Three failure mechanisms can shorten the operating life of a bag. They are related to thermal
durability, abrasion, and chemical attack.
The chief design variable is the upper temperature limit of the fabric, or thermal durability.
As shown in Table 1, fabrics have upper temperature limits which they can withstand continuously.
The table also shows surge limits which are temperatures at which the baghouse can be
operated for short durations. Consult the fabric supplier for the length of time that the surge
temperature can be tolerated. The process exhaust temperature will determine which fabric
material should be used for dust collection. Exhaust gas cooling may be feasible, but the
exhaust gas must be kept hot enough to prevent moisture or acid from condensing on the bags.
Another problem frequently encountered in baghouse operation is abrasion. Bag abrasion can
result from bags rubbing against each other, from the type of bag cleaning used, or where dust
enters the bag and contacts the fabric material. For instance, in a shaker baghouse, vigorous shaking may cause premature bag deterioration, particularly at the points where the bags are
attached. In pulse-jet units, the continual, slight motion of the bags against the supporting
cages can also seriously affect bag life. As a result, a 25% per year bag replacement rate is
common. This can be the single biggest maintenance problem associated with baghouses
(Greiner 1992).
Bag failure can also occur fromchemical attack to the fabric. Changes in dust composition
and exhaust gas temperatures from industrial processes can greatly affect the bag material. If
the exhaust gas stream is lowered to its dew point (either water or acid dew point), the design
of the baghouse (fabric choice) may be completely inadequate. Proper fabric selection and
good process operating practices can help eliminate bag deterioration caused by chemical
attack.
Typical fabrics used for bags
durability, abrasion, and chemical attack.
The chief design variable is the upper temperature limit of the fabric, or thermal durability.
As shown in Table 1, fabrics have upper temperature limits which they can withstand continuously.
The table also shows surge limits which are temperatures at which the baghouse can be
operated for short durations. Consult the fabric supplier for the length of time that the surge
temperature can be tolerated. The process exhaust temperature will determine which fabric
material should be used for dust collection. Exhaust gas cooling may be feasible, but the
exhaust gas must be kept hot enough to prevent moisture or acid from condensing on the bags.
Another problem frequently encountered in baghouse operation is abrasion. Bag abrasion can
result from bags rubbing against each other, from the type of bag cleaning used, or where dust
enters the bag and contacts the fabric material. For instance, in a shaker baghouse, vigorous shaking may cause premature bag deterioration, particularly at the points where the bags are
attached. In pulse-jet units, the continual, slight motion of the bags against the supporting
cages can also seriously affect bag life. As a result, a 25% per year bag replacement rate is
common. This can be the single biggest maintenance problem associated with baghouses
(Greiner 1992).
Bag failure can also occur fromchemical attack to the fabric. Changes in dust composition
and exhaust gas temperatures from industrial processes can greatly affect the bag material. If
the exhaust gas stream is lowered to its dew point (either water or acid dew point), the design
of the baghouse (fabric choice) may be completely inadequate. Proper fabric selection and
good process operating practices can help eliminate bag deterioration caused by chemical
attack.
Typical fabrics used for bags
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