毕业设计--圆振动筛设计的外文翻译

毕业设计--圆振动筛设计的外文翻译辽宁科技大学本科生毕业设计第1页

Screening Vibrating screens

Principles --Vibrating screens save space and weight and operate on little power because the screening surface may be actuated by vibrating, gyrating or pulsating

movement of small amplitude, but at frequencies that normally exceed 3,000/min.

Selection of Proper Vibration Sereen --Be sure the screen supplier knows all details of

the application. The centrifugal force factor, or combination of frequency of vibration

(speed) and amplitude (throw), may affect performance of any

vibrating screen. Also,

a correct combination of slope and direction of mechanism rotation

is vital for

inclined screens. Usually, the larger the opening, the greater the amplitude needed for

a screen.

If the throw is too small, the material may clog or wedge in the openings. Increasing

the throw beyond what is required to prevent blinding or plugging does not

necessarily increase the life of the bearings and reduce screening efficiency.

Increased rate of travel permits more tonnage to be passed over the screen per unit of

time. For a given tonnage, a faster rate of travel results in a thinner bed of material

and high screening efficiency.

Maximum slope is reached when the material travels too fast for the fines to penetrate

the ribbon of material and reach the apertures in the screen cloth. At this point an

excessive amount of fine material passes over the screen with the oversize, resulting

in poor efficiency.

When an existing screen is to be used for an application other than that for which it

was originally intended, check with the Supplier to see if any of the operating

characteristics need modification and if the the screen is structurally suitable for the

new application.

The operator can get the correct vibrating screen by providing the supplier with the

following information:

, Maximum tons per hour to be screened, including any circulating load or any

surges in the feed rate.

, A complete size consist or sieve analysis of the material or, if available, an

estimated analysis.

, Type of material and weight per cubic foot in broken state.

, Separations desired on each deck.

, Surface moisture carried by the material if screening is to be dry or amount of

water with feed if wet.

, Special operating requirements or conditions such as temperature, abrasiveness, corrosiveness or other physical characteristics of the feed,

辽宁科技大学本科生毕业设计第2页

efficiency or product requirements which determine selection of screening

surface, or installation problems which affect screen size selection or capacity.

General Types --Vibrating screens may be divided into two main classes: mechanically-vibrated and electrially-vibrated. The former can be subdivided into classes based on how the vibration is produced--by eccentrics; by unbalanced weight; by cams or bumpers. They can also be subdivided as inclined and horizontal. Sizes --Vibrating screens are