[Previous] [Apsco's Page]
Because dust collection systems require a high pressure performance fan, only the materials-handling paddlewheel or the backward inclined fan is suitable.
The backward inclined wheel is the more efficient wheel but it is generally not designed to handle material. It should, therefore, be located after the baghouse where it handles clean air only. This has the drawback that the fan is located the farthest distance from the dust producing machinery, where the suction is required. Locating the fan here is also inefficient because energy is wasted in high discharge velocities (of no benefit to the dust collection operation, but necessary to produce the suction required) resulting in high noise levels returned through the ductwork to the workspace.
A better location for the fan, in our experience, is to locate it between the dust producing machines and the baghouse. This allows the fan discharge noise to be attenuated through the baghouse before it is returned to the workspace, resulting in very quiet operation without the need for expensive silencers. This necessitates the use of a paddlewheel, materials-hand ling fan, but you do not need to worry about the fan's destruction if the filters fail, as you might with a backward inclined fan.
If the fan supplied with your dust collector is sized to the most efficient operation point on its fan curve, and if it is belt driven, you will have the option to increase its speed by changing the drive (pulleys) and motor (if necessary).
Noise, in a dust control system, is generated by the air rushing into the machine hoods, by material and air carried inside the supply ductwork, and by the fan; some of which is radiated from the fan casing, but the larger amount is carried back to the workspace through the return air duct.
We can do very little about the noise generated at the machine hoods and in the supply ductwork. Happily this noise is of a broad spectrum (like rushing water) and is generally not objectional. Noise generated by the fan is, however, very objectional to plant personnel. This noise is almost a pure tone, caused by the fan blades passing by the fan scroll cutoff. (A six bladed fan wheel, turning at 1500 RPM will create a air pulse frequency of 6 x 1500/60 = 150 cycles per second.) Silencers can greatly reduce this air noise, but locating the fan before the baghouse is a far more successful method of noise control. (See Question 13.) Fan noise radiated from its casing is generally not a problem. As a rule-of-thumb, the larger the fan and the lower the fan's RPM, the less objectional the noise level becomes.
These questions and answers are published as a courtesy by APSCO Engineering Ltd. Please feel free to use this information as you like.
APSCO Engineering Ltd. has been designing, manufacturing, installing, and servicing dust control systems since 1968. Our approach has always been one of service orientation to the whole spectrum of the dust control problem, not just the supply of one component, ie. the dust collector. We recognize that each application is unique and cannot necessarily be handled by standard models without additional considerations. We invite you to compare our equipment and system parameters with that of others. The chart below is designed for just that. Thank you for considering our services.
| PARAMETER |
APSCO
|
Competition 1
|
Competition 2
|
| CFM | |||
| Pressure Drop |
,
|
,
|
,
|
| Cloth Ratio* |
,
|
,
|
,
|
| Filter Material |
,
|
,
|
,
|
| Filter Bag Ratio (length/dia.)** |
,
|
,
|
,
|
| Filter Bag Hanger |
Spring
|
,
|
,
|
| Regeneration |
,
|
,
|
,
|
| Explosion Vent |
Standard
|
,
|
,
|
|
Fan: Location
|
,
|
,
|
,
|
|
Wheel Dia.
|
,
|
,
|
,
|
|
RPM***
|
,
|
,
|
,
|
* The lowest is preferable
(see Question 6)
** 12/1 maximum
(see Question 8)
*** usually the lowest is preferable
[Previous] [Apsco's Page]