep the welder's breathing area as clean as possible. Welding smoke consists of fine particles and gases, which spread at a relatively low speeds from the point of welding and are fairly easy to capture, so why not capture them at the source.
The ACGIH Manual defines Capture Velocity as the minimum hood-induced air velocity necessary to capture and convey a contaminant. It offers the following table:
|Condition of Dispersion Containment
||Capture Velocity, fpm
Released with practically no
velocity into quiet air.
Released at low velocity into
moderately still air.
||Spray booths, container filling, welding, plating, pickling
Active generation into zone of
rapid air motion.
||Spray painting in shallow booth, barrel filling, conveyor loading
Released at high initial velocity into
zone of very rapid air motion.
||Grinding, abrasive blasting,tumbling.
The formula used for converting this capture velocity to required cfm is:
Q = V(5X2 + A) where.
Q= Required Exhaust Air Flow, cfm.
X= Distance From Hood Face To Point Of Contaminant Release, Feet.
A= Hood Face Area, Sq. Ft.
V= Capture Velocity, fpm, T Distance X.
Using this formula for various hose sizes, we come up with the following cfm requirements for cone shaped hoods. (Assuming a face velocity of 1500 fpm and a distance of 9-12 inches from the source.
4" Hose-350-425 cfm
5" Hose-475-550 cfm
6" Hose-625-675 cfm
8" Hose-800-950 cfm
10" Hose-1100-1250 cfm
NOTE: These are suggested airflows for welding fumes only. Applications such as dust or grinding collection require higher airflow and capture velocities.
The Engwald Fume Exhauster Line
Our fume exhaust line is comprised of two main components, counterbalanced fume arms and suspended flexible hoses with magnetic suction hoods that sit directly on the welding surface. Both types are available as stationary mounted portable units.
The counterbalanced stationary mounted fume arms are our W-200, W-300, and W-600 Series in 4", 5", and 6" diameters respectively. The W-200 and 300 Series are available in 9 ft, 12 ft, and 15 ft. models and the W-600 Series comes in 5 ft, 7 ft, 10 ft, and 14 ft. models. all types can be either wall or ceiling mounted and can have direct mounted fans.
Special W-800 series fume arms with 8" hose available on request.
The W-400 Series are our suspended flex hose models with aluminum suction hood, magnetic base with screen and swivel. These units are designed to be used where a counterbalanced arm assembly may not be feasible perhaps because of tight quarters. These units are available in 4" thru 12" diameter models with a standard hose length of 10 ft. Customized hose lengths and diameters are also available.
We also manufacture a line of portable and stand type fume exhausters perfectly suited to eliminate smoke, fumes and toxic gases from confined spaces.
The Engwald Series W-200-75 Welding Booths control fumes, smoke and flashes from arc and acetylene gas welding by the use of high velocity suction. These welding booths are ideal in the training of students in welding techniques without exposing students to dangerous fumes and toxic gases. We offer a wide variety of booth sizes to suit many applications such as Schools, Machine Shops and Manufacturing Plants.