distributions are determined by gas sampling

inlet ductwork and the outlet ductwork. This pressure

and generally conform to statistical

drop is a result of entrance and exit losses, frictional

distributions. See figure 6-8.

losses and loss of rotational kinetic energy in the

(2) A fractional cyclone efficiency curve is used

exiting gas stream. Cyclone pressure drop will increase

to estimate what weight percentage of the

as the square of the inlet velocity.

particles in a certain size range will be

collected at a specific inlet gas flow rate and

ments in the form of fan horsepower are directly pro-

cyclone pressure drop. A fractional efficiency

portional to the volume of gas handled and the cyclone

curve is best determined by actual cyclone

resistance to gas flow. Fan energy requirements are

testing and may be obtained from the cyclone

estimated at one quarter horsepower per 1000 cubic

manufacturer. A typical manufacturer's frac-

feet per minute (cfm) of actual gas volume per one

tion efficiency curve is shown on figure 6-9.

inch, water gauge, pressure drop. Since cyclone

(3) Cyclone collection efficiency is determined by

pressure drop is a function of gas inlet and outlet areas,

multiplying the percentage weight of particles

cyclone energy requirements (for the same gas volume

in each size range (size distribution curve) by

and design collection efficiency) can be minimized by

the collection efficiency corresponding to that

reducing the size of the cyclone while maintaining the

size range (fractional efficiency curve), and

same dimension ratios. This means adding more units

adding all weight collected as a percentage of

in parallel to handle the required gas volume. The

the total weight of dust entering the cyclone.

effect on theoretical cyclone efficiency of using more

units in parallel for a given gas volume and system

pressure drop is shown in figure 6-10. The increased

collection efficiency gained by compounding cyclones

in parallel can be lost if gas recirculation among

individual units is allowed to occur.

will be a loss in static pressure of the gas between the