The skirtboard cover will be fitted with one (or more) dust bags to relieve excess positive airflow and capture airborne dust. Each bag will be sized to relieve 0,5 cubic meters per second (1000 ft3/min) of airflow in the transfer point. The bag will fit over a port in the roof of the skirtboard and be hung from a support arm attached to the cover. The bag will incorporate static-dissipation technology to reduce the risk of dust explosion. The fabric used in the bag will be suitable for the bulk material being handled.
Calculating the Size of a Dust Bag
Dust bags can vent a finite amount of air per interval of time. This airflow rate is proportional to the permeability of the filter media and the area of the bag.
The process of sizing a dust bag to an application is as follows:
- Find airflow. This can be measured or calculated.
- Apply a reasonable safety factor to the airflow.
- Select a filter media that will allow air through but will stop the dust present in an application.
- Verify the need for static-dissipating fabric.
- Find the area of the fabric by dividing the airflow required by the permeability of the fabric.
- Design the bag to have the area required and to fit into the application geometry. This area can be achieved with a single or multiple bags.
To reduce the risk of explosions, the fabric of the dust bag can be woven to incorporate a grounding wire inside the weave of the fabric. These wires will carry any static electrical charge to the ground. The wires provide low electrical resistance, in keeping with Deutsches Institfür Normung (DIN) Standard 54345 Parts 1 and 3. Depending on location and access, it may be necessary to use lockout / tagout / blockout / testout procedures on the conveyor before performing service work on dust bags. If the dust being collected is a health risk, appropriate personal protective equipment (PPE) must be used, and appropriate disposal methods must be followed.
See also: Belt Conveyor Dust Bags Part 1