Long time (30 years) since I worked in imperial units Sean, but I would recon the the constant 5 represents (60 x 1/12).

The 60 will change the top line in the equation from cubic feet per hour to cubic feet per minuite, and the 1/12 is converting the bed depth answer units from feet to inches. ■

Sean

DBD = O x C / (5 x T x W)

Where

DBD= Discharge End Bed Depth

O= Oversize in STPH - that should be T/h feed to screen deck

C= Cubic Feet Per Ton of Material

5= Constant

T= Rate of Travel - in feet per minute

W= Width of Screening Area if Feet - net width of screen in feet (nominal width minus 6")

My question is what does the formula constant 5 represent and how does it relate to the calculation. If possible can you explain it in stages so I can follow what you mean.

Number 5 it is a constant determined during experiment and you do not have to worry about it ( like many other constant numbers)

Regards

Ziggy Gregory ■

I totally agree with John... The equation shown gives you ODB in inches, yet none of your variables have inches for a unit. So there must be a conversion factor to convert the feet in your travel rate to inches. Also the hours in your tons/hour won't cancel out with your ft/min if you don't convert the hours into minutes. If you plug in all of your units into your equation, and cancel out units where you can, you will find this to be true. If you were to give your travel rate in inches/hour then you could eliminate the 5 from the equation.

Rob Brooker

Conveyor Services Inc. ■

The formula works fine for all screens no matter what type, tonnage, decline or color.

Because the tph value that you enter into the formula only represents the oversize passing over the end of the deck (after all the undersize has been removed), we are only calculating bed depth at that single point the discharge end of the screen.

The original feed tph onto the deck does not enter into this calculation.

The capacity calculation is totally different animal used to determine the deck area required to efficiently pass the undersize material. ■

Sean,

The rate of travel will affect your bed depth and I will try to explain why. Your rate of travel affects how much material is on the bed at a time. It is similiar to material flowing through a pipe. Lets say you have a very large pipe, with a cross sectional area of 1 square meter, and you have a flow rate of 1000 liters per hour. The flow is going to be very slow. Now you have a pipe with a CS area of a 1/2 square meter but you maintain the 1000 liters per hour. In order the for this to happen your material is going to have to flow twice as fast. If you look at a 1 meter section of each pipe you will see that the 1 meter square pipe will contain twice as much material.

The same thing happens when you calculate bed depth. The faster your material moves the shorter your bed depth can be because the cross sectional area of the material is smaller. ■