Materials handling equipment is sized on the m3/hr requirement and powered on the te/hr requirement.

You must give this information to the handling equipment supplier so he correctly sizes and powers the machine. ■

It is easy to calculate the tonnage from a screw conveyor knowing the diameter, pitch and speed, dust bulk density and assuming a percentage filling. A bag filter screw will sometimes run 100% full.

If you are designing a new bagfilter system, you can only size the dust handling equipment by estimating the dust load to the bagfilter.

These estimates are always conservative, in my experience, so the screw conv. and rotary valve are over-sized, not a bad thing really.

The dust load depends on the process and the type of dust produced. If you have access to records from a similar process, you may be able to get an accurate figure.

Michael Reid. ■

Is that a good idea?? ■

No, running a screw conveyor 100% full it is not a good idea but it WILL happen in a bag filter, from time to time.

Mall, 50 to 100 mg/m3 is a huge dust load. It means your dust extraction system is picking up too much product. As I said, these estimates tend to be over-estimates so I don't believe you will see this. If you design your screw conveyor for this, you will be safe.

Michael Reid. ■

Mall,

To get an accurate measure of the dust load, you will have to take a sample from the inlet ducting ahead of the bag filter, (or from the inlet of a similar system).

Michael Reid. ■